JP2021129460A - Electric power system and power extraction method - Google Patents

Abstract

To provide an electric power system suitable for taking out large amounts of power in an emergency.SOLUTION: Each of multiple distributed systems 30 has a fuel cell power generation system 40, a characteristic conversion circuit 100, and a diode 63. When the operating mode of an electric power system 105 is a superposition mode, at least two of the multiple distributed systems 30 get into a specific output state. In the distributed system 30 in the specific output state, the fuel cell power generation system 40 outputs a DC power to the characteristic conversion circuit 100. When the output voltage of the characteristic conversion circuit 100 is a certain value, power characteristics of the output voltage-output of the characteristic conversion circuit 100 are adjusted by characteristic conversion control so that the output power of the characteristic conversion circuit 100 is the maximum. The characteristic conversion circuit 100 is MPPT-controlled by a DCDC converter 21, and the characteristic conversion circuit 100 outputs a DC power to the DCDC converter 21 via the diode 63.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a power system and a power extraction method.

A power system including a photovoltaic power generation system and a power storage device is known. Patent Document 1 describes such a power system. Specifically, in the electric power system of Patent Document 1, the electric power of the photovoltaic power generation system and the electric power of the power storage device are output to a single-phase two-wire system or a single-phase three-wire electric circuit, respectively, via an inverter.

Japanese Unexamined Patent Publication No. 2012-01536

Photovoltaic systems cannot generate electricity at night. The power storage device has a limit on the time during which electric power can be supplied. Therefore, the electric power system of Patent Document 1 is not always suitable as a power source in an emergency such as a power failure. Also, in an emergency, a large amount of electric power may be required.

It is an object of the present disclosure to provide a power system suitable for extracting a large amount of power in an emergency.

This disclosure is
A power system including a plurality of distributed systems and one DCDC converter.
Each of the plurality of distributed systems has a fuel cell power generation system, a characteristic conversion circuit, and a diode.
When the operating mode of the power system is the superposition mode, at least two of the plurality of distributed systems take a specific output state.
In the distributed system in the specific output state,
The fuel cell power generation system outputs DC power to the characteristic conversion circuit,
The output voltage-output power characteristic of the characteristic conversion circuit is adjusted by the characteristic conversion control so that the output power of the characteristic conversion circuit is maximized when the output voltage of the characteristic conversion circuit is a certain value.
The characteristic conversion circuit is MPPT-controlled by the DCDC converter, and the characteristic conversion circuit outputs DC power to the DCDC converter via the diode.
Provides a power system.

The fuel cell power generation system can generate power even at night and can generate power for a long time. Extracting power from a plurality of fuel cell power generation systems and performing the power extraction via characteristic conversion control and MPPT control is suitable for extracting a large amount of power. Therefore, the electric power system according to the present disclosure is suitable for extracting a large amount of electric power in an emergency.

FIG. 1 is a block diagram of an electric power system. FIG. 2 is a diagram for explaining the VP characteristic obtained by the characteristic conversion circuit. FIG. 3 is a diagram showing an example of a characteristic conversion circuit. FIG. 4 is a diagram for explaining a current sensor. FIG. 5 is a diagram for explaining the first shunt regulator. FIG. 6 is a diagram for explaining the second shunt regulator. FIG. 7 is a diagram showing a specific example of the characteristic conversion circuit. FIG. 8 is a diagram showing another example of the characteristic conversion circuit. FIG. 9 is a diagram showing another specific example of the characteristic conversion circuit. FIG. 10 is a block diagram of the power system. FIG. 11 is a diagram for explaining the VP characteristic obtained by the characteristic conversion circuit. FIG. 12 is a diagram for explaining the VP characteristics of the reference form. FIG. 13 is a diagram showing an example of a characteristic conversion circuit. FIG. 14 is a diagram showing a specific example of the characteristic conversion circuit. FIG. 15 is a diagram showing another example of the characteristic conversion circuit. FIG. 16 is a diagram showing another specific example of the characteristic conversion circuit. FIG. 17 is a block diagram of the power system. FIG. 18 is a diagram showing an example of a characteristic conversion circuit. FIG. 19 is a diagram showing an example of the regulator. FIG. 20 is a diagram for explaining the influence of individual variation of the current sensor. FIG. 21 is a diagram for explaining the influence of individual variation of the current sensor. FIG. 22 is a diagram for explaining the influence of individual variation of the current sensor. FIG. 23 is a block diagram of the power system. FIG. 24 is a diagram for explaining the output characteristics of the characteristic conversion circuit. FIG. 25 is a diagram for explaining the output characteristics of the characteristic conversion circuit. FIG. 26 is a diagram showing an example of a characteristic conversion circuit. FIG. 27 is a diagram for explaining the first shunt regulator. FIG. 28 is a diagram for explaining a current sensor. FIG. 29 is a diagram for explaining the influence of individual variation of the current sensor. FIG. 30 is a diagram for explaining the influence of individual variation of the current sensor. FIG. 31 is a diagram for explaining the adjustment of the switching current by the variable voltage. FIG. 32 is a diagram showing a specific example of the characteristic conversion circuit. FIG. 33 is a block diagram of the power system. FIG. 34 is a diagram for explaining the VP characteristic obtained by the characteristic conversion circuit. FIG. 35 is a diagram for explaining the VP characteristics of the reference form. FIG. 36 is a diagram for explaining the output characteristics of the characteristic conversion circuit. FIG. 37 is a diagram showing an example of a characteristic conversion circuit. FIG. 38 is a diagram for explaining the influence of individual variation of the current sensor. FIG. 39 is a diagram for explaining the adjustment of the switching current by the variable voltage. FIG. 40 is a diagram for explaining the output characteristics of the characteristic conversion circuit after adjustment. FIG. 41 is a diagram showing a specific example of the characteristic conversion circuit. FIG. 42 is a block diagram of the power system. FIG. 43 is a diagram for explaining the VP characteristic obtained by the characteristic conversion control. FIG. 44 is a diagram for explaining the VP characteristics of the reference embodiment. FIG. 45 is a diagram for explaining the first example. FIG. 46 is a diagram for explaining a second example. FIG. 47 is a diagram for explaining a third example. FIG. 48 is a diagram for explaining the first table data. FIG. 49 is a diagram for explaining a configuration example of the characteristic conversion circuit and the control unit. FIG. 50 shows a flowchart for explaining control by the control unit. FIG. 51 is a diagram for explaining a first specific example of the characteristic conversion circuit and the control unit. FIG. 52 is a diagram for explaining a second specific example of the characteristic conversion circuit and the control unit. FIG. 53 is a diagram for explaining a third specific example of the characteristic conversion circuit and the control unit.

In embodiments, the first, second, third ... ordinal numbers may be used. If an element has an ordinal number, it is not essential that a younger element of the same type exists. For example, the term third characteristic conversion circuit is not used to mean that the first characteristic conversion circuit and the second characteristic conversion circuit always exist together with the third characteristic conversion circuit. In addition, the ordinal numbers can be changed, the ordinal numbers can be deleted, and the ordinal numbers can be added as needed.

In the embodiment, the combination of the output current, the output voltage, and the output power of the characteristic conversion circuit may be referred to as an operating point of the characteristic conversion circuit. The operating point when the output power of the characteristic conversion circuit is maximized is sometimes referred to as the maximum power point.

In the following description, the same or similar components may be designated by the same reference numerals and the description may be omitted.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

(First Embodiment)
FIG. 1 is a block diagram of the power system 105 according to the present embodiment. The power system 105 includes a power station 10, fuel cell power generation systems 40A, 40B and 40C, substrates 60A, 60B and 60C, diodes 63A, 63B and 63C, a photovoltaic power generation system 31A and 31B, and a power storage device 25. , 250A, 250B, 250C and 259.

[Power Station 10]
The power station 10 includes a DC power converter 20, a first DC bus 11, a fourth DCDC converter 12, and a first inverter 13.

The DC power converter 20 is designed to perform maximum power point tracking control for a photovoltaic power generation system in which the output power is maximized when the output voltage is within a predetermined range. A photovoltaic power generation system is a system that generates electricity using a photovoltaic power generation panel. Hereinafter, the maximum power point tracking control may be referred to as MPPT control.

DC power is input to the DC power converter 20 from the photovoltaic power generation systems 31A and 31B and the fuel cell power generation systems 40A, 40B and 40C. The DC power output from the DC power converter 20 is supplied to the first DC bus 11.

Specifically, the DC power converter 20 includes a first DCDC converter 21, a second DCDC converter 22, and a third DCDC converter 23. DC power is input to the first DCDC converter 21 from the fuel cell power generation systems 40A, 40B and 40C. DC power is input to the second DCDC converter 22 from the first photovoltaic power generation system 31A. DC power is input to the third DCDC converter 23 from the second photovoltaic power generation system 31B. The DC power output from these DCDC converters 21, 22, and 23 is supplied to the first DC bus 11.

The 4th DCDC converter 12 converts the DC power input from the 1st DC bus 11 into DC power having different voltages. The DC power converted by the 4th DCDC converter 12 is supplied to the power storage device 25. Further, the 4th DCDC converter 12 converts the electric power input from the power storage device 25 into DC electric power having a different voltage and supplies the electric power to the 1st DC bus 11. That is, the fourth DCDC converter 12 is a bidirectional DCDC converter. The fourth DCDC converter 12 operates so that the terminal voltage of the power storage device 25 is within the rated range.

The first inverter 13 converts the DC power input from the first DC bus 11 into AC power. The obtained AC power is supplied to the specific load 259.

The first inverter 13 can also convert AC power input from a system power supply (not shown) into DC power. The DC power thus obtained is supplied to the power storage device 25 via the first DC bus 11 and the fourth DCDC converter 12.

[Solar power generation systems 31A and 31B]
In this embodiment, the power system 105 includes at least one photovoltaic system that maximizes output power when the output voltage is within a predetermined range. The DC power generated by the at least one photovoltaic power generation system is supplied to the DC power converter 20.

Specifically, the photovoltaic power generation systems 31A and 31B correspond to photovoltaic power generation systems in which the output power is maximized when the output voltage is within a predetermined range. In the illustrated example, the photovoltaic systems 31A and 31B have the same configuration.

Each of the first photovoltaic power generation systems 31A and 31B has at least one photovoltaic power generation panel 36, and power is generated using the at least one photovoltaic power generation panel 36. The DC power generated by the photovoltaic power generation systems 31A and 31B is supplied to the DC power converter 20.

[Fuel cell power generation system 40A, 40B and 40C]
The fuel cell power generation systems 40A, 40B, and 40C are systems that generate power using the fuel cell 41. The DC power generated by the fuel cell power generation systems 40, 40B and 40C can be supplied to the DC power converter 20. In the illustrated example, the fuel cell power generation systems 40A, 40B and 40C have the same configuration.

The AC power generated by the first fuel cell power generation system 40A can be supplied to the first distributed load 250A. The AC power generated by the second fuel cell power generation system 40B can be supplied to the second distributed load 250B. The AC power generated by the third fuel cell power generation system 40C can be supplied to the third distributed load 250C.

The fuel cell power generation systems 40A, 40B, and 40C each include a fuel cell 41, a DCDC converter 42, a DC bus 43, an inverter 44, and a controller 51, respectively.

The fuel cell 41 generates DC electric power. Specifically, the fuel cell 41 includes a stack. The stack then produces DC power from oxygen and hydrogen.

The DCDC converter 42 converts the DC power generated by the fuel cell 41 into DC power having different voltages. In this example, the DCDC converter 42 boosts the DC power generated by the fuel cell 41. The boosted DC power is supplied to the DC bus 43.

The inverter 44 converts the DC power input from the DC bus 43 into AC power. The AC power obtained by the inverter 44 of the first fuel cell power generation system 40A is supplied to the first distributed load 250A. The AC power obtained by the inverter 44 of the second fuel cell power generation system 40B is supplied to the second distributed load 250B. The AC power obtained by the inverter 44 of the third fuel cell power generation system 40C is supplied to the third distributed load 250C.

The controller 51 controls the DCDC converter 42, the inverter 44, and the protection relay 62. In this embodiment, the controller 51 is a micro control unit (MCU).

The distributed loads 250A, 250B and 250C each include at least one device that consumes power. The device is, for example, one that is connected to an outlet. In this embodiment, the device is a household electrical appliance. However, the device may be an industrial electrical device. A specific example of the device is a heater.

In the illustrated example, the distributed loads 250A, 250B and 250C are AC loads. However, the distributed loads 250A, 250B and 250C may be DC loads. In that case, the inverter 44 can be omitted.

Hereinafter, the notation of the fuel cell power generation system 40 may be used. The fuel cell power generation system 40 refers to any one of the first fuel cell power generation system 40A, the second fuel cell power generation system 40B, and the third fuel cell power generation system 40C.

Further, hereinafter, the notation of distributed load 250 may be used. The distributed load 250 refers to any one of the first distributed load 250A, the second distributed load 250B, and the third distributed load 250C.

[Boards 60A, 60B and 60C]
The first substrate 60A is provided on a path connecting the first fuel cell power generation system 40A and the power station 10. The second substrate 60B is provided on a path connecting the second fuel cell power generation system 40B and the power station 10. The third substrate 60C is provided on a path connecting the third fuel cell power generation system 40C and the power station 10. In the illustrated example, the substrates 60A, 60B and 60C have the same configuration.

DC power is supplied to the first substrate 60A from the first fuel cell power generation system 40A, specifically, from the DC bus 43 of the first fuel cell power generation system 40A. DC power is supplied to the second substrate 60B from the second fuel cell power generation system 40B, specifically, from the DC bus 43 of the second fuel cell power generation system 40B. DC power is supplied to the third substrate 60C from the third fuel cell power generation system 40C, specifically, from the DC bus 43 of the third fuel cell power generation system 40C.

The substrates 60A, 60B, and 60C each have a characteristic conversion circuit 100, an LC filter 61, and a protection relay 62, respectively.

Hereinafter, the notation of substrate 60 may be used. The substrate 60 refers to any one of the first substrate 60A, the second substrate 60B, and the third substrate 60C.

Hereinafter, the component of the first substrate 60A is attached with the ordinal number "first", the component of the second substrate 60B is attached with the ordinal number "second", and the component of the third substrate 60C is "third". The ordinal number may be added. For example, the characteristic conversion circuit 100 of the first substrate 60A may be referred to as a first characteristic conversion circuit 100. The characteristic conversion circuit 100 of the second substrate 60B may be referred to as a second characteristic conversion circuit 100. The characteristic conversion circuit 100 of the third substrate 60C may be referred to as a third characteristic conversion circuit 100.

[Diodes 63A, 63B and 63C]
The first diode 63A is associated with the first substrate 60A. The second diode 63B is associated with the second substrate 60B. The third diode 63C is associated with the third substrate 60C.

Hereinafter, the notation of diode 63 may be used. The diode 63 refers to any one of the first diode 63A, the second diode 63B and the third diode 63C.

In the illustrated example, the first distributed system 30A, the second distributed system 30B, and the third distributed system 30C are configured. The first distributed system 30A includes a first fuel cell power generation system 40A, a first substrate 60A, a first distributed load 250A, and a first diode 63A. The second distributed system 30B includes a second fuel cell power generation system 40B, a second substrate 60B, a second distributed load 250B, and a second diode 63B. The third distributed system 30C includes a third fuel cell power generation system 40C, a third substrate 60C, a third distributed load 250C, and a third diode 63C.

DC power can be supplied from the first distributed system 30A to the first DCDC converter 21. DC power can be supplied from the second distributed system 30B to the first DCDC converter 21. DC power can be supplied from the third distributed system 30C to the first DCDC converter 21.

Hereinafter, the notation of distributed system 30 may be used. The distributed system 30 refers to any one of the first distributed system 30A, the second distributed system 30B, and the third distributed system 30C.

The name "distributed system" is not intended to limit the distributed system. For example, the positions of the components of the distributed system 30 such as the diode 63 and the distributed load 250 are not particularly limited. The owner of the component of the distributed system 30 is not particularly limited. All components of the distributed system 30 may belong to a single owner, and one component and another component of the distributed system 30 may have different owners.

The characteristic conversion circuit 100 executes characteristic conversion control. The characteristic conversion control brings about an output voltage-output power characteristic in which the output power of the characteristic conversion circuit 100 is maximized when the output voltage of the characteristic conversion circuit 100 is a certain value.

Hereinafter, the characteristic conversion control performed by the first characteristic conversion circuit 100 may be referred to as a first characteristic conversion control. The characteristic conversion control performed by the second characteristic conversion circuit 100 may be referred to as a second characteristic conversion control. The characteristic conversion control performed by the third characteristic conversion circuit 100 may be referred to as a third characteristic conversion control. A "certain value" in the first characteristic conversion control may be referred to as a "first voltage". A "certain value" in the second characteristic conversion control may be referred to as a "second voltage". A "certain value" in the third characteristic conversion control may be referred to as a "third voltage".

In the present embodiment, each characteristic conversion circuit 100 is designed so that the "certain value" in the characteristic conversion control is the same. Therefore, the "certain value" in each characteristic conversion control is substantially the same. However, the "certain value" in each characteristic conversion control has a variation due to individual variation of each characteristic conversion circuit 100. Therefore, there are variations in the "certain value" in the first, second, and third characteristic conversion controls due to individual variations of the first, second, and third characteristic conversion circuits 100.

In the present embodiment, the DC power converter 20 is designed so that MPPT control can be executed for a photovoltaic power generation system in which the output power is maximized when the output voltage is within a predetermined range. The characteristic conversion control brings about an output voltage-output power characteristic in which the output power of the characteristic conversion circuit 100 is maximized when the output voltage of the characteristic conversion circuit 100 is a certain value. Specifically, the above-mentioned certain value is a value within the above-mentioned predetermined range.

Further, in the characteristic conversion control, in the region where the output voltage of the characteristic conversion circuit 100 straddles the above-mentioned value, the output voltage-output current characteristic of the characteristic conversion circuit 100 becomes smaller as the output voltage of the characteristic conversion circuit 100 increases. Bring. Here, the region where the output voltage of the characteristic conversion circuit 100 straddles the above-mentioned certain value ranges from the first value in which the output voltage of the characteristic conversion circuit 100 is smaller than the above-mentioned certain value to the second value larger than the above-mentioned certain value. The area.

In this embodiment, the characteristic conversion control is executed based on the electric output of the characteristic conversion circuit 100. By doing so, it is easy to improve the accuracy of the characteristic conversion control. Specifically, the electric output is the output voltage and output current of the characteristic conversion circuit 100.

In the present embodiment, the characteristic conversion control includes a first feedback control and a second feedback control. The first feedback control is a control performed when the output current of the characteristic conversion circuit 100 is relatively small. The second feedback control is a control performed when the output current of the characteristic conversion circuit 100 is relatively large.

In the present embodiment, the open circuit voltage of the characteristic conversion circuit 100 is controlled by the first feedback control.

In the characteristic conversion circuit 100 of the present embodiment, a first feedback circuit 110 and a second feedback circuit 120 are provided. The first feedback circuit 110 is used to define the target value of the upper limit of the output voltage of the characteristic conversion circuit 100. The second feedback circuit 120 adjusts the output voltage of the characteristic conversion circuit 100 (hereinafter, may be referred to as the output voltage at the maximum power point) to a certain value when the output power of the characteristic conversion circuit 100 reaches its peak. Used. Specifically, this peak is a single peak.

According to the first feedback circuit 110, it is possible to prevent the output voltage of the characteristic conversion circuit 100 from becoming excessively large. Therefore, according to the first feedback circuit 110, it is possible to prevent the DC power converter 20 from being damaged due to an overvoltage input from the fuel cell power generation system 40 to the first DCDC converter 21.

As described above, the DC power converter 20 is designed so that MPPT control can be executed for a photovoltaic power generation system in which the output power is maximized when the output voltage is within a predetermined range. According to the second feedback circuit 120, the output voltage at the maximum power point of the characteristic conversion circuit 100 can be adjusted to a certain value within the predetermined range. Therefore, MPPT control of the characteristic conversion circuit 100 becomes possible. Further, when the output voltage of the characteristic conversion circuit 100 reaches the above value, the increase in the power sent from the characteristic conversion circuit 100 to the first DCDC converter 21 is stopped. Therefore, it is possible to prevent the power sent from the characteristic conversion circuit 100 to the first DCDC converter 21 from being excessively increased. It is also possible to prevent an excessive increase in the electric power sent from the fuel cell power generation system 40 to the characteristic conversion circuit 100. Therefore, it is possible to prevent the output current of the fuel cell power generation system 40 from being excessively increased as the output power of the fuel cell power generation system 40 increases. Therefore, it is possible to prevent the overcurrent protection function from working to stop the power generation of the fuel cell 41 and stop the power supply from the fuel cell power generation system 40 to the first DCDC converter 21.

The characteristic conversion circuit 100 of this example will be further described with reference to FIG. In FIG. 2, the solid line represents the relationship between the output voltage of the characteristic conversion circuit 100 and the output power of the characteristic conversion circuit 100, that is, the VP characteristic. The dotted line represents the relationship between the output voltage of the characteristic conversion circuit 100 and the output current of the characteristic conversion circuit 100, that is, the VI characteristic. The alternate long and short dash line represents the contribution of the first feedback circuit 110. The alternate long and short dash line represents the contribution of the second feedback circuit 120.

As can be understood from FIG. 2, by the first feedback circuit 110, the VI characteristic of the characteristic conversion circuit 100 is such that the output voltage follows the target value in the region where the output current is small. By the second feedback circuit 120, the VI characteristic of the characteristic conversion circuit 100 is such that the output voltage decreases as the output current increases in the region where the output current is large. Combined with the actions of these circuits 110 and 120, the VI characteristics of the characteristic conversion circuit 100 are shown by the dotted line in FIG. As a result, the VP characteristic of the characteristic conversion circuit 100 has a single peak and is convex as shown by the solid line in FIG. Therefore, MPPT control of the characteristic conversion circuit 100 becomes possible.

It should be noted that a certain value described above is lower than the target value. Therefore, the output voltage at the maximum power point of the characteristic conversion circuit 100 is lower than the target value. Further, in this example, the input voltage of the characteristic conversion circuit 100 (voltage in the DC bus 43 in this example) is larger than the target value. However, even when the input voltage is smaller than the target value, it is possible to obtain the VP characteristic shown in FIG.

In this example, the DC power converter 20 includes a first DCDC converter 21, a second DCDC converter 22, and a third DCDC converter 23. The first DCDC converter 21 changes the output voltage of the characteristic conversion circuit 100 by performing MPPT control. The second DCDC converter 22 changes the output voltage of the first photovoltaic power generation system 31A by performing MPPT control. The third DCDC converter 23 changes the output voltage of the second photovoltaic power generation system 31B by performing MPPT control.

FIG. 3 shows an example of the characteristic conversion circuit 100. The characteristic conversion circuit 100 of FIG. 3 includes a current sensor 128, a voltage / current control circuit 160, and a feedback current supply unit 130. The characteristic conversion circuit 100 includes a first feedback circuit 110 and a second feedback circuit 120.

The first feedback circuit 110 includes a first resistor 111, a second resistor 112, and a first shunt regulator 115. The second feedback circuit 120 includes a third resistor 121, a fourth resistor 122, a fifth resistor 123, a second shunt regulator 125, and a current sensor 128. The feedback current supply unit 130 includes a current supply power supply 131 and a sixth resistor 132. In this embodiment, the current supply power supply 131 is a constant voltage source.

The current sensor 128 detects the output current of the characteristic conversion circuit 100. The current sensor 128 outputs a sensor output representing the result of the detection. In the present embodiment, the current sensor 128 outputs a _{sensor voltage V s indicating the result of the detection. The current sensor 128 outputs the sensor voltage V s} as the output current of the characteristic conversion circuit 100 increases. That is, the sensor voltage V _s increases as the output current of the characteristic conversion circuit 100 increases. Such a current sensor 128 can be realized using, for example, a shunt resistor.

FIG. 4 shows a current sensor 128 according to a specific example. The current sensor 128 includes a shunt resistor 128r and a current sense amplifier 128s. The resistance value of the shunt resistor 128r is R _sense . When a current I _load flows through the shunt resistor 128r, a voltage R _sense I _load is applied to the shunt resistor 128r. The current sense amplifier 128s outputs _{the total voltage of the voltage R sense} I _load multiplied by the gain G and the bias voltage V _bias as the sensor voltage V _{s. That is, the sensor voltage V s} generated by the current sensor 128 of the present embodiment is given by Equation 1. However, another current sensor such as a Hall element type current sensor may be used as the current sensor 128, and the output of the current sensor may be used as the _{sensor voltage V s.} The current I _load corresponds to the output current of the characteristic conversion circuit 100. "*" Is a symbol representing multiplication.
Formula 1: V _s = R _sense * I _load * G + V _bias

In the first feedback circuit 110, the output voltage of the characteristic conversion circuit 100 is divided by the first resistor 111 and the second resistor 112. The divided voltage appears at the connection point p1 of the first resistor 111 and the second resistor 112. Hereinafter, the voltage appearing at the first connection point p1 may be referred to as a _{first reference voltage V ref1.} The first reference voltage V _ref1 is input to the first reference voltage terminal of the first shunt regulator 115. The larger the voltage input to the first reference voltage terminal, the more the current supply power supply 131, the sixth resistor 132, the first shunt regulator 115, and the current flowing through the reference potential in this order (hereinafter, may be referred to as the first current) i1. Becomes larger. In FIG. 3, the first current i1 is the current flowing downward in the drawing through the first shunt regulator 115.

In the second feedback circuit 120, the output voltage of the characteristic conversion circuit 100 is divided by the third resistor 121 and the fourth resistor 122. Further, the current sensor 128 generates a _{sensor voltage V s} that increases as the output current of the characteristic conversion circuit 100 increases. _{The sensor voltage V s} is divided by the fifth resistor 123 and the fourth resistor 122. The voltage obtained by adding the voltage dividing voltage derived from the resistors 123 and 122 to the voltage dividing voltage derived from the resistors 121 and 122 appears at the connection point p2 of the three resistors 121, 122 and 123. Hereinafter, the voltage appearing at the second connection point p2 may be referred to as a _{second reference voltage V ref2.} The second reference voltage V _ref2 is input to the second reference voltage terminal of the second shunt regulator 125. The larger the voltage input to the second reference voltage terminal, the more the current supply power supply 131, the sixth resistor 132, the second shunt regulator 125, and the current flowing through the reference potential in this order (hereinafter, may be referred to as the second current) i2. Becomes larger. In FIG. 3, the second current i2 is the current flowing downward in the drawing through the second shunt regulator 125.

