JP7002011B2 - Power system and its control method - Google Patents

Description

The present disclosure relates to electric power systems and methods thereof.

A power system is known that can generate DC power, convert DC power into AC power with an inverter, reverse power flow to the grid power source, and supply AC power to a load. For example, Patent Document 1 describes such a power system. Patent Document 1 describes that when a system power supply fails, DC power is supplied from the fuel cell power generation system to the inverter, the DC power is converted into AC power by the inverter, and the AC power is used as a load.

Japanese Unexamined Patent Publication No. 2017-117673

The present disclosure provides a technique suitable for terminating the DC power supply from the fuel cell power generation system to the inverter when the grid power supply is restored.

This disclosure is
It is a power system that is connected to the grid power supply.
A fuel cell power generation system having a fuel cell, a power receiving unit, and an AC load connected to the power receiving unit.
Inverters that convert DC power to AC power,
A current detection unit that transmits a signal representing a measured value of the current detection unit to the fuel cell power generation system, and a current detection unit.
A first distribution board having a first branch portion including a plurality of branch breakers, a secondary interconnection breaker, and the like.
A second distribution board with a second branch containing multiple branch breakers,
It has a plurality of input units including a grid power input unit and an independent power input unit, and a power output unit.
A power switching unit for switching which of the plurality of input units is connected to the power output unit is provided.
A DC output path that guides DC power from the fuel cell power generation system to the inverter,
A path for independent operation that guides AC power from the inverter to the independent power input unit,
A grid power supply path that guides AC power from the grid power supply to the grid power input section via the connection point, the current detection section, and the first branch section in this order.
A route to the power receiving unit that guides AC power from the power output unit to the power receiving unit via the second branch unit, and
A reverse power flow path that guides AC power from the inverter to the grid power supply via the connection point, and
An AC output path for guiding AC power from the fuel cell power generation system to the first branch portion via the secondary interconnection breaker is provided.
When the system power supply fails, DC power is supplied from the fuel cell power generation system to the inverter via the DC output path, DC-AC conversion by the inverter, and the path for independent operation and the power from the inverter. AC power supply to the second distribution board via the switching unit is performed, and
When the condition that the measured value of the current detection unit is a value indicating that the system power supply is restored when the power is consumed by the AC load is defined as the first condition.
When the first condition is satisfied M1 times, the DC power supply is terminated.
Provides a power system.
Here, M1 is a natural number of 1 or more.

The technique according to the present disclosure is suitable for terminating the supply of DC power from the fuel cell power generation system to the inverter when the system power supply is restored.

FIG. 1 is a block diagram of an electric power system at the time of grid interconnection. FIG. 2 is a block diagram of an electric power system at the time of a power failure. FIG. 3 is a diagram for explaining the VP characteristics obtained by the characteristic conversion circuit. FIG. 4 is a diagram showing an example of a characteristic conversion circuit. FIG. 5 is a diagram for explaining a current sensor. FIG. 6 is a diagram for explaining the first shunt regulator. FIG. 7 is a diagram for explaining the second shunt regulator. FIG. 8 is a flowchart for explaining a specific example of control. FIG. 9 is a diagram showing a specific example of the characteristic conversion circuit. FIG. 10 is a diagram showing another example of the characteristic conversion circuit. FIG. 11 is a diagram showing another specific example of the characteristic conversion circuit.

(Findings underlying this disclosure)
A power system that can generate DC power, convert DC power to AC power with an inverter, reverse power flow to the grid power supply, and supply it to the load, including a fuel cell power generation system. think of. In such a power system, power is supplied to the load from the fuel cell power generation system via the inverter when the system power supply fails, and power is reverse-flowed from another power generation system to the system power supply via the inverter when the system power supply does not have a power failure. Can be made to. In such a case, it is conceivable to configure the power system so that an electric path connecting the inverter and the load is established in the event of a power failure and an electric path connecting the inverter and the grid power supply is established in the event of a non-power failure. .. As another power generation system described above, for example, a solar power generation system can be adopted.

In the power system configured in this way, power can be supplied to the load by taking advantage of the fuel cell power generation system that power can be generated regardless of the weather in the event of a power failure of the grid power supply. On the other hand, when the grid power supply is not out of power, the user of the power system can enjoy the financial merit by reverse-feeding the power generated by the other power generation system to the grid power supply.

In the power system configured as described above, it is convenient for the user to continuously supply power to the load from the fuel cell power generation system from the occurrence of a power failure to the recovery of power. However, if the DC power supply from the fuel cell power generation system to the inverter is continued even though the electric path connecting the inverter and the grid power supply is established due to the power restoration, the fuel cell power generation system will be switched to the grid power supply. There is a risk of reverse current of electricity. Therefore, the present inventors have studied a technique suitable for terminating the supply of DC power from the fuel cell power generation system to the inverter when the system power supply is restored.

(Summary of one aspect pertaining to this disclosure)
The electric power system according to the first aspect of the present disclosure is
It is a power system that is connected to the grid power supply.
A fuel cell power generation system having a fuel cell, a power receiving unit, and an AC load connected to the power receiving unit.
Inverters that convert DC power to AC power,
A current detection unit that transmits a signal representing a measured value of the current detection unit to the fuel cell power generation system, and a current detection unit.
A first distribution board having a first branch portion including a plurality of branch breakers, a secondary interconnection breaker, and the like.
A second distribution board with a second branch containing multiple branch breakers,
It has a plurality of input units including a grid power input unit and an independent power input unit, and a power output unit.
A power switching unit for switching which of the plurality of input units is connected to the power output unit is provided.
A DC output path that guides DC power from the fuel cell power generation system to the inverter,
A path for independent operation that guides AC power from the inverter to the independent power input unit,
A grid power supply path that guides AC power from the grid power supply to the grid power input section via the connection point, the current detection section, and the first branch section in this order.
A route to the power receiving unit that guides AC power from the power output unit to the power receiving unit via the second branch unit, and
A reverse power flow path that guides AC power from the inverter to the grid power supply via the connection point, and
An AC output path for guiding AC power from the fuel cell power generation system to the first branch portion via the secondary interconnection breaker is provided.
When the system power supply fails, DC power is supplied from the fuel cell power generation system to the inverter via the DC output path, DC-AC conversion by the inverter, and the path for independent operation and the power from the inverter. AC power supply to the second distribution board via the switching unit is performed, and
When the condition that the measured value of the current detection unit is a value indicating that the system power supply is restored when the power is consumed by the AC load is defined as the first condition.
When the first condition is satisfied M1 times, the DC power supply is terminated.
Here, M1 is a natural number of 1 or more.

The technique according to the first aspect is suitable for terminating the DC power supply from the fuel cell power generation system to the inverter when the grid power supply is restored.

In the second aspect of the present disclosure, for example, in the power system according to the first aspect,
The M1 detection may be a plurality of continuous detections.

According to the second aspect, the DC power supply can be terminated when the system power supply is likely to be restored.

In the third aspect of the present disclosure, for example, the electric power system according to the first or second aspect is
When the condition that the measured value of the current detection unit is a value indicating that the system power supply is restored when the power is not consumed by the AC load is defined as the second condition.
Even when M2 continuous detection that the second condition is satisfied is performed, the DC power supply may be terminated.
When the second condition is detected once but the M2 continuous detection is not performed, the AC load may consume power.
Here, M2 is a natural number of 2 or more.

According to the third aspect, when it can be confirmed by using the second condition that the grid power supply is likely to be restored, the DC power supply is performed without consuming the power by the AC load of the fuel cell power generation system. Can be terminated.

In the fourth aspect of the present disclosure, for example, the electric power system according to any one of the first to third aspects is
When the condition that the voltage input to the fuel cell power generation system through the AC output path is a value indicating that the system power supply is restored is defined as the third condition.
Even when the continuous detection of M3 times that the third condition is satisfied is performed, the DC power supply may be terminated.
When the third condition is detected once but the M3 continuous detection is not performed, the AC load may consume power.
Here, M3 is a natural number of 2 or more.

According to the fourth aspect, when it can be confirmed by using the third condition that the grid power supply is likely to be restored, the DC power supply is performed without consuming the power by the AC load of the fuel cell power generation system. Can be terminated.

In the fifth aspect of the present disclosure, for example, the electric power system according to any one of the first to the fourth aspects is
Further equipped with a photovoltaic system with photovoltaic panels,
A path for guiding DC power from the photovoltaic power generation system to the inverter may be provided.

The electric power system of the fifth aspect is a specific example of the electric power system.

In the sixth aspect of the present disclosure, for example, the electric power system according to any one of the first to fifth aspects is
It may be further equipped with a power storage device,
A path for guiding DC power from the power storage device to the inverter may be provided.

