CN113383286B - DC power supply system and power system - Google Patents

DC power supply system and power system Download PDF

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Publication number
CN113383286B
CN113383286B CN201980090722.1A CN201980090722A CN113383286B CN 113383286 B CN113383286 B CN 113383286B CN 201980090722 A CN201980090722 A CN 201980090722A CN 113383286 B CN113383286 B CN 113383286B
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power
current
output
voltage
conversion circuit
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CN113383286A (en
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金野裕则
山田刚
冈本壮平
村岛健介
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Panasonic Intellectual Property Management Co Ltd
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Panasonic Intellectual Property Management Co Ltd
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Priority claimed from JP2019014473A external-priority patent/JP7038309B2/en
Priority claimed from JP2019023375A external-priority patent/JP7138306B2/en
Priority claimed from JP2019092235A external-priority patent/JP7174897B2/en
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/66—Regulating electric power
    • G05F1/67—Regulating electric power to the maximum power available from a generator, e.g. from solar cell
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Control Of Electrical Variables (AREA)

Abstract

The characteristic conversion control brings about the following output voltage-output power characteristics: when the output voltage of the characteristic conversion circuit (100) is a certain value, the output power of the characteristic conversion circuit (100) is maximum. The characteristic conversion control includes a first feedback control and a second feedback control. The first feedback control is control performed when the output current of the characteristic conversion circuit (100) is relatively small. The second feedback control is control performed when the output current of the characteristic conversion circuit (100) is relatively large. When switching between the first feedback control and the second feedback control, the output voltage of the characteristic conversion circuit (100) is at the certain value.

Description

DC power supply system and power system
Technical Field
The present disclosure relates to a dc power supply system and a power system.
Background
Various power generation systems have been proposed. As an example of the power generation system, a solar power generation system that generates power using a solar power generation panel can be cited. As another example of the power generation system, a fuel cell power generation system that generates power using a fuel cell can be cited.
In a power generation system, power conversion may be performed. Patent document 1 describes the following: the output voltages of the solar power generation system and the fuel cell power generation system are changed to a predetermined voltage by power conversion.
In addition, it is known to extract electric power of a solar power generation system by maximum power point tracking control. The maximum power point tracking control is also referred to as MPPT control. The power taken out from the solar power generation system is maximized by MPPT control. Specifically, the dc power conversion device may be connected to the photovoltaic power generation system, and the MPPT control may be executed by the dc power conversion device.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2017-117673
Disclosure of Invention
Problems to be solved by the invention
In the case of configuring a power system capable of performing MPPT control of a solar power generation system, a dc power conversion device is designed to be capable of performing MPPT control of the solar power generation system. The present disclosure provides a dc power supply system including a fuel cell power generation system, which can extract power from the fuel cell power generation system to a dc power conversion device by performing MPPT control in a state of being connected to the dc power conversion device designed as described above.
Means for solving the problems
The present disclosure provides a dc power supply system including:
a fuel cell power generation system; and
a characteristic conversion circuit to which the direct-current power output from the fuel cell power generation system is input, the characteristic conversion circuit being configured to execute characteristic conversion control,
the characteristic conversion control brings about the following output voltage-output power characteristics: the output power of the characteristic conversion circuit is maximized when the output voltage of the characteristic conversion circuit is a certain value,
the characteristic conversion control includes a first feedback control and a second feedback control,
the first feedback control is control performed when the output current of the characteristic conversion circuit is relatively small,
the second feedback control is control performed when the output current of the characteristic conversion circuit is relatively large,
when switching between the first feedback control and the second feedback control, the output voltage of the characteristic conversion circuit takes the above-described certain value.
ADVANTAGEOUS EFFECTS OF INVENTION
The dc power supply system according to the present disclosure includes a fuel cell power generation system. In a connected state in which the dc power supply system according to the present disclosure is connected to a dc power conversion device designed to be able to execute MPPT control of the solar power generation system, the dc power conversion device can extract power from the fuel cell power generation system to the dc power conversion device by executing the MPPT control.
Drawings
Fig. 1 is a block diagram of a power system when the system is connected.
Fig. 2 is a block diagram of an electric power system at the time of power failure.
Fig. 3A is a diagram for explaining the V-P characteristics obtained by the characteristic conversion circuit.
Fig. 3B is a diagram for explaining the V-P characteristics of the comparative method.
Fig. 4 is a diagram showing an example of the characteristic conversion circuit.
Fig. 5 is a diagram for explaining the 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 diagram showing a specific example of the characteristic conversion circuit.
Fig. 9 is a diagram showing another example of the characteristic conversion circuit.
Fig. 10 is a diagram showing another example of the characteristic conversion circuit.
Fig. 11 is a diagram illustrating an example of the characteristic conversion circuit.
Fig. 12 is a diagram showing an example of the regulator.
Fig. 13 is a diagram for explaining an influence due to individual deviation of the current sensor.
Fig. 14 is a diagram for explaining an influence due to individual deviation of the current sensor.
Fig. 15 is a diagram for explaining an influence due to individual variations of the current sensors.
Fig. 16 is a block diagram of the power system when the system is connected.
Fig. 17 is a block diagram of the power system at the time of power failure.
Fig. 18 is a diagram for explaining the output characteristics of the characteristic conversion circuit.
Fig. 19 is a diagram for explaining the output characteristics of the characteristic conversion circuit.
Fig. 20 is a diagram showing an example of the characteristic conversion circuit.
Fig. 21 is a diagram for explaining the first shunt regulator.
Fig. 22 is a diagram for explaining the current sensor.
Fig. 23 is a diagram for explaining an influence due to individual variations of the current sensors.
Fig. 24 is a diagram for explaining an influence due to individual deviation of the current sensor.
Fig. 25 is a diagram for explaining adjustment of the switching current based on the variable voltage.
Fig. 26 is a diagram showing a specific example of the characteristic conversion circuit.
Fig. 27 is a block diagram of the power system at the time of system connection.
Fig. 28 is a block diagram of the power system at the time of power failure.
Fig. 29A is a diagram for explaining the V-P characteristics obtained by the characteristic conversion circuit.
Fig. 29B is a diagram for explaining the V-P characteristics of the comparative method.
Fig. 30 is a diagram for explaining the output characteristics of the characteristic conversion circuit.
Fig. 31 is a diagram illustrating an example of the characteristic conversion circuit.
Fig. 32 is a diagram for explaining an influence due to individual variations of the current sensors.
Fig. 33 is a diagram for explaining adjustment of the switching current based on the variable voltage.
Fig. 34 is a diagram for explaining the output characteristics of the characteristic conversion circuit after adjustment.
Fig. 35 is a diagram showing a specific example of the characteristic conversion circuit.
Detailed Description
In this specification, ordinal numbers such as first, second, and third … are sometimes used. When an ordinal number is added to a certain element, the same kind of element having a smaller ordinal number does not necessarily exist. For example, the use of the term third connection point does not imply that the first connection point and the second connection point must be present at the same time as the third connection point. In addition, the number of ordinal numbers can be changed as necessary.
In this specification, the term path is sometimes used. A path can have multiple lines. The same applies to the connection points and the like. For example, a single-phase three-wire path has two non-grounded lines and one grounded line. The connection point between the single-phase three-wire paths is used to mean a region in the path that includes a portion of each line to which connection is made.
In the embodiments, a combination of the output current, the output voltage, and the output power of the characteristic conversion circuit may be referred to as an operation point of the characteristic conversion circuit. The operating point at which the output power of the characteristic conversion circuit is maximum may be referred to as a maximum power point.
Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.
(first embodiment)
Fig. 1 and 2 are block diagrams of a power system 300 according to a first embodiment. Specifically, fig. 1 shows an example of the flow of power when the system is connected. Fig. 2 shows an example of the flow of power at the time of power failure. In these figures, the solid line represents a case where power is flowing in the circuit.The dashed line represents the case where power does not flow through the circuit. In addition, V AC1 And V AC2 Representing an alternating voltage. AC voltage V AC1 Is less than the AC voltage V AC2 Is determined. AC voltage V AC1 For example 100V. AC voltage V AC2 For example 200V. In this example, the AC voltage V AC1 Is implemented by two wires of a single-phase two-wire type. In addition, an alternating voltage V AC2 Is implemented by two non-grounded lines of three single-phase three-wire type electric wires.
The power system 300 is connected to the system power supply 200. The power system 300 can be supplied with power by the system power supply 200. Further, the power system 300 can reverse the flow of power to the system power supply 200. The power system 300 includes a power station (power station)10, a fuel cell power generation system 40, a base 60, solar power generation systems 31 and 32, a power storage device 25, a power switching unit 28, a first distribution board 80, a second distribution board 90, loads 251, 252, and 253, and an outlet 260. Hereinafter, the first switchboard 80 may be referred to as a main switchboard 80. The second switchboard 90 may be referred to as an independent switchboard 90.
[ Power plant 10]
The power plant 10 includes a DC power conversion device 20, a first DC bus 11, a fourth DCDC converter 12, and a first inverter 13.
The dc power conversion device 20 is designed to be able to perform maximum power point tracking control on a solar power generation system that outputs maximum power when the output voltage is within a prescribed range. A solar power generation system is a system that generates power using a solar 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 conversion device 20 from the solar power generation systems 31 and 32 and the fuel cell power generation system 40. The DC power output from the DC power conversion device 20 is supplied to the first DC bus 11.
Specifically, the dc power conversion device 20 includes a first DCDC converter 21, a second DCDC converter 22, and a third DCDC converter 23. The first DCDC converter 21 receives dc power from the fuel cell power generation system 40. The second DCDC converter 22 receives dc power from the first solar power generation system 31. The second photovoltaic power generation system 32 inputs dc power to the third DCDC converter 23. The DC power output from these DCDC converters 21, 22, and 23 is supplied to the first DC bus 11.
The fourth DCDC converter 12 converts the direct-current power input from the first DC bus 11 into direct-current power having different voltages. The dc power converted by the fourth DCDC converter 12 is supplied to the power storage device 25. The fourth DCDC converter 12 converts the electric power input from the power storage device 25 into direct-current electric power having different voltages, and supplies the direct-current electric power to the first DC bus 11. That is, the fourth DCDC converter 12 is a bidirectional DCDC converter. Fourth DCDC converter 12 operates such that the terminal voltage of power storage device 25 falls within the rated range.
The first inverter 13 converts the direct-current power into alternating-current power. Specifically, the first inverter 13 converts the direct-current power input from the first DC bus 11 into a voltage V AC1 Or voltage V AC2 The alternating current power of (1). Obtaining a voltage V using a first inverter 13 AC1 In the case of the ac power of (3), the power is supplied to the power switching unit 28. Obtaining a voltage V using a first inverter 13 AC2 In the case of the ac power of (3), the power is supplied to the main distribution board 80.
The first inverter 13 can also convert the voltage V input from the system power supply 200 via the main distribution board 80 AC2 The ac power of (a) is converted 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 solar power generation system that maximizes output power when the output voltage is within a predetermined range. The dc power generated in the at least one solar power generation system is supplied to the dc power conversion device 20.
Specifically, the solar power generation systems 31 and 32 correspond to a solar power generation system that maximizes output power when the output voltage is within a predetermined range. The first solar power generation system 31 has at least one solar power generation panel 36. The first solar power generation system 31 generates power using the at least one solar power generation panel 36. The second solar power system 32 has at least one solar power panel 37. The second solar power generation system 32 generates power using the at least one solar power generation panel 37. The dc power generated in the solar power generation systems 31 and 32 is supplied to the dc power conversion device 20.
[ Fuel cell Power Generation System 40]
The fuel cell power generation system 40 is a system that generates power using a fuel cell 41. The dc power generated in the fuel cell power generation system 40 can be supplied to the dc power conversion device 20. The ac power generated in 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 controller 51, a low-voltage power supply 52, and an auxiliary power supply 55. Hereinafter, the auxiliary power supply 55 may be referred to as a D1 power supply 55.
The fuel cell 41 generates direct-current power. Specifically, the fuel cell 41 includes a stack (stack). The stack also generates dc power using oxygen and hydrogen.
The fifth DCDC converter 42 converts the direct-current power generated in the fuel cell 41 into direct-current power having different voltages. In this example, the fifth DCDC converter 42 boosts the direct-current power generated in the fuel cell 41. The boosted DC power is supplied to the second DC bus 43.
The second inverter 44 converts the direct-current power input from the second DC bus 43 into a voltage V AC2 The alternating current power of (1). 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 the water using the dc power converted by the sixth DCDC converter 45. The heated water (hereinafter, sometimes referred to as hot water) is stored in the hot water storage unit 47.