In the region where the output current of the characteristic conversion circuit 100 is small, the second current is substantially zero, and the current flowing out from the current supply power supply 131 is substantially the first current. On the other hand, in the region where the output current of the characteristic conversion circuit 100 is large, the first current is substantially zero, and the current flowing out from the current supply power supply 131 is substantially the second current. That is, it can be said that the characteristic conversion in the characteristic conversion circuit 100 is performed by the first feedback circuit 110 in the region where the output current of the characteristic conversion circuit 100 is small, and by the second feedback circuit 120 in the region where the output current of the characteristic conversion circuit 100 is large. .. The parameters of the resistors 111, 112, 121, 122 and 123 and the shunt regulators 115 and 125 are selected so that the circuits 110 and 120 operate in this way.

The voltage / current control circuit 160 is a DCDC converter. The voltage-current control circuit 160 is provided between the fuel cell power generation system 40 and the current sensor 128. Specifically, the voltage-current control circuit 160 is provided between the DC bus 43 and the current sensor 128.

The transformation ratio of the voltage-current control circuit 160 is changed according to the sensor output so that the output power of the characteristic conversion circuit 100 is maximized when the output voltage of the characteristic conversion circuit 100 is a certain value described above. In the present embodiment, the voltage-current control circuit 160 reduces the ratio of the output voltage to the input voltage of the voltage-current control circuit 160 as the current flowing out from the current supply power supply 131 increases. In this way, the characteristic conversion circuit 100 is adapted so that the above ratio is adjusted according to the current flowing out from the current supply power supply 131. Such a characteristic conversion circuit 100 can be appropriately designed.

The first shunt regulator 115 of the present embodiment will be further described with reference to FIG. The first shunt regulator 115 includes a first reference voltage terminal 115a, a first cathode 115K, a first anode 115A, a first reference voltage source 115s, a first operational amplifier 115о, and a first transistor 115t. The first operational amplifier 115о includes a non-inverting amplification terminal 115оa, an inverting amplification terminal 115оb, and an output terminal 115оc. The first transistor 115t includes a cathode side terminal 115ta, an anode side terminal 115tb, and a control terminal 115tc. The voltage input to the first reference voltage terminal 115a is supplied to the non-inverting amplification terminal 115оa. The voltage of the inverting amplification terminal 115оb is set by the first reference voltage source 115 s to a voltage higher than the voltage of the first anode 115 A by the first reference voltage V _s1 . _{When a voltage larger than the first reference voltage V s1} is input to the first reference voltage terminal 115a and the voltage of the non-inverting amplification terminal 115оa becomes larger than that of the inverting amplification terminal 115оb, the output terminal 115оc is changed to the control terminal 115 tk. A current flows, and a first current i1 flows from the first cathode 115K through the cathode side terminal 115ta and the anode side terminal 115tb to the first anode 115A in this order. In the example of FIG. 5, the first transistor 115t is a bipolar transistor, specifically an NPN transistor. The cathode side terminal 115ta is a collector. The anode side terminal 115tb is an emitter. The control terminal 115tc is a base. In this description, the current flowing between the output terminal 115оc and the control terminal 115 tk, specifically, the base current, is ignored as being sufficiently small.

Based on the explanation with reference to FIG. 5, the operation of the first feedback circuit 110 can be explained as follows. When the output voltage V _out of _the characteristic conversion circuit 100 increases, the first reference voltage V _ref1 is increased. In the first shunt regulator 115, as the first reference voltage V _ref1 becomes larger and the deviation of the first reference voltage V _ref1 from the first reference voltage V _s1 becomes larger, the first current i1 becomes larger. As the first current i1 increases, the current flowing out from the current supply power supply 131 increases. As the outflow current increases, the ratio of the output voltage to the input voltage of the voltage-current control circuit 160 decreases. _{In this way, the first feedback circuit 110 controls the output voltage V out} of the characteristic conversion circuit 100 in cooperation with the voltage / current control circuit 160. Specifically, the first feedback circuit 110 cooperates with the voltage-current control circuit 160 to adjust the transformation ratio of the characteristic conversion circuit 100 so that _{the first reference voltage V ref1} follows the first reference voltage V _s1. Adjust. As a result, the output voltage V _out of the characteristic conversion circuit 100 follows the target value.

The second shunt regulator 125 of the present embodiment will be further described with reference to FIG. The second shunt regulator 125 includes a second reference voltage terminal 125a, a second cathode 125K, a second anode 125A, a second reference voltage source 125s, a second operational amplifier 125о, and a second transistor 125t. The second operational amplifier 125о includes a non-inverting amplification terminal 125оa, an inverting amplification terminal 125оb, and an output terminal 125оc. The second transistor 125t includes a cathode side terminal 125ta, an anode side terminal 125tb, and a control terminal 125tc. The voltage input to the second reference voltage terminal 125a is supplied to the non-inverting amplification terminal 125оa. The voltage of the inverting amplification terminal 125оb is set by the second reference voltage source 125 s to a voltage higher than the voltage of the second anode 125 A by the second reference voltage V _s2 . _{When a voltage larger than the second reference voltage V s2} is input to the second reference voltage terminal 125a and the voltage of the non-inverting amplification terminal 125оa becomes larger than that of the inverting amplification terminal 125оb, the output terminal 125оc is changed to the control terminal 125 tk. A current flows, and a second current i2 flows from the second cathode 125K through the cathode side terminal 125ta and the anode side terminal 125tb to the second anode 125A in this order. In the example of FIG. 6, the second transistor 125t is a bipolar transistor, specifically an NPN transistor. The cathode side terminal 125ta is a collector. The anode side terminal 125tb is an emitter. The control terminal 125tc is a base. In this description, the current flowing between the output terminal 125оc and the control terminal 125 tk, specifically, the base current, is ignored as being sufficiently small.

Based on the explanation with reference to FIG. 6, the operation of the second feedback circuit 120 can be explained as follows. _{When the output voltage V out} of the characteristic conversion circuit 100 increases, and when the output current of the characteristic conversion circuit 100 increases and the sensor voltage V _s increases, the second reference voltage V _ref 2 increases. In the second shunt regulator 125, the greater the deviation from the second reference voltage V _s2 of the second reference voltage V _ref2 by the second reference voltage V _ref2 is increased, the second current i2 is large. When the second current i2 becomes large, the current flowing out from the current supply power supply 131 becomes large. As the outflow current increases, the ratio of the output voltage to the input voltage of the voltage-current control circuit 160 decreases. _{In this way, the second feedback circuit 120 controls the output voltage V out} of the characteristic conversion circuit 100 in cooperation with the voltage / current control circuit 160. Specifically, the second feedback circuit 120 cooperates with the voltage / current control circuit 160 to adjust the transformation ratio of the characteristic conversion circuit 100 so that _{the second reference voltage V ref2} follows the second reference voltage V _s2. Adjust.

In the second feedback control by the second feedback circuit 120, when the output current of the characteristic conversion circuit 100 becomes large and the sensor voltage V _s becomes large, the current flowing from the current sensor 128 to the second connection point p2 via the fifth resistor 123 becomes large. growing. With the second shunt regulator 125, the second reference voltage V _ref2 follows a constant second reference voltage V _s2 . In order to realize this tracking, a constant current flows through the fourth resistor 122. This means that when the current flowing through the fifth resistor 123 toward the second connection point p2 increases, the current flowing through the third resistor 121 toward the second connection point p2 decreases. When this current becomes small, the voltage generated by the third resistor 121 becomes small. For this reason, when the output current of the characteristic conversion circuit 100 increases, the voltage generated by the third resistor 121 decreases while the voltage at _{the second connection point p2 follows the second reference voltage V ref2.} As a result, the output voltage V _out of the characteristic conversion circuit 100 becomes small. In this way, the second feedback control provides an output voltage-output current characteristic as shown in FIG. 2, in which the output current of the characteristic conversion circuit 100 decreases as the output voltage of the characteristic conversion circuit 100 increases.

As can be understood from the above description, the characteristic conversion circuit 100 comprises a feedback control loop in which the output current and output voltage of the characteristic conversion circuit 100 are reflected in the subsequent output current and output voltage of the characteristic conversion circuit 100. Has been done. The feedback control loop is configured using the feedback circuit 110 or 120.

Further, it can be said that the first feedback circuit 110 performs the first feedback control. It can be said that the second feedback circuit 120 performs the second feedback control. Specifically, the first feedback circuit 110 performs the first feedback control in cooperation with the voltage / current control circuit 160. The second feedback circuit 120 performs the second feedback control in cooperation with the voltage / current control circuit 160.

Returning to FIG. 1, the output power of the characteristic conversion circuit 100 is supplied to the DC power conversion device 20, specifically to the first DCDC converter 21, via the LC filter 61, the protection relay 62, and the diode 63.

As shown in FIG. 1, the characteristic conversion circuit 100, the diode 63, and the first DCDC converter 21 are connected so that the characteristic conversion circuit 100, the anode of the diode 63, the cathode of the diode 63, and the first DCDC converter 21 appear in this order. ..

The type of the diode 63 is not particularly limited. The diode 63 can be appropriately selected in consideration of the required withstand voltage and the like. The diode 63 is, for example, a fast recovery diode.

[Power storage device 25]
As described above, power is supplied to the power storage device 25 from the 4th DCDC converter 12. Further, the power storage device 25 supplies electric power to the 4th DCDC converter 12.

The power storage device 25 is, for example, a lithium battery. However, a battery other than the lithium battery may be used as the power storage device 25. A capacitor may be used as the power storage device 25.

[Specific load 259]
The specific load 259 includes at least one device that consumes power. The device is, for example, a pump.

In the present embodiment, power is input from the system power supply to the specific load 259 during a non-power failure of the system power supply (not shown). On the other hand, in the event of a power failure of the system power supply, power is input from at least one distributed system 30 to the specific load 259.

In the illustrated example, the specific load 259 is an AC load. However, the specific load 259 may be a DC load. In that case, the inverter 13 can be omitted.

As will be understood from the above description, the power system 105 includes a plurality of distributed systems 30 and one DCDC converter 21. The expression that the power system 105 includes one DCDC converter 21 is intended that the power system 105 may or may not have a DCDC converter other than the DCDC converter 21.

Specifically, the plurality of distributed systems 30 are connected in parallel to each other. Each of the plurality of distributed systems 30 is connected to one DCDC converter 21.

In the example shown in FIG. 1, the plurality of distributed systems 30 include a first distributed system 30A, a second distributed system 30B, and a third distributed system 30C.

Specifically, the distributed systems 30A, 30B and 30C are connected in parallel to each other. The distributed systems 30A, 30B and 30C are each connected to one DCDC converter 21.

In this embodiment, the DCDC converter 21 has a capacitor (not shown). This point is the same for the DCDC converter 22 and the DCDC converter 23.

Each of the plurality of distributed systems 30 has a fuel cell power generation system 40, a characteristic conversion circuit 100, and a diode 63.

Specifically, in each of the plurality of distributed systems 30, the fuel cell power generation system 40, the characteristic conversion circuit 100, and the diode 63 are connected in this order. The diode 63 is arranged on the path connecting the characteristic conversion circuit 100 and the DCDC converter 21 so that the direction from the characteristic conversion circuit 100 to the DCDC converter 21 is forward. Here, the forward direction of the diode is the direction from the anode to the cathode of the diode.

In the example shown in FIG. 1, the first distributed system 30A includes a first fuel cell power generation system 40A, a first characteristic conversion circuit 100, and a first diode 63A. The second distributed system 30B includes a second fuel cell power generation system 40B, a second characteristic conversion circuit 100, and a second diode 63B. The third distributed system 30C includes a third fuel cell power generation system 40C, a third characteristic conversion circuit 100, and a third diode 63C.

The first characteristic conversion circuit 100 is included in the first substrate 60A. The second characteristic conversion circuit 100 is included in the second substrate 60B. The third characteristic conversion circuit 100 is included in the third substrate 60C.

Specifically, in the first distributed system 30A, the first fuel cell power generation system 40A, the first characteristic conversion circuit 100, and the first diode 63A are connected in this order. In the second distributed system 30B, the second fuel cell power generation system 40B, the second characteristic conversion circuit 100, and the second diode 63B are connected in this order. In the third distributed system 30C, the third fuel cell power generation system 40C, the third characteristic conversion circuit 100, and the third diode 63C are connected in this order.

The first diode 63A is arranged on the path connecting the first characteristic conversion circuit 100 and the DCDC converter 21 so that the direction from the first characteristic conversion circuit 100 to the DCDC converter 21 is the forward direction. The second diode 63B is arranged on the path connecting the second characteristic conversion circuit 100 and the DCDC converter 21 so that the direction from the second characteristic conversion circuit 100 to the DCDC converter 21 is the forward direction. The third diode 63C is arranged on the path connecting the third characteristic conversion circuit 100 and the DCDC converter 21 so that the direction from the third characteristic conversion circuit 100 to the DCDC converter 21 is the forward direction.

The operation mode of the power system 105 includes a superimposition mode and a switching mode.

When the operation mode is the superposition mode, at least two of the plurality of distributed systems 30 take a specific output state. In the superimposition mode, all of the plurality of distributed systems 30 may take a specific output state.

The "plurality of distributed systems 30" of "at least two of the plurality of distributed systems 30" may be two distributed systems 30.

In the example shown in FIG. 1, at least two of the distributed systems 30A, 30B and 30C take a specific output state. In the superimposition mode, all of the distributed systems 30A, 30B and 30C may take a specific output state.

The distributed system 30 in the specific output state satisfies the following requirements (i), (ii), (iii) and (iv).

The requirement (i) is a requirement that the fuel cell power generation system 40 outputs DC power to the characteristic conversion circuit 100.

In the example shown in FIG. 1, when the first fuel cell power generation system 40A outputs DC power to the first characteristic conversion circuit 100, it can be said that the first distributed system 30A satisfies the requirement (i). When the second fuel cell power generation system 40B outputs DC power to the second characteristic conversion circuit 100, it can be said that the second distributed system 30B satisfies the requirement (i). When the third fuel cell power generation system 40C outputs DC power to the third characteristic conversion circuit 100, it can be said that the third distributed system 30C satisfies the requirement (i).

Requirement (ii) is that the output power of the characteristic conversion circuit 100 is maximized when the output voltage-output power characteristic of the characteristic conversion circuit 100 is a certain value of the output voltage of the characteristic conversion circuit 100 by the characteristic conversion control. It is a requirement to be adjusted to.

In the sixth embodiment described later, the control unit 670 performs characteristic conversion control. The requirement (ii) can be satisfied not only when the characteristic conversion control is performed as in the first to fifth embodiments but also when the characteristic conversion control is performed as in the sixth embodiment.

In the example shown in FIG. 1, the output voltage-output power characteristic of the first characteristic conversion circuit 100 is the output of the first characteristic conversion circuit 100 when the output voltage of the first characteristic conversion circuit 100 is the first voltage due to the characteristic conversion control. When the power is adjusted to the maximum, it can be said that the first distributed system 30A satisfies the requirement (ii). By characteristic conversion control, the output voltage-output power characteristic of the second characteristic conversion circuit 100 is set so that the output power of the second characteristic conversion circuit 100 is maximized when the output voltage of the second characteristic conversion circuit 100 is the second voltage. If adjusted, it can be said that the second distributed system 30B meets the requirement (ii). By characteristic conversion control, the output voltage-output power characteristic of the third characteristic conversion circuit 100 is set so that the output power of the third characteristic conversion circuit 100 is maximized when the output voltage of the third characteristic conversion circuit 100 is the third voltage. If adjusted, it can be said that the third distributed system 30C meets the requirement (ii).

The requirement (iii) is that the characteristic conversion circuit 100 is MPPT controlled by the DCDC converter 21.

In the example shown in FIG. 1, when the first characteristic conversion circuit 100 is MPPT controlled by the DCDC converter 21, it can be said that the first distributed system 30A satisfies the requirement (iii). When the second characteristic conversion circuit 100 is MPPT controlled by the DCDC converter 21, it can be said that the second distributed system 30B satisfies the requirement (iii). When the third characteristic conversion circuit 100 is MPPT controlled by the DCDC converter 21, it can be said that the third distributed system 30C satisfies the requirement (iii).

The requirement (iv) is a requirement that the characteristic conversion circuit 100 outputs DC power to the DCDC converter 21 via the diode 63.

In the example shown in FIG. 1, when the first characteristic conversion circuit 100 outputs DC power to the DCDC converter 21 via the first diode 63A, the first distributed system 30A satisfies the requirement (iv). I can say. When the second characteristic conversion circuit 100 outputs DC power to the DCDC converter 21 via the second diode 63B, it can be said that the second distributed system 30B satisfies the requirement (iv). When the third characteristic conversion circuit 100 outputs DC power to the DCDC converter 21 via the third diode 63C, it can be said that the third distributed system 30C satisfies the requirement (iv).

According to the superposition mode, electric power can be extracted from the plurality of fuel cell power generation systems 40. Further, according to the superimposition mode, the power extraction can be performed via the characteristic conversion control and the MPPT control. These are suitable for extracting a large amount of power.

Suppose that AC power and AC power are superimposed. In that case, phase control for matching the phases of the individual AC powers to be superposed, load control for following load fluctuations, and the like are required. In order to perform these controls, dedicated software, control cables for device cooperation, etc. are required. This can lead to increased control complexity and increased costs. On the other hand, in the superimposition mode of the present embodiment, the DC power and the DC power are superposed. This is advantageous from the viewpoint of ease of control and cost reduction.

By the way, the output voltage of the characteristic conversion circuit 100 of each distributed system 30 may decrease transiently. Such a transient drop can occur, for example, due to fluctuations in the flow rate and / or temperature of oxygen and / or hydrogen supplied to the fuel cell 41. However, in the present embodiment, the stability of the input voltage of the DCDC converter 21 can be maintained even if such a transient decrease occurs. Specifically, as described above, in the present embodiment, the DCDC converter 21 has a capacitor. This capacitor and the diode 63 of each dispersion system 30 cooperate with each other to form a peak hold circuit. Specifically, in the first situation where the output voltage of the characteristic conversion circuit 100 is higher than the input voltage of the DCDC converter 21, a current flows through the diode 63, and the output voltage of the characteristic conversion circuit 100 is lower than the input voltage of the DCDC converter 21. In two situations, no current flows through the diode 63. Even if the characteristic conversion circuit 100 shifts from the first situation to the second situation, which can act to increase the input voltage of the DCDC converter 21, the speed at which the electric charge of the capacitor of the DCDC converter 21 is discharged is finite, so that the DCDC converter The input voltage of 21 does not change abruptly. The diode 63 thus contributes to stable power extraction. This can be beneficial in an emergency. This advantage can be enjoyed in both superimposition mode and switching mode.

Further, if the diode 63 is not provided, if the above-mentioned transient decrease occurs in the distributed system 30 while the superposition mode is being executed, a backflow of electric power in the distributed system 30 may occur. When such a backflow of electric power occurs, it may take time for the appropriate power conversion control to be restarted after the transient decrease has subsided, or the characteristic conversion circuit 100 may fail. However, according to the diode 63, the backflow of electric power and the occurrence of defects as described above can be prevented.

When the operation mode is the switching mode, only one of the plurality of distributed systems 30 takes a specific output state. When the operation mode is the switching mode, the output voltage decreases due to the increase in the output current of the characteristic conversion circuit 100 of the distributed system 30 in the specific output state, which is less than the output voltage of the characteristic conversion circuit 100 of the other distributed system 30. When becomes, the distributed system 30 that takes a specific output state is switched to the other distributed system 30. The switching mode is suitable for evenly sharing the power supply to the DCDC converter 21 among the plurality of distributed systems 30.

When the electric power system 105 has the configuration shown in FIG. 1, in the switching mode according to the example, the distributed system 30 that takes a specific output state is the distributed system 30A, the distributed system 30B, the distributed system 30C, the distributed system 30A, ... It switches sequentially like this. In particular,
The output voltage of the first characteristic conversion circuit 100 is the largest among the first characteristic conversion circuit 100, the second characteristic conversion circuit 100, and the third characteristic conversion circuit 100. ・ The first characteristic conversion circuit 100 to the first diode 63A A current flows through the DCDC converter 21. ・ As the output current of the first characteristic conversion circuit 100 increases, the output voltage of the first characteristic conversion circuit 100 decreases (∵, the hatching arrow of the VI characteristic in FIG. 2). Department)
-The output voltage of the second characteristic conversion circuit 100, which has an output current of 0 A, becomes larger than the output current of the first characteristic conversion circuit 100.-The output current of the first characteristic conversion circuit 100 becomes 0 A, and the second characteristic conversion circuit A current flows from 100 to the DCDC converter 21 via the second diode 63B. ・ The output voltage of the second characteristic conversion circuit 100 decreases as the output current of the second characteristic conversion circuit 100 increases. ・ The second characteristic conversion circuit 100 The output current of the third characteristic conversion circuit 100, whose output current is 0A, becomes larger than the output current of the third characteristic conversion circuit 100. ・ The output current of the second characteristic conversion circuit 100 becomes 0A, and the third characteristic conversion circuit 100 to the third diode 63C are used. A current flows through the DCDC converter 21. ・ The output voltage of the third characteristic conversion circuit 100 decreases as the output current of the third characteristic conversion circuit 100 increases. ・ The output is higher than the output voltage of the third characteristic conversion circuit 100. The output voltage of the first characteristic conversion circuit 100 whose current is 0A becomes large. ・ The output current of the third characteristic conversion circuit 100 becomes 0A, and the current from the first characteristic conversion circuit 100 to the DCDC converter 21 via the first diode 63A. Flows ...

In the switching mode, consider the timing at which the output voltage of the first characteristic conversion circuit 100 of the first distributed system 30A in the specific output state drops to less than the output voltage of the second characteristic conversion circuit 100 of the second distributed system 30A. In the first diode 63A, the output voltage from the first characteristic conversion circuit 100 is applied to the anode, and the output voltage from the second characteristic conversion circuit 100 is applied to the cathode via the second diode 63B. Therefore, in the first diode 63A, the potential of the anode is lowered to be lower than the potential of the cathode. With such a change in the voltage between the terminals of the first diode 63A, the current of the first diode 63A sharply drops to zero according to the VI characteristics of the first diode 63A. On the other hand, in the second diode 63B, the output voltage from the second characteristic conversion circuit 100 is applied to the anode, and the output voltage from the first characteristic conversion circuit 100 is applied to the cathode via the first diode 63A. Therefore, in the second diode 63B, the potential of the cathode is lowered to be lower than the potential of the anode. With such a change in the voltage between the terminals of the second diode 63B, the current of the second diode 63B increases sharply from zero according to the VI characteristics of the second diode 63B. In this way, the distributed system 30 in the specific output state is switched from the first distributed system 30A to the second distributed system 30B. The same applies to the case where the distributed system 30 in the specific output state is switched between the other two distributed systems 30. In the switching mode, such switching occurs sequentially. In this way, the diode 63 contributes to the realization of the switching mode. In this explanation, the forward voltage drop of the diode is ignored.

Further, as described above, in the present embodiment, the DCDC converter 21 has a capacitor. Therefore, the stability of the input voltage of the DCDC converter 21 is maintained even if the distributed system 30 in the specific output state is sequentially switched as described above.

In the present embodiment, the superimposition mode is executed when the input power to the DCDC converter 21 is relatively large as compared with the switching mode.

In this embodiment, the power system 300 includes a power station 10 and a specific load 259. The power station 10 includes a DCDC converter 21 and outputs electric power to a specific load 259. The power station 10 should be interpreted as an element to which electric power is input / output, and the configuration should not be construed as limited by its name.

In the present embodiment, the number of distributed systems 30 in the specific output state is adjusted so that the difference obtained by subtracting the required power of the specific load 259 from the input power to the power station 10 is 0 or more and less than the unit power. In this way, an appropriate amount of electric power can be input to the DCDC converter 21.

Here, the unit power is the average of the power output to the DCDC converter 21 by each distributed system 30 in the specific output state. Specifically, this average is the arithmetic mean. In the example shown in FIG. 1, the unit power includes the power output by the first distributed system 30A to the DCDC converter 21 in the specific output state and the power output by the second distributed system 30B to the DCDC converter 21 in the specific output state. , The value obtained by dividing the total of the power output from the third distributed system 30C to the DCDC converter 21 in the specific output state by 3.

The power Px output to the DCDC converter 21 by each distributed system 30 in a specific output state does not have to be exactly the same. This is because, as described above, the characteristic conversion circuit 100 may have individual variations, and other elements of the distribution system 30 may also have individual variations. In the plurality of distributed systems 30, the difference in power Px between the distributed system 30 having the maximum power Px and the distributed system 30 having the minimum power Px is, for example, 20 W or less, and may be 10 W or less.

In the example shown in FIG. 1, the amount of power generated by the photovoltaic power generation systems 31A and 31B can be zero, for example, at night. When the amount of power generated by the photovoltaic power generation systems 31A and 31B is zero, the specific output state is set so that the difference obtained by subtracting the required power of the specific load 259 from the input power to the DCDC converter 21 is 0 or more and less than the unit power. The number of distributed systems 30 to be taken is adjusted. When the photovoltaic power generation systems 31A and 31B are generating power in the daytime, the number of distributed systems 30 that take a specific output state is adjusted according to the amount of power generation.

In the present embodiment, the electric power system 300 includes a specific load 259 and a power storage device 25. Power is input to the specific load 259 from the DCDC converter 21. Electric power is input to the power storage device 25 from the DCDC converter 21. According to the present embodiment, when excess power is input to the DCDC converter 21, the surplus can be temporarily stored in the power storage device 25 and used later.

In the present embodiment, the power that the DCDC converter 21 intends to extract from the plurality of distributed systems 30 is determined according to the required power of the specific load 259. It is automatically determined how many of the plurality of distributed systems 30 take a specific output state so as to cover the electric power to be taken out and not to generate surplus electric power exceeding the unit electric power. The surplus electric power is charged in the power storage device 25. In the above context, "according to the required power of the specific load 259" is a concept including, depending on the required power of the specific load 259 and the generated power of the photovoltaic power generation systems 31A and 31B.