The power system of the sixth aspect is a specific example of the power system.

In the seventh aspect of the present disclosure, for example, the electric power system according to any one of the first to sixth aspects is
A photovoltaic system with a photovoltaic panel and
It may be further equipped with a power storage device,
A route for guiding DC power from the photovoltaic power generation system to the power storage device,
A route for guiding DC power from the fuel cell power generation system to the power storage device,
May be provided.

According to the seventh aspect, the power storage device can be charged not only from the photovoltaic power generation system but also from the fuel cell power generation system.

In the eighth aspect of the present disclosure, for example, the electric power system according to any one of the first to seventh aspects is
A photovoltaic system with a photovoltaic panel and
Power storage device and
You may also have an outlet,
A route for guiding power from the photovoltaic power generation system to the outlet via the inverter, the path for independent operation, the power switching unit, and the second branch portion in this order.
A route for guiding electric power from the fuel cell power generation system to the outlet via the inverter, the path for independent operation, the power switching unit, and the second branch portion in this order.
A path for guiding power from the power storage device to the outlet via the inverter, the path for independent operation, the power switching unit, and the second branch portion in this order may be provided.

According to the eighth aspect, the power can be supplied from the fuel cell power generation system to the outlet to which the power is supplied from the photovoltaic power generation system and the power storage device. This is useful in the event of a power outage for the following reasons: That is, the photovoltaic power generation system cannot generate electricity at night or in the rain. Assuming that power cannot be supplied to the outlet from the fuel cell power generation system, the period during which power can be taken out from the outlet is limited based only on the power storage device when a power failure continues at night or in rainy weather. On the other hand, in the eighth aspect, since electric power can be supplied to the outlet from the fuel cell power generation system, the period can be extended. When a power outage continues at night or in the rain, it is convenient for the user to be able to take out power from one outlet for a long time without replacing it with another outlet.

In the ninth aspect of the present disclosure, for example, in the power system according to the eighth aspect.
A path for guiding power from the power storage device to the power receiving unit may be provided via the inverter, the path for independent operation, the power switching unit, and the second branching unit in this order.

As understood from the above description of the eighth aspect, the power storage device of the eighth aspect functions as an emergency power source capable of supplying electric power to the outlet in the event of a power failure. The power storage device of the ninth aspect also functions as an emergency power source capable of supplying electric power to the power receiving unit of the fuel cell power generation system in the event of a power failure. According to the ninth aspect, the dedicated power source for starting the fuel cell power generation system in the event of a power failure can be omitted.

The control method according to the tenth aspect of the present disclosure is
A fuel cell power generation system having a fuel cell, a power receiving unit, and an AC load connected to the power receiving unit.
Inverters that convert DC power to AC power,
A current detection unit that transmits a signal representing a measured value of the current detection unit to the fuel cell power generation system, and a current detection unit.
A first distribution board having a first branch portion including a plurality of branch breakers, a secondary interconnection breaker, and the like.
A second distribution board with a second branch containing multiple branch breakers,
It has a plurality of input units including a grid power input unit and an independent power input unit, and a power output unit.
A power switching unit for switching which of the plurality of input units is connected to the power output unit is provided.
A DC output path that guides DC power from the fuel cell power generation system to the inverter,
A path for independent operation that guides AC power from the inverter to the independent power input unit,
A grid power supply path that guides AC power from the grid power supply to the grid power input section via the connection point, the current detection section, and the first branch section in this order.
A route to the power receiving unit that guides AC power from the power output unit to the power receiving unit via the second branch unit, and
A reverse power flow path that guides AC power from the inverter to the grid power supply via the connection point, and
An AC output path for guiding AC power from the fuel cell power generation system to the first branch portion via the secondary interconnection breaker is provided.
When the system power supply fails, DC power is supplied from the fuel cell power generation system to the inverter via the DC output path, DC-AC conversion by the inverter, and the path for independent operation and the power from the inverter. It is a control method of a power system in which AC power is supplied to the second distribution board via a switching unit.
When the condition that the measured value of the current detection unit is a value indicating that the system power supply is restored when the power is consumed by the AC load is defined as the first condition.
This includes terminating the DC power supply when the M1 detection that the first condition is satisfied is made.
Here, M1 is a natural number of 1 or more.

The technique according to the tenth aspect is suitable for terminating the DC power supply from the fuel cell power generation system to the inverter when the system power supply is restored.

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 connection point is not used to mean that the first connection point and the second connection point always exist together with the third connection point.

In embodiments, the term route may be used. The route can have multiple lines. The same applies to connection points and the like. For example, a single-phase three-wire path has two ungrounded lines and one grounded line. It should be understood that the point of connection between single-phase, three-wire paths is used to indicate a range of regions, including where each line is connected in the path.

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

(Embodiment)
1 and 2 are block diagrams of the electric power system 300 according to the present embodiment. Specifically, FIG. 1 shows an example of power flow during grid interconnection. FIG. 2 shows an example of power flow during a power outage. In these figures, the solid line indicates that electric power is flowing through the electric circuit. The dotted line indicates that electric power is not flowing in the electric circuit. Further, V _AC1 and V _AC2 represent AC voltage. The effective value of the AC voltage V _AC1 is smaller than the effective value of the AC voltage V _AC2 . The effective value of the AC voltage V _AC1 is, for example, 100V. The effective value of the AC voltage V _AC2 is, for example, 200V. In this example, the electric circuit or path of the AC voltage V _AC1 is realized by two single-phase two-wire electric wires. Further, the electric circuit or path of the AC voltage V _AC2 is realized by two ungrounded lines out of three single-phase three-wire electric wires.

The power system 300 is interconnected with the grid power supply 200. The power system 300 may be supplied with power from the grid power supply 200. Further, the power system 300 can reverse power flow to the system power supply 200. The power system 300 includes a power station 10, a fuel cell power generation system 40, a substrate 60, a photovoltaic power generation system 31 and 32, a power storage device 25, a power switching unit 28, a first distribution board 80, and a first. It has a 2-distribution board 90, loads 251,252 and 253, an outlet 260, and a current detection unit 27. Hereinafter, the first distribution board 80 may be referred to as a main distribution board 80. Further, the second distribution board 90 may be referred to as an independent distribution board 90.

[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 31 and 32 and the fuel cell power generation system 40. 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 system 40. DC power is input to the second DCDC converter 22 from the first photovoltaic power generation system 31. DC power is input to the third DCDC converter 23 from the second photovoltaic power generation system 32. 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 different voltages 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 DC power into AC power. Specifically, the first inverter 13 converts the DC power input from the first DC bus 11 into AC power having a voltage V _AC1 or a voltage V _AC2 . When the AC power of the voltage V _AC1 is obtained by the first inverter 13, the power is supplied to the power switching unit 28. When AC power of voltage V _AC2 is obtained by the first inverter 13, the power is supplied to the main distribution board 80.

The first inverter 13 can also convert the AC power of the voltage V _AC2 input from the system power supply 200 via the main distribution board 80 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 31 and 32]
In the present embodiment, the power system 300 includes at least one photovoltaic power generation system that maximizes the 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 31 and 32 correspond to photovoltaic power generation systems in which the output power is maximized when the output voltage is within a predetermined range. The first photovoltaic power generation system 31 has at least one photovoltaic power generation panel 36. The first photovoltaic power generation system 31 generates electricity using the at least one photovoltaic power generation panel 36. The second photovoltaic power generation system 32 has at least one photovoltaic power generation panel 37. The second photovoltaic power generation system 32 generates electricity using the at least one photovoltaic power generation panel 37. The DC power generated by the photovoltaic power generation systems 31 and 32 is supplied to the DC power converter 20.

[Fuel cell power generation system 40]
The fuel cell power generation system 40 is a system that generates power using the fuel cell 41. The DC power generated by the fuel cell power generation system 40 can be supplied to the DC power conversion device 20. The AC power generated by the fuel cell power generation system 40 can be supplied to the main distribution board 80.

The fuel cell power generation system 40 includes a fuel cell 41, a fifth DCDC converter 42, a second DC bus 43, a second inverter 44, a sixth DCDC converter 45, a heater 46, a hot water storage unit 47, a control unit 51, and the like. It has a low voltage power supply 52, an auxiliary power supply 55, an AC load 56, a voltage detection circuit 57, a current detection circuit 58, and a power receiving unit 59. Hereinafter, the auxiliary power supply 55 may be referred to as a D1 power supply 55. In the present embodiment, the control unit 51 is a micro control unit (MCU).