The fuel cell power generation system 40 outputs all the generated power of the fuel cell 41 from the second inverter 44 when the generated power of the fuel cell 41 is larger than the requested load of the output destination of the second inverter 44. In this case, a part of the electric power output from the second inverter 44 that exceeds the requested load (hereinafter, may be referred to as surplus electric power) flows back to the grid power supply 200. In order to avoid the backflow, 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 a DCDC converter for surplus power. The heater 46 heats water and prevents backflow.
The controller 51 controls the DCDC converters 42 and 45, the second inverter 44, and a protective relay 62 described later. In the present embodiment, the controller 51 is a Micro Control Unit (MCU). The low-voltage power supply 52 supplies control power to the controller 51, the protective relay 62, and a characteristic conversion circuit 100 described later. The D1 power supply 55 is used to operate auxiliary devices of the fuel cell power generation system 40 such as pumps, blowers, and valves.
[ base plate 60]
The base plate 60 is provided on a path connecting the fuel cell power generation system 40 and the power plant 10. DC power is supplied from the fuel cell power generation system 40, specifically, from the second DC bus 43 to the substrate 60. The substrate 60 includes a characteristic conversion circuit 100, an LC filter 61, and a protective relay 62.
As is clear from the above description, the characteristic conversion circuit 100 is provided on a path connecting the fuel cell power generation system 40 and the dc power conversion device 20, specifically, on a path of dc power. The characteristic conversion circuit 100 performs characteristic conversion control. In this example, a dc power supply system including the fuel cell power generation system 40 and the characteristic conversion circuit 100 is configured, and dc power can be supplied from the dc power supply system to the dc power conversion device 20. This is also the same in the embodiment described later.
The characteristic conversion control brings about the following output voltage-output power characteristics: when the output voltage of the characteristic conversion circuit 100 is a certain value, the output power of the characteristic conversion circuit 100 is maximum.
In the present embodiment, the dc power conversion device 20 is designed to be able to execute MPPT control on a solar power generation system that maximizes output power when the output voltage is within a predetermined range. The characteristic conversion control brings about the following output voltage-output power characteristics: when the output voltage of the characteristic conversion circuit 100 is a certain value within the above-described predetermined range, the output power of the characteristic conversion circuit 100 is maximized.
In addition, the characteristic conversion control brings about the following output voltage-output current characteristics: in a region where the output voltage of the characteristic conversion circuit 100 exceeds the certain value, the output current of the characteristic conversion circuit 100 decreases as the output voltage of the characteristic conversion circuit 100 increases. Here, the region in which the output voltage of the characteristic conversion circuit 100 crosses the certain value is a region from when the output voltage of the characteristic conversion circuit 100 is a first value smaller than the certain value to when the output voltage of the characteristic conversion circuit 100 is a second value larger than the certain value.
Fig. 3A shows an example of the output voltage-output power characteristic and the output voltage-output current characteristic described above. In fig. 3A, the output voltage-output power characteristic of the characteristic conversion circuit 100 is described as a V-P characteristic. The output voltage-output current characteristic of the characteristic conversion circuit 100 is described as a V-I characteristic. The solid line represents the V-P characteristic. The dotted line indicates the V-I characteristic.
As described above, the dc power conversion device 20 is designed to be able to perform MPPT control of the solar power generation system. By executing MPPT control using the dc power converter 20 in the characteristic conversion control of the characteristic conversion circuit 100, it is possible to extract electric power from the fuel cell power generation system 40 to the dc power converter 20.
By appropriately adjusting the output voltage-output power characteristic by the characteristic conversion circuit 100, the output voltage of the characteristic conversion circuit 100 can be prevented from excessively increasing. Therefore, it is possible to prevent the dc power conversion device 20 from being damaged by the overvoltage input from the fuel cell power generation system 40 to the dc power conversion device 20.
In addition, according to the output voltage-output power characteristic of the characteristic conversion circuit 100, at a point in time when the output voltage of the characteristic conversion circuit 100 reaches the certain value, the increase in the power transmitted from the characteristic conversion circuit 100 to the dc power conversion device 20 is stopped. Therefore, the power transmitted from the characteristic conversion circuit 100 to the dc power conversion device 20 can be prevented from excessively increasing. It is also possible to prevent the electric power transmitted from the fuel cell power generation system 40 to the characteristic conversion circuit 100 from excessively increasing. Therefore, it is possible to prevent the output current of the fuel cell power generation system 40 from excessively increasing with an increase in the output power of the fuel cell power generation system 40. Therefore, the protection function is activated to prevent the stop of the power generation of the fuel cell 41 and the stop of the power supply from the fuel cell power generation system 40 to the dc power conversion device 20.
In addition, according to the characteristic conversion circuit 100, it is easy to take out large electric power from the fuel cell power generation system 40 to the dc power conversion device 20 based on the MPPT control. This point will be described below with reference to fig. 3A and 3B.
As described above, the characteristic conversion control brings about the following output voltage-output current characteristics: in a region where the output voltage of the characteristic conversion circuit 100 exceeds the certain value, the output current of the characteristic conversion circuit 100 decreases as the output voltage of the characteristic conversion circuit 100 increases. From the output voltage-output current characteristic, the graph of the output voltage-output power characteristic of the characteristic conversion circuit 100 can be a curve shape in which the output power is convex with respect to the output voltage in a region where the output voltage exceeds the certain value. In a typical example, the graph of the output voltage-output power characteristic of the characteristic conversion circuit 100 is a single peak graph in which the output power is the maximum when the output voltage is at the certain value.
It is assumed that the graph of the output voltage-output power characteristic of the characteristic conversion circuit 100 is such that the output power is upward with respect to the output voltage as shown in fig. 3BConvex linear shape. In this case, although the MPPT control is executed, the operating point is adjusted to a point deviated from the maximum power point. Specifically, the output voltage of the characteristic conversion circuit 100 is adjusted to the output voltage V with respect to the maximum power point target Deviated voltage V real . In this case, the output power of the characteristic conversion circuit 100 is reduced as compared with the output power in the case where the operating point is adjusted to the maximum power point. In fig. 3B, the reduction width is denoted by Δ P B 。
Also in the example of fig. 3A, if the output voltage of the characteristic conversion circuit 100 is adjusted to the output voltage V with respect to the maximum power point target Deviated voltage V real The output power of the characteristic conversion circuit 100 is reduced compared to the output power when the operating point is adjusted to the maximum power point. In fig. 3A, the reduction width is denoted as Δ P A 。
As described above, the output power of the characteristic conversion circuit 100 decreases when the operating point deviates from the maximum power point, regardless of whether the graph of the output voltage-output power characteristic of the characteristic conversion circuit 100 is linear or curved. However, the magnitude of the reduction is different. Specifically, the reduction width Δ P in the case of fig. 3A A Reduced by an amplitude Δ P from that of FIG. 3B B Is small. In this way, from the viewpoint of suppressing the reduction in the output power due to the above-described variation, and thus suppressing the reduction in the power taken out from the fuel cell power generation system 40 to the dc power conversion device 20, it is advantageous that the graph of the output voltage-output power characteristic has an upwardly convex curve shape.
In the actual MPPT control, there is a method of controlling the extraction voltage to a predetermined voltage in addition to the hill-climbing method, and it is not always easy to accurately match the operating point with the maximum power point in such control. In the hill climbing method, depending on the resolution of control, the maximum power may not be stably extracted. Therefore, it is actually advantageous that the graph of the output voltage-output power characteristic is a curve shape convex upward in terms of the way of MPPT control and the resolution, in order to suppress the reduction of the output power.
In addition, there may be cases where: the user purchases the characteristic conversion circuit 100 from a certain supplier and purchases the dc power conversion device 20 for MPPT control from another supplier. In this case, the characteristic conversion circuit 100 is connected to the dc power conversion device 20 having a performance unclear from the designer of the characteristic conversion circuit 100. In this case, since the characteristic conversion control and the MPPT control do not completely match, the operating point may be adjusted to a point deviated from the maximum power point. Therefore, it can be said that it is actually advantageous that the graph of the output voltage-output power characteristic is a convex curve. In addition, it can be said that the case where the graph of the output voltage-output power characteristic is a convex curve improves the compatibility of the characteristic conversion circuit 100 and reduces the restrictions on the dc power conversion device 20 that can be used.
As shown in fig. 3A, the characteristic conversion control may also bring about the following output voltage-output current characteristics: in a region where the output voltage of the characteristic conversion circuit 100 is greater than 0 and smaller than the certain value, the output current of the characteristic conversion circuit 100 decreases as the output voltage of the characteristic conversion circuit 100 increases. In addition, the characteristic conversion control may also bring about the following output voltage-output current characteristics: in a region where the output voltage of the characteristic conversion circuit 100 is greater than the certain value and less than the open circuit voltage, the output current of the characteristic conversion circuit 100 decreases as the output voltage of the characteristic conversion circuit 100 increases. Here, the open circuit voltage is an output voltage of the characteristic conversion circuit 100 when an output current of the characteristic conversion circuit 100 is zero.
A value smaller than the certain value is defined as a first value. A value larger than the certain value is defined as a second value. At this time, in the example of fig. 3A, the output characteristic is the following characteristic: in both the region where the output voltage is greater than the first value and less than the certain value and the region where the output voltage is greater than the certain value and less than the second value, the output current decreases more linearly as the output voltage increases. That is, the output characteristic is a characteristic in which the output current becomes smaller as a linear function with respect to the output voltage in the above two regions. Thus, the output characteristic can be a characteristic in which the output power changes in a quadratic function form with respect to the output voltage in the two regions.
Specifically, in the example of fig. 3A, the output characteristic is the following characteristic: in both a region where the output voltage is greater than 0 and less than the certain value and a region from the certain value to the value where the output voltage is the open-circuit voltage, the output current linearly decreases as the output voltage increases. That is, the output characteristic is a characteristic in which the output current becomes smaller as a linear function with respect to the output voltage in the above two regions. Thus, the output characteristic can be a characteristic in which the output power changes in a quadratic function form with respect to the output voltage in the two regions.
In the graph of the output voltage-output power characteristic, a point where the voltage is zero and the power is zero is defined as an origin. In the graph of the output voltage-output power characteristic, the maximum power point may be said to be a point at which the voltage is at a certain value and the power is maximum. In the graph of the output voltage-output power characteristic, a point at which the voltage is an open circuit voltage and the power is zero is defined as an open circuit voltage point. In the graph of the output voltage-output power characteristic, a straight line connecting the origin and the maximum power point is defined as a first straight line. In the graph of the output voltage-output power characteristic, a straight line connecting the maximum power point and the open circuit voltage point is defined as a second straight line. In this case, in the example of fig. 3A, the region in the graph of the output voltage-output power characteristic in which the output voltage is greater than the first value and less than the certain value is on the high power side with respect to the first straight line. In the graph of the output voltage-output power characteristic, a region in which the output voltage is greater than the certain value and less than the second value is on the high power side with respect to the second straight line.
Specifically, in the example of fig. 3A, the region in the graph of the output voltage-output power characteristic in which the output voltage is greater than 0 and less than the certain value is on the high power side with respect to the first straight line. In the graph of the output voltage-output power characteristic, a region from when the output voltage is the certain value to when the output voltage is the open circuit voltage is on the high power side with respect to the second straight line.
In this example, the predetermined range includes an actual machine reference range within ± 20V of the output voltage of the solar power generation system 31 or 32 when the output power of the solar power generation system 31 or 32 reaches the peak. In the characteristic conversion control, the output voltage at the maximum power point of the characteristic conversion circuit 100 is adjusted to a value within the actual engine reference range. Knowing the solar power generation system 31 or 32 used in the power system 300, the power system 300 can be designed to be able to execute MPPT control on the solar power generation system. That is, the predetermined range can be set so as to include the actual machine reference range. Further, the characteristic conversion circuit 100 can be designed such that the output voltage at the maximum power point of the characteristic conversion circuit 100 is adjusted to a value within the actual machine reference range. The power system 300 of this example is advantageous from the viewpoint of ease of design.
In the present embodiment, the characteristic conversion control is performed based on the electrical output of the characteristic conversion circuit 100. Thus, it is easy to improve the accuracy of the characteristic conversion control. Specifically, the electrical outputs are the output voltage and the output current of the characteristic conversion circuit 100.