In the present embodiment, when a power failure occurs, at least one of the plurality of distributed systems 30 starts a power failure output in which power is output to the specific load 259 via the DCDC converter 21 in a specific output state. In the above context, a power outage is a power outage of the grid.

The operating mode of the power system 105 may be a superposition mode or a switching mode when the power failure output is being performed.

In this embodiment, each of the plurality of distributed systems 30 includes a distributed load 250 to which electric power is input from the fuel cell power generation system 40.

In the present embodiment, in each of the plurality of distributed systems 30, power can be supplied from the fuel cell power generation system 40 to the distributed load 250 without going through the characteristic conversion circuit 100. This power supply may be performed via a distribution board, a distribution board, or the like, or may be performed directly.

In the present embodiment, the occurrence of a power failure imposes restrictions on the power supply from the fuel cell power generation system 40 to the distributed load 250 in the at least two distributed systems 30. In this way, it is easy to secure the required power of the specific load 259 in the output at the time of power failure.

For example, the above restriction is that an upper limit of the amount of power supplied from the fuel cell power generation system 40 to the distributed load 250 is set. Further, for example, the above restriction is that the supply of electric power from the fuel cell power generation system 40 to the distributed load 250 is prohibited.

In the example shown in FIG. 1, when the first distributed system 30A is included in the at least two distributed systems 30, power is supplied from the first fuel cell power generation system 40A to the first distributed load 250A in the wake of a power failure. Constraints are imposed. When the second distributed system 30B is included in the at least two distributed systems 30, the power supply from the second fuel cell power generation system 40B to the second distributed load 250B is restricted in the wake of a power failure. When the third distributed system 30C is included in the at least two distributed systems 30, the power supply from the third fuel cell power generation system 40C to the third distributed load 250C is restricted in the wake of a power failure.

In the event of a power outage, the power supply from the fuel cell power generation system 40 to the distributed load 250 may be restricted in all the distributed systems 30.

In the present embodiment, in the non-power failure, the power supply from the fuel cell power generation system 40 to the distributed load 250 is not restricted in the at least two distributed systems 30.

In the example shown in FIG. 1, when the first distributed system 30A is included in the at least two distributed systems 30, there is a restriction on the power supply from the first fuel cell power generation system 40A to the first distributed load 250A in the absence of a power failure. Not imposed. When the second distributed system 30B is included in the at least two distributed systems 30, no restriction is imposed on the power supply from the second fuel cell power generation system 40B to the second distributed load 250B during non-power failure. When the third distributed system 30C is included in the at least two distributed systems 30, no restriction is imposed on the power supply from the third fuel cell power generation system 40C to the third distributed load 250C in the absence of a power failure.

In the non-power failure, all the distributed systems 30 do not have to impose restrictions on the power supply from the fuel cell power generation system 40 to the distributed load 250.

In one specific example, the power system 105 is incorporated in an apartment or condominium. The distributed system 30 is arranged in different dwelling units in an apartment house. The specific load is a pump for circulating water in an apartment house.

In the present embodiment, among the characteristic conversion circuits 100 in the plurality of distributed systems 30, the characteristic conversion circuit 100 in which the "certain value" is the maximum and the characteristic conversion circuit in which the "certain value" is the minimum are "a certain value". The difference is 20 V or less. When this difference is as small as this, it is easy to carry out the superposition mode. Specifically, in this embodiment, this difference is 10 V or less.

In the example shown in FIG. 1, the difference between the first voltage and the second voltage is 20 V or less. The difference between the second voltage and the third voltage is 20 V or less. The difference between the third voltage and the first voltage is 20 V or less. Specifically, the difference between the first voltage and the second voltage is 10 V or less. The difference between the second voltage and the third voltage is 10 V or less. The difference between the third voltage and the first voltage is 10 V or less.

In the present embodiment, the characteristic conversion control is an output voltage-output in which the output voltage of the characteristic conversion circuit 100 decreases as the output current of the characteristic conversion circuit 100 increases in a region where the output voltage of the characteristic conversion circuit 100 is larger than a certain value. Provides current characteristics. Such an output voltage-output current characteristic is a typical example of the output voltage-output current characteristic brought about by the characteristic conversion circuit 100. Also, such output voltage-output current characteristics are suitable for executing the switching mode.

In the example shown in FIG. 1, in the first characteristic conversion control, when the output current of the first characteristic conversion circuit 100 increases in a region where the output voltage of the first characteristic conversion circuit 100 is larger than the first voltage, the first characteristic conversion circuit 100 Provides an output voltage-output current characteristic that reduces the output voltage of. The second characteristic conversion control is an output in which the output voltage of the second characteristic conversion circuit 100 decreases as the output current of the second characteristic conversion circuit 100 increases in a region where the output voltage of the second characteristic conversion circuit 100 is larger than the second voltage. Provides voltage-output current characteristics. The second characteristic conversion control is an output in which the output voltage of the third characteristic conversion circuit 100 decreases as the output current of the third characteristic conversion circuit 100 increases in a region where the output voltage of the third characteristic conversion circuit 100 is larger than the third voltage. Provides voltage-output current characteristics.

[Specific example of characteristic conversion circuit]
As can be understood from the above description, in this example, the characteristic conversion circuit 100 includes a voltage-current control circuit 160 which is a DCDC converter. When the output current of the characteristic conversion circuit 100 is less than a predetermined value, the voltage / current control circuit 160 and the first feedback circuit 110 work together to obtain the output voltage of the characteristic conversion circuit 100 according to the output voltage of the characteristic conversion circuit 100. The first feedback control is performed so that the output voltage of the characteristic conversion circuit 100 follows the target value by adjusting. Further, when the output current of the characteristic conversion circuit 100 is equal to or higher than a predetermined value, the voltage / current control circuit 100 and the second feedback circuit 120 cooperate with each other, and the larger the output current of the characteristic conversion circuit 100, the larger the output current of the characteristic conversion circuit 100. Second feedback control is performed to adjust the output voltage of the characteristic conversion circuit 100 to a certain value when the output power of the characteristic conversion circuit 100 peaks by lowering the output voltage.

The characteristic conversion circuit 100 that realizes such first and second feedback control can be appropriately designed, but the characteristic conversion circuit 100X, which is a specific example of the characteristic conversion circuit 100, will be described below with reference to FIG. 7. do. In the following, the elements already described with reference to FIG. 3 may be designated by the same reference numerals and the description thereof may be omitted.

In the characteristic conversion circuit 100X, an LLC converter is configured. The LLC converter is configured so that the higher the current flowing out from the current supply power supply 131, the higher the oscillation frequency is defined, and the higher the oscillation frequency, the smaller the ratio of the output voltage to the input voltage of the characteristic conversion circuit 100X.

Specifically, the characteristic conversion circuit 100X includes a first feedback circuit 110, a second feedback circuit 120, a feedback current supply unit 130X, a current resonance control unit 140, and a voltage / current control circuit 160X. The voltage-current control circuit 160X constitutes the above LLC converter.

The feedback current supply unit 130X has a first light emitting diode 135 in addition to the current supply power supply 131 and the sixth resistor 132. The current flowing out from the current supply power supply 131 flows through the first light emitting diode 135.

The current resonance control unit 140 includes a seventh resistor 141, a first capacitor 142, an eighth resistor 143, a first phototransistor 145, and a control IC 146. The seventh resistor 141, the first capacitor 142, and the combination of the eighth resistor 143 and the first phototransistor 145 are connected in parallel with each other. The first phototransistor 145 cooperates with the first light emitting diode 135 to form the first photocoupler 150. The control IC 146 has a constant current source 147, a feedback terminal 148, a high-side driver output terminal 149a, and a low-side driver output terminal 149b.

In the current resonance control unit 140, a period during which the first capacitor 142 is charged with an electric charge (hereinafter, may be referred to as a charging period) and a period during which the electric charge is discharged from the first capacitor 142 (hereinafter, referred to as a discharging period). There is) and visit alternately. The discharge period and the charge period are switched based on the voltage of the feedback terminal 148.

Specifically, during the charging period, the first capacitor 142 is charged with electric charge from the constant current source 147 via the feedback terminal 148. As the charging progresses, the voltage of the feedback terminal 148 rises. When the voltage of the feedback terminal 148 reaches the first voltage, the discharge period is switched. During the discharge period, charging of the electric charge from the constant current source 147 to the first capacitor 142 is stopped. During the discharge period, the electric charge charged in the first capacitor 142 is discharged via the seventh resistor 141. During the discharge period, the charge is further discharged via the eighth resistor 143 and the first phototransistor 145. As the discharge progresses, the voltage of the feedback terminal 148 decreases. When the voltage of the feedback terminal 148 reaches the second voltage, the charging period is switched.

The larger the current flowing through the first light emitting diode 135, the larger the current flows through the first phototransistor 145, and the faster the electric charge is discharged through the eighth resistor 143 and the first phototransistor 145 during the discharge period, and the shorter the discharge period is. Therefore, the charge / discharge frequency becomes high. The charge / discharge frequency corresponds to the above oscillation frequency.

In a certain discharge period, a drive signal is output from the high-side driver output terminal 149a. In the next discharge period, a drive signal is output from the low-side driver output terminal 149b. In the next discharge period, a drive signal is output from the high-side driver output terminal 149a. In the next discharge period, a drive signal is output from the low-side driver output terminal 149b. This is repeated, and drive pulse signals having opposite phases are output from the driver output terminals 149a and 149b. The frequency of these drive pulse signals increases as the charge / discharge frequency increases. The charging period is a dead time in which no drive signal is output from either of the driver output terminals 149a and 149b.

The voltage / current control circuit 160X includes a second capacitor 161, a first switching element 162a, a second switching element 162b, a third capacitor 163a, a fourth capacitor 163b, a fifth capacitor 164, a transformer 165, and a third capacitor. It has a 1 diode 166a, a 2nd diode 166b, and a 6th capacitor 167.

The switching elements 162a and 162b form a series circuit by being connected in series. A second capacitor 161 is connected in parallel to this series circuit. A third capacitor 163a is connected in parallel to the first switching element 162a. A fourth capacitor 163b is connected in parallel to the second switching element 162b.

In this example, the switching elements 162a and 162b are MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). Further, the fifth capacitor 164 is a resonance capacitor.

The transformer 165 has a first winding 165a, which is a primary winding, and a second winding 165b and a third winding 165c, which are secondary windings.

A current outflow terminal of the first switching element 162a and a current inflow terminal of the second switching element 162b are connected to one end of the first winding 165a. A fifth capacitor 164 is connected between the other end of the first winding 165a and the current outflow terminal of the second switching element 162b. In this example, the current outflow terminal is the source terminal. The current inflow terminal is a drain terminal.

The anode of the first diode 166a is connected to one end of the second winding 165b. One end of the sixth capacitor 167 and the cathode of the second diode 166b are connected to the cathode of the first diode 166a. The other end of the sixth capacitor 167 and the reference potential are connected to the other end of the second winding 165b.

The other end of the sixth capacitor 167 and the reference potential are connected to one end of the third winding 165c. The anode of the second diode 166b is connected to the other end of the third winding 165c.

A drive pulse signal is supplied from the high-side driver output terminal 149a to the control terminal of the first switching element 162a. A drive pulse signal is supplied from the low-side driver output terminal 149b to the control terminal of the second switching element 162b. As a result, the switching elements 162a and 162b are alternately turned on and off by supplying drive pulse signals having opposite phases to each other. In this example, the control terminal is a gate terminal.

The higher the frequency of the drive pulse signals supplied to the switching elements 162a and 162b, the smaller the ratio of the output voltage to the input voltage of the voltage-current control circuit 160X based on the LLC resonance.

[Another example of characteristic conversion circuit]
FIG. 8 shows another example of the characteristic conversion circuit. In the following, the description of the same parts as those in the example of FIG. 3 may be omitted.

In the characteristic conversion circuit 190 shown in FIG. 8, a feedback current supply unit 195 is provided in place of the feedback current supply unit 130 of the characteristic conversion circuit 100 of FIG. The feedback current supply unit 195 has a ninth resistor 191 in addition to the current supply power supply 131 and the sixth resistor 132.

In the characteristic conversion circuit 190, as in the characteristic conversion circuit 100, the larger the voltage input to the first reference voltage terminal of the first shunt regulator 115, the more the current supply power supply 131, the sixth resistor 132, the first shunt regulator 115, and the reference. The current flowing through the potentials in this order, that is, the first current increases. On the other hand, in the characteristic conversion circuit 190, unlike the characteristic conversion circuit 100, the larger the voltage input to the second reference voltage terminal of the second shunt regulator 125, the more the current supply power supply 131, the ninth resistor 191 and the second shunt regulator 125. And the current flowing through the reference potential in this order, that is, the second current becomes larger.

In the region where the output current of the characteristic conversion circuit 190 is small, the second current is substantially zero, and the current flowing out from the current supply power supply 131 is substantially the first current. On the other hand, in the region where the output current of the characteristic conversion circuit 100 is large, the first current is substantially zero, and the current flowing out from the current supply power supply 131 is substantially the second current. That is, it can be said that the characteristic conversion in the characteristic conversion circuit 190 is performed by the first feedback circuit 110 in the region where the output current of the characteristic conversion circuit 190 is small, and by the second feedback circuit 120 in the region where the output current of the characteristic conversion circuit 190 is large. .. In these respects, the characteristic conversion circuit 190 is common to the characteristic conversion circuit 100. Therefore, in the characteristic conversion circuit 190, the ratio of the output voltage to the input voltage of the voltage / current control circuit 160 is adjusted in the same manner as in the characteristic conversion circuit 100.

FIG. 9 shows a characteristic conversion circuit 190X which is a specific example of the characteristic conversion circuit 190. In the following, the description of the same parts as those in the example of FIG. 7 may be omitted.

In the characteristic conversion circuit 190X shown in FIG. 9, a feedback current supply unit 195X is provided in place of the feedback current supply unit 130X of the characteristic conversion circuit 100X of FIG. Further, in the characteristic conversion circuit 190X, a current resonance control unit 199 is provided in place of the current resonance control unit 140 of the characteristic conversion circuit 100X.

The feedback current supply unit 195X has a ninth resistor 191 and a second light emitting diode 192 in addition to the current supply power supply 131, the sixth resistor 132, and the first light emitting diode 135. The current resonance control unit 199 has a tenth resistor 196 and a second phototransistor 197 in addition to the seventh resistor 141, the first capacitor 142, the eighth resistor 143, the first phototransistor 145 and the control IC 146.

The seventh resistor 141, the first capacitor 142, the combination of the eighth resistor 143 and the first phototransistor 145, and the combination of the tenth resistor 196 and the second phototransistor 197 are connected in parallel with each other. The second light emitting diode 192 and the second phototransistor 197 cooperate to form the second photocoupler 198.

In the current resonance control unit 199, similarly to the current resonance control unit 140, a period in which the first capacitor 142 is charged with an electric charge (hereinafter, may be referred to as a charging period) and a period in which the electric charge is discharged from the first capacitor 142. (Hereinafter, it may be referred to as a discharge period) and appear alternately.

Specifically, during the charging period, the first capacitor 142 is charged with electric charge from the constant current source 147 via the feedback terminal 148. As the charging progresses, the voltage of the feedback terminal 148 rises. When the voltage of the feedback terminal 148 reaches the first voltage, the discharge period is switched. During the discharge period, charging of the electric charge from the constant current source 147 to the first capacitor 142 is stopped. During the discharge period, the electric charge charged in the first capacitor 142 is discharged via the seventh resistor 141. During the discharge period, the charge is further discharged via the eighth resistor 143 and the first phototransistor 145, or through the tenth resistor 196 and the second phototransistor 197. As the discharge progresses, the voltage of the feedback terminal 148 decreases. When the voltage of the feedback terminal 148 reaches the second voltage, the charging period is switched.

The state of charge of the electric charge of the first capacitor 142 in the current resonance control unit 199 changes in the same manner as in the current resonance control unit 140. Therefore, in the characteristic conversion circuit 190X, the ratio of the output voltage to the input voltage of the voltage / current control circuit 160X is adjusted in the same manner as in the characteristic conversion circuit 100X.

It should be noted again that the specific example of the characteristic conversion circuit 100 of FIG. 3 is not limited to the characteristic conversion circuit 100X of FIG. 7. For example, the larger the current flowing out from the current supply power supply 131, the smaller the duty ratio is defined, and a DCDC converter that operates based on the duty ratio can be configured in the characteristic conversion circuit. The same applies to the specific example of the characteristic conversion circuit 190 of FIG.

Further, the configurations of the first feedback circuit 110 and the second feedback circuit 120 of FIGS. 3 and 7 are not essential.

(Second Embodiment)
FIG. 10 is a block diagram of the power system 205 according to the present embodiment. In the present embodiment, the characteristic conversion control provides an output voltage-output power characteristic in which the output power of the characteristic conversion circuit 200 is maximized when the output voltage of the characteristic conversion circuit 200 is a certain value. Specifically, the above-mentioned certain value is a value within a predetermined range as in the first embodiment.

Further, in the characteristic conversion control, in the region where the output voltage of the characteristic conversion circuit 200 straddles the above-mentioned value, the output voltage-output current characteristic of the characteristic conversion circuit 200 becomes smaller as the output voltage of the characteristic conversion circuit 200 increases. Bring. Here, the region where the output voltage of the characteristic conversion circuit 200 straddles the above-mentioned certain value ranges from the first value in which the output voltage of the characteristic conversion circuit 200 is smaller than the above-mentioned certain value to the second value larger than the above-mentioned certain value. The area.

An example of the above output voltage-output power characteristic and output voltage-output current characteristic is shown in FIG. In FIG. 11, the output voltage-output power characteristic of the characteristic conversion circuit 200 is described as a VP characteristic. The output voltage-output current characteristic of the characteristic conversion circuit 200 is described as a VI characteristic. The solid line represents the VP characteristic. Dotted lines represent VI characteristics.

According to the characteristic conversion circuit 200, it is easy to take out a large amount of electric power from the fuel cell power generation system 40 to the first DCDC converter 21 based on the MPPT control. Hereinafter, this point will be described with reference to FIG. 11 and FIG.

As described above, in the characteristic conversion control, the output voltage of the characteristic conversion circuit 200 decreases as the output voltage of the characteristic conversion circuit 200 increases in the region where the output voltage of the characteristic conversion circuit 200 straddles the above-mentioned value. Brings characteristics. Due to this output voltage-output current characteristic, the graph of the output voltage-output power characteristic of the characteristic conversion circuit 200 has a curved shape in which the output power is convex upward with respect to the output voltage in the region where the output voltage straddles the above-mentioned value. obtain. In a typical example, the graph of the output voltage-output power characteristic of the characteristic conversion circuit 200 is a graph of a single peak in which the output power is maximized when the output voltage has the above-mentioned value.

It is assumed that the graph of the output voltage-output power characteristic of the characteristic conversion circuit 200 has a linear shape in which the output power is convex upward with respect to the output voltage as shown in FIG. In this case, it is assumed that the MPPT control is executed, but the operating point is adjusted to a point deviated from the maximum power point. Specifically, it is assumed that the output voltage of the characteristic conversion circuit 200 is adjusted to a voltage V _{real deviated from the output voltage V target of the maximum power point.} In this case, the output power of the characteristic conversion circuit 200 is reduced as compared with the case where the operating point is adjusted to the maximum power point. In FIG. 12, this reduction range is referred to as ΔP _B.

Also in the example of FIG. 11, when the output voltage of the characteristic conversion circuit 200 is adjusted to the voltage V _{real deviated from the output voltage V target} of the maximum power point, the output power of the characteristic conversion circuit 200 has the operating point at the maximum power point. It decreases compared to the case where it is adjusted to. In Figure 11, the decline to as [Delta] P _A.

As described above, regardless of whether the graph of the output voltage-output power characteristic of the characteristic conversion circuit 200 is linear or curved, if the operating point deviates from the maximum power point, the output power of the characteristic conversion circuit 200 will be increased. Decrease. However, the amount of decrease is different. Specifically, the reduction width ΔP _{A in} the case of FIG. 11 is smaller than the reduction width ΔP _{B in FIG.} The fact that the graph of the output voltage-output power characteristic has an upwardly convex curve suppresses the decrease in the output power due to the above deviation, and from the fuel cell power generation system 40 to the first DCDC converter 21. It is advantageous from the viewpoint of suppressing the decrease in the power taken out. However, the characteristic conversion control may bring about the output voltage-output power characteristic of FIG.

In the actual MPPT control, in addition to the mountain climbing method, there is also a method of controlling the extraction voltage to a predetermined voltage, and it is not always easy to match the operating point with the maximum power point with high accuracy in such control. .. Even with the hill climbing method, it may not be possible to stably extract the maximum power depending on the control resolution. Therefore, the fact that the graph of the output voltage-output power characteristic has an upwardly convex curve is actually advantageous in that the decrease in output power due to the MPPT control method and resolution can be suppressed. ..

It is also possible that the user purchases the characteristic conversion circuit 200 from one vendor and the DC power converter 20 that performs MPPT control from another vendor. In that case, the characteristic conversion circuit 200 will be connected to the DC power conversion device 20 having a performance unknown to the designer of the characteristic conversion circuit 200. In this case, the operating point may be adjusted to a point deviated from the maximum power point due to the fact that the characteristic conversion control and the MPPT control are not completely matched. From this, it can be said that the fact that the graph of the output voltage-output power characteristic has a convex curved shape is actually advantageous. Further, it can be said that the fact that the graph of the output voltage-output power characteristic has a convex curved shape enhances the compatibility of the characteristic conversion circuit 200 and reduces the restrictions of the DC power conversion device 20 that can be adopted.

As shown in FIG. 11, in the characteristic conversion control, in a region where the output voltage of the characteristic conversion circuit 200 is larger than 0 and smaller than the above-mentioned certain value, the output current of the characteristic conversion circuit 200 increases as the output voltage of the characteristic conversion circuit 200 increases. It may provide an output voltage-output current characteristic that reduces. Further, in the characteristic conversion control, in a region where the output voltage of the characteristic conversion circuit 200 is larger than a certain value and smaller than the open circuit voltage, the output current of the characteristic conversion circuit 200 becomes smaller as the output voltage of the characteristic conversion circuit 200 becomes larger. It may provide a voltage-output current characteristic. Here, the open circuit voltage is the output voltage of the characteristic conversion circuit 200 when the output current of the characteristic conversion circuit 200 is zero.

A value smaller than a certain value is defined as a first value. A value larger than a certain value is defined as a second value. At this time, in the example of FIG. 11, the output characteristics are both a region where the output voltage is larger than the first value and smaller than the above-mentioned certain value and a region where the output voltage is larger than the above-mentioned certain value and smaller than the second value. The characteristic is that the output current decreases linearly as the output voltage increases. That is, the output characteristic is a characteristic in which the output current becomes smaller in the form of a linear function with respect to the output voltage in both of the above regions. As a result, the output characteristic can be a characteristic in which the output power changes in the form of a quadratic function with respect to the output voltage in both of the above regions.

Specifically, in the example of FIG. 11, the output characteristic shows the output voltage in both the region where the output voltage is larger than 0 and smaller than the above-mentioned value and the region where the output voltage is from the above-mentioned value to the open circuit voltage value. The characteristic is that the output current decreases linearly as the value increases. That is, the output characteristic is a characteristic in which the output current becomes smaller in the form of a linear function with respect to the output voltage in both of the above regions. As a result, the output characteristic can be a characteristic in which the output power changes in the form of a quadratic function with respect to the output voltage in both of the above regions.

In the graph of output voltage-output power characteristics, the point where the voltage is zero and the power is zero is defined as the origin. In the graph of output voltage-output power characteristic, it can be said that the maximum power point is the point where the voltage is the above-mentioned value and the power is the maximum. In the graph of output voltage-output power characteristics, the point where the voltage is the open circuit voltage and the power is zero is defined as the open circuit voltage point. In the graph of output voltage-output power characteristics, the straight line connecting the origin and the maximum power point is defined as the first straight line. In the graph of output voltage-output power characteristics, the straight line connecting the maximum power point and the open circuit voltage point is defined as the second straight line. At this time, in the example of FIG. 11, the region where the output voltage in the graph of the output voltage-output power characteristic is larger than the first value and smaller than the above-mentioned certain value is on the higher power side than the first straight line. The region in which the output voltage in the graph of output voltage-output power characteristics is larger than a certain value and smaller than the second value is on the higher power side than the second straight line.

Specifically, in the example of FIG. 11, the region where the output voltage in the graph of the output voltage-output power characteristic is larger than 0 and smaller than the above-mentioned value is on the higher power side than the first straight line. The region from the above-mentioned value to the open circuit voltage in the graph of output voltage-output power characteristic is on the higher power side than the second straight line.

In the present embodiment, the characteristic conversion control includes a first feedback control and a second feedback control. The first feedback control is a control performed when the output current of the characteristic conversion circuit 200 is relatively small. The second feedback control is a control performed when the output current of the characteristic conversion circuit 200 is relatively large. When the first feedback control and the second feedback control are switched, the output voltage of the characteristic conversion circuit 200 becomes the above-mentioned value.

Specifically, the first feedback control is performed when the output current of the characteristic conversion circuit 200 is relatively small and the output voltage is relatively large. In the first feedback control, the output current of the characteristic conversion circuit 200 is reduced as the output voltage of the characteristic conversion circuit 200 increases. In the first feedback control, the output power of the characteristic conversion circuit 200 decreases as the output voltage of the characteristic conversion circuit 200 increases. The second feedback control is performed when the output current of the characteristic conversion circuit 200 is relatively large and the output voltage is relatively small. In the second feedback control, the output current of the characteristic conversion circuit 200 is reduced as the output voltage of the characteristic conversion circuit 200 increases. In the second feedback control, the output power of the characteristic conversion circuit 200 increases as the output voltage of the characteristic conversion circuit 200 increases. According to such a first feedback control and a second feedback control, the output voltage-output power characteristic and the output voltage-output current characteristic can be realized. In FIG. 11, the alternate long and short dash line represents the contribution of the first feedback control. The alternate long and short dash line represents the contribution of the second feedback control.