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

The second inverter 44 converts the DC power input from the second DC bus 43 into AC power having a voltage V _AC2 . The AC power obtained by the second inverter 44 is supplied to the main distribution board 80.

The sixth DCDC converter 45 converts the DC power input from the second DC bus 43 into DC power having different voltages. In this example, the sixth DCDC converter 45 steps down the DC power input from the second DC bus 43.

The heater 46 heats water using the DC power converted by the sixth DCDC converter 45. The warmed water (hereinafter, may be referred to as hot water) is stored in the hot water storage unit 47.

It is assumed that when the generated power of the fuel cell 41 is larger than the required load of the output destination of the second inverter 44, the fuel cell power generation system 40 outputs all the generated power of the fuel cell 41 from the second inverter 44. In that case, of the electric power output from the second inverter 44, the portion exceeding the required load (hereinafter, may be referred to as surplus electric power) is reverse-fed to the system power supply 200. In order to avoid reverse power flow, in this example, when the power obtained by adding a predetermined margin to the surplus power is larger than zero, the power is supplied from the second DC bus 43 to the heater 46 via the sixth DCDC converter 45. That is, the sixth DCDC converter 45 is for surplus power. Further, the heater 46 warms the water and prevents reverse power flow.

The AC load 56 is a load driven by the AC voltage V _AC1 . In this example, the AC load 56 is an auxiliary machine of the fuel cell power generation system 40, specifically, a heater.

The control unit 51 controls the DCDC converters 42 and 45, the second inverter 44, and the protection relay 62 described later. The low-voltage power supply 52 supplies power for control to the control unit 51, the protection relay 62, and the characteristic conversion circuit 100 described later. The D1 power source 55 is used to operate auxiliary equipment of the fuel cell power generation system 40 such as a pump, a blower, and a valve. Further, the control unit 51 receives signals from the voltage detection circuit 57 and the current detection circuit 58.

[Board 60]
The substrate 60 is provided on a path connecting the fuel cell power generation system 40 and the power station 10. DC power is supplied to the substrate 60 from the fuel cell power generation system 40, specifically, from the second DC bus 43. The substrate 60 includes a characteristic conversion circuit 100, an LC filter 61, and a protection relay 62.

As is clear from the above description, the characteristic conversion circuit 100 is provided on the path connecting the fuel cell power generation system 40 and the DC power conversion device 20, specifically, on the DC power path. The characteristic conversion circuit 100 of the present embodiment includes a first feedback circuit 110 and a second feedback circuit 120. 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 value within a predetermined range when the output power of the characteristic conversion circuit 100 reaches its peak. Used to do. 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 conversion device 20 from being damaged due to an overvoltage input from the fuel cell power generation system 40 to the DC power conversion device 20.

The DC power conversion device 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 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 transmitted from the characteristic conversion circuit 100 to the DC power conversion device 20 is stopped. Therefore, it is possible to prevent the power transmitted from the characteristic conversion circuit 100 to the DC power conversion device 20 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 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 DC power conversion device 20.

The characteristic conversion circuit 100 of this example will be further described with reference to FIG. In FIG. 3, 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. 3, 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. Due to 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.

The value within the above predetermined range 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 (in this example, the voltage in the second DC bus 43) 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 above-mentioned predetermined range includes an actual machine reference range which is within ± 20 V of the output voltage of the photovoltaic power generation system 31 or 32 when the output power of the photovoltaic power generation system 31 or 32 peaks. The second feedback circuit 120 is used to adjust the output voltage at the maximum power point of the characteristic conversion circuit 100 to a value within the reference range of the actual machine. If the PV system 31 or 32 used in the power system 300 is known, the power system 300 can be designed so that MPPT control for the PV system can be performed. That is, the above predetermined range can be set so as to include the actual machine reference range. Further, the characteristic conversion circuit 100 can be designed so that the output voltage at the maximum power point of the characteristic conversion circuit 100 is adjusted to a value within the reference range of the actual machine. The power system 300 of this example is advantageous from the viewpoint of ease of design.

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 MPPT control. The second DCDC converter 22 changes the output voltage of the first photovoltaic power generation system 31 by MPPT control. The third DCDC converter 23 changes the output voltage of the second photovoltaic power generation system 32 by MPPT control. As described above, in this example, the multi-string type DC power conversion device 20 that individually MPPT controls the photovoltaic power generation systems 31 and 32 and the characteristic conversion circuit 100 is realized. However, the DC power conversion device may be a centralized type that collectively controls MPPT.

FIG. 4 shows an example of the characteristic conversion circuit 100. The characteristic conversion circuit 100 of FIG. 4 includes a first feedback circuit 110, a second feedback circuit 120, a feedback current supply unit 130, and a voltage / current control circuit 160.

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 constant voltage source 131 and a sixth resistor 132.

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 representing 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. 5 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 the current I _load flows through the shunt resistor 128r, the 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 resistance 111 and the second resistance 112. The divided voltage appears at the connection point p1 of the first resistance 111 and the second resistance 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 constant voltage source 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. 4, the first current i1 is a 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 resistance 121 and the fourth resistance 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 resistance 123 and the fourth resistance 122. A 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 constant voltage source 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. 4, the second current i2 is the current flowing downward in the second shunt regulator 125 in the drawing.

In the region where the output current of the characteristic conversion circuit 100 is small, the second current becomes substantially zero, and the current flowing out from the constant voltage source 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 constant voltage source 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.

The voltage / current control circuit 160 is a DCDC converter. 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 value within the above predetermined range. .. 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 constant voltage source 131 increases. In this way, the characteristic conversion circuit 100 is adapted to adjust the above ratio according to the current flowing out from the constant voltage source 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 115s to a voltage higher than the voltage of the first anode 115A 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 becomes the control terminal 115 tk. A current flows, and the first current i1 flows from the first cathode 115K to the first anode 115A via the cathode side terminal 115ta and the anode side terminal 115tb in this order. In the example of FIG. 6, 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 115tc, specifically, the base current, is ignored as being sufficiently small.

Based on the explanation with reference to FIG. 6, the operation of the first feedback circuit 110 can be described as follows. As the output voltage V _out of the characteristic conversion circuit 100 increases, the first reference voltage V _ref1 increases. In the first shunt regulator 115, the larger the deviation of the first reference voltage V _ref1 from the first reference voltage V _s1 due to the larger first reference voltage V _ref1 , the larger the first current i1 becomes. When the first current i1 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 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. 7. 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 becomes the control terminal 125 tc. A current flows, and a second current i2 flows from the second cathode 125K to the second anode 125A via the cathode side terminal 125ta and the anode side terminal 125tb in this order. In the example of FIG. 7, 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 ct, specifically, the base current, is ignored as being sufficiently small.

Based on the explanation with reference to FIG. 7, 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 larger the deviation of the second reference voltage V _ref2 from the second reference voltage V _s2 due to the larger second reference voltage V _ref2 , the larger the second current i2. 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 flows. 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 resistance 122. This means that when the current flowing through the fifth resistance 123 toward the second connection point p2 increases, the current flowing through the third resistance 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 becomes large, the voltage generated by the third resistance 121 becomes small while the voltage of 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. 3, 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.

Returning to FIGS. 1 and 2, 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 and the protection relay 62.

[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.

[Current detection unit 27]
The current detection unit 27 has at least one current sensor. Specifically, the current detection unit 27 is composed of at least one current sensor. The current sensor is, for example, a current transformer. The current detection unit 27 can be used for power failure detection and power recovery detection of the system power supply 200. The current detection unit 27 transmits a signal representing the measured value of the current detection unit 27 to the fuel cell power generation system 40. Specifically, the current detection unit 27 transmits the above signal to the current detection circuit 58. In the illustrated example, the current detection unit 27 and the fuel cell power generation system 40 (specifically, the current detection circuit 58) are connected by wire. However, these may be connected wirelessly.

[Main distribution board 80]
The main distribution board 80 includes an interconnection breaker 81, a main breaker 82, a secondary interconnection breaker 83, and a first branch portion 85. The first branch portion 85 includes a plurality of branch breakers. In this example, the first branch 85 includes branch breakers 85a, 85b and 85c.

The main breaker 82 is connected to the system power supply 200 by the upstream electric circuit 88. The upstream electric circuit 88 is connected to the downstream electric circuit 89 via the main breaker 82.

A secondary interconnection breaker 83 is connected to the downstream electric circuit 89. The secondary interconnection breaker 83 is provided on a path connecting the main breaker 82 and the second inverter 44. The secondary interconnection breaker 83 is electrically connected to the first branch portion 85.