In the present embodiment, the characteristic conversion control includes first feedback control and second feedback control. The first feedback control is control performed when the output current of the characteristic conversion circuit 100 is relatively small. The second feedback control is control performed when the output current of the characteristic conversion circuit 100 is relatively large. When switching between the first feedback control and the second feedback control, the output voltage of the characteristic conversion circuit 100 is the above-described certain value.
Specifically, the first feedback control is performed when the output current of the characteristic conversion circuit 100 is relatively small and the output voltage is relatively large. In the first feedback control, the output current of the characteristic conversion circuit 100 is made smaller as the output voltage of the characteristic conversion circuit 100 is larger. In the first feedback control, the output power of the characteristic conversion circuit 100 is made smaller as the output voltage of the characteristic conversion circuit 100 is larger. The second feedback control is performed when the output current of the characteristic conversion circuit 100 is relatively large and the output voltage is relatively small. In the second feedback control, the output current of the characteristic conversion circuit 100 is made smaller as the output voltage of the characteristic conversion circuit 100 is larger. In the second feedback control, the output power of the characteristic conversion circuit 100 is made larger as the output voltage of the characteristic conversion circuit 100 is larger. According to such first feedback control and second feedback control, the output voltage-output power characteristic and the output voltage-output current characteristic described above can be realized. In fig. 3A, the single-dot chain line indicates the contribution of the first feedback control. The two-dot chain line indicates the contribution of the second feedback control.
The characteristic conversion circuit may also have the following features: in the first feedback control, a ratio of a decrease in the output current to an increase in the output voltage-output current characteristic is larger than that in the second feedback control; and/or a ratio of a decrease in the output voltage to an increase in the output current in the output voltage-output current characteristic is smaller than that in the second feedback control. In this way, the output characteristic of the characteristic conversion circuit 100 can be easily brought close to the output characteristic of the solar power generation system. This feature is a concept including a mode as shown in fig. 18 and 19 described later, that is, in the first feedback control, the output voltage does not change even if the output current changes.
In the example of fig. 3A, in the first feedback control, the ratio of the decrease in the output current to the increase in the output voltage-output current characteristic is larger than that in the second feedback control. In addition, in the example of fig. 3A, in the first feedback control, the ratio of the decrease in the output voltage to the increase in the output current in the output voltage-output current characteristic is smaller than that in the second feedback control.
In the present embodiment, the open-circuit voltage of the characteristic conversion circuit 100 is controlled by the first feedback control.
Referring back to fig. 1 and 2, in the present embodiment, the dc power conversion device 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 varies the output voltage of the first solar power generation system 31 by MPPT control. The third DCDC converter 23 varies the output voltage of the second solar power generation system 32 by MPPT control. In this way, in this example, the multi-string dc power conversion device 20 is realized in which the MPPT control is individually performed on the solar power generation systems 31 and 32 and the characteristic conversion circuit 100. However, the dc power conversion device may be a concentrated dc power conversion device that performs MPPT control in a batch manner on the solar power generation systems 31 and 32 and the characteristic conversion circuit 100.
Fig. 4 shows an example of the characteristic conversion circuit 100. The characteristic conversion circuit 100 of fig. 4 includes a voltage/current control circuit 160, a first feedback circuit 110, a second feedback circuit 120, and a feedback current supply unit 130.
The first feedback circuit 110 has a first resistor 111, a second resistor 112, a third resistor 113, a first shunt regulator 115, and a current sensor 128. The second feedback circuit 120 has a fourth resistor 121, a fifth resistor 122, a sixth resistor 123, a second shunt regulator 125, and a current sensor 128. The current sensor 128 is shared by the first feedback circuit 110 and the second feedback circuit 120. The feedback current supply unit 130 includes a current supply power source 131 and a seventh resistor 132. In the present embodiment, the current supply power source 131 is a constant voltage source.
The current sensor 128 detects the output current of the characteristic conversion circuit 100. In the present embodiment, the current sensor 128 outputs a sensor output indicating the result of the detection. The larger the output current of the characteristic conversion circuit 100 is, the larger the sensor output is output from the current sensor 128. That is, the larger the output current of the characteristic conversion circuit 100 is, the larger the sensor output is. Such a current sensor 128 can be implemented using, for example, a shunt resistor. The sensor output from the current sensor 128 is supplied to the connection point ps. In particular, sensingThe output of the sensor is the sensor voltage V s . In addition, the current sensor 128 includes an output sensor voltage V s The sensor output portion 128 a.
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 128 s. The shunt resistor 128R has a resistance value of R sense . When current I load When the voltage is applied to the shunt resistor 128R, the voltage R is applied to the shunt resistor 128R sense I load . The current sense amplifier 128s will be coupled to the voltage R sense I load Voltage multiplied by gain G and bias voltage V bias As the sensor voltage V s And (6) outputting. That is, the sensor voltage V generated by the current sensor 128 of the present embodiment s Given by equation 1. However, another current sensor such as a hall-element 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 . In addition, the current I load Corresponding to the output current of the characteristic conversion circuit 100. "" is a symbol representing a multiplication operation.
The numerical formula 1: v s ＝R sense *I load *G+V bias
In the first feedback circuit 110, the output voltage V of the characteristic conversion circuit 100 is coupled via the first resistor 111 and the second resistor 112 out Partial pressure is carried out. The sensor voltage V is coupled via a third resistor 113 and a second resistor 112 s Partial pressure is carried out. The voltage resulting from summing these two divided voltages appears at the connection point p1 of the three resistors 111, 112, and 113. Hereinafter, the voltage appearing at the first connection point p1 may be referred to as a first reference voltage V ref1 . First reference voltage V ref1 Is input to a first reference voltage terminal of the first shunt regulator 115. As the voltage input to the first reference voltage terminal increases, the current i1 flowing through the current supply source 131, the seventh resistor 132, the first shunt regulator 115, and the reference potential in this order (hereinafter, may be referred to as a first current) increases. In fig. 4, the first current i1 is shown in the first shunt regulator 115The current flowing.
In the second feedback circuit 120, the output voltage V of the characteristic conversion circuit 100 is coupled to the output voltage V of the characteristic conversion circuit 100 through the fourth resistor 121 and the fifth resistor 122 out Partial pressure is carried out. The sensor voltage V is coupled via a sixth resistor 123 and a fifth resistor 122 s Partial pressure is carried out. The voltage resulting from summing these two divided voltages appears at the junction 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 . Second reference voltage V ref2 Is input to the second reference voltage terminal of the second shunt regulator 125. As the voltage input to the second reference voltage terminal increases, the current i2 flowing in this order among the current supply power source 131, the seventh resistor 132, the second shunt regulator 125, and the reference potential (hereinafter, may be referred to as a second current) increases. In fig. 4, the second current i2 is a current flowing downward in the drawing in the second shunt regulator 125.
In a region where the output current of the characteristic conversion circuit 100 is small, the second current i2 is substantially zero, and the current flowing from the current supply power source 131 is substantially the first current i 1. On the other hand, in a region where the output current of the characteristic conversion circuit 100 is large, the first current i1 is substantially zero, and the current flowing from the current supply power source 131 is substantially the second current i 2. 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 a region where the output current of the characteristic conversion circuit 100 is small, and the characteristic conversion in the characteristic conversion circuit 100 is performed by the second feedback circuit 120 in a region where the output current of the characteristic conversion circuit 100 is large. In order for circuits 110 and 120 to operate in this manner, the parameters of resistors 111, 112, 113, 121, 122, 123 and shunt regulators 115 and 125 are selected.
In this embodiment, it can be said that the output characteristic of the characteristic conversion circuit 100 is determined by an analog circuit included in the characteristic conversion circuit 100. Here, the output characteristic can be regarded as a relationship between the output current, the output voltage, and the output power. Specifically, it can be said that the output characteristic of the characteristic conversion circuit 100 is determined by a circuit constant of an analog circuit included in the characteristic conversion circuit 100. Here, the circuit constant refers to a resistance value of a resistor or the like.
The voltage current control circuit 160 is a DCDC converter. In the voltage-current control circuit 160, the ratio of the output voltage of the voltage-current control circuit 160 to the input voltage is decreased as the current flowing from the current supply source 131 increases. In this way, the characteristic conversion circuit 100 adjusts the ratio in accordance with the current flowing from the current supply power source 131. Such a characteristic conversion circuit 100 can be designed appropriately.
The first shunt regulator 115 of the present embodiment is further explained with reference to fig. 6. 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 115o, and a first transistor 115 t. The first operational amplifier 115o includes a non-inverting amplification terminal 115oa, an inverting amplification terminal 115ob, and an output terminal 115 oc. The first transistor 115t includes a cathode-side terminal 115ta, an anode-side terminal 115tb, and a control terminal 115 tc. The voltage input to the first reference voltage terminal 115a is supplied to the non-inverting amplification terminal 115 oa. The voltage of the inverting amplification terminal 115ob is set higher than the voltage of the first anode 115A by a first reference voltage source 115s by a first reference voltage V s1 The voltage of (c). When a voltage is inputted to the first reference voltage terminal 115a, the voltage is higher than a first reference voltage V s1 When the voltage of the non-inverting amplification terminal 115oa is larger than the voltage of the inverting amplification terminal 115ob due to a large voltage, a current flows from the output terminal 115oc to the control terminal 115tc, and a first current i1 flows from the first cathode 115K to the first anode 115A through 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 115oc and the control terminal 115tc, specifically, the base current is ignored as a very small current.
Based on the description with reference to fig. 6, the operation of the first feedback circuit 110 can be described as follows. If the output voltage V of the characteristic conversion circuit 100 out Becomes large, and, if the output current of the characteristic conversion circuit 100 becomes large so that the sensor voltage V becomes large s When the voltage becomes larger, the first reference voltage V becomes larger ref1 Becomes larger. In the first shunt regulator 115, due to the first reference voltage V ref1 Becomes larger and the first reference voltage V ref1 Relative to a first reference voltage V s1 The larger the deviation, the larger the first current i 1. If the first current i1 becomes large, the current flowing from the current supply power source 131 becomes large. If the outflow current becomes large, the ratio of the output voltage of the voltage current control circuit 160 to the input voltage becomes small. The first feedback circuit 110 controls the output voltage V of the characteristic conversion circuit 100 in this manner out . Specifically, the first feedback circuit 110 adjusts the transformation ratio of the characteristic conversion circuit 100 such that the first reference voltage V ref1 Track a first reference voltage V s1 。
In the first feedback control by the first feedback circuit 110, if the output current of the characteristic conversion circuit 100 becomes large and the sensor voltage V becomes large s As the current increases, the current flowing from the current sensor 128 to the first connection point p1 via the connection point ps and the third resistor 113 in this order increases. A first reference voltage V via a first shunt regulator 115 ref1 Tracking a constant first reference voltage V s1 . To achieve this tracking, a constant current is passed through the second resistor 112. This means that if the current flowing to the first connection point p1 in the third resistor 113 becomes large, the current flowing to the first connection point p1 in the first resistor 111 becomes small. If the current becomes small, the voltage generated in the first resistor 111 becomes small. For this reason, if the output current of the characteristic conversion circuit 100 becomes large, the voltage at the first connection point p1 follows the first reference voltage V ref1 The voltage generated in the first resistor 111 in the state of (1) becomes small. As a result, the output voltage V of the characteristic conversion circuit 100 out And becomes smaller. As described above, the first feedback control provides the output voltage-output current characteristic such that the output current of the characteristic conversion circuit 100 decreases as the output voltage of the characteristic conversion circuit 100 increases, as shown in fig. 3A.
The second shunt regulator 125 of the present embodiment is further explained 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 125o, and a second transistor 125 t. The second operational amplifier 125o includes a non-inverting amplification terminal 125oa, an inverting amplification terminal 125ob, and an output terminal 125 oc. The second transistor 125t includes a cathode-side terminal 125ta, an anode-side terminal 125tb, and a control terminal 125 tc. The voltage input to the second reference voltage terminal 125a is supplied to the non-inverting amplification terminal 125 oa. The voltage of the inverting amplification terminal 125ob is set higher than the voltage of the second anode 125A by a second reference voltage source 125s by a second reference voltage V s2 The voltage of (c). When a second reference voltage V is input to the second reference voltage terminal 125a s2 When the voltage of the non-inverting amplification terminal 125oa is larger than the voltage of the inverting amplification terminal 125ob due to the large voltage, a current flows from the output terminal 125oc to the control terminal 125tc, and a second current i2 flows from the second cathode 125K to the second anode 125A through 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 125oc and the control terminal 125tc, specifically, the base current is ignored as a very small current.