The characteristic conversion circuit has the following features; in the first feedback control, the ratio of the decrease in the output current to the increase in the output voltage in the output voltage-output current characteristic is larger than that in the second feedback control, and / or the second feedback. It may have a feature that the ratio of the decrease in the output voltage to the increase in the output current in the output voltage-output current characteristic is smaller than that in the control. In this way, the output characteristics of the characteristic conversion circuit 200 can be easily brought close to the output characteristics of the photovoltaic power generation system. It should be noted that this feature is a concept including a form in which the output voltage does not change even if the output current changes in the first feedback control, as shown in FIGS. 24 and 25 described later.

In the example of FIG. 11, in the first feedback control, the ratio of the decrease in the output current to the increase in the output voltage in the output voltage-output current characteristic is larger than that in the second feedback control. Further, in the example of FIG. 11, in the first feedback control, the ratio of the decrease in the output voltage to the increase in the output current in the output voltage-output current characteristic is smaller than that in the second feedback control.

In the present embodiment, the open circuit voltage of the characteristic conversion circuit 200 is controlled by the first feedback control.

FIG. 13 shows an example of the characteristic conversion circuit 200. In the characteristic conversion circuit 200 of FIG. 13, a voltage / current control circuit 160, a first feedback circuit 210, a second feedback circuit 220, and a feedback current supply unit 130 are provided.

The first feedback circuit 210 includes a first resistor 111, a second resistor 112, an eleventh resistor 113, a first shunt regulator 115, and a current sensor 128. The second feedback circuit 220 includes a third resistor 121, a fourth resistor 122, a fifth resistor 123, a second shunt regulator 125, and a current sensor 128. The current sensor 128 is shared by the first feedback circuit 210 and the second feedback circuit 220. The feedback current supply unit 130 includes a current supply power supply 131 and a sixth resistor 132.

Similar to the first embodiment, the current sensor 128 detects the output current of the characteristic conversion circuit 200. The current sensor 128 outputs a sensor output representing the result of the detection. The current sensor 128 outputs a larger sensor output as the output current of the characteristic conversion circuit 200 increases. That is, the sensor output increases as the output current of the characteristic conversion circuit 200 increases. The sensor output output by the current sensor 128 is supplied to the connection point ps. Specifically, the sensor output is the sensor voltage V _s . Further, the current sensor 128 includes a sensor output unit 128a that outputs a sensor _{voltage V s.}

_{In the first feedback circuit 210, the output voltage V out} of the characteristic conversion circuit 200 is divided by the first resistor 111 and the second resistor 112. _{The sensor voltage V s} is divided by the 11th resistor 113 and the 2nd resistor 112. The sum of these two voltage divider voltages appears at the connection point p1 of the three resistors 111, 112 and 113. Hereinafter, the voltage appearing at the first connection point p1 may be referred to as a _{first reference voltage V ref1.} The first reference voltage V _ref1 is input to the first reference voltage terminal of the first shunt regulator 115. The larger the voltage input to the first reference voltage terminal, the more the current supply power supply 131, the sixth resistor 132, the first shunt regulator 115, and the current flowing through the reference potential in this order (hereinafter, may be referred to as the first current) i1. Becomes larger. In FIG. 13, the first current i1 is the current flowing downward in the drawing through the first shunt regulator 115.

_{In the second feedback circuit 220, the output voltage V out} of the characteristic conversion circuit 200 is divided by the third resistor 121 and the fourth resistor 122. _{The sensor voltage V s} is divided by the fifth resistor 123 and the fourth resistor 122. The sum of these two voltage divider voltages appears at the connection point p2 of the three resistors 121, 122 and 123. Hereinafter, the voltage appearing at the second connection point p2 may be referred to as a _{second reference voltage V ref2.} The second reference voltage V _ref2 is input to the second reference voltage terminal of the second shunt regulator 125. The larger the voltage input to the second reference voltage terminal, the more the current supply power supply 131, the sixth resistor 132, the second shunt regulator 125, and the current flowing through the reference potential in this order (hereinafter, may be referred to as the second current) i2. Becomes larger. In FIG. 13, the second current i2 is the current flowing downward in the drawing through the second shunt regulator 125.

In the region where the output current of the characteristic conversion circuit 200 is small, the second current i2 becomes substantially zero, and the current flowing out from the current supply power supply 131 is substantially the first current i1. On the other hand, in the region where the output current of the characteristic conversion circuit 200 is large, the first current i1 becomes substantially zero, and the current flowing out from the current supply power supply 131 is substantially the second current i2. That is, it can be said that the characteristic conversion in the characteristic conversion circuit 200 is performed by the first feedback circuit 210 in the region where the output current of the characteristic conversion circuit 200 is small and by the second feedback circuit 220 in the region where the output current of the characteristic conversion circuit 200 is large. .. The parameters of the resistors 111, 112, 113, 121, 122 and 123 and the shunt regulators 115 and 125 are selected so that the circuits 210 and 220 operate in this way.

In the present embodiment, it can be said that the output characteristics of the characteristic conversion circuit 200 are determined by the analog circuit included in the characteristic conversion circuit 200. Here, the output characteristic can be considered as the relationship between the output current, the output voltage, and the output power. Specifically, it can be said that the output characteristics of the characteristic conversion circuit 200 are determined by the circuit constants of the analog circuit included in the characteristic conversion circuit 200. Here, the circuit constant refers to the resistance value of a resistor or the like.

Based on the explanation with reference to FIG. 5, the operation of the first feedback circuit 210 can be explained as follows. When the output voltage V _out of _the characteristic conversion circuit 200 becomes large, the output current of the characteristic conversion circuit 200 is a sensor voltage V _s becomes larger increases, the first reference voltage V _ref1 is increased. In the first shunt regulator 125, as the first reference voltage V _ref1 becomes larger and the deviation of the first reference voltage V _ref1 from the first reference voltage V _s1 becomes larger, the first current i1 becomes larger. As the first current i1 increases, the current flowing out from the current supply power supply 131 increases. As the outflow current increases, the ratio of the output voltage to the input voltage of the voltage-current control circuit 160 decreases. In this way, the first feedback circuit 210 controls _{the output voltage V out of the characteristic conversion circuit 200.} More specifically, the first feedback circuit 210, as the first reference voltage V _ref1 follows the first reference voltage V _s1, adjusting the transformation ratio of the characteristic conversion circuit 200.

In the first feedback control by the first feedback circuit 210, when the output current of the characteristic conversion circuit 200 becomes large and the sensor voltage V _s becomes large, the current sensor 128 first connects the connection point ps and the eleventh resistor 113 in this order. The current flowing at point p1 increases. With the first shunt regulator 115, the first reference voltage V _ref1 follows a constant first reference voltage V _s1 . In order to realize this tracking, a constant current flows through the second resistor 112. This means that as the current flowing through the 11th resistor 113 toward the first connection point p1 increases, the current flowing through the first resistor 111 toward the first connection point p1 decreases. When this current becomes small, the voltage generated by the first resistor 111 becomes small. For this reason, when the output current of the characteristic conversion circuit 200 increases, the voltage generated in the first resistor 111 decreases while the voltage at _{the first connection point p1 follows the first reference voltage V ref1.} As a result, the output voltage V _out of the characteristic conversion circuit 200 becomes small. In this way, the first feedback control provides an output voltage-output current characteristic as shown in FIG. 11, in which the output current of the characteristic conversion circuit 200 decreases as the output voltage of the characteristic conversion circuit 200 increases.

Based on the explanation with reference to FIG. 6, the operation of the second feedback circuit 220 can be explained as follows. _{When the output voltage V out} of the characteristic conversion circuit 200 increases, and when the output current of the characteristic conversion circuit 200 increases and the sensor voltage V _s increases, the second reference voltage V _ref 2 increases. In the second shunt regulator 125, the greater the deviation from the second reference voltage V _s2 of the second reference voltage V _ref2 by the second reference voltage V _ref2 is increased, the second current i2 is large. When the second current i2 becomes large, the current flowing out from the current supply power supply 131 becomes large. As the outflow current increases, the ratio of the output voltage to the input voltage of the voltage-current control circuit 160 decreases. In this way, the second feedback circuit 220 controls _{the output voltage V out of the characteristic conversion circuit 200.} Specifically, the second feedback circuit 220 adjusts the transformation ratio of the characteristic conversion circuit 200 so that _{the second reference voltage V ref} 2 follows the second reference voltage V _s2.

In the second feedback control by the second feedback circuit 220, when the output current of the characteristic conversion circuit 200 becomes large and the sensor voltage V _s becomes large, the current sensor 128 connects the connection point ps and the fifth resistor 123 in this order to the second connection. The current flowing at point p2 increases. With the second shunt regulator 125, the second reference voltage V _ref2 follows a constant second reference voltage V _s2 . In order to realize this tracking, a constant current flows through the fourth resistor 122. This means that when the current flowing through the fifth resistor 123 toward the second connection point p2 increases, the current flowing through the third resistor 121 toward the second connection point p2 decreases. When this current becomes small, the voltage generated by the third resistor 121 becomes small. For this reason, when the output current of the characteristic conversion circuit 200 increases, the voltage generated at the third resistor 121 decreases while the voltage at _{the second connection point p2 follows the second reference voltage V ref2.} As a result, the output voltage V _out of the characteristic conversion circuit 200 becomes small. In this way, the second feedback control provides an output voltage-output current characteristic as shown in FIG. 11, in which the output current of the characteristic conversion circuit 200 decreases as the output voltage of the characteristic conversion circuit 200 increases.

As will be understood from the above description, in this embodiment, the characteristic conversion circuit 200 includes a current sensor 128, at least one voltage dividing resistor, and a voltage-current control circuit 160 which is a DCDC converter. The characteristic conversion circuit 200 uses the current sensor 128 to reflect the output current of the characteristic conversion circuit 200 in the characteristic conversion control. The characteristic conversion circuit 200 uses at least one voltage dividing resistor to reflect the output voltage of the characteristic conversion circuit 200 in the characteristic conversion control. The characteristic conversion circuit 200 adjusts the transformation ratio of the voltage / current control circuit 160 by the characteristic conversion control. In the example of FIG. 13, at least one voltage dividing resistor includes a first voltage dividing resistor and a second voltage dividing resistor. The first voltage dividing resistor is composed of a first resistor 111 and a second resistor 112. The second voltage dividing resistor is composed of a third resistor 121 and a fourth resistor 122.

In the present embodiment, specifically, in the characteristic conversion circuit 200, the voltage / current control circuit 160 which is a DCDC converter, the first feedback circuit 210 which performs the first feedback control, and the second feedback circuit which performs the second feedback control. 220 and are provided. The first feedback circuit 210 has a first shunt regulator 115 to which a _{first reference voltage V ref1} that changes according to the output current and output voltage of the characteristic conversion circuit 200 is input. The second feedback circuit 220 has a second shunt regulator 125 to which a _{second reference voltage V ref2,} which changes according to the output current and output voltage of the characteristic conversion circuit 200, is input. In the first feedback control, the transformation ratio of the voltage-current control circuit 160 is adjusted by using the first shunt regulator 115 so that the first reference voltage V _{ref1 is kept constant.} In the second feedback control, the transformation ratio of the voltage-current control circuit 160 is adjusted by using the second shunt regulator 125 so that the second reference voltage V _{ref2 is kept constant.}

More specifically, the first feedback circuit has a first voltage divider resistor. The second feedback circuit has a second voltage divider resistor. The first feedback circuit 210 and the second feedback circuit 220 share the current sensor 128. _{The first voltage dividing} resistor is used to reflect the output voltage of the characteristic conversion circuit 200 in the first reference voltage V ref1. The current sensor 128 is used to reflect the output current of the characteristic conversion circuit 200 in the first reference voltage V _{ref1. The second voltage dividing} resistor is used to reflect the output voltage of the characteristic conversion circuit 200 in the second reference voltage V ref 2. The current sensor 128 is used to reflect the output current of the characteristic conversion circuit 200 in the second reference voltage V _{ref 2.} In the example of FIG. 13, the first voltage dividing resistor is composed of the first resistor 111 and the second resistor 112. The second voltage dividing resistor is composed of a third resistor 121 and a fourth resistor 122.

Further, the first feedback circuit has a third voltage dividing resistor. The second feedback circuit has a fourth voltage divider resistor. _{The third voltage dividing} resistor is used to reflect the output current of the characteristic conversion circuit 200 in the first reference voltage V ref1. _{The fourth voltage dividing} resistor is used to reflect the output current of the characteristic conversion circuit 200 in the second reference voltage V ref 2. In the example of FIG. 13, the third voltage dividing resistor is composed of the eleventh resistor 113 and the second resistor 112. The fourth voltage dividing resistor is composed of a fifth resistor 123 and a fourth resistor 122.

FIG. 14 shows a characteristic conversion circuit 200X which is a specific example of the characteristic conversion circuit 200. As can be understood from FIG. 14, the characteristic conversion circuit 200X can be configured following the characteristic conversion circuit 100X of FIG. 7 of the first embodiment. Therefore, a detailed description of the characteristic conversion circuit 200X will be omitted.

FIG. 15 shows a characteristic conversion circuit 290, which is another example of the characteristic conversion circuit 200. FIG. 16 shows a characteristic conversion circuit 290X which is a specific example of the characteristic conversion circuit 290. As can be understood from FIGS. 15 and 16, the characteristic conversion circuit 290 and the characteristic conversion circuit 290X can be configured following the characteristic conversion circuit 190 and the characteristic conversion circuit 190X of FIGS. 8 and 9 of the first embodiment. Therefore, detailed description of the characteristic conversion circuit 290 and the characteristic conversion circuit 290X will be omitted.

(Third Embodiment)
FIG. 17 is a block diagram of the power system 305 according to the present embodiment. FIG. 18 shows a characteristic conversion circuit 300 according to the third embodiment. Hereinafter, the characteristic conversion circuit according to the third embodiment will be described with reference to FIG.

In the characteristic conversion circuit 300 of FIG. 18, the first feedback circuit 310 includes a current sensor 128 and a regulator 170. The second feedback circuit 320 includes a current sensor 128 and a regulator 170. The current sensor 128 and the regulator 170 are shared by the first feedback circuit 310 and the second feedback circuit 320.

Similar to the first embodiment, the current sensor 128 detects the output current of the characteristic conversion circuit 300. The current sensor 128 outputs a sensor output representing the result of the detection. The current sensor 128 outputs a larger sensor output as the output current of the characteristic conversion circuit 300 increases. That is, the sensor output increases as the output current of the characteristic conversion circuit 300 increases. Specifically, the sensor output is the sensor voltage V _s . The current sensor 128 includes a sensor output unit 128a that outputs a sensor _{voltage V s.} In the present embodiment, the sensor voltage V _s output by the current sensor 128 may be referred to as the first sensor voltage V _s.

The regulator 170 is configured to be able to adjust variable parameters. The variable parameters may be manually adjustable or automatically adjustable. Regulator 170, a first sensor voltage V _s inputted to the regulator 170, adjusts to the second sensor voltage V _M.

In this embodiment, the regulator 170 is a DCDC converter that transforms _{the first sensor voltage V s.} The variable parameter is a parameter that changes the transformation ratio of the DCDC converter.

Specifically, in this embodiment, the regulator 170 has the configuration shown in FIG. The regulator 170 of FIG. 19 includes a voltage dividing circuit 170a and an amplifier circuit 170b. The variable parameter is a parameter included in the voltage dividing circuit 170a or the amplifier circuit 170b. The sensor output unit 128a, the voltage dividing circuit 170a, the amplifier circuit 170b, and the connection point ps are connected in this order.

In the example of FIG. 19, the voltage divider circuit 170a includes a resistor FR1, a resistor FR2, and a variable resistor VR1. The sensor output unit 128a, the resistor FR1, the resistor FR2, the variable resistor VR1, and the reference potential are connected in this order. The voltage dividing circuit 170a divides the first sensor voltage V _s by using the resistors FR1, FR2 and VR1. By this voltage division, the voltage dividing voltage V _D shown in the following equation 2 is generated. Here, FR1 is the resistance value of the resistor FR1. FR1 is the resistance value of the resistor FR2. VR1 is the resistance value of the variable resistor VR1. "*" Is a symbol representing multiplication.
Formula 2: V _D = V _s * (FR2 + VR1) / (FR1 + FR2 + VR1)

The amplifier circuit 170b includes a resistor FR3, a resistor FR4, and an operational amplifier 175. The operational amplifier 175 includes a first input terminal 175a, a second input terminal 175b, and an output terminal 175c. A voltage dividing voltage V _D is input to the first input terminal 175a. The second input terminal 175b is connected to the output terminal 175c via the resistor FR3. The second input terminal 175b is connected to the reference potential via the resistor FR4. Further, the output terminal 175c, the resistor FR3, the resistor FR4, and the reference potential are connected in this order. Amplifier circuit 170b generates a second sensor voltage V _M based on the divided voltage V _D, and outputs a second sensor voltage V _M from the output terminal 175 c. The second sensor voltage V _M, is given by Equation 3 below. Here, FR3 is the resistance value of the resistor FR3. FR4 is the resistance value of the resistor FR4.
Equation _{3: V M = V D *} (FR3 + FR4) / FR4

Specifically, the first input terminal 175a is a non-inverting amplification terminal. The second input terminal 175b is an inverting amplification terminal.

The second sensor voltage V _M, is supplied to the connection point ps. After that, the voltage at the connection point ps is used in the same manner as in the second embodiment.

In the example shown in FIG. 19, the voltage divider circuit 170a includes a variable resistor VR1. The variable parameter is the resistance value of the variable resistor VR1. By adjusting the resistance value of the variable resistor VR1, it can be adjusted divided voltage V _D and the second sensor voltage V _M.

The resistor FR1 or the resistor FR2 may be a variable resistor. Even in this case, by adjusting the resistance value of the variable resistor can be adjusted to the divided voltage V _D and the second sensor voltage V _M.

Further, the amplifier circuit 170b may include a variable resistor instead of the voltage dividing circuit 170a. Specifically, the resistor FR3 or the resistor FR4 may be a variable resistor. Even in this case, by adjusting the resistance value of the variable resistor, can be adjusted second sensor voltage V _M.

Similar to the second embodiment, in the third embodiment, the sensor outputs are relative so as to provide the output voltage-output power characteristic of (i) and the output current-output power characteristic of (ii) described below. The first feedback control is executed when the value is small, and the second feedback control is executed when the sensor output is relatively large. As described above, the sensor output is specifically the first sensor voltage V _s .

The output voltage-output power characteristic of (i) is an output voltage-output power characteristic in which the output power of the characteristic conversion circuit 300 is maximized when the output voltage of the characteristic conversion circuit 300 is a certain value. The output current-output power characteristic of (ii) is an output current-output power characteristic in which the output power of the characteristic conversion circuit 300 is maximized when _{the output current of the characteristic conversion circuit 300 is the switching current sw.} Here, the switching current _sw is the output current of the characteristic conversion circuit 300 when the first feedback control and the second feedback control are switched. Specifically, the above-mentioned certain value is a value within a predetermined range as in the first embodiment.

In the present embodiment, the switching current _sw is dependent on the error of detecting the output current of the characteristic conversion circuit 300 by the current sensor 128, and changes when the variable parameter is changed.

If there are individual variations in the current sensor 128, an error may occur in the detection of the current sensor 128. That is, an error may occur in the sensor output. If the sensor output having an error is used for control in the characteristic conversion circuit 300, the switching current _sw may deviate from the target value (hereinafter, may be referred to as a target current). If the switching current i _sw deviates, the maximum power point may deviate from the target point. If the maximum power point deviates, the maximum power of the characteristic conversion circuit 300 may deviate from the target value (hereinafter, may be referred to as a target power).

In this regard, according to the third embodiment, the switching current i _sw can be adjusted by changing the variable parameter. As a result, _{the deviation of the switching current sw from} the target current can be reduced, the deviation of the maximum power point from the target point can be reduced, and the deviation of the maximum power from the target power can be reduced. It is also possible to adjust the maximum power of the characteristic conversion circuit 300 according to the situation by adjusting the variable parameter and adjusting the switching current _sw. For example, when the generated power of the photovoltaic power generation system connected to the DC power converter 20 is small, the maximum power may be increased, and when the generated power of the photovoltaic power generation system is large, the maximum power may be decreased. can. Further, the maximum output power of the fuel cell power generation system 40 may decrease due to, for example, aged deterioration of the stack of the fuel cell 41. In such a case, by lowering the maximum power output from the characteristic conversion circuit 300, the maximum power can be kept within a range that can be supplied by the fuel cell power generation system 40.

By reducing the deviation of the maximum power from the target power, it is possible to reduce the deviation of the extracted power from the target power when the power is taken out from the characteristic conversion circuit 300 by MPPT control. By adjusting the maximum power of the characteristic conversion circuit 300 according to the situation, when the power is taken out from the characteristic conversion circuit 300 by MPPT control, the electric power taken out can be adjusted to a value according to the situation. For example, when the generated power of the photovoltaic power generation system connected to the DC power converter 20 is small, the extracted power is increased, and when the generated power of the photovoltaic power generation system is large, the extracted power is decreased. Can be done. Further, when the maximum output power of the fuel cell power generation system 40 is lowered, the power taken out can be reduced.

[Individual variation of current sensor 128 and its suppression]
As described above, the current sensor 128 may have individual variations. The influence of individual variation will be described in detail with reference to FIGS. 20 to 22.

In this embodiment, the current sensor 128 has the configuration shown in FIG. The resistance value R _sense , gain G, and bias voltage V _bias of the shunt resistor 128r are ideally reference values. However, the resistance value R _sense , the gain G and / or the bias voltage V _bias may have an error in the range of tolerance. In the present embodiment, the current sensor 128 outputs a _{first sensor voltage V s} that is larger when the resistance value of the shunt resistor 128r is larger than the reference value, as compared with the case where the resistance value of the shunt resistor 128r is the reference value. It is configured in. The current sensor 128 is configured to output a _{first sensor voltage V s} that is larger when the gain G is larger than the reference value, as compared with when the gain G is the reference value. Current sensor 128, when the bias voltage V _bias is larger than the reference value, than when the bias voltage V _bias is the reference value, and is configured to output a large first sensor voltage V _s.

In FIG. 20, the horizontal axis represents the output current of the characteristic conversion circuit 300. FIG. 20 shows the output characteristics of the characteristic conversion circuit 300 when the _{bias voltage V bias} is changed when the resistance value R _sense and the gain G are at the reference values.

Specifically, in FIG. 20, “output voltage (0) of the characteristic conversion circuit” indicates the output voltage of the characteristic conversion circuit 300 when the _{bias voltage V bias is a reference value.} The “output voltage (A) of the characteristic conversion circuit” indicates the output voltage of the characteristic conversion circuit 300 when the _{bias voltage V bias is 101% of the reference value.} The “output voltage (B) of the characteristic conversion circuit” indicates the output voltage of the characteristic conversion circuit 300 when the _{bias voltage V bias is 99% of the reference value.} The “output voltage (C) of the characteristic conversion circuit” indicates the output voltage of the characteristic conversion circuit 300 when the _{bias voltage V bias is 102% of the reference value.} The “output voltage (D) of the characteristic conversion circuit” indicates the output voltage of the characteristic conversion circuit 300 when the _{bias voltage V bias is 98% of the reference value.} “Output power (0) of the characteristic conversion circuit” indicates the output power of the characteristic conversion circuit 300 when the _{bias voltage V bias is a reference value.} “Output power (A) of the characteristic conversion circuit” indicates the output power of the characteristic conversion circuit 300 when the _{bias voltage V bias is 101% of the reference value.} “Output power (B) of the characteristic conversion circuit” indicates the output power of the characteristic conversion circuit 300 when the _{bias voltage V bias is 99% of the reference value.} “Output power (C) of the characteristic conversion circuit” indicates the output power of the characteristic conversion circuit 300 when the _{bias voltage V bias is 102% of the reference value.} The “output power (D) of the characteristic conversion circuit” indicates the output power of the characteristic conversion circuit 300 when the _{bias voltage V bias is 98% of the reference value.} In FIG. 20, the five dotted lines extending vertically are the switching current i _sw (C), the switching current i _sw (A), the switching current i _sw (0), and the switching current i _sw (B), respectively, in order from the left. And the switching current i _sw (D). “Switching current i _sw (0)” indicates the _{switching current i sw when the bias voltage V bias} is a reference value. “Switching current i _sw (A)” indicates the _{switching current i sw when the bias voltage V bias} is 101% of the reference value. “Switching current i _sw (B)” indicates the _{switching current i sw when the bias voltage V bias} is 99% of the reference value. “Switching current i _sw (C)” indicates the _{switching current i sw when the bias voltage V bias} is 102% of the reference value. “Switching current i _sw (D)” indicates the _{switching current i sw when the bias voltage V bias} is 98% of the reference value. As described above, the switching current _sw is the output current of the characteristic conversion circuit 300 when the first feedback control and the second feedback control are switched.

From FIG. 20, it is understood that the switching current _{sw fluctuates as the bias voltage V bias fluctuates.}

When the bias voltage V _bias is the reference value, the maximum power point is at the target point. This situation is as shown in FIG. 11 relating to the second embodiment.

When the bias voltage V _bias is at the reference value, the switching current _sw matches the target current. When the bias voltage V _bias is larger than the reference value _{, the switching current sw} is smaller _{than when the bias voltage V bias} is at the reference value. Conversely, when the bias voltage V _bias is smaller than the reference value, than when the bias voltage V _bias is at the reference value, the switching current i _sw is large.

When the bias voltage V _bias is at the reference value, the maximum power of the characteristic conversion circuit 300 matches the target power. When the bias voltage V _bias is larger than the reference value, the maximum power is smaller than when _{the bias voltage V bias is at the reference value.} On the contrary, when the bias voltage V _bias is smaller than the reference value, the maximum power is larger than when _{the bias voltage V bias is at the reference value.}

As shown in FIG. 20, _{individual variation of the bias voltage V bias} causes variation of the maximum power point of the characteristic conversion circuit 300. The variation of the maximum power point causes the variation of the switching current _sw and the maximum power.