The first branch portion 85 is also connected to the downstream electric circuit 89. The branch breaker 85a of the first branch portion 85 is provided on a path connecting the main breaker 82 and the system power input unit 28a of the power switching unit 28. The branch breaker 85b is provided on a path connecting the main breaker 82 and the second load 252. The branch breaker 85c is provided on a path connecting the main breaker 82 and the third load 253.

The upstream electric circuit 88 has a third connection point p3. The interconnection breaker 81 is provided on a path connecting the third connection point p3 and the first inverter 13. A current detection unit 27 is provided at a position between the third connection point p3 and the main circuit breaker 82 in the upstream electric circuit 88.

In this example, AC power of voltage V _AC2 can be supplied from the system power supply 200 to the main breaker 82 via the third connection point p3. AC power of voltage V _AC2 can be supplied from the grid power supply 200 to the first inverter 13 via the third connection point p3 and the interconnection breaker 81 in this order. AC power of voltage V _AC2 can be reverse-flowed from the first inverter 13 to the system power supply 200 via the interconnection breaker 81 and the third connection point p3 in this order. AC power of voltage V _AC2 can be supplied from the first inverter 13 to the main breaker 82 via the interconnection breaker 81 and the third connection point p3 in this order. AC power of voltage V _AC2 can be supplied to the secondary interconnection breaker 83 from the second inverter 44. AC power of voltage V _AC1 can be supplied from the branch breaker 85a to the power switching unit 28. AC power of voltage V _AC1 can be supplied from the branch breaker 85b to the second load 252. AC power of voltage V _AC2 can be supplied from the branch breaker 85c to the third load 253.

[Power switching unit 28]
The power switching unit 28 has a plurality of input units and a power output unit 28c. The plurality of input units include a grid power input unit 28a and an independent power input unit 28b. The power switching unit 28 switches which of the plurality of input units is connected to the power output unit 28c. In this example, the power switching unit 28 switches which of the grid power input unit 28a and the self-sustaining power input unit 28b is connected to the power output unit 28c. In this example, the power switching unit 28 thus selectively connects either the first inverter 13 or the branch breaker 85a to the self-sustaining distribution board 90, specifically to the main breaker 92.

[Independent distribution board 90]
The self-supporting distribution board 90 has a main breaker 92 and a second branch portion 95. The second branch portion 95 includes a plurality of branch breakers. In this example, the second branch 95 includes branch breakers 95a, 95b and 95c.

The main breaker 92 is connected to the power switching unit 28 by the upstream electric circuit 98. The upstream electric circuit 98 is connected to the downstream electric circuit 99 via the main breaker 92.

The second branch portion 95 is connected to the downstream electric circuit 99. The branch breaker 95a of the second branch portion 95 is provided on a path connecting the main breaker 92, the D1 power supply 55, and the AC load 56. The branch breaker 95b is provided on a path connecting the main breaker 92 and the hot water storage unit 47. The branch breaker 95c is provided on a path connecting the main breaker 92 and the first load 251.

In this example, AC power of voltage V _AC1 can be supplied from the power switching unit 28 to the downstream electric circuit 99 via the main breaker 92. AC power of voltage V _AC1 can be supplied from the branch breaker 95a to the D1 power supply 55 and the AC load 56. AC power of voltage V _AC1 can be supplied from the branch breaker 95b to the hot water storage unit 47. AC power of voltage V _AC1 can be supplied from the branch breaker 95c to the first load 251 via the outlet 260.

[Operation of power system 300 during grid connection]
As shown in FIG. 1, at the time of grid connection, the protection relay 62 is in the open state based on the disconnection command from the control unit 51. Here, the open state refers to a state in which current is prohibited from flowing through itself. Further, in the power switching unit 28, the system power input unit 28a and the power output unit 28c are connected. In this way, the power switching unit 28 connects the branch breaker 85a and the self-sustaining distribution board 90.

The electric power generated by the fuel cell 41 is supplied to the second DC bus 43 via the fifth DCDC converter 42. Part or all of the electric power supplied to the second DC bus 43 is supplied to the secondary interconnection breaker 83 via the second inverter 44.

A part of the electric power supplied to the secondary interconnection breaker 83 is supplied to the main breaker 92 via the branch breaker 85a and the electric power switching unit 28 in this order. A part of the electric power supplied to the main breaker 92 is supplied to the D1 power supply 55 and the AC load 56 via the branch breaker 95a. Another part of the electric power supplied to the main breaker 92 is supplied to the hot water storage unit 47 via the branch breaker 95b. Yet another portion of the power supplied to the main breaker 92 is supplied to the first load 251 via the branch breaker 95c and the outlet 260 in this order.

Another portion of the power supplied to the secondary interconnection breaker 83 is supplied to the second load 252 via the branch breaker 85b. Yet another portion of the power supplied to the secondary interconnection breaker 83 is supplied to the third load 253 via the branch breaker 85c.

When the power obtained by adding the predetermined margin to the surplus power is larger than zero, the power is supplied from the second DC bus 43 to the heater 46 via the sixth DCDC converter 45.

Specifically, the DC power converter 20 takes out electric power from the first photovoltaic power generation system 31 by MPPT control, and supplies the taken out electric power to the first DC bus 11. Specifically, the DC power converter 20 takes out electric power from the second photovoltaic power generation system 32 by MPPT control, and supplies the taken out electric power to the first DC bus 11.

When the power storage device 25 is not in the fully charged state, a part of the electric power supplied to the first DC bus 11 is supplied to the power storage device 25, and the rest of the power is supplied to the first inverter 13. When the power storage device 25 is in a fully charged state, all of the electric power supplied to the first DC bus 11 is supplied to the first inverter 13. The electric power supplied to the first inverter 13 is supplied to the interconnection breaker 81.

As can be understood from the above description, in the power system 300 of this example, the power supplied from the second inverter 44 to the secondary interconnection breaker 83 is the load 251 to 253, D1 by at least the above margin. It is configured to be insufficient for the total required load of the power supply 55, the AC load 56, and the hot water storage unit 47. The electric power corresponding to this shortage is supplied from the interconnection breaker 81 to the downstream electric circuit 89 via the main breaker 82, and together with the electric power supplied from the second inverter 44 to the secondary interconnection breaker 83, the second It is supplied to one branch portion 85. The balance of the electric power supplied to the interconnection breaker 81 is reverse-flowed to the grid power supply 200.

When the power generation by the photovoltaic power generation systems 31 and 32 is insufficient, the above-mentioned insufficient power is supplied from the system power supply 200 to the downstream electric circuit 89 via the main breaker 82, and is supplied from the second inverter 44 to the second. Together with the electric power supplied to the next interconnection breaker 83, it is supplied to the first branch portion 85. Further, when the power storage device 25 is not in a fully charged state and the power generation by the photovoltaic power generation systems 31 and 32 is insufficient to charge the power storage device 25, the system power supply 200, the first inverter 13, and the first DC bus 11 Power is supplied to the power storage device 25 via the fourth DCDC converter 12.

[Operation of power system 300 in the event of a power failure]
As shown in FIG. 2, at the time of a power failure, the protection relay 62 is closed based on the parallel command from the control unit 51. Here, the closed state refers to a state in which an electric current is allowed to flow through itself. Further, the power switching unit 28 connects the first inverter 13 and the self-sustaining distribution board 90.

The electric power generated by the fuel cell 41 is supplied to the second DC bus 43 via the DCDC converter 42. Part or all of the DC power supplied to the second DC bus 43 is supplied to the characteristic conversion circuit 100. Specifically, the DC power converter 20 takes out the electric power from the characteristic conversion circuit 100 (strictly speaking, via the LC filter 61) by the first DCDC converter 21 by MPPT control, and supplies the taken out electric power to the first DC bus 11. do.

Further, the DC power conversion device 20 takes out electric power from the photovoltaic power generation systems 31 and 32 and supplies the taken out electric power to the first DC bus 11 as in the case of grid interconnection.

Insufficient if the total power extracted from the solar power generation systems 31 and 32 and the characteristic conversion circuit 100 by the DC power converter 20 is smaller than the required load of the first load 251, the D1 power supply 55, the AC load 56 and the hot water storage unit 47. The electric power corresponding to the minute is further supplied from the power storage device 25 to the first DC bus 11 via the fourth DCDC converter 12. If the extracted power is larger than the required load, the excess power is charged to the power storage device 25 via the 4th DCDC converter 12, and if the excess power is surplus even after this charging, the second DC bus 43 A part of the electric power of the above is supplied to the heater 46 via the sixth DCDC converter 45.

In this way, the electric power that is made to follow or is brought close to the required load is supplied from the first DC bus 11 to the main breaker 92 via the first inverter 13 and the electric power switching unit 28. The electric power supplied to the main breaker 92 is supplied to the D1 power supply 55, the AC load 56, the hot water storage unit 47, and the first load 251 as in the case of grid interconnection.