Based on the description with reference to fig. 7, the operation of the second feedback circuit 120 can be described as follows. If the output voltage V of the characteristic conversion circuit 100 out Becomes large, and, if the output current of the characteristic conversion circuit 100 becomes large so that the sensor voltage V becomes large s Becomes larger, the second reference voltage V ref2 Becomes larger. In the second shunt regulator 125, due to the second reference voltage V ref2 Becomes larger and the second reference voltage V ref2 Relative to a second reference voltage V s2 The larger the deviation, the larger the second current i 2. If the second current i2 becomes large, the current flowing from the current supply power source 131 becomes large. If it isAs the outflow current increases, the ratio of the output voltage of the voltage-current control circuit 160 to the input voltage decreases. The second feedback circuit 120 controls the output voltage V of the characteristic conversion circuit 100 in this manner out . Specifically, the second feedback circuit 120 adjusts the transformation ratio of the characteristic conversion circuit 100 such that the second reference voltage V ref2 Track the second reference voltage V s2 。
In the second feedback control by the second feedback circuit 120, if the output current of the characteristic conversion circuit 100 becomes large and the sensor voltage V becomes large s As it becomes larger, the current flowing from the current sensor 128 to the second connection point p2 via the connection point ps and the sixth resistor 123 in this order becomes larger. A second reference voltage V via a second shunt regulator 125 ref2 Tracking a constant second reference voltage V s2 . To achieve this tracking, a constant current is passed through the fifth resistor 122. This means that if the current flowing to the second connection point p2 in the sixth resistor 123 becomes large, the current flowing to the second connection point p2 in the fourth resistor 121 becomes small. If the current becomes small, the voltage generated in the fourth resistor 121 becomes small. For this reason, if the output current of the characteristic conversion circuit 100 becomes large, the voltage at the second connection point p2 follows the second reference voltage V ref2 The voltage generated in the fourth resistor 121 in the state of (1) becomes small. As a result, the output voltage V of the characteristic conversion circuit 100 out And becomes smaller. As described above, the second feedback control provides the output voltage-output current characteristic such that the output current of the characteristic conversion circuit 100 decreases as the output voltage of the characteristic conversion circuit 100 increases, as shown in fig. 3A.
As can be understood from the above description, in the present embodiment, the characteristic conversion circuit 100 includes the current sensor 128, at least one voltage-dividing resistor, and the voltage-current control circuit 160, where the voltage-current control circuit 160 is a DCDC converter. The characteristic conversion circuit 100 uses the current sensor 128 to reflect the output current of the characteristic conversion circuit 100 in the characteristic conversion control. The characteristic conversion circuit 100 reflects the output voltage of the characteristic conversion circuit 100 in the characteristic conversion control using at least one voltage dividing resistance. The characteristic conversion circuit 100 adjusts the transformation ratio of the voltage-current control circuit 160 by characteristic conversion control. In the example of fig. 4, the at least one voltage-dividing resistor includes a first voltage-dividing resistor and a second voltage-dividing resistor. The first voltage dividing resistor is composed of a first resistor 111 and a second resistor 112. The second voltage dividing resistor is composed of a fourth resistor 121 and a fifth resistor 122.
In the present embodiment, specifically, the characteristic conversion circuit 100 is provided with a voltage-current control circuit 160, a first feedback circuit 110 that performs first feedback control, and a second feedback circuit 120 that performs second feedback control, wherein the voltage-current control circuit 160 is a DCDC converter. The first feedback circuit 110 has a first shunt regulator 115, and the first shunt regulator 115 is inputted with a first reference voltage V which varies depending on the output current and the output voltage of the characteristic conversion circuit 100 ref1 . The second feedback circuit 120 has a second shunt regulator 125, and the second shunt regulator 125 is inputted with a second reference voltage V that varies according to the output current and the output voltage of the characteristic conversion circuit 100 ref2 . In the first feedback control, the voltage-to-current ratio of the voltage-to-current control circuit 160 is adjusted using the first shunt regulator 115 so that the first reference voltage V ref1 And is maintained constant. In the second feedback control, the voltage-to-current ratio of the voltage-to-current control circuit 160 is adjusted using the second shunt regulator 125 so that the second reference voltage V ref2 And is maintained constant.
More specifically, the first feedback circuit has a first voltage dividing resistance. The second feedback circuit has a second voltage-dividing resistor. The first feedback circuit 110 and the second feedback circuit 120 share a current sensor 128. The first voltage dividing resistor is used for reflecting the output voltage of the characteristic conversion circuit 100 to the first reference voltage V ref1 . The current sensor 128 is used for reflecting the output current of the characteristic conversion circuit 100 to the first reference voltage V ref1 . The second voltage dividing resistor is used for reflecting the output voltage of the characteristic conversion circuit 100 to the second reference voltage V ref2 . The current sensor 128 is used for reflecting the output current of the characteristic conversion circuit 100 to the second reference voltage V ref2 . In the example of fig. 4, the first divider resistor is composed of the first resistor 111 and the second resistorTwo resistors 112. The second voltage dividing resistor is composed of a fourth resistor 121 and a fifth resistor 122.
In addition, the first feedback circuit has a third voltage dividing resistance. The second feedback circuit has a fourth voltage dividing resistor. The third voltage dividing resistor is used for reflecting the output current of the characteristic conversion circuit 100 to the first reference voltage V ref1 . The fourth voltage dividing resistor is used for reflecting the output current of the characteristic conversion circuit 100 to the second reference voltage V ref2 . In the example of fig. 4, the third voltage dividing resistor is constituted by a third resistor 113 and a second resistor 112. The fourth voltage dividing resistor is composed of a sixth resistor 123 and a fifth resistor 122.
As can be understood from the above description, the characteristic conversion circuit 100 constitutes a feedback control loop in which the output current and the output voltage of the characteristic conversion circuit 100 are reflected in the subsequent output current and output voltage of the characteristic conversion circuit 100. The feedback control loop is constructed using the feedback circuit 110 or 120.
Returning to fig. 1 and 2, the output power of the characteristic conversion circuit 100 is supplied to the direct-current power conversion device 20, specifically, to the first DCDC converter 21 via the LC filter 61 and the protection relay 62.
[ Electrical storage device 25]
As described above, electric power is supplied from fourth DCDC converter 12 to power storage device 25. Power storage device 25 supplies electric power to fourth DCDC converter 12.
The power storage device 25 is, for example, a lithium battery. However, a battery other than a lithium battery may be used as power storage device 25. As the power storage device 25, a capacitor may be used.
[ Main switchboard 80]
The main switchboard 80 has a connection breaker 81, a main breaker 82, a secondary connection 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 portion 85 includes branch breakers 85a, 85b and 85 c.
The main breaker 82 is connected to the system power supply 200 via the upstream circuit 88. The upstream circuit 88 is connected to the downstream circuit 89 via the main breaker 82.
A secondary connection breaker 83 is connected to the downstream side circuit 89. The secondary connection breaker 83 is provided on a path connecting the main breaker 82 and the second inverter 44. The secondary connection breaker 83 is electrically connected to the first branch portion 85.
The downstream circuit 89 is also connected to the first branch portion 85. 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 portion 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 side circuit 88 has a third connection point p 3. The connection breaker 81 is provided on a path connecting the third connection point p3 and the first inverter 13.
In this example, the voltage V can be supplied from the system power supply 200 to the main breaker 82 via the third connection point p3 AC2 The alternating current power of (1). The voltage V can be supplied from the system power supply 200 to the first inverter 13 via the third connection point p3 and the connection breaker 81 in this order AC2 The alternating current power of (1). Voltage V AC2 The ac power of (2) can flow backward from the first inverter 13 to the system power supply 200 via the connecting breaker 81 and the third connecting point p3 in this order. The voltage V can be supplied from the first inverter 13 to the main breaker 82 via the connecting breaker 81 and the third connecting point p3 in this order AC2 The alternating current power of (1). The voltage V can be supplied from the second inverter 44 to the secondary connection breaker 83 AC2 The alternating current power of (1). The voltage V can be supplied from the branch breaker 85a to the power switching unit 28 AC1 The alternating current power of (1). The voltage V can be supplied from the branch breaker 85b to the second load 252 AC1 The alternating current power of (1). The voltage V can be supplied from the branch breaker 85c to the third load 253 AC2 The alternating current power of (1).
[ Power switching Unit 28]
The power switching unit 28 has a plurality of input sections and a power output section 28 c. The plurality of inputs includes a system power input 28a and an independent power input 28 b. The power switching unit 28 is used to switch which of the plurality of input portions is connected to the power output portion 28 c. In this example, the power switching unit 28 is used to switch which of the system power input section 28a and the independent power input section 28b is connected to the power output section 28 c. In this example, the power switching unit 28 selectively connects one of the first inverter 13 and the branch breaker 85a to the independent switchboard 90, specifically to the main breaker 92, in this manner.
[ independent switchboard 90]
The individual switchboard 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 portion 95 includes branch breakers 95a, 95b, and 95 c.
The main breaker 92 is connected to the power switching unit 28 via an upstream circuit 98. The upstream circuit 98 is connected to the downstream circuit 99 via the main breaker 92.
The downstream circuit 99 is connected to the second branch portion 95. The branch breaker 95a of the second branch portion 95 is provided on a path connecting the main breaker 92 and the D1 power supply 55. 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, the voltage V can be supplied from the power switching unit 28 to the downstream-side circuit 99 via the main breaker 92 AC1 The alternating current power of (1). The voltage V can be supplied from the branch breaker 95a to the D1 power supply 55 AC1 The alternating current power of (1). The voltage V can be supplied from the branch breaker 95b to the hot water storage unit 47 AC1 The alternating current power of (1). The voltage V can be supplied from the branch breaker 95c to the first load 251 via the outlet 260 AC1 The alternating current power of (1).
[ operation of the Power System 300 during System connection ]
As shown in fig. 1, when the system is connected, the protective relay 62 is turned off based on a disconnection command from the controller 51. Here, the off state is a state in which a current flow is prohibited. In the power switching unit 28, the grid power input unit 28a is connected to the power output unit 28 c. In this way, the power switching unit 28 connects the branch breaker 85a to the individual switchboard 90.
The electric power generated by the fuel cell 41 is supplied to the second DC bus 43 via the fifth DCDC converter 42. A part or all of the electric power supplied to the second DC bus 43 is supplied to the secondary connection breaker 83 via the second inverter 44.
Part of the power supplied to the secondary connection breaker 83 is supplied to the main breaker 92 via the branch breaker 85a and the power switching unit 28 in this order. Part of the electric power supplied to the main breaker 92 is supplied to the D1 power supply 55 via the branch breaker 95 a. 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 95 b. Still another part 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 order.
Another part of the power supplied to the secondary connection breaker 83 is supplied to the second load 252 via the branch breaker 85 b. Yet another part of the power supplied to the secondary connection breaker 83 is supplied to the third load 253 via the branch breaker 85 c.
When the electric power obtained by adding a predetermined margin to the surplus electric power is larger than zero, the electric power is supplied from the second DC bus 43 to the heater 46 via the sixth DCDC converter 45.
The DC power conversion device 20, specifically, the second DCDC converter 22 extracts electric power from the first solar power generation system 31 by MPPT control and supplies the extracted electric power to the first DC bus 11. The DC power conversion device 20, specifically, the third DCDC converter 23 extracts power from the second solar power generation system 32 by MPPT control and supplies the extracted power to the first DC bus 11.
In the case where the electrical 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 electrical storage device 25, and the remaining part of the electric power is supplied to the first inverter 13. When the electric storage device 25 is in the fully charged state, all 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 connection breaker 81.
As can be understood from the above description, the power system 300 of this example is configured such that: the electric power supplied from the second inverter 44 to the secondary connection breaker 83 differs by at least the margin from the total requested load of the loads 251 to 253, the D1 power supply 55, and the hot water storage unit 47. The electric power corresponding to the shortage is supplied from the connection breaker 81 to the downstream side circuit 89 via the main breaker 82, and the electric power is supplied to the first branch portion 85 together with the electric power supplied from the second inverter 44 to the secondary connection breaker 83. The remaining part of the electric power supplied to the connection breaker 81 flows backward to the system power supply 200.
In the case where the power generation in the solar power generation systems 31 and 32 is insufficient, the power of the above-described insufficient portion is supplied from the system power source 200 to the downstream side circuit 89 via the main breaker 82, and the power is supplied to the first branch portion 85 together with the power supplied from the second inverter 44 to the secondary connection breaker 83. If the power storage device 25 is not in the fully charged state and the power generation in the solar power generation systems 31 and 32 is insufficient to charge the power storage device 25, electric power is supplied from the system power supply 200 to the power storage device 25 via the first inverter 13, the first DC bus 11, and the fourth DCDC converter 12.