In this regard, in the third embodiment, the switching current _sw of the characteristic conversion circuit 300 can be adjusted and the maximum power can be adjusted by adjusting the resistance value of the variable resistor VR1.

For example, consider a case where the bias voltage V _bias is smaller than the reference value and the switching current _sw and the maximum power are larger _{than when the bias voltage V bias is at the reference value.} In this case, by increasing the second sensor voltage V _M as compared with the case where the bias voltage V _bias is in the reference value by adjusting the resistance value of the variable resistor VR1, reducing the switching current i _sw and maximum power Can be done. As a result, the switching current _sw and the maximum power can be brought close to the target current and the target power. Specifically, by increasing the resistance value of the variable resistor VR1, the switching current _sw and the maximum power can be brought close to the target current and the target power.

On the contrary, consider the case where the bias voltage V _bias is larger than the reference value and the switching current _sw and the maximum power are smaller _{than when the bias voltage V bias is at the reference value.} In this case, by decreasing the second sensor voltage V _M as compared with the case where the bias voltage V _bias is in the reference value by adjusting the resistance value of the variable resistor VR1, increasing the switching current i _sw and maximum power Can be done. As a result, the switching current _sw and the maximum power can be brought close to the target current and the target power. Specifically, by reducing the resistance value of the variable resistor VR1, the switching current _sw and the maximum power can be brought close to the target current and the target power.

By adjusting the variable resistor VR1, the switching current _sw and the maximum power can be brought close to the values when the _{bias voltage V bias is at the reference value.} That is, the switching current _sw and the maximum power can be brought close to the target current and the target power. Generally speaking, the output characteristic of the characteristic conversion circuit 300 can be brought close to that when the _{bias voltage V bias is at the reference value.}

Even when there is an error in both the gain G and the bias voltage V _{bias , the switching current sw} of the characteristic conversion circuit 300 can be adjusted and the maximum power can be adjusted by adjusting the resistance value of the variable resistor VR1. ..

In FIGS. 21 and 22, the horizontal axis represents the output current of the characteristic conversion circuit 300. 21 and 22 show the output characteristics of the characteristic conversion circuit 300 when the gain G and the bias voltage V _{bias are changed when the resistance value R sense} of the shunt resistor 128r is at the reference value.

Specifically, in FIG. 21, “output voltage (0) of the characteristic conversion circuit” indicates the output voltage of the characteristic conversion circuit 300 when the _{gain G and the bias voltage V bias are reference values.} The “characteristic conversion circuit output voltage (E)” indicates the output voltage of the characteristic conversion circuit 300 when the gain G is 101% of the reference value and the bias voltage V _{bias is 102% of the reference value.} The “characteristic conversion circuit output voltage (F)” indicates the output voltage of the characteristic conversion circuit 300 when the gain G is 99% of the reference value and the bias voltage V _{bias is 98% of the reference value.} “Output power (0) of the characteristic conversion circuit” indicates the output power of the characteristic conversion circuit 300 when the gain G and the bias voltage V _{bias are reference values.} The “output power (E) of the characteristic conversion circuit” indicates the output power of the characteristic conversion circuit 300 when the gain G is 101% of the reference value and the bias voltage V _{bias is 102% of the reference value.} “Output power (F) of the characteristic conversion circuit” indicates the output power of the characteristic conversion circuit 300 when the gain G is 99% of the reference value and the bias voltage V _{bias is 98% of the reference value.} “Switching current i _sw (0)” indicates the switching current i _sw when the gain G and the bias voltage V _{bias are reference values.} "Switching current i _sw (E)" is when the gain G is 101% of the reference value and the bias voltage V _bias is 102% of the reference value, indicating the switching current i _sw. "Switching current i _sw (F)" is when the gain G is 99% of the reference value and the bias voltage V _bias is 98% of the reference value, indicating the switching current i _sw.

Further, in FIG. 22, “output voltage (0) of the characteristic conversion circuit” indicates the output voltage of the characteristic conversion circuit 300 when the _{gain G and the bias voltage V bias are reference values.} The “characteristic conversion circuit output voltage (G)” indicates the output voltage of the characteristic conversion circuit 300 when the gain G is 99% of the reference value and the bias voltage V _{bias is 102% of the reference value.} The “characteristic conversion circuit output voltage (H)” indicates the output voltage of the characteristic conversion circuit 300 when the gain G is 101% of the reference value and the bias voltage V _{bias is 98% of the reference value.} “Output power (0) of the characteristic conversion circuit” indicates the output power of the characteristic conversion circuit 300 when the gain G and the bias voltage V _{bias are reference values.} The “output power (G) of the characteristic conversion circuit” indicates the output power of the characteristic conversion circuit 300 when the gain G is 99% of the reference value and the bias voltage V _{bias is 102% of the reference value.} “Output power (H) of the characteristic conversion circuit” indicates the output power of the characteristic conversion circuit 300 when the gain G is 101% of the reference value and the bias voltage V _{bias is 98% of the reference value.} “Switching current i _sw (0)” indicates the switching current i _sw when the gain G and the bias voltage V _{bias are reference values.} "Switching current i _sw (G)" is when the gain G is 99% of the reference value and the bias voltage V _bias is 102% of the reference value, indicating the switching current i _sw. "Switching current i _sw (H)" is obtained when the gain G is 101% of the reference value and the bias voltage V _bias is 98% of the reference value, indicating the switching current i _sw.

From FIGS. 21 and 22, it is understood that the switching current _sw fluctuates as the gain G and the bias voltage V _{bias fluctuate.} However, in both the example of FIG. 21 and the example of FIG. 22, by adjusting the resistance value of the variable resistor VR1, the switching current _sw and the maximum power can be brought close to the target current and the target power. Generally speaking, the output characteristics of the characteristic conversion circuit 300 can be brought close to those when the _{gain G and the bias voltage V bias are at the reference values.}

Specifically, in the case of FIG. 21 (E), by reducing the second sensor voltage V _M to reduce the resistance of the variable resistor VR1, the switching current i _sw and maximum power, the target current and target power Can be approached to.

For Figure 21 (F), by increasing the second sensor voltage V _M to increase the resistance value of the variable resistor VR1, the switching current i _sw and maximum power can be brought close to the target current and target power ..

For Figure 22 (G), by reducing the second sensor voltage V _M to reduce the resistance of the variable resistor VR1, the switching current i _sw and maximum power can be brought close to the target current and target power ..

For Figure 22 (H), by increasing the second sensor voltage V _M to increase the resistance value of the variable resistor VR1, the switching current i _sw and maximum power can be brought close to the target current and target power ..

As a matter of course, _{even if there is an error in the resistance value R sense , the switching current sw} and the maximum power can be brought close to the target current and the target power by adjusting the resistance value of the variable resistor VR1.

The technique of the third embodiment can be applied not only to the configuration of FIG. 13 of the second embodiment but also to the configurations of FIGS. 14 to 16. The technique of the third embodiment is also applicable to the configurations of FIGS. 3 and 7-9 of the first embodiment. Specifically, the regulator 170 is also applicable to the configurations of FIGS. 3, 7 to 9 and 14 to 16.

(Fourth Embodiment)

FIG. 23 is a block diagram of the power system 405 according to the present embodiment. 24 and 25 show the output characteristics of the characteristic conversion circuit 400. FIG. 26 shows a characteristic conversion circuit 400 according to this embodiment.

Similar to the second embodiment, the characteristic conversion control performed by the characteristic conversion circuit 400 is an output voltage-output power characteristic in which the output power of the characteristic conversion circuit 400 is maximized when the output voltage of the characteristic conversion circuit 400 is a certain value. Bring. The characteristic conversion control includes a first feedback control and a second feedback control. The first feedback control is a control performed when the output current of the characteristic conversion circuit 400 is relatively small. The second feedback control is a control performed when the output current of the characteristic conversion circuit 400 is relatively large. When the first feedback control and the second feedback control are switched, the output voltage of the characteristic conversion circuit 400 becomes the above-mentioned value.

As shown in FIG. 26, the characteristic conversion circuit 400 includes a voltage-current control circuit 160, a current sensor 128, and a regulator 180.

Similar to the first embodiment, the current sensor 128 detects the output current of the characteristic conversion circuit 400. The current sensor 128 outputs a sensor output representing the result of the detection. The current sensor 128 outputs a larger sensor output as the output current of the characteristic conversion circuit 400 increases. That is, the sensor output increases as the output current of the characteristic conversion circuit 400 increases. In this embodiment, the sensor output is the first sensor voltage V1. The current sensor 128 includes a sensor output unit 128a that outputs the first sensor voltage V1. The first sensor voltage V1 corresponds to _{the sensor voltage V s of the first embodiment.}

The regulator 180 is configured to be able to adjust variable parameters. In this embodiment, the regulator 180 is a variable output power supply and the variable parameters are variable outputs. In the following, the regulator 180 which is a variable output power supply may be referred to as a variable output power supply 180.

The variable output power supply 180 outputs a variable output. In this embodiment, the variable output is a variable voltage V4. The variable output power supply 180 is, for example, a digital-analog port of the controller 51.

In the characteristic conversion circuit 400, a first circuit 410 and a second circuit 420 are provided. The first circuit 410 executes the first feedback control in which the output power of the characteristic conversion circuit 400 increases as the sensor output increases. The second circuit 420 executes the second feedback control in which the output power of the characteristic conversion circuit 400 decreases as the sensor output increases in cooperation with the first circuit 410. In the characteristic conversion circuit 400, a feedback current supply unit 130 is also provided.

The first circuit 410, the second circuit 420, and the voltage / current control circuit 160 cooperate to execute the characteristic conversion control.

Specifically, the first circuit 410 executes the first feedback control in cooperation with the voltage / current control circuit 160. The second circuit executes the second feedback control in cooperation with the first circuit 410 and the voltage / current control circuit 160.

In the characteristic conversion circuit 400, the first feedback control is performed when the sensor output is relatively small so that the output voltage-output power characteristic of (i) and the output current-output power characteristic of (ii) described below are obtained. Is executed and the second feedback control is executed when the sensor output is relatively large.

The output voltage-output power characteristic of (i) is the output voltage-output power characteristic at which the output power of the characteristic conversion circuit 400 is maximized when the output voltage of the characteristic conversion circuit 400 is a certain value, as shown in FIG. Is. Specifically, the above-mentioned certain value is a value within a predetermined range as in the first embodiment.

The output current-output power characteristic of (ii) is the output current-output at which the output power of the characteristic conversion circuit 400 is maximized when _{the output current of the characteristic conversion circuit 400 is the switching current sw, as shown in FIG.} It is a power characteristic. Here, the switching current _sw is the output current of the characteristic conversion circuit 400 when the first feedback control and the second feedback control are switched.

The switching current _sw is dependent on the error of detecting the output current of the characteristic conversion circuit 400 by the current sensor 128, and changes when the variable parameter is changed. As described above, the variable parameter is a variable output in this embodiment, specifically a variable voltage V4.

If there are individual variations in the current sensor 128, an error may occur in the detection of the current sensor 128. That is, an error may occur in the sensor output. If the sensor output having an error is used for control in the characteristic conversion circuit 400, the switching current _sw may deviate from the target value (hereinafter, may be referred to as a target current). If the switching current _sw deviates, the maximum power point shown in FIGS. 24 and 25 may deviate from the target point. If the maximum power point deviates, the maximum power of the characteristic conversion circuit 400 may deviate from the target value (hereinafter, may be referred to as a target power).

In this regard, according to the present embodiment, the switching current _sw can be adjusted by changing the variable parameter. As a result, _{the deviation of the switching current sw from} the target current can be reduced, the deviation of the maximum power point from the target point can be reduced, and the deviation of the maximum power from the target power can be reduced. It is also possible to adjust the maximum power of the characteristic conversion circuit 400 according to the situation by adjusting the variable parameter and adjusting the switching current _sw. For example, when the generated power of the photovoltaic power generation system connected to the DC power converter 20 is small, the maximum power may be increased, and when the generated power of the photovoltaic power generation system is large, the maximum power may be decreased. can. Further, the maximum output power of the fuel cell power generation system 40 may decrease due to, for example, aged deterioration of the stack of the fuel cell 41. In such a case, by lowering the maximum power output from the characteristic conversion circuit 400, the maximum power can be kept within a range that can be supplied by the fuel cell power generation system 40.

By reducing the deviation of the maximum power from the target power, it is possible to reduce the deviation of the extracted power from the target power when the power is taken out from the characteristic conversion circuit 400 by MPPT control. By adjusting the maximum power of the characteristic conversion circuit 400 according to the situation, when the power is taken out from the characteristic conversion circuit 400 by MPPT control, the electric power taken out can be adjusted to a value according to the situation. For example, when the generated power of the photovoltaic power generation system connected to the DC power converter 20 is small, the extracted power is increased, and when the generated power of the photovoltaic power generation system is large, the extracted power is decreased. Can be done. Further, when the maximum output power of the fuel cell power generation system 40 is lowered, the power taken out can be reduced.

Typically, the characteristic conversion circuit 400 output voltage-output power characteristic is a characteristic in which the output power has a single peak with respect to the output voltage. The output voltage-output power characteristic in (i) above shows such a characteristic.

The output characteristics of the characteristic conversion circuit 400 will be further described.

In FIG. 24, the solid line represents the relationship between the output voltage of the characteristic conversion circuit 400 and the output power of the characteristic conversion circuit 400, that is, the output voltage-output power characteristic. The short broken line represents the relationship between the output voltage of the characteristic conversion circuit 400 and the output current of the characteristic conversion circuit 400, that is, the output voltage-output current characteristic. The alternate long and short dash line represents the contribution of the first feedback control. The alternate long and short dash line represents the contribution of the second feedback control. The long dashed line represents the first sensor voltage V1.

As can be understood from FIG. 24, in the present embodiment, the output voltage-output current characteristic of the characteristic conversion circuit 400 follows the specified value in the region where the output current is small by the first feedback control. .. Due to the second feedback control, the output voltage-output current characteristic of the characteristic conversion circuit 400 becomes such that the output voltage decreases as the output current increases in the region where the output current is large. Combined with these feedback controls, the output voltage-output current characteristic of the characteristic conversion circuit 400 is shown by the short dashed line in FIG. 24. As a result, the output voltage-output power characteristic of the characteristic conversion circuit 400 has a single peak and is convex as shown by the solid line in FIG. 24.

As described above, the output voltage-output power characteristic that is convex above the characteristic conversion circuit 400 enables MPPT control by the first DCDC converter 21. The MPPT control of the characteristic conversion circuit 400 can be executed by the first DCDC converter 21.

The configuration of the characteristic conversion circuit 400 will be further described.

As shown in FIG. 26, the first circuit 410 has a resistor 421, a resistor 422, and a first shunt regulator 425. The second circuit 420 includes a current sensor 128, a sensor voltage adjusting circuit 420a, and a voltage-current conversion circuit 420b. The feedback current supply unit 130 includes a current supply power supply 131 and a sixth resistor 132.

In the voltage-current control circuit 160, the smaller the current flowing out from the current supply power supply 131, the larger the ratio of the output voltage to the input voltage of the voltage-current control circuit 160. In this way, the characteristic conversion circuit 400 is adapted to adjust the above ratio according to the current flowing out from the current supply power supply 131.

In the first circuit 410, the output voltage of the characteristic conversion circuit 400 is divided by the resistors 421 and 422. The divided voltage appears at the first connection point p1 of the resistors 421 and 422. Hereinafter, the voltage appearing at the first connection point p1 may be referred to as a _{first reference voltage V ref1.} The first reference voltage V _ref1 is input to the first reference voltage terminal 425a of the first shunt regulator 425. _{The larger the first reference voltage V ref1} input to the first reference voltage terminal 425a, the larger the current i1 flowing through the current supply power supply 131, the sixth resistor 132, the first shunt regulator 425, and the reference potential in this order. In FIG. 26, the current i1 is the current flowing downward in the drawing through the first shunt regulator 425. Hereinafter, the current i1 may be referred to as a first current i1.

In the present embodiment, the open circuit voltage of the characteristic conversion circuit 400 is controlled by the first feedback control. Here, the open circuit voltage is the output voltage of the characteristic conversion circuit 400 when the output current of the characteristic conversion circuit 400 is zero. Specifically, in the first feedback control, the open circuit voltage is defined by the action of the first shunt regulator 425 and the voltage / current control circuit 160 so that the first reference voltage V _ref1 follows the first reference voltage V _{s1 described later.} Set to a value.

The first shunt regulator 425 of the present embodiment will be further described with reference to FIG. 27. The first shunt regulator 425 includes a first reference voltage terminal 425a, a first cathode 425K, a first anode 425A, a first reference voltage source 425s, a first operational amplifier 425о, and a first transistor 425t. The first operational amplifier 425о includes a non-inverting amplification terminal 425оa, an inverting amplification terminal 425оb, and an output terminal 425оc. The first transistor 425t includes a cathode side terminal 425ta, an anode side terminal 425tb, and a control terminal 425tc. The voltage input to the first reference voltage terminal 425a is supplied to the non-inverting amplification terminal 425оa. The voltage of the inverting amplification terminal 425оb is set by the first reference voltage source 425 s to a voltage higher than the voltage of the first anode 425 A by the first reference voltage V _s1 . _{When a voltage larger than the first reference voltage V s1} is input to the first reference voltage terminal 425a and the voltage of the non-inverting amplification terminal 425оa becomes larger than that of the inverting amplification terminal 425оb, the output terminal 425оc is changed to the control terminal 425 tk. A current flows, and a first current i1 flows from the first cathode 425K to the first anode 425A via the cathode side terminal 425ta and the anode side terminal 425tb in this order. In the example of FIG. 27, the first transistor 425t is a bipolar transistor, specifically an NPN transistor. The cathode side terminal 425ta is a collector. The anode side terminal 425tb is an emitter. The control terminal 425 ct is a base. In this description, the current flowing between the output terminal 425оc and the control terminal 425 tk, specifically, the base current, is ignored as being sufficiently small.

Based on the explanation with reference to FIG. 27, the operation of the first circuit 410 can be explained as follows. When the output voltage V _out of _the characteristic conversion circuit 400 increases, the first reference voltage V _ref1 is increased. In the first shunt regulator 425, as the first reference voltage V _ref1 becomes larger and the deviation of the first reference voltage V _ref1 from the first reference voltage V _s1 becomes larger, the first current i1 becomes larger. As the first current i1 increases, the current flowing out from the current supply power supply 131 increases. As the outflow current increases, the ratio of the output voltage to the input voltage of the voltage-current control circuit 160 decreases. _{In this way, the first circuit 410 controls the output voltage V out} of the characteristic conversion circuit 400 in cooperation with the voltage / current control circuit 160. Specifically, the first circuit 410 cooperates with the voltage-current control circuit 160 to make the first reference voltage V _ref1 follow the first reference voltage V _s1 and defines _{the output voltage V out} of the characteristic conversion circuit 400. Follow the value.

Returning to FIG. 26, the sensor voltage adjusting circuit 420a of the second circuit 420 includes a variable output power supply 180, an input resistor R1, a feedback resistor R2, and a sensor voltage adjusting operational amplifier 124.

As described above, the current sensor 128 outputs the first sensor voltage V1. The variable output power supply 180 outputs a variable voltage V4. The sensor voltage adjusting circuit 420a generates a second sensor voltage V2 that changes according to the first sensor voltage V1 and the variable voltage V4.

If there are individual variations in the current sensor 128, an error may occur in the first sensor voltage V1. When the first sensor voltage V1 having an error is used for control in the characteristic conversion circuit 400, the switching current _sw deviates from the target current, the maximum power point deviates from the target point, and the maximum power of the characteristic conversion circuit 400 deviates from the target power. There is a risk of misalignment. In this regard, according to the present embodiment, the second sensor voltage V2 reflecting the first sensor voltage V1 and the variable voltage V4 can be generated. By using the second sensor voltage V2, which reflects the appropriately set variable voltage V4, for control in the characteristic conversion circuit 400 _{, the deviation of the switching current sw from} the target current is reduced, and the deviation from the target point of the maximum power point is reduced. The deviation of the maximum power from the target power can be reduced. Further, by adjusting the variable voltage V4 and adjusting the switching current _sw , it is possible to adjust the maximum power of the characteristic conversion circuit 400 according to the situation.

Specifically, the sensor voltage adjusting operational amplifier 124 includes a sensor input terminal 124a, a variable voltage input terminal 124b, and a second sensor voltage output terminal 124c. The sensor input terminal 124a is connected to the sensor output unit 128a via the input resistor R1. A variable voltage V4 is input to the variable voltage input terminal 124b. The second sensor voltage output terminal 124c is connected to the sensor input terminal 124a via the feedback resistor R2. The sensor voltage adjusting operational capacitor 124 generates the second sensor voltage V2 based on the voltage difference between the sensor input terminal 124a and the variable voltage input terminal 124b, and outputs the second sensor voltage V2 from the second sensor voltage output terminal 124c.

Specifically, the sensor input terminal 124a is an inverting amplification terminal. The variable voltage input terminal 124b is a non-inverting amplification terminal.

The voltage-current conversion circuit 420b of the second circuit 420 includes a voltage supply power supply 129, an intervening resistor R3, a transistor drive operational amplifier 126, and a regulated current output transistor 127. The voltage supply power supply 129 outputs the threshold voltage V3. In this embodiment, the voltage supply power supply 129 is a constant voltage source.

In the voltage-current conversion circuit 420b, the adjustment current i3 starts to flow when the second sensor voltage V2 changes across the threshold voltage V3 due to the increase in the first sensor voltage V1. When the adjustment current i3 starts to flow, the first feedback control is switched to the second feedback control. The characteristic conversion circuit 400 whose control is switched at the timing when the current starts to flow is easy to design.

Specifically, the transistor drive operational amplifier 126 includes a power supply input terminal 126a, a second sensor voltage input terminal 126b, and a control voltage output terminal 126c. The power input terminal 126a is connected to the voltage supply power supply 129 via an intervening resistor R3. The second sensor voltage V2 is input to the second sensor voltage input terminal 126b. _{The transistor-driven operational amplifier 126 generates a control voltage V c} based on the voltage difference between the power input terminal 126a and the second sensor voltage input terminal 126b, and outputs the _{control voltage V c} from the control voltage output terminal 126c.

Specifically, the power input terminal 126a is an inverting amplification terminal. The second sensor voltage input terminal 126b is a non-inverting amplification terminal.

The adjusting current output transistor 127 includes a control terminal 127c, a first terminal 127a, and a second terminal 127b. The control voltage V _c is input to the control terminal 127 c. The first terminal 127a is connected to the voltage supply power supply 129 via the intervening resistor R3. The second terminal 127b outputs the adjustment current i3.

In the example of FIG. 26, the adjusting current output transistor 127 is a bipolar transistor, specifically a PNP transistor. The control terminal 127c is a base. The first terminal 127a is an emitter. The second terminal 127b is a collector.

The first sensor voltage V1, the second sensor voltage V2, the adjustment current i3, and the output voltage V _out of the second circuit 420 will be further described using mathematical formulas.

FIG. 28 shows the current sensor 128 of this embodiment. The current sensor 128 includes a shunt resistor 128r and a current sense amplifier 128s. The resistance value of the shunt resistor 128r is R _sense . When a current I _load flows through the shunt resistor 128r, a voltage R _sense I _load is applied to the shunt resistor 128r. The current sense amplifier 128s outputs _{the total voltage of the voltage R sense} I _load multiplied by the gain G and the bias voltage V _bias as the first sensor voltage V1. That is, the first sensor voltage V1 generated by the current sensor 128 of the present embodiment is given by the mathematical formula 4. However, another current sensor such as a Hall element type current sensor may be used as the current sensor 128, and the output of the current sensor may be used as the first sensor voltage V1. The current I _load corresponds to the output current of the characteristic conversion circuit 400. "*" Is a symbol representing multiplication. As can be seen from FIGS. 4 and 28, the configuration of the current sensor 128 in FIG. 28 is similar to the configuration of the current sensor in FIG.
Formula 4: V1 = R _sense * I _load * G + V _bias

In the sensor voltage adjusting circuit 420a, the second sensor voltage V2 is generated by the differential amplification using the sensor voltage adjusting operational amplifier 124. The second sensor voltage V2 is given by the following mathematical formula 5. Here, R1 is the resistance value of the input resistor R1. R2 is the resistance value of the feedback resistor R2.
Formula 5: V2 = V4 + (V4-V1) * R2 / R1

In the voltage-current conversion circuit 420b, the transistor-driven operational amplifier 126 sets the adjustment current output transistor 127 so that the voltage of the power input terminal 126a follows the voltage of the second sensor voltage input terminal 126b due to a virtual short circuit when V2 <V3. Drive. Specifically, in the transistor drive operational amplifier 126, when V2 <V3, the voltage of the power input terminal 126a becomes the second sensor voltage V2, and the voltage difference V3-V2 between the threshold voltage V3 and the second sensor voltage V2 is an intervening resistance. The control terminal 127c is driven so that the current (V3-V2) / R3 flows from the intervening resistor R3 to the first terminal 127a while being applied to R3. More specifically, during this drive, a current flows between the control voltage output terminal 126c and the control terminal 127c. Here, R3 is the resistance value of the intervening resistor R3. When V2 <V3, the adjustment current i3 is given by the following equation 6. When V2 ≧ V3, the adjustment current i3 is given by the following equation 7. In Equation 6, the current flowing between the control voltage output terminal 126c and the control terminal 127c, and the base current in the example of FIG. 26, are ignored as being sufficiently small.
Formula 6: i3 = (V3-V2) / R3
Formula 7: i3 = 0

In the illustrated example, the transistor drive operational amplifier 126 suppresses the change in the adjustment current i3 due to the change in the voltage between the terminals 127c-127a of the adjustment current output transistor 127 due to the temperature. Specifically, if the second sensor voltage V2 is directly supplied to the control terminal 127c of the transistor 127, the voltage of the first terminal 127a is the sum of the second sensor voltage V2 and the voltage between the terminals 127c-127a. Since it is a value, it is affected by the voltage between the terminals 127c-127a. On the other hand, in the present embodiment, since the terminals 126a and 126b of the operational amplifier 126 are virtually short-circuited, the voltage of the first terminal 127a and the second sensor voltage V2 are substantially the same, and the adjustment current i3 is the terminal 127c. It is virtually unaffected by the voltage between -127a. Specifically, as described above, the control terminal 127c is a base. The first terminal 127a is an emitter. The second terminal 127b is a collector. The voltage between terminals 127c-127a is the voltage between the base and the emitter.