[Route provided in the power system 300]
As can be seen from the above description and FIGS. 1 and 2, in the power system 300, the grid power supply path 351 and the reverse power flow path 352, the self-sustained operation path 353, the DC output path 354, and the AC output. A route 355 and a route 356 to the power receiving unit are provided. The grid power supply path 351 is a path for guiding AC power from the grid power supply 200 to the grid power input section 28a of the power switching unit 28 via the third connection point p3, the current detection section 27, and the first branch section 85 in this order. Is. The reverse power flow path 352 is a path for guiding AC power from the inverter 13 to the system power supply 200 via the third connection point p3. The path 353 for self-sustaining operation is a path for guiding AC power from the inverter 13 to the self-sustaining power input unit 28b of the power switching unit 28. The DC output path 354 is a path for guiding DC power from the fuel cell power generation system 40 to the inverter 13. The AC output path 355 is a path for guiding AC power from the fuel cell power generation system 40 to the first branch portion 85 via the secondary interconnection breaker 83. The route 356 to the power receiving unit is a path for guiding AC power from the power output unit 28c of the power switching unit 28 to the power receiving unit 59 of the fuel cell power generation system 40 via the second branch unit 95. In this example, the grid power supply path 351 and the reverse power flow path 352 overlap at the portion on the grid power supply 200 side when viewed from the third connection point p3.

The voltage detection circuit 57 is connected to the AC output path 355. The current detection circuit 58 acquires a signal from the current detection unit 27. The power receiving unit 59 has a first portion to which power is supplied from the branch breaker 95a and a second portion to which power is supplied from the branch breaker 95b. The first portion is connected to the D1 power supply 55 and the AC load 56. The second part is connected to the hot water storage unit 47.

In this example, the power system 300 includes photovoltaic systems 31 and 32 with photovoltaic panels. In the power system 300, a path for guiding DC power from the photovoltaic power generation system 31 to the inverter 13 is provided. Further, a path for guiding DC power from the photovoltaic power generation system 32 to the inverter 13 is provided.

In this example, the power system 300 includes a power storage device 25. In the power system 300, a path for guiding DC power from the power storage device 25 to the inverter 13 is provided.

In this example, the power system 300 includes a photovoltaic power generation system 31 and 32 having a photovoltaic power generation panel, and a power storage device 25. In the power system 300, a path for guiding DC power from the photovoltaic power generation system 31 to the power storage device 25 is provided. A path for guiding DC power from the photovoltaic power generation system 32 to the power storage device 25 is provided. Further, a path for guiding DC power from the fuel cell power generation system 40 to the power storage device 25 is provided. Therefore, the power storage device 25 can be charged not only from the photovoltaic power generation systems 31 and 32 but also from the fuel cell power generation system 40.

In this example, the power system 300 includes solar power generation systems 31 and 32 having a solar power generation panel, a power storage device 25, and an outlet 260. The power system 300 is provided with a path for guiding power from the photovoltaic power generation system 31 to the outlet 260 via the inverter 13, the path 353 for independent operation, the power switching unit 28, and the second branch portion 95 in this order. A path for guiding electric power from the photovoltaic power generation system 32 to the outlet 260 via the inverter 13, the path 353 for independent operation, the power switching unit 28, and the second branch portion 95 is provided in this order. A path for guiding electric power from the fuel cell power generation system 40 to the outlet 260 via the inverter 13, the path 353 for independent operation, the power switching unit 28, and the second branch portion 95 is provided in this order. A path for guiding electric power from the power storage device 25 to the outlet 260 via the inverter 13, the path 353 for independent operation, the power switching unit 28, and the second branch portion 95 is provided in this order. Therefore, in this example, power can also be supplied from the fuel cell power generation system 40 to the outlet 260 to which power is supplied from the photovoltaic power generation systems 31 and 32 and the power storage device 25. This is useful in the event of a power outage for the following reasons: That is, the photovoltaic power generation systems 31 and 32 cannot generate power at night, in rainy weather, and the like. Assuming that power cannot be supplied to the outlet 260 from the fuel cell power generation system 40, the period during which power can be taken out from the outlet 260 is limited based only on the power storage device 25 when a power failure continues at night or in the rain. Become. On the other hand, in this example, since the power can be supplied to the outlet 260 from the fuel cell power generation system 40, the above period can be extended. When a power outage continues at night or in the rain, it is convenient for the user to be able to take out power from one outlet for a long time without replacing it with another outlet.

Further, in this example, the same connection as the above connection to the outlet 260 is also made to the hot water storage unit 47. Therefore, when a power failure continues at night, in the rain, or the like, the electric power required for the operation can be supplied to the hot water storage unit 47 for a long time.

In the power system 300 of this example, a path for guiding power from the power storage device 25 to the power receiving unit 59 via the inverter 13, the self-sustained operation path 353, the power switching unit 28, and the second branch unit 95 is provided in this order. .. Further, the same connection as the above connection to the outlet 260 is also made to the power receiving unit 59. As can be understood from the above description, the power storage device 25 of this example functions as an emergency power source capable of supplying power to the outlet 260 in the event of a power failure. In this example, the power storage device 25 also functions as an emergency power source capable of supplying power to the power receiving unit 59 in the event of a power failure. By doing so, it is possible to omit a dedicated power source for starting the fuel cell power generation system 40 in the event of a power failure, for example, a dedicated power source for supplying power to the auxiliary equipment of the system 40.

[Reverse power flow to grid power supply and DC power supply from fuel cell power generation system to inverter]
The electric power system 300 is a system capable of generating DC electric power, converting the DC electric power into AC electric power by the inverter 13, back-feeding the AC electric power to the grid power supply 200, and supplying the AC power to the load. Further, in the electric power system 300, a fuel cell power generation system 40 is applied, and DC power can be supplied from the fuel cell power generation system 40 to the inverter 13. The electric power system 300 is designed to avoid reverse power flow from the fuel cell power generation system 40 to the grid power source 200.

Specifically, in the electric power system 300, reverse power flow of electric power from a power generation system different from the fuel cell power generation system 40 to the grid power source 200 is performed at the time of grid interconnection. In this example, the other power generation systems are the photovoltaic systems 31 and 32. In order to prevent the power generated by the fuel cell power generation system 40 from being mixed with the reverse power flow power, the DC power supply from the fuel cell power generation system 40 to the inverter 13 is limited to the time of power failure of the system power supply 200.

The power system 300 can detect a power failure of the system power supply 200. In one example of the power system 300, power failure detection is realized by using a known method such as an active method. When a power failure is detected, the power system 300 changes the electrical connection state from the state of FIG. 1 to the state of FIG.

In the state of FIG. 2, power is not reverse power flowed from the inverter 13 to the system power supply 200 via the reverse power flow path 352. On the other hand, in the state of FIG. 2, the power receiving unit 59, the D1 power supply 55, the AC load 56, the hot water storage unit 47 and Power can be supplied to the first load 251. That is, in the state of FIG. 2, the power supplied to the inverter 13 can be supplied to the power receiving unit 59, the D1 power supply 55, the AC load 56, the hot water storage unit 47, and the first load 251 while the system power supply 200. No reverse power flow.

As described above, in the power generation system 300, when the power failure is detected, the DC power is supplied from the fuel cell power generation system 40 to the inverter 13, and the power generated by the fuel cell power generation system 40 can be supplied to the second branch portion 95. .. In this way, in a situation where the system power supply 200 is out of power, the fuel cell power generation system 40 can supply electric power to the connection destination of the second branch portion 95 for a long time. For example, when the load 251 is an electric appliance, the electric appliance can be used for a long time. Further, it is possible to supply electric power to the power receiving unit 59.

[Timing to end the DC power supply from the fuel cell power generation system to the inverter]
As can be understood from the above description, in the power system 300, power is supplied from the fuel cell power generation system 40 to the load 251 via the inverter 13 when the system power supply 200 fails, and another power generation occurs when the system power supply 200 does not have a power failure. Electric power can be reverse-flowed from the system to the system power source 200 via the inverter 13. Specifically, in the event of a power failure of the grid power supply 200, DC power is supplied from the fuel cell power generation system 40 to the inverter 13 via the DC output path 354, DC-AC conversion is performed by the inverter 13, and the inverter 13 is used for independent operation. AC power supply to the second distribution board 90 via the path 353 and the power switching unit 28 is performed. Further, when the grid power supply 200 does not have a power failure, the DC power supply from the other power generation system to the inverter 13, the DC-AC conversion by the inverter 13, and the alternating current from the inverter 13 to the grid power supply 200 via the reverse power flow path 352. With the reverse flow of electricity, is done. In this embodiment, the other power generation systems are the photovoltaic power generation systems 31 and 32.