[ operation of Power System 300 during Power failure ]
As shown in fig. 2, the protection relay 62 is closed based on the parallel command from the controller 51 at the time of power failure. Here, the closed state refers to a state in which a current is allowed to flow in itself. The power switching unit 28 connects the first inverter 13 to the individual 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. A part or all of the direct-current power supplied to the second DC bus 43 is supplied to the characteristic conversion circuit 100. The DC power conversion device 20, specifically, the first DCDC converter 21 extracts power from the characteristic conversion circuit 100 (strictly, via the LC filter 61) by MPPT control and supplies the extracted power to the first DC bus 11.
In addition, the DC power conversion device 20 takes out electric power from the solar power generation systems 31 and 32 in the same manner as when the systems are connected, and supplies the taken-out electric power to the first DC bus 11.
When the total power taken out from the solar power generation systems 31 and 32 and the characteristic conversion circuit 100 by the DC power conversion device 20 is smaller than the requested loads of the first load 251, the D1 power supply 55 and the hot water storage unit 47, the electric power corresponding to the shortage is also supplied from the electric storage device 25 to the first DC bus 11 via the fourth DCDC converter 12. When the extracted electric power is larger than the requested load, the surplus electric power is charged into the power storage device 25 via the fourth DCDC converter 12, and when the surplus electric power remains even after the charging, a part of the electric power of the second DC bus 43 is supplied to the heater 46 via the sixth DCDC converter 45.
The power that has traced to or is close to the above-described request load is supplied from the first DC bus 11 to the main breaker 92 via the first inverter 13 and the power switching unit 28 in this manner. The electric power supplied to the main breaker 92 is supplied to the D1 power supply 55, the hot water storage unit 47, and the first load 251 in the same manner as when the system is connected.
[ advantages of connection mode of devices in Power System 300 ]
In this example, the power system 300 includes the power storage device 25. The solar power generation systems 31 and 32, the dc power conversion device 20, and the power storage device 25 are connected in this order. The fuel cell power generation system 40, the characteristic conversion circuit 100, the dc power conversion device 20, and the power storage device 25 are connected in this order. Therefore, not only the power storage device 25 can be charged from the solar power generation systems 31 and 32, but also the power storage device 25 can be charged from the fuel cell power generation system 40.
In this example, the power system 300 includes the power storage device 25, the outlet 260, and the inverter 13 that converts dc power into ac power. The solar power generation systems 31 and 32, the dc power conversion device 20, the inverter 13, and the socket 260 are connected in this order. The fuel cell power generation system 40, the characteristic conversion circuit 100, the dc power conversion device 20, the inverter 13, and the outlet 260 are connected in this order. Power storage device 25, inverter 13, and socket 260 are connected in this order. Therefore, in this example, the power can also be supplied from the fuel cell power generation system 40 to the outlet 260 to which the power is supplied from the solar power generation systems 31 and 32 and the power storage device 25. This configuration is convenient at the time of power failure for the following reasons. That is, at night, rainy day, etc., the solar power generation systems 31 and 32 cannot generate power. If a power failure continues at night, during a rainy day, or the like when power cannot be supplied from fuel cell power generation system 40 to outlet 260, the period during which power can be taken out from outlet 260 is a limited period based only on power storage device 25. In contrast, in this example, since electric power can be supplied from fuel cell power generation system 40 to outlet 260, the above-described period can be extended. In the case where power failure continues at night, in rainy days, or the like, it is convenient for a user to be able to take out power from one outlet for a long time without replacing the outlet with another outlet.
In this example, the same connection as that to socket 260 is also made to hot water storage unit 47. Therefore, when power failure continues at night, in rainy days, or the like, electric power necessary for the operation can be supplied to the hot water storage unit 47 for a long time.
In this example, the power system 300 is configured to be able to supply electric power from the power storage device 25 to the fuel cell power generation system 40 (specifically, to the D1 power supply 55). Specifically, the D1 power supply 55 is also connected in the same manner as the connection described above with respect to the outlet 260. In this case, a dedicated power supply for starting the fuel cell power generation system 40 at the time of power failure can be omitted. The dedicated power supply is typically a power supply for supplying electric power to the auxiliary machines of the fuel cell power generation system 40.
[ specific example of characteristic conversion Circuit ]
Hereinafter, a characteristic conversion circuit 100X as a specific example of the characteristic conversion circuit 100 will be described with reference to fig. 8. Hereinafter, the same reference numerals are given to the elements already described with reference to fig. 4, and the description thereof will be omitted.
The LLC converter is configured in the characteristic conversion circuit 100X. The LLC converter is configured to: the higher the current flowing from the current supply power source 131, the higher the oscillation frequency is defined, and the higher the oscillation frequency is, the smaller the ratio of the output voltage to the input voltage of the characteristic conversion circuit 100X is.
Specifically, the characteristic conversion circuit 100X is provided with 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 LLC converter described above.
The feedback current supply unit 130X includes a first light emitting diode 135 in addition to the current supply power source 131 and the seventh resistor 132. The current flowing from the current supply source 131 flows to the first light emitting diode 135.
The current resonance control unit 140 includes an eighth resistor 141, a first capacitor 142, a ninth resistor 143, a first phototransistor 145, and a control IC 146. The eighth resistor 141, the first capacitor 142, and a combination of the ninth resistor 143 and the first phototransistor 145 are connected in parallel with each other. The first phototransistor 145 and the first light emitting diode 135 cooperate to constitute a 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 149 b.
In the current resonance control unit 140, a period in which the first capacitor 142 is charged with electric charge (hereinafter, sometimes referred to as a charge period) and a period in which the first capacitor 142 is discharged with electric charge (hereinafter, sometimes referred to as a discharge period) alternately come. The switching between the discharge period and the charge period is performed based on the voltage of the feedback terminal 148.
Specifically, during charging, the first capacitor 142 is charged with electric charge from the constant current source 147 via the feedback terminal 148. As charging proceeds, 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 discharging period, the charge from the constant current source 147 to the first capacitor 142 is stopped. During the discharging, the charge charged to the first capacitor 142 is discharged via the eighth resistor 141. During discharging, charge is also discharged via the ninth resistor 143 and the first phototransistor 145. As the discharge progresses, the voltage of the feedback terminal 148 decreases. When the voltage of the feedback terminal 148 reaches the second voltage, the charging period is switched.
As the current flowing through the first light emitting diode 135 increases, a larger current flows through the first phototransistor 145, and the discharge period of the electric charge via the ninth resistor 143 and the first phototransistor 145 is faster, and the discharge period is shorter and the charge/discharge frequency is higher. The charge and discharge frequency corresponds to the oscillation frequency described above.
In a certain discharge period, a drive signal is output from the high-side driver output terminal 149 a. During the next discharge, a drive signal is output from the low side driver output terminal 149 b. During the next discharge period, a drive signal is output from the high-side driver output terminal 149 a. During the next discharge, a drive signal is output from the low side driver output terminal 149 b. This operation is repeated, and drive pulse signals having opposite phases to each other are output from the driver output terminals 149a and 149 b. The higher the charge/discharge frequency is, the higher the frequency of these drive pulse signals is. Further, the charging period is a dead time (dead time) during which no drive signal is output from both driver output terminals 149a and 149 b.
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, a 1 st diode 166a, a 2 nd diode 166b, and a sixth capacitor 167.
The switching elements 162a and 162b constitute a series circuit by being connected in series. A second capacitor 161 is connected in parallel to the series circuit. The third capacitor 163a is connected in parallel with the first switching element 162 a. The fourth capacitor 163b is connected in parallel with the second switching element 162 b.
In this example, the switching elements 162a and 162b are MOSFETs (Metal-Oxide-Semiconductor Field-Effect transistors). In addition, the fifth capacitor 164 is a resonance capacitor.
The transformer 165 has a first winding 165a as a primary side winding, and a second winding 165b and a third winding 165c as secondary side windings.
A current outlet terminal of the first switching element 162a and a current inlet terminal of the second switching element 162b are connected to one end of the first winding 165 a. A fifth capacitor 164 is connected between the other end of the first winding 165a and the current outgoing terminal of the second switching element 162 b. Further, in this example, the current outflow terminal is a source terminal. The current inflow terminal is a drain terminal.
An anode of the 1 st diode 166a is connected to one end of the second winding 165 b. To the cathode of the 1 st diode 166a, one end of a sixth capacitor 167 and the cathode of the 2 nd diode 166b are connected. The other end of the second winding 165b is connected to the other end of the sixth capacitor 167 and a reference potential.
The other end of the sixth capacitor 167 and the reference potential are connected to one end of the third winding 165 c. The other end of the third winding 165c is connected to the anode of the 2 nd diode 166 b.
The drive pulse signal is supplied from the high-side driver output terminal 149a to the control terminal of the first switching element 162 a. A drive pulse signal is supplied from the low-side driver output terminal 149b to the control terminal of the second switching element 162 b. Thereby, the switching elements 162a and 162b are alternately turned on and off by being supplied with drive pulse signals that are inverted from each other. Further, 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. 9 shows another example of the characteristic conversion circuit. Hereinafter, the same portions as those in the example of fig. 4 are denoted by the same reference numerals, and the description thereof is omitted.
The characteristic conversion circuit 190 shown in fig. 9 is provided with a feedback current supply unit 195 instead of the feedback current supply unit 130 of the characteristic conversion circuit 100 shown in fig. 4. The feedback current supply unit 195 includes a tenth resistor 191 in addition to the current supply power source 131 and the seventh resistor 132.
In the characteristic conversion circuit 190, as in the characteristic conversion circuit 100, as the voltage input to the first reference voltage terminal of the first shunt regulator 115 increases, the first current, which is the current flowing in this order among the current supply power source 131, the seventh resistor 132, the first shunt regulator 115, and the reference potential, 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 larger the second current, which is the current flowing in this order among the current supply power source 131, the tenth resistor 191, the second shunt regulator 125, and the reference potential.
In a region where the output current of the characteristic conversion circuit 190 is small, the second current i2 is substantially zero, and the current flowing from the current supply power source 131 is substantially the first current i 1. On the other hand, in a region where the output current of the characteristic conversion circuit 190 is large, the first current i1 is substantially zero, and the current flowing from the current supply power source 131 is substantially the second current i 2. 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 a region where the output current of the characteristic conversion circuit 190 is small, and the characteristic conversion in the characteristic conversion circuit 190 is performed by the second feedback circuit 120 in a region where the output current of the characteristic conversion circuit 190 is large. In this regard, the characteristic conversion circuit 190 is common to the characteristic conversion circuit 100. Therefore, in the characteristic conversion circuit 190, the ratio of the output voltage to the input voltage of the voltage current control circuit 160 is adjusted in the same manner as in the characteristic conversion circuit 100.
Fig. 10 shows a characteristic conversion circuit 190X as a specific example of the characteristic conversion circuit 190. Hereinafter, the same portions as those in the example of fig. 8 are denoted by the same reference numerals, and the description thereof is omitted.
In the characteristic conversion circuit 190X shown in fig. 10, a feedback current supply unit 195X is provided instead of the feedback current supply unit 130X of the characteristic conversion circuit 100X shown in fig. 8. In addition, the characteristic conversion circuit 190X is provided with 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 includes a tenth resistor 191 and a second light emitting diode 192 in addition to the current supply power source 131, the seventh resistor 132, and the first light emitting diode 135. The current resonance controller 199 includes an eleventh resistor 196 and a second phototransistor 197 in addition to the eighth resistor 141, the first capacitor 142, the ninth resistor 143, the first phototransistor 145, and the control IC 146.
The eighth resistor 141, the first capacitor 142, and the combination of the ninth resistor 143 and the first phototransistor 145 are connected in parallel with the combination of the eleventh resistor 196 and the second phototransistor 197. The second light emitting diode 192 cooperates with a second phototransistor 197 to form a second photocoupler 198.
In the current resonance controller 199, similarly to the current resonance controller 140, a period during which the first capacitor 142 is charged with electric charge (hereinafter, sometimes referred to as a charge period) and a period during which the first capacitor 142 is discharged with electric charge (hereinafter, sometimes referred to as a discharge period) alternately come.
Specifically, during charging, the first capacitor 142 is charged with electric charge 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 discharging period, the charge from the constant current source 147 to the first capacitor 142 is stopped. During the discharging, the charge charged to the first capacitor 142 is discharged via the eighth resistor 141. During discharging, charge is also discharged via the ninth resistor 143 and the first phototransistor 145 or via the eleventh resistor 196 and the second phototransistor 197. As the discharge progresses, the voltage of the feedback terminal 148 decreases. When the voltage of the feedback terminal 148 reaches the second voltage, the charging period is switched.