As understood from the above description with reference to FIG. 27, the first shunt regulator 425 causes the first reference voltage V _ref1 to follow a constant first reference voltage V _s1. The output voltage V _out is given by the following equation 8. Here, R421 is the resistance value of the resistor 421. R422 is the resistance value of the resistor 422. Equation 8 shows that _{the output voltage V out} of the characteristic conversion circuit 400 decreases as the adjustment current i3 increases.
Formula 8: V _out = (V _ref1 / R422-i3) * R421 + V _ref1

As can be seen from Equation 8 and FIG. 25, the output voltage V _out becomes smaller when the adjustment current i3 flows. In this way, the adjustment current i3 acts to adjust the _{output voltage V out.}
The adjustment current i3 can be referred to as an output voltage adjustment current i3.

As can be understood from the above description, in the present embodiment, the second feedback control is realized by adjusting the first feedback control. Specifically, this adjustment is performed by the second circuit 420. The second circuit 420 can be referred to as an adjustment circuit.

In the present embodiment, the output characteristics of the fuel cell power generation system 40 are converted using the first circuit 410 and the second circuit 420.

The method of character conversion using a circuit is compatible with the fuel cell power generation system. Specifically, the output voltage and output power of the fuel cell power generation system are easy to maintain constant, unlike the wind power generation system and the like. In one embodiment, the output voltage and output power of the fuel cell power generation system are maintained constant in the rated power generation. Therefore, when the power generation system connected to the characteristic conversion circuit is a fuel cell power generation system, it is less necessary to change the characteristics of the characteristic conversion according to the output voltage and / or the output power of the power generation system, and the circuit is used. It is easy to adopt a method of character conversion.

[Individual variation of current sensor 128 and its suppression]
As described above, the current sensor 128 may have individual variations. The effects of individual variation will be described in detail with reference to FIGS. 29 and 30.

In this embodiment, the current sensor 128 has the configuration shown in FIG. 28. The resistance value R _sense , gain G, and bias voltage V _bias of the shunt resistor 128r are ideally reference values. However, the resistance value R _sense , the gain G and / or the bias voltage V _bias may have an error in the range of tolerance. In the present embodiment, when the resistance value of the shunt resistor 128r is larger than the reference value, the current sensor 128 outputs a first sensor voltage V1 which is larger than when the resistance value of the shunt resistor 128r is the reference value. It is configured. The current sensor 128 is configured to output a first sensor voltage V1 that is larger when the gain G is larger than the reference value, as compared with when the gain G is the reference value. Current sensor 128, when the bias voltage V _bias is larger than the reference value, than when the bias voltage V _bias is the reference value, and is configured to output a large first sensor voltage V1.

In FIG. 29, the horizontal axis represents the output voltage of the characteristic conversion circuit 400. FIG. 29 shows the output characteristics of the characteristic conversion circuit 400 when the _{resistance value R sense} is changed when the gain G and the bias voltage V _bias are at the reference values.

Specifically, in FIG. 29, “output current (0) of the characteristic conversion circuit” indicates the output current of the characteristic conversion circuit 400 when the _{resistance value R sense of the shunt resistor 128r is at the reference value.} The “output current (+) of the characteristic conversion circuit” indicates the same output current when the _{resistance value R sense is larger than the reference value.} The “output current (−) of the characteristic conversion circuit” indicates the same output current when the _{resistance value R sense is smaller than the reference value.} The “output power of the characteristic conversion circuit (0)” indicates the output power of the characteristic conversion circuit 400 when the _{resistance value R sense is at the reference value.} The “output power (+) of the characteristic conversion circuit” indicates the same output power when the _{resistance value R sense is larger than the reference value.} “Output power (−) of the characteristic conversion circuit” indicates the same output power when the _{resistance value R sense is smaller than the reference value.}

In FIG. 30, the horizontal axis represents the output current of the characteristic conversion circuit 400. FIG. 30 shows the output characteristics of the characteristic conversion circuit 400 when the _{resistance value R sense} is changed when the gain G and the bias voltage V _bias are at the reference values.

Specifically, in FIG. 30, “output voltage (0) of the characteristic conversion circuit” indicates the output voltage of the characteristic conversion circuit 400 when the _{resistance value R sense of the shunt resistor 128r is at the reference value.} The “output voltage (+) of the characteristic conversion circuit” indicates the same output voltage when the _{resistance value R sense is larger than the reference value.} The “output voltage (−) of the characteristic conversion circuit” indicates the same output voltage when the _{resistance value R sense is smaller than the reference value.} “Adjustment current i3 (0)” indicates the adjustment current i3 when the _{resistance value R sense of the shunt resistor 128r is at the reference value.} “Adjustment current i3 (+)” indicates the adjustment current i3 when the _{resistance value R sense is larger than the reference value.} “Adjustment current i3 (−)” indicates the adjustment current i3 when the _{resistance value R sense is smaller than the reference value.} The “output power of the characteristic conversion circuit (0)” indicates the output power of the characteristic conversion circuit 400 when the _{resistance value R sense is at the reference value.} The “output power (+) of the characteristic conversion circuit” indicates the same output power when the _{resistance value R sense is larger than the reference value.} “Output power (−) of the characteristic conversion circuit” indicates the same output power when the _{resistance value R sense is smaller than the reference value.} “Switching current i _sw (0)” indicates the _{switching current i sw when the resistance value R sense} is at the reference value. “Switching current i _sw (+)” indicates the _{switching current i sw when the resistance value R sense} is larger than the reference value. “Switching current i _sw (−)” indicates the _{switching current i sw when the resistance value R sense} is smaller than the reference value. As described above, the switching current _sw is the output current of the characteristic conversion circuit 400 when the first feedback control and the second feedback control are switched.

When the resistance value R _sense is the reference value, the maximum power point is at the target point. This situation is as shown in FIGS. 24 and 25.

When the resistance value R _sense is at the reference value, the switching current _sw matches the target current. The "switching current i _sw (0)" corresponds to the target current. When the resistance value R _sense is greater than the reference value, than when the resistance value R _sense is in the reference value, the switching current i _sw is small. On the contrary, when the resistance value R _sense is smaller than the reference value, the switching current i _sw is larger _{than when the resistance value R sense is at the reference value.}

When the resistance value R _sense is at the reference value, the maximum power of the characteristic conversion circuit 400 matches the target power. The "output power (0) of the characteristic conversion circuit" when the output current of the characteristic conversion circuit 400 is the "switching current is _{sw (0)" corresponds to the target power.} When the resistance value R _sense is larger than the reference value, the maximum power is smaller than when _{the resistance value R sense is at the reference value.} On the contrary, when the resistance value R _sense is smaller than the reference value, the maximum power is larger than when _{the resistance value R sense is at the reference value.}

As shown in FIGS. 29 and 30, _{individual variation in the resistance value R sense} of the shunt resistor 128r causes variation in the maximum power point of the characteristic conversion circuit 400. The variation of the maximum power point causes the variation of the switching current _sw and the maximum power.

In this respect, in the present embodiment, the switching current _sw of the characteristic conversion circuit 400 can be adjusted and the maximum power can be adjusted by adjusting the variable voltage V4.

For example, consider a case where the resistance value R _sense is smaller than the reference value and the switching current _sw and the maximum power are larger _{than when the resistance value R sense is at the reference value. In this case, the switching current sw} and the maximum power can be reduced by reducing the variable voltage V4 as compared with the case where the resistance value R _{sense is at the reference value.} As a result, the switching current _sw and the maximum power can be brought close to the target current and the target power.

On the contrary, consider the case where the resistance value R _sense is larger than the reference value and the switching current _sw and the maximum power are smaller _{than when the resistance value R sense is at the reference value. In this case, the switching current sw} and the maximum power can be increased by increasing the variable voltage V4 as compared with the case where the resistance value R _{sense is at the reference value.} As a result, the switching current _sw and the maximum power can be brought close to the target current and the target power.

It will be further described with reference to FIG. 31 that the adjustment of the variable voltage V4 can change the adjustment current i3 and the maximum power.

FIG. 31A shows the first sensor voltage V1. However, the first sensor voltage V1 may have an error due to individual variation of the current sensor 128.

FIG. 31 (b) shows the second sensor voltage V2. The voltage V2a is the second sensor voltage V2 before adjusting the variable voltage V4. The variable voltage V4 before adjustment may or may not be 0V. As can be understood from Equation 5, when the variable voltage V4 is increased, the second sensor voltage V2 is increased. The voltage V2b is the second sensor voltage V2 after being increased in this way. On the contrary, when the variable voltage V4 is reduced, the second sensor voltage V2 becomes smaller. The voltage V2c is the second sensor voltage V2 after being reduced in this way. The arrow AR1 indicates that the second sensor voltage V2 can be adjusted by adjusting the variable voltage V4.

FIG. 31 (c) shows the adjustment current i3 and the switching current i _sw . The current i3a is the adjustment current i3 before adjusting the variable voltage V4 and the second sensor voltage V2. The current i _sw a is the switching current i _sw at this time. When the second sensor voltage V2 is increased to the voltage V2b, the adjustment current i3 starts to flow when the output current of the characteristic conversion circuit 400 is larger. The current i3b is the adjustment current i3 after the timing at which the current starts to flow changes in this way. The current i _sw b is the switching current i _sw at this time. On the contrary, when the second sensor voltage V2 is reduced to the voltage V2c, the adjustment current i3 starts to flow when the output current of the characteristic conversion circuit 400 is smaller. The current i3c is the adjusted current i3 after the timing at which the current starts to flow changes in this way. The current i _sw c is the switching current i _sw at this time. _{The arrow AR2 indicates that the switching current sw} can be adjusted by adjusting the variable voltage V4 and adjusting the second sensor voltage V2. This adjustment adjusts the maximum power.

By adjusting the variable voltage V4, the switching current _sw and the maximum power can be brought close to the values when the _{resistance value R sense is at the reference value.} That is, the switching current _sw and the maximum power can be brought close to the target current and the target power.

When the current sensor 128 has the configuration shown in FIG. 28, _{individual variation of the bias voltage V bias} can also cause variation of the maximum power point of the characteristic conversion circuit 400. Individual variations in gain G can also result in variations in the maximum power point of the characteristic conversion circuit 400. Even when the current sensor 128 is another sensor such as a Hall element type current sensor, an error due to individual variation of the current sensor 128 may cause variation in the maximum power point of the characteristic conversion circuit 400. However, in these cases as well, as in the case where the resistance value R _sense of the shunt resistor 128r varies, the maximum power point of the characteristic conversion circuit 400 is brought closer to the target point by adjusting the variable voltage V4, and the switching current is _sw and the maximum. The power can be brought closer to the target current and the target power.

[Example of how to adjust variable voltage V4]
Hereinafter, a first adjustment example and a second adjustment example of the variable voltage V4 will be described.

Consider the case where there is a target value of the switching current i _{sw, that is, a target current.} In the first adjustment example and the second adjustment example, the variable voltage V4 is adjusted so that the output voltage becomes the target voltage and the output power becomes the maximum power and the target power when the output current is the target current, and the characteristic conversion circuit 400 To calibrate. Specifically, in the first adjustment example and the second adjustment example, the target current is the “switching current i _sw (0)” in FIG. The target voltage is the “output voltage (0) of the characteristic conversion circuit” when the output current in FIG. 30 is the “switching current is _{sw (0)”.} The maximum power and the target power are the “output power (0) of the characteristic conversion circuit” when the output current in FIG. 30 is the “switching current _{sw (0)”.}

In the first adjustment example, the variable voltage V4 is adjusted as follows. First, the fuel cell power generation system 40 supplies DC power to the characteristic conversion circuit 400 while causing the first DCDC converter 21 to perform constant current control so that the output current of the characteristic conversion circuit 400 is fixed to the target current. Next, the variable voltage V4 is adjusted so that the output voltage of the characteristic conversion circuit 400 becomes the target voltage.

Specifically, in the first adjustment example, it is assumed that the characteristic conversion circuit 400 has the output current-output voltage characteristic shown in the “output voltage (+) of the characteristic conversion circuit” of FIG. In that case, when the output current is "switching current is _sw (0)", the output voltage is lower than the target voltage. Therefore, the variable voltage V4 is increased. Then, the output current-output voltage characteristic changes, and the output voltage approaches the target voltage. By appropriately increasing the variable voltage V4, the output voltage can be matched with the target voltage. Further, by setting the variable voltage V4, the switching current _sw matches the target current, and the output power becomes the maximum power and the target power. As a result, the above calibration is realized.

Further, in the first adjustment example, it is assumed that the characteristic conversion circuit 400 has the output current-output voltage characteristic shown in the “output voltage (−) of the characteristic conversion circuit” of FIG. In that case, when the output current is "switching current is _sw (0)", the output voltage is the same as the target voltage. Here, the variable voltage V4 is reduced. When the decrease of the variable voltage V4 reaches a certain level, the output voltage starts to decrease from the target voltage. By setting the variable voltage V4 to the value when the output voltage starts to decrease, the switching current _sw is matched with the target current while the output voltage is matched with the target voltage, and the output power can be set to the maximum power and the target power. As a result, the above calibration is realized.

In the second adjustment example, the variable voltage V4 is adjusted as follows. First, the fuel cell power generation system 40 supplies DC power to the characteristic conversion circuit 400 while causing the first DCDC converter 21 to perform constant current control so that the output current of the characteristic conversion circuit 400 is fixed to the target current. Next, the variable voltage V4 is adjusted so that the output power of the characteristic conversion circuit 400 becomes the target power. The output power of the characteristic conversion circuit 400 can be measured using a power meter or the like.

Specifically, in the second adjustment example, it is assumed that the characteristic conversion circuit 400 has the output current-output power characteristic shown in the “output power (+) of the characteristic conversion circuit” of FIG. In that case, when the output current is "switching current is _sw (0)", the output power is lower than the target power. Therefore, the variable voltage V4 is increased. Then, the output current-output power characteristic changes, and the output power approaches the target power. By appropriately increasing the variable voltage V4, the output power can be set to the maximum power and the target power. Further, by setting the variable voltage V4, the switching current _sw matches the target current, and the output voltage matches the target voltage. As a result, the above calibration is realized.

Further, in the second adjustment example, it is assumed that the characteristic conversion circuit 400 has the output current-output power characteristic shown in the “output power (−) of the characteristic conversion circuit” of FIG. In that case, when the output current is "switching current is _sw (0)", the output power is not the maximum power, but is the same as the target power. Here, the variable voltage V4 is reduced. When the decrease of the variable voltage V4 reaches a certain level, the output power starts to decrease from the target power. By setting the variable voltage V4 to the value when the output power starts to decrease, it is possible _{to match the switching current sw} with the target current and match the output voltage with the target voltage while setting the output power to the maximum power and the target power. can. As a result, the above calibration is realized.

[Adjustment of maximum power of characteristic conversion circuit 400 according to the situation]
By adjusting the variable parameters, it is also possible to adjust the maximum power of the characteristic conversion circuit 400 according to the situation. In one example, the variable parameters are adjusted according to the power generation status of the photovoltaic power generation system connected to the DC power converter 20. Hereinafter, such an example will be described.

The power system 405 of this embodiment includes a controller 51. Specifically, in the present embodiment, the fuel cell power generation system 40 includes a controller 51. However, the controller 51 may not be included in the fuel cell power generation system 40.

In one specific example, the controller 51 changes variable parameters according to the power output of at least one photovoltaic power generation system. In this way, the output power of the characteristic conversion circuit 400 can be adjusted according to the power generation output of the photovoltaic power generation system.

The power generation output is, for example, a power generation voltage, a power generation power, a power generation current, or the like. The power output of at least one photovoltaic power generation system may be the power generation output of one photovoltaic power generation system included in at least one photovoltaic power generation system, and a plurality of photovoltaic power generation systems included in at least one photovoltaic power generation system. It may be a value determined by the power generation output of the photovoltaic power generation system of the above, or may be a value determined by the power generation output of all the photovoltaic power generation systems included in at least one photovoltaic power generation system. The value determined by the power output of multiple or all PV systems can be the sum or average. Specifically, the power generation output of at least one photovoltaic power generation system may be one of the photovoltaic power generation systems 31 and 32, and the total value or the average of the power generation outputs of the photovoltaic power generation systems 31 and 32. It may be a value.

In one embodiment, the power generation output is the power generation voltage of at least one photovoltaic system. _{The controller 51 (a) changes the variable parameter so that the switching current sw} becomes smaller when the power generation voltage increases across the threshold power generation voltage, or (b) switches as the power generation voltage becomes larger. The variable parameter is changed so that the _{current sw becomes smaller.} Typically, when the generated voltage of the photovoltaic power generation system is large, the generated power of the photovoltaic power generation system is large. In this embodiment, in such a case, the switching current i _sw changes the variable parameter so as to reduce. In this way, the maximum power of the characteristic conversion circuit 400 becomes small. By doing so, the power taken out from the characteristic conversion circuit 400 to the first DCDC converter 21 by the MPPT control becomes small. For the above reasons, according to this specific example, just enough electric power can be supplied to the first DCDC converter 21.

In one specific example, the controller 51 changes the variable parameters using a control signal representing the power generation output. In this way, the variable parameters can be easily adjusted according to the power generation output. The control signal is generated by, for example, the DC power converter 20. Alternatively, the power system 405 may include an output sensor that produces a control signal that represents the power generation output.

The contents of "Adjustment of the maximum power of the characteristic conversion circuit 400 according to the situation" can also be applied to the third and fifth embodiments.

FIG. 32 shows a characteristic conversion circuit 400X which is a specific example of the characteristic conversion circuit 400. As can be understood from FIG. 32, the characteristic conversion circuit 400X can be configured following the characteristic conversion circuit 100X of FIG. 8 of the first embodiment. Therefore, a detailed description of the characteristic conversion circuit 400X will be omitted.

(Fifth Embodiment)

FIG. 33 is a block diagram of the power system 505 according to the present embodiment. 34 and 36 show the output characteristics of the characteristic conversion circuit 500 according to the fifth embodiment. FIG. 37 shows the characteristic conversion circuit 500 according to the fifth embodiment.

In a fifth embodiment, the first circuit 510 executes the first feedback control in cooperation with the voltage-current control circuit 160. The second circuit 520 executes the second feedback control in cooperation with the first circuit 510 and the voltage / current control circuit 160. The current sensor 128 is used in both the first feedback control and the second feedback control.

In the characteristic conversion circuit 500, the first feedback control is performed when the sensor output is relatively small so that the output voltage-output power characteristic of (i) and the output current-output power characteristic of (ii) described below are obtained. Is executed and the second feedback control is executed when the sensor output is relatively large.

The output voltage-output power characteristic of (i) of the characteristic conversion circuit 500 is the output at which the output power of the characteristic conversion circuit 500 is maximized when the output voltage of the characteristic conversion circuit 500 is a certain value, as shown in FIG. Voltage-output power characteristic. Further, the output voltage-output current characteristic of (i) is characterized as the output voltage of the characteristic conversion circuit 500 increases in a region where the output voltage of the characteristic conversion circuit 500 straddles a certain value as shown in FIGS. 34 and 36. It is an output voltage-output current characteristic that reduces the output current of the circuit 500. Here, the region where the output voltage of the characteristic conversion circuit 500 straddles the above-mentioned certain value is the region from the first value where the output voltage of the characteristic conversion circuit 500 is smaller than the above-mentioned certain value to the second value larger than the above-mentioned certain value. be. Specifically, the above-mentioned certain value is a value within a predetermined range as in the first embodiment.

According to the characteristic conversion circuit 500, it is easy to take out a large amount of electric power from the fuel cell power generation system 40 to the first DCDC converter 21 based on the MPPT control. Hereinafter, this point will be described with reference to FIGS. 34 and 35.

As described above, in the region where the output voltage of the characteristic conversion circuit 500 straddles the above-mentioned value, the output voltage of the characteristic conversion circuit 500 becomes smaller as the output voltage of the characteristic conversion circuit 500 increases, resulting in an output voltage-output current characteristic. Due to this output voltage-output current characteristic, as shown in FIG. 34, in the graph of the output voltage-output power characteristic of the characteristic conversion circuit 500, the output power is convex upward with respect to the output voltage in the region straddling the above-mentioned value. Can be curved. In a typical example, the graph of the output voltage-output power characteristic of the characteristic conversion circuit 500 is a graph of a single peak in which the output power is maximized when the output voltage has the above-mentioned value.

Temporarily, the graph of the output voltage-output power characteristic of the characteristic conversion circuit 500 is. As shown in FIG. 35, it is assumed that the output power is a linear shape that is convex upward with respect to the output voltage. In this case, it is assumed that the MPPT control is executed, but the operating point is adjusted to a point deviated from the maximum power point. Specifically, it is assumed that the output voltage of the characteristic conversion circuit 500 is adjusted to a voltage V _{real deviated from the output voltage V target of the maximum power point.} In this case, the output power of the characteristic conversion circuit 500 is reduced as compared with the case where the operating point is adjusted to the maximum power point. In FIG. 35, this decrease is described _{as δP B.}

On the other hand, also in the example of FIG. 34, when the output voltage of the characteristic conversion circuit 500 is adjusted to the voltage V _{real deviated from the output voltage V target} of the maximum power point, the output power of the characteristic conversion circuit 500 has the maximum operating point. It decreases compared to the case where it is adjusted to the power point. In Figure 34, it describes the decline and [delta] P _A.

As described above, regardless of whether the graph of the output voltage-output power characteristic of the characteristic conversion circuit 500 is linear or curved, if the operating point deviates from the maximum power point, the output power of the characteristic conversion circuit 500 will be increased. Decrease. However, the amount of decrease is different. Specifically, the reduction width δP _{A in} the case of FIG. 34 is smaller than the reduction width δP _{B in FIG. 35.} The fact that the graph of the output voltage-output power characteristic has an upwardly convex curve suppresses the decrease in the output power due to the above deviation, and from the fuel cell power generation system 40 to the first DCDC converter 21. It is advantageous from the viewpoint of suppressing the decrease in the power taken out. However, the characteristic conversion control may bring about the output voltage-output power characteristic of FIG. 35.

Similar to the second embodiment, the output characteristic of the characteristic conversion circuit 500 of the fifth embodiment has an advantage that the reduction width of the output power due to the MPPT control method and the resolution can be suppressed. This output characteristic has a practical merit. Further, this output characteristic has an advantage that the compatibility of the characteristic conversion circuit 500 is improved and the restriction of the DC power conversion device 20 that can be adopted is reduced.

Further, the output current-output power characteristic of (ii) is such that the output power of the characteristic conversion circuit 500 is the maximum when _{the output current of the characteristic conversion circuit 500 is the switching current sw, as shown in FIGS. 34 and 36.} Output current-output power characteristic. Here, the switching current _sw is the output current of the characteristic conversion circuit 500 when the first feedback control and the second feedback control are switched.

The switching current _sw is dependent on the error of detecting the output current of the characteristic conversion circuit 500 by the current sensor 128, and changes when the variable parameter is changed. Since this point is the same as that of the fourth embodiment, detailed description thereof will be omitted.

As can be seen from FIG. 34, in the present embodiment, due to the first feedback control and the second feedback control, the characteristic conversion circuit 500 has the output voltage of the characteristic conversion circuit 500 larger than a certain value and smaller than the open circuit voltage. In the region, the larger the output voltage of the characteristic conversion circuit 500, the smaller the output current of the characteristic conversion circuit 500, resulting in an output voltage-output current characteristic. Further, in a region where the output voltage of the characteristic conversion circuit 500 is larger than 0 and smaller than a certain value, the output voltage of the characteristic conversion circuit 500 becomes smaller as the output voltage of the characteristic conversion circuit 500 increases. Bring. Here, the open circuit voltage is the output voltage of the characteristic conversion circuit 500 when the output current of the characteristic conversion circuit 500 is zero.

A value smaller than a certain value is defined as a first value. A value larger than a certain value is defined as a second value. At this time, in the example of FIG. 34, the output characteristics are both a region where the output voltage is larger than the first value and smaller than the above-mentioned certain value and a region where the output voltage is larger than the above-mentioned certain value and smaller than the second value. The characteristic is that the output current decreases linearly as the output voltage increases. That is, the output characteristic is a characteristic in which the output current becomes smaller in the form of a linear function with respect to the output voltage in both of the above regions. As a result, the output characteristic can be a characteristic in which the output power changes in the form of a quadratic function with respect to the output voltage in both of the above regions.

Specifically, in the example of FIG. 34, the output characteristic shows the output voltage in both the region where the output voltage is larger than 0 and smaller than the above-mentioned value and the region where the output voltage is from the above-mentioned value to the open circuit voltage value. The characteristic is that the output current decreases linearly as the value increases. That is, the output characteristic is a characteristic in which the output current becomes smaller in the form of a linear function with respect to the output voltage in both of the above regions. As a result, the output characteristic can be a characteristic in which the output power changes in the form of a quadratic function with respect to the output voltage in both of the above regions.

In the graph of output voltage-output power characteristics, the point where the voltage is zero and the power is zero is defined as the origin. In the graph of output voltage-output power characteristic, it can be said that the maximum power point is the point where the voltage is the above-mentioned value and the power is the maximum. In the graph of output voltage-output power characteristics, the point where the voltage is the open circuit voltage and the power is zero is defined as the open circuit voltage point. In the graph of output voltage-output power characteristics, the straight line connecting the origin and the maximum power point is defined as the first straight line. In the graph of output voltage-output power characteristics, the straight line connecting the maximum power point and the open circuit voltage point is defined as the second straight line. At this time, in the example of FIG. 34, the region where the output voltage in the graph of the output voltage-output power characteristic is larger than the first value and smaller than the above-mentioned certain value is on the higher power side than the first straight line. The region in which the output voltage in the graph of output voltage-output power characteristics is larger than a certain value and smaller than the second value is on the higher power side than the second straight line.

Specifically, in the example of FIG. 34, the region where the output voltage in the graph of the output voltage-output power characteristic is larger than 0 and smaller than the above-mentioned value is on the higher power side than the first straight line. The region from the above-mentioned value to the open circuit voltage in the graph of output voltage-output power characteristic is on the higher power side than the second straight line.