In the power system 300, power can be supplied to the load 251 by taking advantage of the fuel cell power generation system 40 that power can be generated regardless of the weather in the event of a power failure of the system power supply 200. On the other hand, when the grid power supply 200 is not out of power, the user of the power system 300 can enjoy the financial merit by reverse-feeding the power generated by the other power generation system to the grid power supply 200.

In the electric power system 300, an electric path for connecting the fuel cell power generation system 40, the inverter 13, the electric power switching unit 28, and the load 251 in this order is established in the event of a power failure. Specifically, at the time of a power failure, as shown in FIG. 2, the protection relay 62 is in the closed state (that is, the on state), and the inverter 13 converts the DC power input to itself into the AC power V _AC1 to generate power. The first state of outputting to the switching unit 28 is taken, and in the power switching unit 28, the connection destination of the power output unit 28c is set to the self-sustaining power input unit 28b.

On the other hand, at the time of non-power failure, an electric path connecting the photovoltaic power generation systems 31 and 32, the inverter 13, and the system power supply 200 in this order is established. The electrical connection between the fuel cell power generation system 40 and the inverter 13 is cut off. An electric path connecting the system power supply 200, the power switching unit 28, and the load 251 in this order is established. Specifically, when there is no power failure, as shown in FIG. 1, the protection relay 62 is in the open state (that is, in the open state), and the inverter 13 converts the DC power input to itself into the AC power V _AC2 . The second state of outputting to the main distribution board 80 is taken, and in the power switching unit 28, the connection destination of the power output unit 28c is set to the system power input unit 28a.

When the grid power supply 200 is restored, the inverter 13 switches from the first state to the second state, and the connection destination of the power output unit 28c is switched from the self-sustaining power input unit 28b to the system power input unit 28a. These switchings are performed in conjunction with each other or independently of each other. For example, switching from the first state to the second state of the inverter 13 due to the power recovery is performed by the power station 10. In one example, a second current detection unit is provided between the third connection point p3 and the system power supply 200. The power station 10 receives a signal from the second current detection unit by wire or wirelessly, and detects power recovery based on the signal. In one specific example, the second current detection unit may have the same configuration as the current detection unit 27. The signal transmitted by the second current detection unit to the power station 10 is the same as the signal transmitted by the current detection unit 27 to the fuel cell power generation system 40. The power station 10 has a second current detection circuit similar to the current detection circuit 58, and detects power recovery using the second current detection circuit.

In the present embodiment, it is the fuel cell power generation system 40 that terminates the DC power supply from the fuel cell power generation system 40 to the inverter 13 via the DC output path 354 when the grid power supply 200 is restored. Specifically, when the grid power supply 200 is restored, the fuel cell power generation system 40 switches the protection relay 62 from the closed state to the open state by transmitting a disconnection command to the protection relay 62.

In the power system 300, power is continuously supplied from the fuel cell power generation system 40 to the load 251 from the occurrence of a power failure to the recovery of power. This is convenient for the user. On the other hand, the power system 300 has a configuration suitable for ending the DC power supply from the fuel cell power generation system 40 to the inverter 13 when the system power supply 200 recovers power. As a result, the DC power supply from the fuel cell power generation system 40 to the inverter 13 is continued even though the electric path connecting the inverter 13 and the system power supply 200 is established due to the power restoration, and the fuel cell power generation system 40 continues to supply DC power. It is possible to avoid a situation in which a reverse power flow to the grid power source 200 occurs. This point will be described below.

In the following description, the terms first condition, second condition and third condition may be used. The first condition is that the measured value of the current detection unit 27 is a value indicating that the system power supply 200 is recovering power when the AC load 56 is consuming power. The second condition is that the measured value of the current detection unit 27 is a value indicating that the system power supply 200 is recovering power when the AC load 56 is not consuming power. The third condition is that the voltage input to the fuel cell power generation system 40 through the AC output path 355 is a value indicating that the system power supply 200 is recovering power.

The establishment of the first condition can be detected by the current detection circuit 58. Further, the control unit 51 can determine that the satisfaction of the first condition has been detected by receiving the signal from the current detection circuit 58.

The establishment of the second condition can be detected by the current detection circuit 58. Further, the control unit 51 can determine that the satisfaction of the second condition has been detected by receiving the signal from the current detection circuit 58.

The establishment of the third condition can be detected by the voltage detection circuit 57. Further, the control unit 51 can determine that the satisfaction of the third condition has been detected by receiving the signal from the voltage detection circuit 57.

The power system 300 stops the supply of DC power from the fuel cell power generation system 40 to the inverter 13 via the DC output path 354 when the first condition is detected M1 times. This is suitable for ending the DC power supply from the fuel cell power generation system 40 to the inverter 13 when the system power supply 200 recovers power. Here, M1 is a natural number of 1 or more.

In the present embodiment, the M1 detection is a plurality of continuous detections. By doing so, the DC power supply can be terminated when the system power supply 200 is likely to be restored. The plurality of M1s are, for example, 2 or more and 20 or less, and may be 5 or more and 15 or less.

As will be understood from the following explanation, the expression "stopping the DC power supply when the first condition is satisfied is detected M1 times" is also DC in other cases. It is an expression that does not exclude stopping the power supply.

Specifically, in the present embodiment, the DC power supply is terminated even when M2 continuous detection that the second condition is satisfied is performed. When the second condition is detected once but M2 times are not continuously detected, the AC load 56 consumes power. Here, M2 is a natural number of 2 or more. By doing so, when it can be confirmed by using the second condition that the system power supply 200 is likely to be restored, the DC power supply can be terminated without consuming the power with the AC load 56. can. M2 is, for example, a value of 2 or more and 20 or less, and may be a value of 5 or more and 15 or less.

Further, in the present embodiment, the DC power supply is terminated even when M3 continuous detection that the third condition is satisfied is performed. When the third condition is detected once but M3 times are not continuously detected, the AC load 56 consumes power. Here, M3 is a natural number of 2 or more. By doing so, when it can be confirmed by using the third condition that the system power supply is likely to be restored, the DC power supply can be terminated without consuming the power with the AC load 56. .. M3 is, for example, a value of 2 or more and 20 or less, and may be a value of 3 or more and 10 or less.

Hereinafter, a specific example of the above-mentioned control based on the first to third conditions will be further described with reference to the flowchart of FIG.

In step S101, the control unit 51 determines whether or not the establishment of the third condition is detected once by the voltage detection circuit 57. If this detection is made, the flow proceeds to step S102. If this detection is not made, the flow proceeds to step S103.

In step S102, the control unit 51 determines whether or not the establishment of the third condition is continuously detected M3 times by the voltage detection circuit 57. If this continuous detection is made, the flow proceeds to step S107. If this continuous detection is not made, the flow proceeds to step S105. It should be noted that M3 times may be the number of times including one time detected in step S101, or may be the number of times not including this.

In step S103, the control unit 51 determines whether or not the satisfaction of the second condition is detected once by the current detection circuit 58. If this detection is made, the flow proceeds to step S104. If this detection is not made, the flow proceeds to step S101.

In step S104, the control unit 51 determines whether or not the establishment of the second condition is continuously detected M2 times by the current detection circuit 58. If this continuous detection is made, the flow proceeds to step S107. If this continuous detection is not made, the flow proceeds to step S105. The M2 times may be the number of times including one time detected in step S103, or may be the number of times not including this.

In step S105, the AC load 56 of the fuel cell power generation system 40 consumes electric power. After step S105, the flow proceeds to step S106.

In step S106, the control unit 51 determines whether or not the establishment of the first condition is continuously detected M1 times by the current detection circuit 58. If this continuous detection is made, the flow proceeds to step S107. If this continuous detection is not made, the flow proceeds to step S101.

In step S107, the fuel cell power generation system 40 stops the supply of DC power from the fuel cell power generation system 40 to the inverter 13 via the DC output path 354. Specifically, this stop is performed by stopping the output of the DC power from the substrate 60. More specifically, this stop is performed by opening (ie, opening) the protection relay 62. More specifically, opening the protection relay 62 in the open state is performed by the control unit 51 transmitting a disconnection command to the protection relay 62. Since the control unit 51 is configured to receive the signals from the voltage detection circuit 57 and the current detection circuit 58, the protection relay 62 is set according to the received signal (that is, according to the result of steps S101 to S106). It can be opened.