The state of charge of the first capacitor 142 in the current resonance control section 199 changes in the same manner as the current resonance control section 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.
Again, a specific example of the characteristic conversion circuit 100 in fig. 4 is not limited to the characteristic conversion circuit 100X in fig. 8. For example, as the current flowing from the current supply source 131 increases, a smaller duty ratio is defined, and a DCDC converter that operates based on the duty ratio can be configured in the characteristic conversion circuit. The same applies to a specific example of the characteristic conversion circuit 190 in fig. 9.
The configurations of the first feedback circuit 110 and the second feedback circuit 120 in fig. 4 and 8 are not essential.
(second embodiment)
The characteristic conversion circuit according to the second embodiment shown in fig. 11 can also be used. Hereinafter, a characteristic conversion circuit according to a second embodiment will be described with reference to fig. 11. Hereinafter, the same portions as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
In the characteristic conversion circuit 400 of fig. 11, the first feedback circuit 410 has the current sensor 128 and the regulator 170. The second feedback circuit 420 has a current sensor 128 and a regulator 170. The current sensor 128 and the regulator 170 are shared by the first feedback circuit 410 and the second feedback circuit 420.
As in the first embodiment, the current sensor 128 detects the output current of the characteristic conversion circuit 400. The current sensor 128 outputs a sensor output indicating the result of the detection. The larger the output current of the characteristic conversion circuit 400, the larger the sensor output is output from the current sensor 128. That is, the larger the output current of the characteristic conversion circuit 400 is, the larger the sensor output is. Specifically, the sensor output is a sensor voltage V s . The current sensor 128 includes an output sensor voltage V s The sensor output portion 128 a. In the present embodiment, the sensor voltage V output from the current sensor 128 may be set s Referred to as the first sensor voltage V s 。
The adjuster 170 is configured to adjust the variable parameter. The variable parameter may be a parameter that can be adjusted manually or may be a parameter that can be adjusted automatically. The adjuster 170 is to be inputted to the second of the adjuster 170A sensor voltage V s Adjusted to the second sensor voltage V M 。
In the present embodiment, the regulator 170 is for the first sensor voltage V s A DCDC converter for performing voltage transformation. The variable parameter is a parameter for changing the transformation ratio of the DCDC converter.
Specifically, in the present embodiment, the adjuster 170 has the structure shown in fig. 12. The regulator 170 of fig. 12 includes a voltage dividing circuit 170a and an amplifying circuit 170 b. The variable parameter is a parameter possessed by the voltage dividing circuit 170a or the amplifying circuit 170 b. The sensor output unit 128a, the voltage divider circuit 170a, the amplifier circuit 170b, and the connection point ps are connected in this order.
In the example of fig. 12, the voltage divider circuit 170a includes a resistor FR1, a resistor FR2, and a variable resistor VR 1. The sensor output unit 128a, the resistor FR1, the resistor FR2, the variable resistor VR1, and the reference potential are connected in this order. The voltage divider 170a uses the resistors FR1, FR2 and the variable resistor VR1 to couple the first sensor voltage V s Partial pressure is carried out. By this voltage division, a divided voltage V shown by the following expression 2 is generated D . Here, FR1 is the resistance value of the resistor FR 1. FR2 is the resistance value of resistor FR 2. VR1 is the resistance value of variable resistor VR 1. "" is a symbol representing a multiplication operation.
The numerical formula 2: v D ＝V s *(FR2+VR1)/(FR1+FR2+VR1)
The amplifying circuit 170b includes a resistor FR3, a resistor FR4, and an operational amplifier 175. The operational amplifier 175 includes a first input terminal 175a, a second input terminal 175b, and an output terminal 175 c. The divided voltage V is input to the first input terminal 175a D . The second input terminal 175b is connected to the output terminal 175c via a resistor FR 3. The second input terminal 175b is connected to the reference potential via a resistor FR 4. The output terminal 175c, the resistor FR3, the resistor FR4, and the reference potential are connected in this order. The amplifying circuit 170b is based on the divided voltage V D Generating a second sensor voltage V M And outputs a second sensor voltage V from an output terminal 175c M . Second sensor voltage V M This is given by the following equation 3. Here, FR3 is the resistance value of the resistor FR3. FR4 is the resistance value of resistor FR 4.
Numerical formula 3: v M ＝V D *(FR3+FR4)/FR4
Specifically, the first input terminal 175a is a non-inverting amplification terminal. The second input terminal 175b is an inverting amplification terminal.
Second sensor voltage V M Is supplied to the connection point ps. Thereafter, the voltage at the connection point ps is used as in the first embodiment.
In the example shown in fig. 12, voltage divider circuit 170a includes variable resistor VR 1. The variable parameter is the resistance value of variable resistor VR 1. The divided voltage V can be adjusted by adjusting the resistance value of the variable resistor VR1 D And a second sensor voltage V M 。
The resistor FR1 or the resistor FR2 may be a variable resistor. Even in this case, the divided voltage V can be adjusted by adjusting the resistance value of the variable resistor D And a second sensor voltage V M 。
In addition, the amplifier circuit 170b may include a variable resistor instead of the voltage divider circuit 170 a. Specifically, the resistor FR3 or the resistor FR4 may be a variable resistor. Even in this case, the second sensor voltage V can be adjusted by adjusting the resistance value of the variable resistor M 。
In the second embodiment, as in the first embodiment, in order to bring about the output voltage-output power characteristic of (i) and the output current-output power characteristic of (ii) described below, the first feedback control is executed when the sensor output is relatively small, and the second feedback control is executed when the sensor output is relatively large. As described above, specifically, the sensor output is the first sensor voltage V s 。
(i) The output voltage-output power characteristic of (2) is an output voltage-output power characteristic in which the output power of the characteristic conversion circuit 400 is maximum when the output voltage of the characteristic conversion circuit 400 is a certain value. (ii) The output current-output power characteristic of (1) is that the output current of the characteristic conversion circuit 400 is a switching current i sw Output current-output power characteristic of the time characteristic conversion circuit 400 with the maximum output powerIt is also good. Here, the current i is switched sw Is the output current of the characteristic conversion circuit 400 when switching between the first feedback control and the second feedback control. Specifically, as in the first embodiment, the certain value is a value within a predetermined range.
In the present embodiment, the current i is switched sw Depends on an error of detection of the output current of the characteristic conversion circuit 400 by the current sensor 128, and switches the current i if a variable parameter is made to vary sw And (4) changing.
If there is an individual deviation of the current sensor 128, an error may be generated in the detection of the current sensor 128. That is, an error may be generated in the sensor output. If the sensor output with an error is used for control in the characteristic conversion circuit 400, the current i is switched sw There is a possibility that the current may deviate from a target value (hereinafter, sometimes referred to as a target current). If switching the current i sw If a deviation occurs, the maximum power point may deviate from the target point. If the maximum power point deviates, the maximum power of the characteristic conversion circuit 400 may deviate from a target value (hereinafter, may be referred to as a target power).
In this regard, according to the second embodiment, the switching current i can be adjusted by varying the variable parameter sw . Thereby, the switching current i can be reduced sw Deviation from the target current, reduction of deviation of the maximum power point from the target point, reduction of deviation of the maximum power from the target power. In addition, the variable parameter is adjusted to adjust the switching current i sw Thus, the maximum power of the characteristic conversion circuit 400 can be adjusted according to the situation. For example, the maximum power can be increased when the generated power of the solar power generation system connected to the dc power conversion device 20 is small, and the maximum power can be decreased when the generated power of the solar power generation system is large. The maximum output of the fuel cell power generation system 40 may be reduced due to, for example, the aged deterioration of the stack of the fuel cells 41. In this case, the maximum power output from the characteristic conversion circuit 400 can be reducedThe maximum power converges in the range that the fuel cell power generation system 40 can supply.
By reducing the deviation of the maximum power from the target power, the deviation of the extracted power from the target power can be reduced when the power is extracted from the characteristic conversion circuit 400 by MPPT control. By adjusting the maximum power of the characteristic conversion circuit 400 according to the situation, when power is extracted from the characteristic conversion circuit 400 by MPPT control, the extracted power can be adjusted to a value according to the situation. For example, when the generated power of the solar power generation system connected to the dc power conversion device 20 is small, the extracted power can be increased, and when the generated power of the solar power generation system is large, the extracted power can be decreased. In addition, when the maximum output of the fuel cell power generation system 40 is reduced, the extracted power can be reduced.
[ Individual bias of Current sensor 128 and suppression thereof ]
As described above, the current sensor 128 sometimes has an individual deviation. The influence of the individual deviation is explained in detail with reference to fig. 13 to 15.
In the present embodiment, the current sensor 128 has the structure shown in fig. 5. Ideally, the resistance value R of the shunt resistor 128R sense Gain G and bias voltage V bias Is a reference value. However, the resistance value R sense Gain G and/or bias voltage V bias There may be errors within the tolerance range. In the present embodiment, the current sensor 128 is configured to: when the resistance value of the shunt resistance 128r is larger than the reference value, the current sensor 128 outputs a first sensor voltage V1 larger than when the resistance value of the shunt resistance 128r is the reference value. The current sensor 128 is configured to: when the gain G is larger than the reference value, the current sensor 128 outputs a first sensor voltage V1 larger than when the gain G is the reference value. The current sensor 128 is configured to: at a bias voltage V bias Above the reference value, the current sensor 128 outputs a voltage compared to the bias voltage V bias The first sensor voltage V1, which is larger for the reference value.
In fig. 13, the horizontal axis represents a characteristic transitionThe output current of the converter circuit 400. The resistance value R is shown in FIG. 13 sense When the sum gain G is at the reference value, the bias voltage V is enabled bias The output characteristic of the characteristic conversion circuit 400 in the case where the change has occurred.
Specifically, in fig. 13, "output voltage (0) of the characteristic conversion circuit" represents bias voltage V bias The output voltage of the characteristic conversion circuit 400 at the reference value. "output voltage (a) of characteristic conversion circuit" represents bias voltage V bias The output voltage of the characteristic conversion circuit 400 at 101% of the reference value. "output voltage (B) of characteristic conversion circuit" represents bias voltage V bias The output voltage of the characteristic conversion circuit 400 at 99% of the reference value. "output voltage (C) of characteristic conversion circuit" represents bias voltage V bias The output voltage of the characteristic conversion circuit 400 at 102% of the reference value. "output voltage (D) of characteristic conversion circuit" represents bias voltage V bias The output voltage of the characteristic conversion circuit 400 at 98% of the reference value. "output power (0) of characteristic conversion circuit" represents bias voltage V bias The output power of the characteristic conversion circuit 400 at the reference value. "output power (a) of characteristic conversion circuit" means bias voltage V bias The output power of the characteristic conversion circuit 400 at 101% of the reference value. "output power (B) of characteristic conversion circuit" means bias voltage V bias The output power of the characteristic conversion circuit 400 at 99% of the reference value. "output power (C) of characteristic conversion circuit" means bias voltage V bias The output power of the characteristic conversion circuit 400 at 102% of the reference value. "output power (D) of characteristic conversion circuit" represents bias voltage V bias The output power of the characteristic conversion circuit 400 at 98% of the reference value. In fig. 13, five broken lines extending vertically represent switching currents i in order from the left sw (C) Switching current i sw (A) Switching current i sw (0) Switching current i sw (B) And a switching current i sw (D) In that respect "switching Current i sw (0) "denotes a bias voltage V bias Switching current i at reference value sw . "switching Current i sw (A)”Representing the bias voltage V bias Switching current i at 101% of the reference value sw . "switching Current i sw (B) "denotes a bias voltage V bias Switching current i at 99% of the reference value sw . "switching Current i sw (C) "denotes a bias voltage V bias Switching current i at 102% of the reference value sw . "switching Current i sw (D) "denotes a bias voltage V bias Switching current i at 98% of the reference value sw . As described above, the current i is switched sw Is the output current of the characteristic conversion circuit 400 when switching between the first feedback control and the second feedback control.
As can be understood from fig. 13, the switching current i sw With bias voltage V bias May vary.
At a bias voltage V bias At the reference value, the maximum power point is at the target point. This situation is as shown in fig. 3A according to the first embodiment.
At a bias voltage V bias At a reference value, the current i is switched sw In agreement with the target current. At a bias voltage V bias Greater than a reference value, compared to the bias voltage V bias At a reference value, the switching current i sw Is smaller. On the contrary, when the bias voltage V bias Less than a reference value, compared to the bias voltage V bias At the reference value, the switching current i sw Is relatively large.