Combined with the first feedback control and the second feedback control, the output voltage-output current characteristic of the characteristic conversion circuit 500 is shown by the broken line in FIGS. 34 and 36. As a result, the output voltage-output power characteristic of the characteristic conversion circuit 500 has a single peak and is convex as shown by the solid line in FIG.

As described above, the output voltage-output power characteristic that is convex above the characteristic conversion circuit 500 enables MPPT control by the first DCDC converter 21. The MPPT control of the characteristic conversion circuit 500 can be executed by the first DCDC converter 21.

The configuration of the characteristic conversion circuit 500 will be further described.

As shown in FIG. 37, the first circuit 510 has a resistor 421, a resistor 422, a resistor 550, a current sensor 128, and a first shunt regulator 425. The second circuit 520 includes a resistor 550, a current sensor 128, a sensor voltage adjusting circuit 520a, and a voltage-current conversion circuit 520b. The current sensor 128 and the resistor 550 are shared by the first circuit 510 and the second circuit 520. The feedback current supply unit 130 includes a current supply power supply 131 and a sixth resistor 132.

In the voltage-current control circuit 160, the smaller the current flowing out from the current supply power supply 131, the larger the ratio of the output voltage to the input voltage of the voltage-current control circuit 160. In this way, the characteristic conversion circuit 500 is adapted to adjust the above ratio according to the current flowing out from the current supply power supply 131.

In the fifth embodiment, the current sensor 128 has the configuration shown in FIG. 28 as in the fourth embodiment. The first sensor voltage V1 generated by the current sensor 128 is given by the above equation 4. However, another current sensor such as a Hall element type current sensor may be used as the current sensor 128, and the output of the current sensor may be used as the first sensor voltage V1.

In a fifth embodiment, the first shunt regulator 425 has the configuration shown in FIG. 27, similar to the fourth embodiment. Due to the first shunt regulator 425, the first reference voltage V _ref1 follows a constant first reference voltage V _s1 .

In the first circuit 510 shown in FIG. 37, the output voltage V _out of the characteristic conversion circuit 500 in the first feedback control is given by the following mathematical formula 9. Here, R421 is the resistance value of the resistor 421, R422 is the resistance value of the resistor 422, and R550 is the resistance value of the resistor 550.

As can be understood from Equation 9, when the output current of the characteristic conversion circuit 500 increases and the first sensor voltage V1 increases, the output voltage V _out decreases. In this way, the first sensor voltage V1 acts to adjust the _{output voltage V out.}

Specifically, in the first feedback control by the first circuit 510, when the first sensor voltage V1 becomes large, the current flowing from the current sensor 128 to the first connection point p1 via the resistor 550 and the connection point ps in this order becomes large. Become. Due to the first shunt regulator 425, the first reference voltage V _ref1 follows a constant first reference voltage V _s1 . In order to realize this tracking, a constant current flows through the resistor 422. This means that as the current flowing through the resistor 550 toward the first connection point p1 increases, the current flowing through the resistor 421 toward the first connection point p1 decreases. When this current becomes small, it means that the voltage generated by the resistor 421 becomes small.

Based on the explanation with reference to FIG. 37, the operation of the first circuit 510 in the first feedback control can be explained as follows. When the output current of the characteristic conversion circuit 500 increases, the voltage generated in the resistor 421 decreases while the voltage at _{the first connection point p1 follows the first reference voltage V ref1.} As a result, the output voltage V _out of the characteristic conversion circuit 500 becomes small. In this way, the first feedback control provides an output voltage-output current characteristic as shown in FIGS. 34 and 36, in which the output current of the characteristic conversion circuit 500 decreases as the output voltage of the characteristic conversion circuit 500 increases. ..

Further, the open circuit voltage of the characteristic conversion circuit 500 is controlled by the first feedback control. Here, the open circuit voltage is the output of the characteristic conversion circuit 500 when the output current of the characteristic conversion circuit 500 is zero. Since the output current of the characteristic conversion circuit 500 is zero, I _load becomes zero in Equation 4, and V1 becomes equal to the _{bias voltage V bias. Therefore, V out} defined by Equation 9 is a fixed value. This fixed value corresponds to the open circuit voltage of the characteristic conversion circuit 500. As described above, in the present embodiment, the first current i1 is controlled by the functions of the first shunt regulator 425 and the voltage / current control circuit 160 so that the output voltage V _out of the voltage / current control circuit 160 becomes the voltage determined by the equation 9. By doing so, the open circuit voltage is set to the specified value.

In the fifth embodiment, as in the fourth embodiment, the second sensor voltage V2 is given by the above equation 5. The adjustment current i3 when V2 <V3 is given by the above equation 6. The adjustment current i3 when V2 ≧ V3 is given by the above equation 7.

On the other hand, in the fifth embodiment, the output voltage V _out is given by a mathematical formula different from the mathematical formula 8 described in the fourth embodiment. Specifically, the first reference voltage V _ref1 follows a constant first reference voltage V _s1 by the first shunt regulator 425. The output voltage V _out is given by the following equation 10. Here, R421 is the resistance value of the resistor 421. R422 is the resistance value of the resistor 422, and R550 is the resistance value of the resistor 550. Equation 10 shows that _{the output voltage V out} of the characteristic conversion circuit 500 decreases as the sensor output from the current sensor 128 (specifically, the first sensor voltage V1) increases and the adjustment current i3 increases. There is.

As can be seen from Equation 10 and FIG. 36, the output voltage V _out becomes smaller when the adjustment current i3 flows. In this way, the adjustment current i3 acts to adjust the _{output voltage V out.} The adjustment current i3 can be referred to as an output voltage adjustment current i3. Further, the second circuit 520 can be referred to as an adjustment circuit.

[Individual variation of current sensor 128 and its suppression]
As described in the fourth embodiment, the current sensor 128 may have individual variations. However, according to the fifth embodiment, as in the fourth embodiment, it is possible to make adjustments that suppress the influence of individual variation. This point will be described in detail below with reference to FIGS. 38 to 40. FIG. 38 shows the output characteristics of the characteristic conversion circuit 500 before the adjustment for suppressing the influence of individual variation is performed. FIG. 39 is a diagram for explaining the adjustment. FIG. 40 shows the output characteristics of the characteristic conversion circuit 500 after adjustments are made to suppress the influence of individual variations.

In this embodiment, the current sensor 128 has the configuration shown in FIG. 28. The resistance value R _sense , gain G, and bias voltage V _bias of the shunt resistor 128r are ideally reference values. However, the resistance value R _sense , the gain G and / or the bias voltage V _bias may have an error in the range of tolerance. In the present embodiment, when the resistance value of the shunt resistor 128r is larger than the reference value, the current sensor 128 outputs a first sensor voltage V1 which is larger than when the resistance value of the shunt resistor 128r is the reference value. It is configured. The current sensor 128 is configured to output a first sensor voltage V1 that is larger when the gain G is larger than the reference value, as compared with when the gain G is the reference value. Current sensor 128, when the bias voltage V _bias is larger than the reference value, than when the bias voltage V _bias is the reference value, and is configured to output a large first sensor voltage V1.

In FIG. 38, the horizontal axis represents the output current of the characteristic conversion circuit 500. FIG. 38 shows the output characteristics of the characteristic conversion circuit 500 when the _{resistance value R sense} is changed when the gain G and the bias voltage V _bias are at the reference values.

Specifically, in FIG. 38, “output voltage (0) of the characteristic conversion circuit” indicates the output voltage of the characteristic conversion circuit 500 when the _{resistance value R sense of the shunt resistor 128r is at the reference value.} The “output voltage (+) of the characteristic conversion circuit” indicates the same output voltage when the _{resistance value R sense is larger than the reference value.} The “output voltage (−) of the characteristic conversion circuit” indicates the same output voltage when the _{resistance value R sense is smaller than the reference value.} “Adjustment current i3 (0)” indicates the adjustment current i3 when the _{resistance value R sense of the shunt resistor 128r is at the reference value.} “Adjustment current i3 (+)” indicates the adjustment current i3 when the _{resistance value R sense is larger than the reference value.} “Adjustment current i3 (−)” indicates the adjustment current i3 when the _{resistance value R sense is smaller than the reference value.} The “output power of the characteristic conversion circuit (0)” indicates the output power of the characteristic conversion circuit 500 when the _{resistance value R sense is at the reference value.} The “output power (+) of the characteristic conversion circuit” indicates the same output power when the _{resistance value R sense is larger than the reference value.} “Output power (−) of the characteristic conversion circuit” indicates the same output power when the _{resistance value R sense is smaller than the reference value.} “Switching current i _sw (0)” indicates the _{switching current i sw when the resistance value R sense} is at the reference value. “Switching current i _sw (+)” indicates the _{switching current i sw when the resistance value R sense} is larger than the reference value. “Switching current i _sw (−)” indicates the _{switching current i sw when the resistance value R sense} is smaller than the reference value. As described above, the switching current _sw is the output current of the characteristic conversion circuit 500 when the first feedback control and the second feedback control are switched.

When the resistance value R _sense is the reference value, the maximum power point is at the target point. This situation is as shown in FIGS. 34 and 36.

When the resistance value R _sense is at the reference value, the switching current _sw matches the target current. The "switching current i _sw (0)" corresponds to the target current. As shown in FIG. 38, the resistance value R _sense is greater than the reference value, than when the resistance value R _sense is in the reference value, the switching current i _sw is small. On the contrary, when the resistance value R _sense is smaller than the reference value, the switching current i _sw is larger _{than when the resistance value R sense is at the reference value.}

When the resistance value R _sense is at the reference value, the maximum power of the characteristic conversion circuit 500 matches the target power. The "output power (0) of the characteristic conversion circuit" when the output current of the characteristic conversion circuit 500 is the "switching current is _{sw (0)" corresponds to the target power.} When the resistance value R _sense is larger than the reference value, the maximum power is smaller than when _{the resistance value R sense is at the reference value.} On the contrary, when the resistance value R _sense is smaller than the reference value, the maximum power is larger than when _{the resistance value R sense is at the reference value.}

[Example of how to adjust variable voltage V4]
As shown in FIG. 38, _{the individual variation of the resistance value R sense} of the shunt resistor 128r causes the variation of the maximum power point of the characteristic conversion circuit 500. The variation of the maximum power point causes the variation of the switching current _sw and the maximum power.

In this respect, in the present embodiment, the switching current _sw of the characteristic conversion circuit 500 can be adjusted and the maximum power can be adjusted by adjusting the variable voltage V4.

For example, when the resistance value R _sense is smaller than the reference value, the maximum power is targeted by adjusting the _{switching current sw} by making the variable voltage V4 smaller than when _{the resistance value R sense is at the reference value.} It can be close to electric power.

On the contrary, when the resistance value R _sense is larger than the reference value, the maximum power is _{increased by adjusting the switching current i sw} by increasing the variable voltage V4 as compared with the case where _{the resistance value R sense is at the reference value.} It can approach the target power.

Here, as understood from Equation 5, when the variable voltage V4 is increased, the second sensor voltage V2 is increased. On the contrary, when the variable voltage V4 is reduced, the second sensor voltage V2 becomes smaller.

When the second sensor voltage V2 is increased, the adjustment current i3 starts to flow when the output current of the characteristic conversion circuit 500 is larger. On the contrary, when the second sensor voltage V2 is reduced, the adjustment current i3 starts to flow when the output current of the characteristic conversion circuit 500 is smaller. It is shown that the _{switching current i sw} can be adjusted by adjusting the variable voltage V4 and adjusting the second sensor voltage V2. This adjustment adjusts the maximum power.

Next, it will be further described with reference to FIG. 39 that the adjustment of the variable voltage V4 can change the adjustment current i3 and the maximum power.

In adjusting the variable voltage V4, as an example, a wattmeter for measuring the output power and an electronic load device as a load are connected to the output unit of the characteristic conversion circuit 500.

In this adjustment example, the initial value of the variable voltage V4 is set to a sufficiently large voltage. Then, in this adjustment example, the value of the variable voltage V4 after being properly adjusted is assumed to be smaller than the initial value. Strictly speaking, as shown in FIG. 38, the output current-output power characteristic of the characteristic conversion circuit 500 in the first feedback control fluctuates due to the influence of individual variation of the _{resistance value R sense.} In the description, this variation is small enough and negligible.

As shown in FIG. 39 (a), the characteristic conversion circuit 500 is operated. The output current from the characteristic conversion circuit 500 is gradually increased, and the output power of the characteristic conversion circuit 500 is adjusted to reach the target value. This target value is a value corresponding to the adjusted maximum power point. Next, the variable voltage V4 is gradually lowered. Thus, the switching current i _sw gradually decreases, the output power with a decrease in the maximum power when a value is a variable voltage V4 starts to decrease from the target value. The operating point of the characteristic conversion circuit 500 is set as the operating point when this decrease starts. In this way, the output voltage of the characteristic conversion circuit 500 is adjusted to the maximum power point (target value).

A known electronic load device can be used. In one example, the electronic load device comprises a constant current (CC) mode. When the CC mode is used, the output current from the characteristic conversion circuit 500 can be gradually increased by gradually increasing the set value of the load current, which is the current flowing through the electronic load device. In another example, the electronic load device comprises a constant resistance (CR) mode. When the CR mode is used, the output current from the characteristic conversion circuit 500 can be gradually increased by gradually reducing the set value of the load resistance, which is the resistance of the electronic load device. The electronic load device may include both a CC mode and a CR mode, or may include one of them.

FIG. 39 (b) shows the adjustment current i3a and the switching current i _swa . The current i3a is the adjusted current i3 after adjusting the variable voltage V4 and the second sensor voltage V2. Current i _swa is switched current i _sw of this time. _{The switching current iswa} is also shown in FIG. 39 (a) for the purpose of making the explanation easier to understand.

By adjusting the switching current i _sw by adjusting the variable voltage V4, the maximum power point can be brought closer to the operating point when the _{resistance value R sense is at the reference value.}

Further, from Equation 4, Equation 5 and Equation 6, _{the relationship between the resistance value R sense} and the adjustment current i3 is given by Equation 11.

From Equation 11, as shown in FIG. 38, it is understood that when the resistance value R _sense is large, the slope of the adjustment current i3 is large, and conversely, when the resistance value R _sense is small, the slope of the adjustment current i3 is small. .. This tendency is also shown in FIG. 40.

Further, when the current sensor 128 has the configuration shown in FIG. 28, _{individual variations in the bias voltage V bias} and the gain G can also cause variations in the maximum power point of the characteristic conversion circuit 500. Even when the current sensor 128 is another sensor such as a Hall element type current sensor, an error due to individual variation of the current sensor 128 may cause variation in the maximum power point of the characteristic conversion circuit 500. However, in these cases as well, as in the case where the resistance value R _sense of the shunt resistor 128r varies, the maximum power point of the characteristic conversion circuit 500 is brought closer to the target point by adjusting the variable voltage V4, and the switching current is _sw and the maximum. The power can be brought closer to the target current and the target power.

FIG. 41 shows a characteristic conversion circuit 500X, which is a specific example of the characteristic conversion circuit 500. As can be understood from FIG. 41, the characteristic conversion circuit 500X can be configured following the characteristic conversion circuit 100X of FIG. 8 of the second embodiment. Therefore, a detailed description of the characteristic conversion circuit 500X will be omitted.

(Sixth Embodiment)
FIG. 42 is a block diagram of the power system 605 according to the present embodiment. The power system 605 is provided with a control unit 670. The control unit 670 executes characteristic conversion control. The characteristic conversion control is a control that causes the electrical output characteristics of the characteristic conversion circuit 600 to follow the reference table data. The control unit 670 can be realized by using software.

In this embodiment, each of the plurality of distributed systems 30 has a control unit 670. In each of the plurality of distributed systems 30, the control unit 670 executes characteristic conversion control and adjusts the electrical output characteristics of the characteristic conversion circuit 600. The control unit 670 may be provided on the substrate 60 of each distributed system 30. The control unit 670 may be provided in the fuel cell power generation system 40 of each distributed system 30. When the control unit 670 is provided on either the substrate 60 or the fuel cell power generation system 40, the distributed system 30 has the above requirement (ii), that is, the output voltage-output power characteristic of the characteristic conversion circuit by the characteristic conversion control. Can satisfy the requirement that the output voltage of the characteristic conversion circuit be adjusted to be maximized when the output voltage of the characteristic conversion circuit is a certain value.

The control unit 670 may be provided at a position inside the power system 605 and outside the distributed system 30. In this case as well, the distributed system 30 can satisfy the above requirement (ii).

Further, a configuration may be adopted in which one control unit 670 in the power system 605 executes the characteristic conversion control related to the characteristic conversion circuit 600 in the plurality of distributed systems 30. In this case as well, the plurality of distributed systems 30 can satisfy the above requirement (ii).

The electrical output characteristic represented by the reference table data is the characteristic in which the output power is maximized when the output voltage is a certain value. That is, the output voltage-output power characteristic represented by the reference table data is such an output voltage-output power characteristic. Specifically, the above-mentioned certain value is a value within a predetermined range as in the first embodiment.

Further, the electrical output characteristic represented by the reference table data is a characteristic that the output current decreases as the output voltage increases in the region where the output voltage straddles the above-mentioned certain value. That is, the output voltage-output current characteristic represented by the reference table data is such an output voltage-output current characteristic. Here, the region in which the output voltage straddles the certain value is the region from the first value in which the output voltage is smaller than the certain value to the second value in which the output voltage is larger than the certain value.

An example of the above output voltage-output power characteristic and output voltage-output current characteristic is shown in FIG. 43. In FIG. 43, the output voltage-output power characteristic is described as the VP characteristic. The output voltage-output current characteristic is described as the VI characteristic. The solid line represents the VP characteristic. Dotted lines represent VI characteristics.

According to the output voltage-output power characteristic obtained by the characteristic conversion control, it is easy to take out a large amount of power from the fuel cell power generation system 40 to the first DCDC converter 21 based on the MPPT control. Hereinafter, this point will be described with reference to FIG. 43 and FIG. 44.

As described above, the characteristic conversion control provides an output voltage-output power characteristic in which the output power of the characteristic conversion circuit 600 is maximized when the output voltage of the characteristic conversion circuit 600 is a certain value. Further, the characteristic conversion control brings about an output voltage-output current characteristic in which the output current of the characteristic conversion circuit 600 decreases as the output voltage of the characteristic conversion circuit 600 increases in a region where the output voltage of the characteristic conversion circuit 600 straddles the above-mentioned value. .. Due to this output voltage-output current characteristic, the graph of the output voltage-output power characteristic of the characteristic conversion circuit 600 has a curved shape in which the output current is convex upward with respect to the output voltage in the region where the output voltage straddles the above-mentioned value. obtain. In a typical example, the graph of the output voltage-output power characteristic of the characteristic conversion circuit 600 is a graph of a single peak in which the output power is maximized when the output voltage has the above-mentioned value.

Assuming that the graph of the output voltage-output power characteristic represented by the reference table data is a linear shape in which the output current is convex upward with respect to the output voltage as shown in FIG. 44, the actual output voltage-output power characteristic is obtained. It is assumed that the output voltage-output power characteristic of the characteristic conversion circuit 600 follows. In this case, it is assumed that the MPPT control is executed, but the operating point is adjusted to a point deviated from the maximum power point. Specifically, it is assumed that the output voltage of the characteristic conversion circuit 600 is adjusted to a voltage V _{real deviated from the output voltage V target of the maximum power point.} In this case, the output power of the characteristic conversion circuit 600 is reduced as compared with the case where the operating point is adjusted to the maximum power point. In FIG. 44, this decrease is referred to as ΔP _B.

Also in the example of FIG. 43, when the output voltage of the characteristic conversion circuit 600 is adjusted to the voltage V _{real deviated from the output voltage V target} of the maximum power point, the output power of the characteristic conversion circuit 600 has the operating point at the maximum power point. It decreases compared to the case where it is adjusted to. In Figure 43, the decline to as [Delta] P _A.

As described above, the operating point is the maximum power point regardless of whether the graph of output voltage-output power characteristics represented by the reference table data (that is, the characteristic conversion circuit 600 should follow) is linear or curved. If it deviates from the above, the output power of the characteristic conversion circuit 600 decreases. However, the amount of decrease is different. Specifically, the reduction width ΔP _{A in} the case of FIG. 43 is smaller than the reduction width ΔP _{B in FIG. 44.} The fact that the graph of the output voltage-output power characteristic has an upwardly convex curve suppresses the decrease in the output power due to the above deviation, and from the fuel cell power generation system 40 to the first DCDC converter 21. It is advantageous from the viewpoint of suppressing the decrease in the power taken out. However, the characteristic conversion control may bring about the output voltage-output power characteristic of FIG.

Similar to the second embodiment, the output characteristic of the characteristic conversion circuit 600 of the sixth embodiment has an advantage that the reduction width of the output power due to the MPPT control method and the resolution can be suppressed. This output characteristic has a practical merit. Further, this output characteristic has an advantage that the compatibility of the characteristic conversion circuit 600 is improved and the restriction of the DC power conversion device 20 that can be adopted is reduced.

As shown in FIG. 43, the electrical output characteristic represented by the reference table data may be a characteristic in which the output current decreases as the output voltage increases in a region where the output voltage is larger than 0 and smaller than the above-mentioned certain value. Further, the electrical output characteristic represented by the reference table data may be a characteristic in which the output current decreases as the output voltage increases in a region where the output voltage is larger than a certain value and smaller than the open circuit voltage. Here, the open circuit voltage is the output voltage when the output current is zero.

A value smaller than a certain value is defined as a first value. A value larger than a certain value is defined as a second value. At this time, in the example of FIG. 43, the electric output characteristic represented by the reference table data is a region in which the output voltage is larger than the first value and smaller than the above-mentioned certain value, and the output voltage is larger than the above-mentioned certain value and is the second value. It is a characteristic that the output current linearly decreases as the output voltage increases in both of the smaller regions. That is, the electrical output characteristic represented by the reference table data is a characteristic in which the output current becomes smaller in the form of a linear function with respect to the output voltage in both of the above regions. As a result, the electrical output characteristic represented by the reference table data can be a characteristic in which the output power changes in the form of a quadratic function with respect to the output voltage in both of the above regions.

Specifically, in the example of FIG. 43, the electrical output characteristics represented by the reference table data are a region where the output voltage is larger than 0 and smaller than the above-mentioned certain value and a region where the output voltage is from the above-mentioned certain value to the open circuit voltage value. In both cases, the output current decreases linearly as the output voltage increases. That is, the electrical output characteristic represented by the reference table data is a characteristic in which the output current becomes smaller in the form of a linear function with respect to the output voltage in both of the above regions. As a result, the electrical output characteristic represented by the reference table data can be a characteristic in which the output power changes in the form of a quadratic function with respect to the output voltage in both of the above regions.

In the graph of output voltage-output power characteristics, the point where the voltage is zero and the power is zero is defined as the origin. In the graph of output voltage-output power characteristic, it can be said that the maximum power point is the point where the voltage is the above-mentioned value and the power is the maximum. In the graph of output voltage-output power characteristics, the point where the voltage is the open circuit voltage and the power is zero is defined as the open circuit voltage point. In the graph of output voltage-output power characteristics, the straight line connecting the origin and the maximum power point is defined as the first straight line. In the graph of output voltage-output power characteristics, the straight line connecting the maximum power point and the open circuit voltage point is defined as the second straight line. At this time, in the example of FIG. 43, the region where the output voltage in the graph of the output voltage-output power characteristic is larger than the first value and smaller than the above-mentioned certain value is on the higher power side than the first straight line. In the graph of output voltage-output power characteristic, both regions where the output voltage is larger than a certain value and smaller than the second value are on the higher power side than the second straight line.

Specifically, in the example of FIG. 43, the region where the output voltage in the graph of the output voltage-output power characteristic is larger than 0 and smaller than the above-mentioned value is on the higher power side than the first straight line. Both of the regions where the output voltage in the graph of the output voltage-output power characteristic is from the above-mentioned value to the open circuit voltage are on the higher power side than the second straight line.

In the electrical output characteristics represented by the reference table data, a region where the output voltage is smaller than a certain value is defined as a second region, and a region where the output voltage is larger than a certain value is defined as a first region. At this time, in the example of FIG. 43, in the first region, the ratio of the decrease in the output current to the increase in the output voltage is larger than that in the second region. In this way, the output characteristics of the characteristic conversion circuit 600 can be easily brought close to the output characteristics of the photovoltaic power generation system.

[Example of reference table data]
In the present embodiment, the control unit 670 includes a memory in which a plurality of table data are stored. One of the plurality of table data is selected as the reference table data. In this way, it is possible to give variation to the characteristic conversion control. For example, reference table data can be manually selected from a plurality of table data according to the specifications of equipment such as the fuel cell power generation system 40 and / or the DC power converter 20. This selection may be made by the installer of the power system 605, the user of the power system 605, and the like.

In the first example, the plurality of table data includes A table data. The maximum value of the output power in the electric output characteristic of the characteristic conversion circuit 600 represented by the A table data is different from each other. Here, A is a natural number of 2 or more. According to the first example, the maximum value of the output power in the electric output characteristic of the characteristic conversion circuit 600 can be varied. Specifically, according to the first example, the DC power conversion device 20 that can be adopted is not likely to be restricted by the power that can be received. When the maximum output power of the fuel cell power generation system 40 is reduced for some reason, the maximum power output from the characteristic conversion circuit 600 is reduced to bring the maximum power within the range that can be supplied by the fuel cell power generation system 40. Can fit. Further, the control unit 670 can be diverted to various characteristic conversion circuits 600 having different outputable powers (or to various substrates 60 having different outputable powers). FIG. 45 shows an example of a plurality of VP characteristics represented by A table data.

The maximum value of the output power in the electric output characteristic of the characteristic conversion circuit 600 represented by the A table data is the output power at the maximum power point.

In the second example, the plurality of table data includes B table data. The maximum values of the output voltages in the electrical output characteristics of the characteristic conversion circuit 600 represented by the B table data are different from each other. Here, B is a natural number of 2 or more. According to the second example, the maximum value of the output voltage in the electric output characteristic of the characteristic conversion circuit 600 can be varied. Specifically, according to the second example, the DC power conversion device 20 that can be adopted is not likely to be restricted by the voltage that can be received. FIG. 46 shows an example of a plurality of VP characteristics represented by B table data.