If the detection in step S101 is made, it can be said that there is a sign of power recovery of the system power supply 200. When the continuous detection in step S102 is performed, it is highly probable that the system power supply 200 has been restored. Therefore, in this case, even if the DC power supply is stopped in step S107, the problem that the user cannot use the load 251 is unlikely to occur. On the other hand, if the continuous detection in step S102 is not performed, the determination as to whether or not the system power supply 200 has been restored is suspended, and the determination is made in step S106. By such holding and execution of step S106, it is possible to suppress the risk of determining that the power has been restored even though the power has not actually been restored due to noise or the like.

In addition, the secondary interconnection breaker 83 may be cut off due to a setting error during construction, a disconnection, or malicious intent. In this case, even if the grid power supply 200 is actually restored, the voltage of the grid power supply 200 cannot flow into the fuel cell power generation system 40 through the AC output path 355, so that the voltage detection circuit 57 detects the power recovery. Can not. In this respect, in the present embodiment, if step S101 is not detected, the process proceeds to step S103. Therefore, even if the secondary interconnection breaker 83 is in the cutoff state, the current detection circuit 58 can detect the power recovery.

If the detection in step S103 is made, it can be said that there is a sign of power recovery of the system power supply 200. When the continuous detection in step S104 is performed, it is highly probable that the system power supply 200 has been restored. Therefore, in this case, even if the DC power supply is stopped in step S107, the problem that the user cannot use the load 251 is unlikely to occur. On the other hand, if the continuous detection in step S104 is not performed, the determination as to whether or not the system power supply 200 has been restored is suspended, and the determination is made in step S106. By such holding and execution of step S106, it is possible to suppress the risk of determining that the power has been restored even though the power has not actually been restored due to noise or the like.

Further, the load such as loads 252 and 253 and the electric power flowing out from the first branch portion 85 to the power switching unit 28 may be small. For example, the case where the power consumption of electric appliances in the home is small corresponds to such a case. Even if the system power supply 200 is restored, if the outflow power is small, the current detection unit 27 may not be able to stably obtain a measured value at a level at which it can be recognized that the power has been restored. In such a case, a phenomenon may occur in which the detection of step S103 is performed but the continuous detection of step S104 is not performed. In the example of FIG. 8, in such a case, power is consumed by the AC load 56 of the fuel cell power generation system 40 in step S105. By doing so, the system power supply 200 is restored, and the system power supply 200 is connected to the system power supply 200 via the current detection unit 27, the first branch unit 85, the power switching unit 28, the second branch unit 95, and the power receiving unit 59. If an electric path leading to the AC load 56 is established, a current based on the power consumption of the AC load 56 can be forcibly flowed to a portion of the electric path provided with the current detection unit 27. If the power is restored and the electric path is established, the current detection unit 27 obtains a large level measured value reflecting the forced current, and the current detection circuit 58 obtains the large level measured value. The situation is such that recovery can be detected based on. That is, in step S106, it becomes easy to execute an appropriate power recovery detection.

In the flowchart of FIG. 8, the combination of steps S101 and S102 and the combination of steps S103 and S104 may be interchanged. That is, in step S101, it is determined whether or not the establishment of the second condition is detected, in step S102, it is determined whether or not the M2 continuous detection is performed, and in step S103, the establishment of the third condition is detected. It may be determined whether or not the detection is performed, and whether or not the M3 continuous detection is performed in step S104 may be determined.

Hereinafter, specific examples of the voltage detection circuit 57, the current detection unit 27, and the current detection circuit 58 will be described.

[Specific example of voltage detection circuit 57]
In one example, the voltage detection circuit 57 is configured to be able to convert the voltage input to the fuel cell power generation system 40 by the AC output path 355 into a zero cross pulse. Specifically, the voltage detection circuit 57 continuously generates zero cross pulses during the period in which the AC voltage V _AC2 is supplied to the fuel cell power generation system 40 via the AC output path 355. If one zero cross pulse is generated, the detection in step S101 of FIG. 8 can be made. When M3 or more consecutive zero cross pulses are generated, M3 continuous detection in step S102 can be performed. Here, the zero cross pulse refers to a pulse in which the instantaneous value of the signal changes over 0V.

[Specific example of current detection unit 27 and current detection circuit 58]
As described above, in the present embodiment, the current detection unit 27 has at least one current sensor. The measured value of the current detection unit 27 refers to the measured value of the current sensor when the current detection unit 27 is composed of one current sensor. When the current detection unit 27 is composed of a plurality of current sensors, the measured value of the current detection unit 27 may be the sum of the measured values of the plurality of current sensors. In one specific example, the portion of the system power supply path 351 provided with the current detection unit 27 is composed of a single-phase three-wire system. The current detection unit 27 includes a first current sensor provided on the first ungrounded line of the single-phase three-wire system, a second current sensor provided on the second ungrounded line of the single-phase three-wire system, and the second current sensor. It is composed of. The measured value of the current detection unit 27 is the total of the measured value of the first current sensor and the measured value of the second current sensor.

The current detection circuit 58 extracts the measured value of the current detection unit 27 at a constant time interval Tp, and counts the number of times N in which the measured value larger than the first threshold current is continuously extracted. When the number of times N is 1 or more, the detection in step S103 of FIG. 8 can be performed. When the number of times N is M2 or more, continuous detection of M2 times in step S104 can be performed. Further, when the number of times N is M1 or more, continuous detection of M1 times in step S106 can be performed. The time interval Tp is, for example, an interval of 50 msec (milliseconds) or more and 1000 msec or less, and may be an interval of 100 msec or more and 500 msec or less. The first threshold current may be, for example, a current having an effective value of 0.1 A or more and 5 A or less, and an effective value of 0.2 A or more and 3 A or less.

It is obligatory to provide the current detection unit 27 at the positions shown in FIGS. 1 and 2 by the grid interconnection regulation. Therefore, confirmation of the establishment of the first condition and the second condition is unlikely to cause an increase in the cost of the electric power system 300. Further, the voltage confirmation using the fuel cell power generation system 40 does not cost much. Therefore, confirmation of the establishment of the third condition is unlikely to cause an increase in the cost of the electric power system 300. For the above reasons, the first to third conditions can be realized at low cost.

[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 to make the output voltage of the characteristic conversion circuit 100 follow 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 is, the larger the output current of the characteristic conversion circuit 100 is. The second feedback control is performed to adjust the output voltage of the characteristic conversion circuit 100 to a value within a predetermined range when the output power of the characteristic conversion circuit 100 reaches its peak by lowering the output voltage.

The characteristic conversion circuit 100 that realizes the first and second feedback controls 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. do. In the following, the elements already described with reference to FIG. 4 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. This LLC converter is configured so that the higher the current flowing out from the constant voltage source 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 constant voltage source 131 and the sixth resistor 132. The current flowing out from the constant voltage source 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 combination of the seventh resistor 141, the first capacitor 142, 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 from the constant current source 147 via the feedback terminal 148. As 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, the charge charging 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 resistance 141. During the discharge period, the charge is further discharged via the eighth resistance 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, the faster the 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 becomes higher as the charge / discharge frequency is higher. 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 second capacitor. It has one diode 166a, a second diode 166b, and a sixth capacitor 167.

The switching elements 162a and 162b are connected in series to form a series circuit. 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 Transistor). Further, the fifth capacitor 164 is a resonance capacitor.

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

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 being supplied with 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 signal 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. 10 shows another example of the characteristic conversion circuit. In the following, the description of the same parts as those in the example of FIG. 4 may be omitted.

The characteristic conversion circuit 190 shown in FIG. 10 has a feedback current supply unit 195 instead 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 constant voltage source 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 constant voltage source 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 constant voltage source 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 constant voltage source 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 constant voltage source 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 as in the characteristic conversion circuit 100.

FIG. 11 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. 9 may be omitted.

The characteristic conversion circuit 190X shown in FIG. 11 has a feedback current supply unit 195X in place of the feedback current supply unit 130X of the characteristic conversion circuit 100X of FIG. Further, the characteristic conversion circuit 190X has a current resonance control unit 199 instead of the current resonance control unit 140 of the characteristic conversion circuit 100X.

The feedback current supply unit 195X has a ninth resistance 191 and a second light emitting diode 192 in addition to the constant voltage source 131, the sixth resistance 132 and the first light emitting diode 135. The current resonance control unit 199 has a 10th resistance 196 and a 2nd phototransistor 197 in addition to the 7th resistance 141, the 1st capacitor 142, the 8th resistance 143, the 1st phototransistor 145 and the control IC 146.

The combination of the seventh resistor 141, the first capacitor 142, 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 are alternately visited.