At a bias voltage V bias At the reference value, the maximum power of the characteristic conversion circuit 400 coincides with the target power. At a bias voltage V bias Greater than a reference value, compared to the bias voltage V bias At the reference value, the maximum power is small. On the contrary, when the bias voltage V is bias Less than a reference value, compared to the bias voltage V bias At the reference value, the maximum power is large.
As shown in fig. 13, the bias voltage V bias Causes a deviation of the maximum power point of the characteristic conversion circuit 400. The deviation of the maximum power point results in a switching current i sw And deviation from maximum powerAnd (4) poor.
In this regard, in the second embodiment, the switching current i of the characteristic conversion circuit 400 can be adjusted by adjusting the resistance value of the variable resistor VR1 sw Thereby enabling adjustment of the maximum power.
Consider, for example, the following: at a bias voltage V bias Less than the reference value, compared with the bias voltage V bias At the reference value, the switching current i sw And the maximum power is larger. In this case, the resistance value of the variable resistor VR1 is adjusted to adjust the second sensor voltage V M Compared to the bias voltage V bias Increases at the reference value, thereby enabling the switching current i to be reduced sw And maximum power. Thereby, the switching current i can be switched sw And the maximum power is close to the target current and the target power. Specifically, by increasing the resistance value of the variable resistor VR1, the switching current i can be increased sw And the maximum power is close to the target current and the target power.
Conversely, consider the following: at a bias voltage V bias Greater than a reference value, compared to the bias voltage V bias At the reference value, the switching current i sw And the maximum power is small. In this case, the resistance value of the variable resistor VR1 is adjusted to adjust the second sensor voltage V M Compared to the bias voltage V bias Decreases at the reference value, thereby enabling an increase in the switching current i sw And maximum power. Thereby, the switching current i can be switched sw And the maximum power is close to the target current and the target power. Specifically, by reducing the resistance value of the variable resistor VR1, the switching current i can be reduced sw And the maximum power is close to the target current and the target power.
By adjusting the variable resistor VR1, the switching current i can be adjusted sw And maximum power near bias voltage V bias The value at the reference value. That is, the switching current i can be made to be sw And the maximum power is close to the target current and the target power. In summary, the output characteristic of the characteristic conversion circuit 400 can be made close to the bias voltage V bias Output characteristic at the reference value.
At gain G and bias voltage V bias Even when there is an error between the two, the switching current i of the characteristic conversion circuit 400 can be adjusted by adjusting the resistance value of the variable resistor VR1 sw Thereby adjusting the maximum power.
In fig. 14 and 15, the horizontal axis represents the output current of the characteristic conversion circuit 400. Fig. 14 and 15 show the resistance value R of the shunt resistor 128R sense At the reference value, the gain G and the bias voltage V are set bias The output characteristic of the characteristic conversion circuit 400 in the case where the change has occurred.
Specifically, in fig. 14, "output voltage (0) of the characteristic conversion circuit" indicates gain G and bias voltage V bias The output voltage of the characteristic conversion circuit 400 at the reference value. "output voltage (E) of the characteristic conversion circuit" means that the gain G is 101% of the reference value and the bias voltage V bias The output voltage of the characteristic conversion circuit 400 at 102% of the reference value. "output voltage (F) of characteristic conversion circuit" indicates that gain G is 99% of a reference value and bias voltage V bias The output voltage of the characteristic conversion circuit 400 at 98% of the reference value. "output power (0) of characteristic conversion circuit" represents gain G and bias voltage V bias The output power of the characteristic conversion circuit 400 at the reference value. "output power (E) of the characteristic conversion circuit" means that the gain G is 101% of the reference value and the bias voltage V bias The output power of the characteristic conversion circuit 400 at 102% of the reference value. "output power (F) of the characteristic conversion circuit" means that the gain G is 99% of the reference value and the bias voltage V bias The output power of the characteristic conversion circuit 400 at 98% of the reference value. "switching Current i sw (0) "indicates the gain G and the bias voltage V bias Switching current i at reference value sw . "switching Current i sw (E) "indicates that the gain G is 101% of the reference value and the bias voltage V bias Switching current i at 102% of the reference value sw . "switching Current i sw (F) "indicates that the gain G is 99% of the reference value and the bias voltage V bias Switching current i at 98% of the reference value sw 。
In fig. 15, "output voltage (0) of the characteristic conversion circuit" indicates gain G and bias voltage V bias The output voltage of the characteristic conversion circuit 400 at the reference value. "output voltage (G) of characteristic conversion circuit" means that gain G is 99% of a reference value and bias voltage V bias The output voltage of the characteristic conversion circuit 400 at 102% of the reference value. "output voltage (H) of characteristic conversion circuit" indicates that gain G is 101% of a reference value and bias voltage V bias The output voltage of the characteristic conversion circuit 400 at 98% of the reference value. "output power (0) of characteristic conversion circuit" represents gain G and bias voltage V bias The output power of the characteristic conversion circuit 400 at the reference value. "output power (G) of characteristic conversion circuit" means that gain G is 99% of a reference value and bias voltage V bias The output power of the characteristic conversion circuit 400 at 102% of the reference value. "output power (H) of the characteristic conversion circuit" means that the gain G is 101% of the reference value and the bias voltage V bias The output power of the characteristic conversion circuit 400 at 98% of the reference value. "switching Current i sw (0) "indicates the gain G and the bias voltage V bias Switching current i at reference value sw . "switching Current i sw (G) "indicates that the gain G is 99% of the reference value and the bias voltage V bias Switching current i at 102% of the reference value sw . "switching Current i sw (H) "indicates that the gain G is 101% of the reference value and the bias voltage V bias Switching current i at 98% of the reference value sw 。
As can be understood from fig. 14 and 15, the switching current i sw With gain G and bias voltage V bias May vary. However, in both the example of fig. 14 and the example of fig. 15, the switching current i can be set by adjusting the resistance value of the variable resistor VR1 sw And the maximum power is close to the target current and the target power. In summary, the output characteristic of the characteristic conversion circuit 400 can be made close to the gain G and the bias voltage V bias Output characteristic at the reference value.
Specifically, in the case of (E) of fig. 14, the variable resistance VR1 is decreasedThereby reducing the second sensor voltage V M Can make the switching current i sw And the maximum power is close to the target current and the target power.
In the case of fig. 14 (F), the resistance value of the variable resistor VR1 is increased to increase the second sensor voltage V M Can make the switching current i sw And the maximum power is close to the target current and the target power.
In the case of (G) of fig. 15, the second sensor voltage V is reduced by reducing the resistance value of the variable resistor VR1 M Can make the switching current i sw And the maximum power is close to the target current and the target power.
In the case of fig. 15 (H), the resistance value of the variable resistor VR1 is increased to increase the second sensor voltage V M Can make the switching current i sw And the maximum power is close to the target current and the target power.
Of course, in the resistance value R sense Even when there is an error, the switching current i can be adjusted by adjusting the resistance value of the variable resistor VR1 sw And the maximum power is close to the target current and the target power.
The technique of the second embodiment can be applied not only to the configuration of fig. 4 of the first embodiment but also to the configurations of fig. 8 to 10. Specifically, the adjuster 170 can also be applied to the structures of fig. 8 to 10.
(third embodiment)
A third embodiment of the present disclosure will be described below. Hereinafter, the same portions as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
Fig. 16 and 17 are block diagrams of a power system 500 according to the third embodiment. Specifically, fig. 16 shows an example of the flow of electric power when the system is connected. Fig. 17 shows an example of the flow of power at the time of power failure.
As shown in fig. 16 and 17, the power system 500 has a substrate 560. The base plate 560 is provided on a path connecting the fuel cell power generation system 40 and the power plant 10. DC power is supplied from the fuel cell power generation system 40, specifically, from the second DC bus 43 to the substrate 560. The substrate 560 has the characteristic conversion circuit 600, the LC filter 61, and the protective relay 62.
The characteristic conversion circuit 600 is provided on a path connecting the fuel cell power generation system 40 and the dc power conversion device 20, specifically, on a path of dc power. The characteristic conversion circuit 600 performs characteristic conversion control.
The output characteristics of the characteristic conversion circuit 600 are shown in fig. 18 and 19. Fig. 20 shows an example of the characteristic conversion circuit 600.
As in the first embodiment, the characteristic conversion control performed by the characteristic conversion circuit 600 brings about the following output voltage-output power characteristics: when the output voltage of the characteristic conversion circuit 600 is a certain value, the output power of the characteristic conversion circuit 600 is maximum. The characteristic conversion control includes a first feedback control and a second feedback control. The first feedback control is control performed when the output current of the characteristic conversion circuit 600 is relatively small. The second feedback control is control performed when the output current of the characteristic conversion circuit 600 is relatively large. When switching between the first feedback control and the second feedback control, the output voltage of the characteristic conversion circuit 600 is the certain value described above.
As shown in fig. 20, the characteristic conversion circuit 600 includes a voltage current control circuit 160, a current sensor 128, and a regulator 180.
As in the first embodiment, the voltage-current control circuit 160 is a DCDC converter. The voltage current control circuit 160 is provided between the fuel cell power generation system 40 and the current sensor 128. Specifically, the voltage-current control circuit 160 is disposed between the second DC bus 43 and the current sensor 128.
As in the first embodiment, the current sensor 128 detects the output current of the characteristic conversion circuit 600. The current sensor 128 outputs a sensor output indicating the result of the detection. The larger the output current of the characteristic conversion circuit 600 is, the larger the sensor output is output from the current sensor 128. That is, the larger the output current of the characteristic conversion circuit 600, the larger the sensor output. In this embodiment, the sensor output is the first sensorVoltage V1. The current sensor 128 includes a sensor output portion 128a that outputs a first sensor voltage V1. The first sensor voltage V1 corresponds to the sensor voltage V of the first embodiment s 。
The adjuster 180 is configured to adjust the variable parameter. In this embodiment, the regulator 180 is a variable output power source, and the variable parameter is a variable output. Hereinafter, the regulator 180 as a variable output power source may be referred to as a variable output power source 180.
The variable output power supply 180 outputs a variable output. In the present embodiment, the variable output is a variable voltage V4. The variable output power supply 180 is, for example, a digital-to-analog port of the controller 51.
The characteristic conversion circuit 600 is provided with a first circuit 610 and a second circuit 620. The first circuit 610 performs a first feedback control in which the larger the sensor output, the larger the output power of the characteristic conversion circuit 600 is made. The second circuit 620 performs a second feedback control in which the output power of the characteristic conversion circuit 600 is made smaller as the sensor output is larger, in cooperation with the first circuit 610. The characteristic conversion circuit 600 is also provided with a feedback current supply unit 130.
The first circuit 610, the second circuit 620, and the voltage-current control circuit 160 cooperate to perform characteristic conversion control.
Specifically, the first circuit 610 performs the first feedback control in cooperation with the voltage-current control circuit 160. The second circuit performs the second feedback control in cooperation with the first circuit 610 and the voltage-current control circuit 160.
In the characteristic conversion circuit 600, in order to bring about the output voltage-output power characteristic of (i) and the output current-output power characteristic of (ii) described below, the first feedback control is performed when the sensor output is relatively small, and the second feedback control is performed when the sensor output is relatively large.
(i) The output voltage-output power characteristic of (2) is an output voltage-output power characteristic in which the output power of the characteristic conversion circuit 600 is the maximum when the output voltage of the characteristic conversion circuit 600 is a certain value, as shown in fig. 18. Specifically, as in the first embodiment, the certain value is a value within a predetermined range.
As described above, the dc power conversion device 20 is designed to be able to execute MPPT control of the solar power generation system that maximizes the output power when the output voltage is within a predetermined range. In the present embodiment, the characteristic conversion circuit 600 has the output voltage-output power characteristic (i) described above, in which the output power is the maximum when the output voltage is a value within the predetermined range. The output voltage-output power characteristic of the fuel cell power generation system is not necessarily suitable for extraction of electric power by MPPT control. However, the characteristic conversion circuit 600 having the output voltage-output power characteristic (i) can extract power from the fuel cell power generation system 40 to the dc power conversion device 20 by executing MPPT control using the dc power conversion device 20.
(ii) The output current-output power characteristic of (2) is that the output current of the characteristic conversion circuit 600 is the switching current i as shown in FIG. 19 sw The output current-output power characteristic of the time characteristic conversion circuit 600 at which the output power is maximum. In this case, the current i is switched sw Is the output current of the characteristic conversion circuit 600 when switching between the first feedback control and the second feedback control.