The maximum value of the output voltage in the electrical output characteristics of the characteristic conversion circuit 600 represented by the B table data is the output voltage of the characteristic conversion circuit 600, that is, the open circuit voltage when the output current of the characteristic conversion circuit 600 is zero.

In the third example, the plurality of table data includes C table data. The output voltages at the maximum power points in the electrical output characteristics of the characteristic conversion circuit 600 represented by the plurality of table data are different from each other. Here, C is a natural number of 2 or more. The output voltage at the maximum power point corresponds to the above value. FIG. 47 shows an example of a plurality of VP characteristics represented by C table data.

A table data, B table data, and C table data may have one or more table data overlapping with each other.

Further, the control unit 670 may be configured so that the first table data can be set as the reference table data. The electric output characteristic represented by the first table data is a characteristic having a region in which the output voltage is smaller than half of the maximum value (that is, half of the open circuit voltage) and the output power is 75% or more of the maximum value. This is suitable for realizing the output voltage-output current characteristic in which the output power is large when the output voltage of the characteristic conversion circuit 600 is small. FIG. 48 shows an example of the VP characteristic represented by the first table data. In FIG. 48, the hatch is attached to a region where the output voltage is smaller than half of the maximum value and the output power is 75% or more of the maximum value. It is also possible to use a part or all of the C table data in the third example as the table data corresponding to the first table data.

As can be understood from the above description, the degree of freedom of the table data that can be selected as the reference table data is high. According to the characteristic conversion control, the electric output characteristic of the characteristic conversion circuit 600 can be made to follow the table data having such a high degree of freedom. Therefore, the characteristic conversion control has an advantage that the degree of freedom of the obtained electric output characteristics is high. This merit can reduce the restrictions of adoptable devices such as the fuel cell power generation system 40 and / or the DC power converter 20.

In the present embodiment, reference table data having the same contents is used in the characteristic conversion control relating to the plurality of characteristic conversion circuits 100. However, reference table data having different contents may be used for the characteristic conversion control for a certain characteristic conversion circuit 100 and the characteristic conversion control for another characteristic conversion circuit 100.

[Configuration example of characteristic conversion circuit 600 and control unit 670]
FIG. 49 shows a configuration example of the characteristic conversion circuit 600 and the control unit 670. In FIG. 49, the LC filter 61, the protection relay 62, and the diode 63 are not shown.

In this example, a feedback control loop using the characteristic conversion circuit 600 and the control unit 670 is configured. In this feedback control loop, the output current and output voltage of the characteristic conversion circuit 600 are reflected in the subsequent output current and output voltage of the characteristic conversion circuit 600.

The characteristic conversion circuit 600 shown in FIG. 49 includes a voltage-current control circuit 160 and a current sensor 128. The voltage / current control circuit 160 is a DCDC converter. In the example of FIG. 49, in the characteristic conversion control, the transformation ratio of the voltage / current control circuit 160 is adjusted so that the electrical output characteristic of the characteristic conversion circuit 600 follows the reference table data.

The current sensor 128 detects the output current of the characteristic conversion circuit 600. Specifically, the current sensor 128 detects the output current of the voltage-current control circuit 160. A value representing the output current based on this detection is given to the control unit 670.

Further, a value representing the output voltage of the characteristic conversion circuit 600 is given to the control unit 670. Specifically, a value representing the output voltage of the voltage-current control circuit 160 is given to the control unit 670.

The control unit 670 shown in FIG. 49 includes a voltage value acquisition unit 671, a current value acquisition unit 672, a memory 673, a comparison unit 674, a correction signal generation unit 675, and a drive unit 676.

Hereinafter, the operation of the components of the control unit 670 shown in FIG. 49 will be described with reference to the flowchart of FIG.

In step S1, the voltage value acquisition unit 671 acquires the voltage value V _val representing the output voltage of the characteristic conversion circuit 600.

In step S2, the current value acquisition unit 672 acquires the current value I _val representing the output current of the characteristic conversion circuit 600.

In step S3, the control unit 670 reads the reference table data from the memory 673. The reference table data in this example is data in which the output voltage and the output current of the characteristic conversion circuit 600 are associated with each other on a one-to-one basis.

In step S4, the comparison unit 674 compares the voltage value V _val and the current value I _val with the reference table data. Specifically, the comparison unit 674 specifies the output voltage corresponding to the output current of the characteristic conversion circuit 600 when the output current of the characteristic conversion circuit 600 is the current value I _{val from the reference table data.} Then, the comparison unit 674 calculates the difference ΔV between the corresponding output voltage and the voltage value V _val.

In step S5, the correction signal generation unit 675 generates a correction signal based on the difference ΔV. In this example, the correction signal is a voltage signal.

In step S6, the drive unit 676 drives the voltage / current control circuit 160 based on the correction signal. Specifically, the drive unit 676 drives the voltage-current control circuit 160 so that the voltage-current control circuit 160 performs DC-DC conversion at a transformation ratio based on the correction signal.

[First Specific Example of Characteristic Conversion Circuit 600 and Control Unit 670]
Hereinafter, the characteristic conversion circuit 600X and the control unit 670A, which are the first specific examples of the characteristic conversion circuit 600 and the control unit 670, will be described with reference to FIG. 51. In the following, the elements already described may be designated by the same reference numerals and the description thereof may be omitted. Further, in the following, the notation of voltage / current control circuit 160X may be used. The voltage-current control circuit 160X is a specific example of the voltage-current control circuit 160. These points are the same for the second specific example and the third specific example described later.

In this specific example, the current sensor 128 detects the output current of the characteristic conversion circuit 600 and outputs a sensor voltage V _s indicating the result of the detection. _{The current sensor 128 outputs the sensor voltage V s} as the output current of the characteristic conversion circuit 600 increases. That is, the sensor voltage V _s increases as the output current of the characteristic conversion circuit 600 increases. Such a current sensor 128 can be realized using, for example, a shunt resistor. _{The sensor voltage V s} output by the current sensor 128 is reflected in the control by the control unit 670A. The current sensor 128 may have the configuration shown in FIG.

In the specific example of FIG. 51, the characteristic conversion circuit 600X has a 14th resistor 691 and a 15th resistor 694, a light emitting diode 194, a phototransistor 195, and a power supply 193. The light emitting diode 194 and the phototransistor 195 constitute a photocoupler 196. The power supply 193 is typically a constant voltage source.

The current sensor 128, the 14th resistor 691, the light emitting diode 194, and the reference potential are connected in this order. The power supply 193, the 15th resistor 694, the phototransistor 195, and the reference potential are connected in this order.

In this specific example, _{a current corresponding to the sensor voltage V s} flows through the 14th resistor 691, the light emitting diode 194, and the reference potential in this order. By the action of the photocoupler 196, a current corresponding to this current flows in this order to the power supply 193, the 15th resistor 694, the phototransistor 195, and the reference potential. A voltage corresponding to this current appears at the connection point p2 of the 15th resistor 694 and the phototransistor 195, and is input to the current value acquisition unit 672. The current value acquisition unit 672 obtains the current value I _val based on the input voltage.

Further, in this specific example, the characteristic conversion circuit 600X has a twelfth resistor 681 and a thirteenth resistor 684, a light emitting diode 182, a phototransistor 185, and a power supply 183. The light emitting diode 182 and the phototransistor 185 constitute the photocoupler 186. The power supply 183 is typically a constant voltage source.

_{The portion where the output voltage V out} of the characteristic conversion circuit 600X appears, the 12th resistor 681, the light emitting diode 182, and the reference potential are connected in this order. The power supply 183, the 13th resistor 684, the phototransistor 185, and the reference potential are connected in this order.

In this specific example, _{a current corresponding to the output voltage V out} flows through the 12th resistor 681, the light emitting diode 182, and the reference potential in this order. By the action of the photocoupler 186, a current corresponding to this current flows in this order to the power supply 183, the 13th resistor 684, the phototransistor 185, and the reference potential. A voltage corresponding to this current appears at the connection point p1 of the 13th resistor 684 and the phototransistor 185, and is input to the voltage value acquisition unit 671. The voltage value acquisition unit 671 obtains a voltage value V _val based on the input voltage.

In this specific example, the control unit 670A is provided on the substrate 60. In the control unit 670A, as described with reference to FIG. 49, a correction signal is generated based on the _{voltage value V val} and the current value I _val.

The drive unit 676 has a high-side driver output terminal 149a and a low-side driver output terminal 149b. A drive pulse signal based on the correction signal is supplied to the voltage / current control circuit 160X from these terminals 149a and 149b. In this way, the voltage-current control circuit 160X is driven.

The voltage-current control circuit 160X constitutes an LLC converter. The configuration of the voltage-current control circuit 160X is as described in the first embodiment.

A drive pulse signal is supplied from the high-side driver output terminal 149a to the control terminal of the first switching element 162a. A drive pulse signal is supplied from the low-side driver output terminal 149b to the control terminal of the second switching element 162b. As a result, the switching elements 162a and 162b are alternately turned on and off by supplying drive pulse signals having opposite phases to each other.

The higher the frequency of the drive pulse signals supplied to the switching elements 162a and 162b, the smaller the ratio of the output voltage to the input voltage of the voltage-current control circuit 160X based on the LLC resonance. The frequency of the drive pulse signal is determined based on the correction signal.

[Second Specific Example of Characteristic Conversion Circuit 600 and Control Unit 670]
Hereinafter, the characteristic conversion circuit 600Y and the control unit 670B, which are the second specific examples of the characteristic conversion circuit 600 and the control unit 670, will be described with reference to FIG. 52.

In the second specific example, the control unit 670B is provided on the substrate 60 as in the first specific example. On the other hand, in the second specific example, unlike the first specific example, the drive unit is provided not in the control unit 670B but in the characteristic conversion circuit 600Y.

The characteristic conversion circuit 600Y includes a voltage dividing circuit 665 and a drive unit 679. The drive unit 679 includes a feedback current supply unit 130X and a current resonance control unit 140.

The voltage divider circuit 665 has a 16th resistor 611 and a 17th resistor 612.

_{In the voltage dividing circuit 665, the output voltage V out} of the characteristic conversion circuit 600 is divided by the 16th resistor 611 and the 17th resistor 612. This voltage dividing voltage appears at the connection point p3 of the resistors 611 and 612 and is input to the voltage value acquisition unit 671. The voltage value acquisition unit 671 obtains a voltage value V _val based on the input voltage.

On the other hand, the sensor voltage V _s is input to the current value acquisition unit 672. The current value acquisition unit 672 obtains the current value I _val based on the input voltage.

In the control unit 670B, as described with reference to FIG. 49, a correction signal is generated based on the _{voltage value V val} and the current value I _val. The correction signal is a voltage signal.

The operation of the feedback current supply unit 130X is defined by the correction signal. Specifically, the feedback current supply unit 130X includes a current supply power supply 131, a sixth resistor 132, and a first light emitting diode 135. The current flowing out from the current supply power supply 131 flows through the first light emitting diode 135. Specifically, the voltage of the correction signal output from the correction signal generation unit 675 defines the current flowing out from the current supply power supply 131. In the characteristic conversion circuit 600Y, the higher the current, the higher the oscillation frequency is defined, and the higher the oscillation frequency, the smaller the ratio of the output voltage to the input voltage of the voltage-current control circuit 160X, and the output to the input voltage of the characteristic conversion circuit 600X. It is configured so that the voltage ratio is small.

The configuration of the current resonance control unit 140 is as described in the first embodiment.

In the second specific example, as in the first specific example, the drive pulse signal is supplied from the high side driver output terminal 149a to the control terminal of the first switching element 162a. A drive pulse signal is supplied from the low-side driver output terminal 149b to the control terminal of the second switching element 162b. As a result, the switching elements 162a and 162b are alternately turned on and off by supplying drive pulse signals having opposite phases to each other.

In the second specific example, as in the first specific example, the higher the frequency of the drive pulse signal supplied to the switching elements 162a and 162b, the higher the frequency of the output voltage with respect to the input voltage of the voltage-current control circuit 160X based on the LLC resonance. The ratio becomes smaller. The frequency of the drive pulse signal is determined based on the correction signal.

In the second specific example, the larger the current flowing out from the current supply power supply 131, the smaller the ratio of the output voltage to the input voltage of the voltage-current control circuit 160. The current is defined by a correction signal, which is a voltage signal. In short, the control unit 670B generates a correction signal so that an appropriate current flows out from the current supply power supply 131 and the transformation ratio of the voltage / current control circuit 160X is appropriately set.

[Third Specific Example of Characteristic Conversion Circuit 600 and Control Unit 670]
Hereinafter, the characteristic conversion circuit 600Z and the control unit 670B, which are the third specific examples of the characteristic conversion circuit 600 and the control unit 670, will be described with reference to FIG. 53.

In the third embodiment, as in the first embodiment, the characteristic conversion circuit 600Z has a 14th resistor 691 and a 15th resistor 694, a light emitting diode 194, a phototransistor 195, and a power supply 193. The light emitting diode 194 and the phototransistor 195 constitute a photocoupler 196. In the third specific example, the current value acquisition unit 672 obtains the current value I _val in the same manner as in the first specific example.

Further, the third specific example has a twelfth resistor 681 and a thirteenth resistor 684, a light emitting diode 182, a phototransistor 185, and a power supply 183, as in the first specific example. The light emitting diode 182 and the phototransistor 185 constitute the photocoupler 186. In the third specific example, the voltage value acquisition unit 671 obtains the voltage value V _val in the same manner as in the first specific example.

In the third specific example, in the same manner as in the second specific example, the control unit 670B generates a correction signal based on the _{voltage value V val} and the current value I _val. The correction signal is a voltage signal.

In the third specific example, the drive unit 679 drives the voltage / current control circuit 160X based on the correction signal in the same manner as in the second specific example.

In the third specific example, the control unit 670B is provided in the fuel cell power generation system 40. The control unit 670B and the characteristic conversion circuit 600Z are connected by a harness extending between the fuel cell power generation system 40 and the substrate 60. The control unit 670B may be the controller 51.

Specific examples of the characteristic conversion circuit 600 of FIG. 49 are not limited to the characteristic conversion circuits 600X to 600Z of FIGS. 51 to 53. For example, the voltage-current control circuit 160 does not have to be an LLC converter, and a configuration in which the transformation ratio of the voltage-current control circuit 160 is adjusted by adjusting the duty ratio may be adopted. Specific examples of the control unit 670 are not limited to the control units 670A and 670B of FIGS. 51 to 53.

Various other modifications may also be applied to this disclosure. For example, the plurality of fuel cell power generation systems 40 do not have to have the same configuration. The plurality of substrates 60 do not have to have the same configuration. Each characteristic conversion circuit 100 does not have to be designed so that the "certain value" in the characteristic conversion control is the same. The plurality of photovoltaic power generation systems do not have to have the same configuration. The number of photovoltaic power generation systems in the electric power system may be one or three or more. The power system may not have a photovoltaic system. The number of distributed systems 30 may be two or four or more. The same applies to the number of fuel cell systems 40 and the number of characteristic conversion circuits. In addition to the specific load 259, there may be a load to which power is supplied from the DCDC converter 21. The DC power converter does not have to be built into the power station.

[effect]
As described above, the power system according to the first aspect of the present disclosure is
A power system including a plurality of distributed systems and one DCDC converter.
Each of the plurality of distributed systems has a fuel cell power generation system, a characteristic conversion circuit, and a diode.
When the operating mode of the power system is the superposition mode, at least two of the plurality of distributed systems take a specific output state.
In the distributed system in the specific output state,
The fuel cell power generation system outputs DC power to the characteristic conversion circuit,
The output voltage-output power characteristic of the characteristic conversion circuit is adjusted by the characteristic conversion control so that the output power of the characteristic conversion circuit is maximized when the output voltage of the characteristic conversion circuit is a certain value.
The characteristic conversion circuit is MPPT-controlled by the DCDC converter, and the characteristic conversion circuit outputs DC power to the DCDC converter via the diode.

The fuel cell power generation system can generate power even at night and can generate power for a long time. Extracting power from a plurality of fuel cell power generation systems and performing the power extraction via characteristic conversion control and MPPT control is suitable for extracting a large amount of power. Therefore, the electric power system according to the first aspect is suitable for extracting a large amount of electric power in an emergency.

In the second aspect of the present disclosure, for example, in the power system according to the first aspect,
When the operation mode of the power system is the switching mode,
Only one of the plurality of distributed systems may take the specific output state.
When the output voltage decreases due to an increase in the output current of the characteristic conversion circuit of the distributed system in the specific output state and becomes less than the output voltage of the characteristic conversion circuit of another distributed system, the specific output The state-taking distributed system may be switched to the other distributed system.

The switching mode of the second aspect is suitable for evenly sharing the power supply to the DCDC converter among a plurality of distributed systems.

In the third aspect of the present disclosure, for example, in the power system according to the second aspect,
The superimposition mode may be executed when the input power to the DCDC converter is larger than that of the switching mode.

According to the third aspect, the operation mode can be switched according to the input power to the DCDC converter.

In the fourth aspect of the present disclosure, for example, the power system according to any one of the first to third aspects includes a power station including the DCDC converter and a specific load to which power is input from the power station. You may have more
When the average power output to the DCDC converter in the specific output state is defined as the unit power, the difference obtained by subtracting the required power of the specific load from the input power to the power station is 0 or more and the said. The number of the distributed systems in the specific output state may be adjusted so as to be less than the unit power.

According to the fourth aspect, an appropriate amount of electric power can be input to the DCDC converter.

In the fifth aspect of the present disclosure, for example, in the power system according to any one of the first to fourth aspects, a specific load to which power is input from the DCDC converter and a storage storage to which power is input from the DCDC converter. The device may be further provided.

According to the fifth aspect, when excess power is input to the DCDC converter, the surplus can be temporarily stored in the power storage device and used later.

In the sixth aspect of the present disclosure, for example, the power system according to any one of the first to fifth aspects may further include a specific load to which power is input from the DCDC converter.
When a power failure occurs, at least one of the plurality of distributed systems may start a power failure output in which power is output to the specific load via the DCDC converter in the specific output state.

According to the sixth aspect, power can be supplied to a specific load in the event of a power failure.

In the seventh aspect of the present disclosure, for example, in the power system according to the sixth aspect,
Each of the plurality of distributed systems may include a distributed load to which power is input from the fuel cell power generation system.
In the wake of a power outage, the fuel cell power generation system may impose restrictions on the power supply from the fuel cell power generation system to the distributed load in the at least two distributed systems.

In the seventh aspect, it is easy to secure the required power of a specific load in the output at the time of a power failure.

In the eighth aspect of the present disclosure, for example, in the electric power system according to any one of the first to seventh aspects.
In the plurality of distributed systems, the difference between the characteristic conversion circuit having the maximum value and the characteristic conversion circuit having the minimum value may be 20 V or less.

When the difference of "a certain value" is small to the extent specified in the eighth aspect, it is easy to carry out the superposition mode.

In the ninth aspect of the present disclosure, for example, in the electric power system according to any one of the first to eighth aspects.
The characteristic conversion control is an output voltage-output current characteristic in which the output voltage of the characteristic conversion circuit decreases as the output current of the characteristic conversion circuit increases in a region where the output voltage of the characteristic conversion circuit is larger than a certain value. You may bring it.

The output voltage-output current characteristic of the ninth aspect is a typical example of the output voltage-output current characteristic brought about by the characteristic conversion circuit. Also, such output voltage-output current characteristics are suitable for executing the switching mode.

The power extraction method according to the tenth aspect of the present disclosure is
Each of the plurality of distributed systems includes a plurality of distributed systems and one DCDC converter, and each of the plurality of distributed systems is a power extraction method using a power system having a fuel cell power generation system, a characteristic conversion circuit, and a diode.
In at least two of the plurality of distributed systems
The fuel cell power generation system outputs DC power to the characteristic conversion circuit, and
The output voltage-output power characteristic of the characteristic conversion circuit is adjusted by the characteristic conversion control so that the output power of the characteristic conversion circuit is maximized when the output voltage of the characteristic conversion circuit is a certain value. ,
The characteristic conversion circuit is MPPT controlled by the DCDC converter, and
The characteristic conversion circuit outputs DC power to the DCDC converter via the diode at the same time.

According to the tenth aspect, the same effect as that of the first aspect can be obtained.

The tenth aspect may be combined with the techniques of the second to ninth aspects.

The electric power system according to the present disclosure is applicable to apartment houses and the like.

10 Power station 11,43 DC bus 12,21,22,23,42 DCDC converter 13,44 Inverter 20 DC power converter 25 Power storage device 30, 30A, 30B, 30C Distributed system 31A, 31B Solar power generation system 36 Solar Power generation panel 40, 40A, 40B, 40C Fuel cell power generation system 41 Fuel cell 51 Controller 60, 60A, 60B, 60C Board 61 LC filter 62 Protection relay 63, 63A, 63B, 63C, 166a, 166b Diode 100, 100X, 190 , 190X, 200, 200X, 290, 290X, 300, 400, 400X, 500, 500X, 600, 600X, 600Y, 600Z Characteristic conversion circuits 105, 205, 305, 405, 505, 605 Power systems 110, 120, 210, 220,310,320 Feedback circuits 111,112,113,121,122,123,132,141,143,191,196,611,612,681,684,691,694, R1, R2, R3, FR1, FR2 , FR3, FR4, VR1,421,422,550 Resistance 115,125,425 Shunt regulator 115A, 125A, 425A Anode 115K, 125K, 425K Cone 115a, 125a, 425a Reference voltage terminal 115о, 124, 126, 125о, 175, 425о Operational amplifier 115t, 125t, 127,425t Transistor 170,180 Regulator 128 Current sensor 128a Sensor output unit 128r Shunt resistance 128s Current sense amplifier 129, 131, 183, 193 Power supply 130, 130X, 195, 195X Feedback current supply unit 135, 182,192,194 Light emitting diode 140,199 Current resonance control unit 142,161,163a, 163b, 164,167 Capacitor 145,185,195,197 Phototransistor 146 control IC
147 Constant current source 148, 149a, 149b Terminal 150, 186, 196, 198 Photocoupler 160, 160X Voltage / current control circuit 162a, 162b Switching element 165 Transformer 165a, 165b, 165c Winding 170a, 665 Voltage divider circuit 170b Amplifier circuit 250A , 250B, 250C, 259 Load 410, 420, 510, 520 Circuit 420a Sensor voltage adjustment circuit 420b Voltage current conversion circuit 670 Control unit 671 Voltage value acquisition unit 672 Current value acquisition unit 673 Memory 674 Comparison unit 675 Correction signal generation unit 676 679 Drive unit p1, p2, p3, ps Connection point

Claims (10)

A power system including a plurality of distributed systems and one DCDC converter.
Each of the plurality of distributed systems has a fuel cell power generation system, a characteristic conversion circuit, and a diode.
When the operating mode of the power system is the superposition mode, at least two of the plurality of distributed systems take a specific output state.
In the distributed system in the specific output state,
The fuel cell power generation system outputs DC power to the characteristic conversion circuit,
The output voltage-output power characteristic of the characteristic conversion circuit is adjusted by the characteristic conversion control so that the output power of the characteristic conversion circuit is maximized when the output voltage of the characteristic conversion circuit is a certain value.
The characteristic conversion circuit is MPPT-controlled by the DCDC converter, and the characteristic conversion circuit outputs DC power to the DCDC converter via the diode.
Power system. When the operation mode of the power system is the switching mode,
Only one of the plurality of distributed systems takes the specific output state and
When the output voltage decreases due to an increase in the output current of the characteristic conversion circuit of the distributed system in the specific output state and becomes less than the output voltage of the characteristic conversion circuit of another distributed system, the specific output The state-taking distributed system switches to the other distributed system.
The power system according to claim 1. The superimposition mode is executed when the input power to the DCDC converter is larger than that of the switching mode.
The power system according to claim 2. A power station including the DCDC converter and
With a specific load to which power is input from the power station,
With more
When the average power output to the DCDC converter in the specific output state is defined as the unit power, the difference obtained by subtracting the required power of the specific load from the input power to the power station is 0 or more and the said. The number of the distributed systems in the specific output state is adjusted so that the power is less than the unit power.
The electric power system according to any one of claims 1 to 3. A specific load to which power is input from the DCDC converter,
A power storage device to which power is input from the DCDC converter, and
Further prepare,
The electric power system according to any one of claims 1 to 4. Further equipped with a specific load to which power is input from the DCDC converter,
When a power failure occurs, at least one of the plurality of distributed systems starts a power failure output in which power is output to the specific load via the DCDC converter in the specific output state.
The electric power system according to any one of claims 1 to 5. Each of the plurality of distributed systems includes a distributed load to which power is input from the fuel cell power generation system.
In the wake of a power outage, the fuel cell power generation system imposes restrictions on the power supply from the fuel cell power generation system to the distributed load in the at least two distributed systems.
The power system according to claim 6. In the plurality of distributed systems, the difference between the characteristic conversion circuit having the maximum value and the characteristic conversion circuit having the minimum value is 20 V or less.
The electric power system according to any one of claims 1 to 7. The characteristic conversion control is an output voltage-output current characteristic in which the output voltage of the characteristic conversion circuit decreases as the output current of the characteristic conversion circuit increases in a region where the output voltage of the characteristic conversion circuit is larger than a certain value. Bring, bring
The electric power system according to any one of claims 1 to 8. Each of the plurality of distributed systems includes a plurality of distributed systems and one DCDC converter, and each of the plurality of distributed systems is a power extraction method using a power system having a fuel cell power generation system, a characteristic conversion circuit, and a diode.
In at least two of the plurality of distributed systems
The fuel cell power generation system outputs DC power to the characteristic conversion circuit, and
The output voltage-output power characteristic of the characteristic conversion circuit is adjusted by the characteristic conversion control so that the output power of the characteristic conversion circuit is maximized when the output voltage of the characteristic conversion circuit is a certain value. ,
The characteristic conversion circuit is MPPT controlled by the DCDC converter, and
The characteristic conversion circuit outputs DC power to the DCDC converter via the diode at the same time.
Power extraction method.

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