Specifically, during the charging period, the first capacitor 142 is charged from the constant current source 147 via the feedback terminal 148. As 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, the charge charging 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 resistance 141. During the discharge period, the charge is further discharged via the eighth resistance 143 and the first phototransistor 145, or through the tenth resistance 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 charge state of the 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. 4 is not limited to the characteristic conversion circuit 100X of FIG. For example, a smaller duty ratio is defined as the current flowing out from the constant voltage source 131 is larger, 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. 4 and 10 are not essential. For example, the voltage sensor detects the output voltage of the voltage-current control circuit 160, the current sensor detects the output current of the voltage-current control circuit 160, and in the region where the output current is small, the output voltage is maintained at a constant voltage and the output current is increased. In a large region, the output current may generate a control signal in which the output voltage decreases as the output current increases, and the voltage-current control circuit 160 may be controlled using the control signal.

Various other modifications may also be applied to this disclosure. For example, 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 DC power converter, the first inverter, and the like may not be incorporated in the power station. The power system may not have some of the illustrated elements such as a power storage device, a hot water storage unit, and the like. Further, the connection path between the power generation unit and the load is not limited to the one shown in the figure. For example, it is possible to omit the outlet 260 and supply electric power to the first load 251.

The technique according to the present disclosure can be used, for example, in a power system having a DC power conversion device designed for a photovoltaic power generation system and a fuel cell power generation system.

10 Power station 11,43 DC bus 12,21,22,23,42,45 DCDC converter 13,44 Inverter 20 DC power converter 25 Power storage device 27 Current detection unit 28 Power switching unit 28a System power input unit 28b Independent power input Unit 28c Power output unit 31, 32 Solar power generation system 36, 37 Solar power generation panel 40 Fuel cell power generation system 41 Fuel cell 46 Heater 47 Hot water storage unit 51 Control unit 52 Low-voltage power supply 55 D1 power supply 56, 251, 252, 253 Load 57 Voltage detection circuit 58 Current detection circuit 59 Power receiving section 60 Board 61 LC filter 62 Protection relay 80, 90 Distribution board 81, 82, 83, 85a, 85b, 85c, 92, 95a, 95b, 95c Breaker 85, 95 Branch section 88 , 89,98,99 Electric circuit 100,100X, 190,190X Characteristic conversion circuit 110,120 Feedback circuit 111,112,121,122,123,132,141,143,191,196 Resistance 115,125 Shunt regulator 115A, 125A Ahead 115K, 125K Cathode 115a, 125a Reference voltage terminal 115о, 125о Operator 115t, 125t Transistor 128 Current sensor 130, 130X, 195X Feedback current supply unit 131 Constant voltage source 135, 192 Light emitting diode 140, 199 Current resonance control unit 142, 161 , 163a, 163b, 164,167 Condenser 145,197 Phototransistor 146 Control IC
147 Constant current source 148, 149a, 149b Terminal 150, 198 Optocoupler 160, 160X Voltage / current control circuit 162a, 162b Switching element 165 Transformer 165a, 165b, 165c Winding 166a, 166b Diode 200 System power supply 260 Outlet 300 Power system 351, 352,353,354,355,356 Route p1, p2, p3 Connection point

Claims (10)

It is a power system that is connected to the grid power supply.
A fuel cell power generation system having a fuel cell, a power receiving unit, and an AC load connected to the power receiving unit.
Inverters that convert DC power to AC power,
A current detection unit that transmits a signal representing a measured value of the current detection unit to the fuel cell power generation system, and a current detection unit.
A first distribution board having a first branch portion including a plurality of branch breakers, a secondary interconnection breaker, and the like.
A second distribution board with a second branch containing multiple branch breakers,
It has a plurality of input units including a grid power input unit and an independent power input unit, and a power output unit.
A power switching unit for switching which of the plurality of input units is connected to the power output unit is provided.
A DC output path that guides DC power from the fuel cell power generation system to the inverter,
A path for independent operation that guides AC power from the inverter to the independent power input unit,
A grid power supply path that guides AC power from the grid power supply to the grid power input section via the connection point, the current detection section, and the first branch section in this order.
A route to the power receiving unit that guides AC power from the power output unit to the power receiving unit via the second branch unit, and
A reverse power flow path that guides AC power from the inverter to the grid power supply via the connection point, and
An AC output path for guiding AC power from the fuel cell power generation system to the first branch portion via the secondary interconnection breaker is provided.
When the system power supply fails, DC power is supplied from the fuel cell power generation system to the inverter via the DC output path, DC-AC conversion by the inverter, and the path for independent operation and the power from the inverter. AC power supply to the second distribution board via the switching unit is performed, and
When the condition that the measured value of the current detection unit is a value indicating that the system power supply is restored when the power is consumed by the AC load is defined as the first condition.
When the first condition is satisfied M1 times, the DC power supply is terminated.
Power system.
Here, M1 is a natural number of 1 or more. The M1 detection is a plurality of continuous detections.
The power system according to claim 1. When the condition that the measured value of the current detection unit is a value indicating that the system power supply is restored when the power is not consumed by the AC load is defined as the second condition.
Even when M2 continuous detection that the second condition is satisfied is performed, the DC power supply is terminated.
When the second condition is detected once but the M2 continuous detection is not performed, the AC load consumes power.
The power system according to claim 1 or 2.
Here, M2 is a natural number of 2 or more. When the condition that the voltage input to the fuel cell power generation system through the AC output path is a value indicating that the system power supply is restored is defined as the third condition.
Even when the continuous detection of M3 times that the third condition is satisfied is performed, the DC power supply is terminated.
When the third condition is detected once but the M3 continuous detection is not performed, the AC load consumes power.
The electric power system according to any one of claims 1 to 3.
Here, M3 is a natural number of 2 or more. Further equipped with a solar power generation system with a solar power generation panel,
A path for guiding DC power from the photovoltaic power generation system to the inverter is provided.
The electric power system according to any one of claims 1 to 4. Equipped with a power storage device,
A path for guiding DC power from the power storage device to the inverter is provided.
The power system according to any one of claims 1 to 5. A photovoltaic system with a photovoltaic panel and
Further equipped with a power storage device,
A route for guiding DC power from the photovoltaic power generation system to the power storage device,
A path for guiding DC power from the fuel cell power generation system to the power storage device is provided.
The power system according to any one of claims 1 to 6. A photovoltaic system with a photovoltaic panel and
Power storage device and
With an outlet,
A route for guiding power from the photovoltaic power generation system to the outlet via the inverter, the path for independent operation, the power switching unit, and the second branch portion in this order.
A route for guiding electric power from the fuel cell power generation system to the outlet via the inverter, the path for independent operation, the power switching unit, and the second branch portion in this order.
A path for guiding electric power from the power storage device to the outlet via the inverter, the path for independent operation, the power switching unit, and the second branch portion in this order is provided.
The power system according to any one of claims 1 to 7. A path for guiding power from the power storage device to the power receiving unit via the inverter, the path for independent operation, the power switching unit, and the second branching unit is provided in this order.
The power system according to claim 8. A fuel cell power generation system having a fuel cell, a power receiving unit, and an AC load connected to the power receiving unit.
Inverters that convert DC power to AC power,
A current detection unit that transmits a signal representing a measured value of the current detection unit to the fuel cell power generation system, and a current detection unit.
A first distribution board having a first branch portion including a plurality of branch breakers, a secondary interconnection breaker, and the like.
A second distribution board with a second branch containing multiple branch breakers,
It has a plurality of input units including a grid power input unit and an independent power input unit, and a power output unit.
A power switching unit for switching which of the plurality of input units is connected to the power output unit is provided.
A DC output path that guides DC power from the fuel cell power generation system to the inverter,
A path for independent operation that guides AC power from the inverter to the independent power input unit,
A grid power supply path that guides AC power from the grid power supply to the grid power input section via the connection point, the current detection section, and the first branch section in this order.
A route to the power receiving unit that guides AC power from the power output unit to the power receiving unit via the second branch unit, and
A reverse power flow path that guides AC power from the inverter to the grid power supply via the connection point, and
An AC output path for guiding AC power from the fuel cell power generation system to the first branch portion via the secondary interconnection breaker is provided.
When the system power supply fails, DC power is supplied from the fuel cell power generation system to the inverter via the DC output path, DC-AC conversion by the inverter, and the path for independent operation and the power from the inverter. It is a control method of a power system in which AC power is supplied to the second distribution board via a switching unit.
When the condition that the measured value of the current detection unit is a value indicating that the system power supply is restored when the power is consumed by the AC load is defined as the first condition.
This includes terminating the DC power supply when M1 detection that the first condition is satisfied is made.
Control method.
Here, M1 is a natural number of 1 or more.

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