Switching current i sw Depends on an error in detection of the output current of the characteristic conversion circuit 600 by the current sensor 128, and if a variable parameter is made to vary, the switching current i sw And (4) changing. As described above, in the present embodiment, the variable parameter is a variable output, specifically, a variable voltage V4.
If there is an individual deviation of the current sensor 128, an error may be generated in the detection of the current sensor 128. That is, an error may be generated in the sensor output. If the sensor output with an error is used for control in the characteristic conversion circuit 600, the current i is switched sw There is a possibility that the current may deviate from a target value (hereinafter, sometimes referred to as a target current). If switching the current i sw If a deviation occurs, the maximum power point shown in fig. 18 and 19 may deviate from the target point. If it is the most importantWhen the large power point varies, the maximum power of the characteristic conversion circuit 600 may vary from a target value (hereinafter, may be referred to as a target power).
In this regard, according to the present embodiment, the switching current i can be adjusted by changing the variable parameter sw . Thereby, the switching current i can be reduced sw Deviation from the target current, reduction of deviation of the maximum power point from the target point, reduction of deviation of the maximum power from the target power. In addition, the variable parameter is adjusted to adjust the switching current i sw Thus, the maximum power of the characteristic conversion circuit 600 can be adjusted according to the situation. For example, the maximum power can be increased when the generated power of the photovoltaic power generation system connected to the dc power conversion device 20 is small, and the maximum power can be decreased when the generated power of the photovoltaic power generation system is large. The maximum output of the fuel cell power generation system 40 may be reduced due to, for example, the aged deterioration of the stack of the fuel cells 41. In this case, by reducing the maximum power output from the characteristic conversion circuit 600, the maximum power can be made to fall within a range that can be supplied by the fuel cell power generation system 40.
By reducing the deviation of the maximum power from the target power, the deviation of the extracted power from the target power can be reduced when the power is extracted from the characteristic conversion circuit 600 by the MPPT control. By adjusting the maximum power of the characteristic conversion circuit 600 according to the situation, when power is extracted from the characteristic conversion circuit 600 by MPPT control, the extracted power can be adjusted to a value according to the situation. For example, when the generated power of the solar power generation system connected to the dc power conversion device 20 is small, the extracted power can be increased, and when the generated power of the solar power generation system is large, the extracted power can be decreased. In addition, when the maximum output of the fuel cell power generation system 40 is reduced, the extracted power can be reduced.
Typically, the output voltage-output power characteristic of the characteristic conversion circuit 600 is a characteristic in which the output power has a single peak with respect to the output voltage. The output voltage-output power characteristic of the above (i) shows such a characteristic.
The output characteristic of the characteristic conversion circuit 600 is further explained.
In fig. 18, a solid line indicates an output voltage-output power characteristic which is a relationship between the output voltage of the characteristic conversion circuit 600 and the output power of the characteristic conversion circuit 600. The short dashed line indicates the relationship between the output voltage of the characteristic conversion circuit 600 and the output current of the characteristic conversion circuit 600, that is, the output voltage-output current characteristic. The one-dot chain line indicates the contribution of the first feedback control. The two-dot chain line indicates the contribution of the second feedback control. The long dashed line represents the first sensor voltage V1.
As can be understood from fig. 18, in the present embodiment, the output voltage-output current characteristic of the characteristic conversion circuit 600 is a characteristic in which the output voltage follows a predetermined value in a region where the output current is small, by the first feedback control. By the second feedback control, the output voltage-output current characteristic of the characteristic conversion circuit 600 is a characteristic in which the output voltage decreases as the output current increases in a region where the output current is large. These feedback controls are combined, and the output voltage-output current characteristic of the characteristic conversion circuit 600 is the characteristic shown by the short dashed line in fig. 18. As a result, the output voltage-output power characteristic of the characteristic conversion circuit 600 is an upward convex characteristic having a single peak as shown by a solid line in fig. 18.
As described above, the upwardly convex output voltage-output power characteristic of the characteristic conversion circuit 600 enables MPPT control by the dc power conversion device 20. The MPPT control of the characteristic conversion circuit 600 can be performed by the dc power conversion device 20.
The structure of the characteristic conversion circuit 600 is further explained.
As shown in fig. 20, the first circuit 610 has a first resistor 621, a second resistor 622, and a first shunt regulator 625. The second circuit 620 has a current sensor 128, a sensor voltage adjustment circuit 620a, and a voltage-to-current conversion circuit 620 b. The feedback current supply unit 130 includes a current supply power source 131 and a third resistor 132. In the present embodiment, the current supply power source 131 is a constant voltage source. The third resistor 132 of the third embodiment corresponds to the seventh resistor 132 of the first embodiment.
With regard to the voltage-current control circuit 160, the smaller the current flowing from the current supply power source 131, the larger the ratio of the output voltage to the input voltage of the voltage-current control circuit 160 is made. In this way, the characteristic conversion circuit 600 adjusts the ratio in accordance with the current flowing from the current supply power source 131.
In the first circuit 610, the output voltage of the characteristic conversion circuit 600 is divided by the first resistor 621 and the second resistor 622. The divided voltage appears at a first connection point p1 between the resistor 621 and the resistor 622. Hereinafter, the voltage appearing at the first connection point p1 may be referred to as a first reference voltage V ref1 . First reference voltage V ref1 Is input to a first reference voltage terminal 625a of the first shunt regulator 625. A first reference voltage V input to a first reference voltage terminal 625a ref1 The larger the current i1 flows in this order among the current supply source 131, the third resistor 132, the first shunt regulator 625, and the reference potential. In fig. 20, the current i1 is a current flowing downward in the drawing in the first shunt regulator 625. Hereinafter, the current i1 may be referred to as a first current i 1.
In the present embodiment, the open-circuit voltage of the characteristic conversion circuit 600 is controlled by the first feedback control. Here, the open circuit voltage is an output voltage of the characteristic conversion circuit 600 when the output current of the characteristic conversion circuit 600 is zero. Specifically, in the first feedback control, the first reference voltage V is generated by the operation of the first shunt regulator 625 and the voltage current control circuit 160 ref1 Following a first reference voltage V described later s1 Thereby, the open circuit voltage is set to a predetermined value.
The first shunt regulator 625 of the present embodiment is further explained with reference to fig. 21. The first shunt regulator 625 includes a first reference voltage terminal 625A, a first cathode 625K, a first anode 625A, a first reference voltage source 625s, a first operational amplifier 625o, and a first transistor 625 t. The first operational amplifier 625o includes a non-inverting amplification terminal 625oa, an inverting amplification terminal 625ob, and an output terminal 625And oc. The first transistor 625t includes a cathode-side terminal 625ta, an anode-side terminal 625tb, and a control terminal 625 tc. The voltage input to the first reference voltage terminal 625a is supplied to the non-inverting amplification terminal 625 oa. The voltage of the inverting amplification terminal 625ob is set higher than the voltage of the first anode 625A by a first reference voltage V by a first reference voltage source 625s s1 The voltage of (c). When a first reference voltage V is input to the first reference voltage terminal 625a s1 When the voltage of the non-inverting amplification terminal 625oa is larger than the voltage of the inverting amplification terminal 625ob due to a large voltage, a current flows from the output terminal 625oc to the control terminal 625tc, and a first current i1 flows from the first cathode 625K to the first anode 625A through the cathode side terminal 625ta and the anode side terminal 625tb in this order. In the example of fig. 21, the first transistor 625t is a bipolar transistor, specifically, an NPN transistor. The cathode terminal 625ta is a collector. The anode-side terminal 625tb is an emitter. Control terminal 625tc is a base. In this description, a current flowing between the output terminal 625oc and the control terminal 625tc, specifically, a base current is ignored as a very small current.
Based on the description with reference to fig. 21, the operation of the first circuit 610 can be described as follows. If the output voltage V of the characteristic conversion circuit 600 out When the voltage becomes larger, the first reference voltage V becomes larger ref1 Becomes larger. In the first shunt regulator 625, due to the first reference voltage V ref1 Becomes larger and the first reference voltage V ref1 Relative to a first reference voltage V s1 The larger the deviation, the larger the first current i 1. If the first current i1 becomes large, the current flowing from the current supply power source 131 becomes large. If the outflow current becomes large, the ratio of the output voltage of the voltage current control circuit 160 to the input voltage becomes small. In this way, the first circuit 610 cooperates with the voltage-current control circuit 160 to control the output voltage V of the characteristic conversion circuit 600 out . Specifically, the first circuit 610 cooperates with the voltage-current control circuit 160 to control the first reference voltage V ref1 Track a first reference voltage V s1 Thereby making the output voltage V of the characteristic conversion circuit 600 out The specified value is tracked.
Returning to fig. 20, the sensor voltage adjustment circuit 620a of the second circuit 620 includes the variable output power supply 180, the input resistor R1, the feedback resistor R2, and the sensor voltage adjustment operational amplifier 124.
As described above, the current sensor 128 outputs the first sensor voltage V1. The variable output power supply 180 outputs a variable voltage V4. The sensor voltage adjustment circuit 620a generates the second sensor voltage V2 that varies according to the first sensor voltage V1 and the variable voltage V4.
If there is an individual deviation in the current sensor 128, an error may be generated in the first sensor voltage V1. If the first sensor voltage V1 having an error is used for control in the characteristic conversion circuit 600, it is possible to switch the current i sw The deviation occurs from the target current, the deviation occurs from the target point at the maximum power point, and the deviation occurs from the target power at the maximum power of the characteristic conversion circuit 600. In this regard, according to the present embodiment, the second sensor voltage V2 reflecting the first sensor voltage V1 and the variable voltage V4 can be generated. By using the second sensor voltage V2 reflecting the appropriately set variable voltage V4 for control in the characteristic conversion circuit 600, the switching current i can be reduced sw Deviation from the target current, reduction of deviation of the maximum power point from the target point, reduction of deviation of the maximum power from the target power. In addition, the variable voltage V4 is adjusted to adjust the switching current i sw Thus, the maximum power of the characteristic conversion circuit 600 can be adjusted according to the situation.
Specifically, the sensor voltage adjusting operational amplifier 124 includes a sensor input terminal 124a, a variable voltage input terminal 124b, and a second sensor voltage output terminal 124 c. The sensor input terminal 124a is connected to the sensor output unit 128a via an input resistor R1. The variable voltage V4 is input to the variable voltage input terminal 124 b. The second sensor voltage output terminal 124c is connected to the sensor input terminal 124a via a feedback resistor R2. The sensor voltage adjusting operational amplifier 124 generates a second sensor voltage V2 based on a voltage difference between the sensor input terminal 124a and the variable voltage input terminal 124b, and outputs a second sensor voltage V2 from a second sensor voltage output terminal 124 c.
Specifically, the sensor input terminal 124a is an inverting amplification terminal. The variable voltage input terminal 124b is a non-inverting amplification terminal.
The voltage-current conversion circuit 620b of the second circuit 620 includes the voltage supply power source 129, the intermediate resistor R3, the transistor drive operational amplifier 126, and the adjustment current output transistor 127. The voltage supply power source 129 outputs a threshold voltage V3. In the present embodiment, the voltage supply power source 129 is a constant voltage source.
In the voltage-current conversion circuit 620b, the adjustment current i3 starts flowing when the second sensor voltage V2 changes in a manner of crossing the threshold voltage V3 because the first sensor voltage V1 becomes large. When the adjustment current i3 starts to flow, the first feedback control is switched to the second feedback control. The characteristic conversion circuit 600 that switches control at the timing when the current starts to flow is easy to design.
Specifically, the transistor driving operational amplifier 126 includes a power supply input terminal 126a, a second sensor voltage input terminal 126b, and a control voltage output terminal 126 c. The power supply input terminal 126a is connected to the voltage supply source 129 via an intermediate resistor R3. The second sensor voltage V2 is input to the second sensor voltage input terminal 126 b. The transistor-driven operational amplifier 126 generates the control voltage V based on a voltage difference between the power input terminal 126a and the second sensor voltage input terminal 126b c And outputs a control voltage V from a control voltage output terminal 126c c 。
Specifically, the power supply input terminal 126a is an inverting amplification terminal. The second sensor voltage input terminal 126b is a non-inverting amplification terminal.
The regulated current output transistor 127 includes a control terminal 127c, a first terminal 127a, and a second terminal 127 b. A control voltage V is input to the control terminal 127c c . The first terminal 127a is connected to the voltage supply source 129 via an intermediate resistor R3. The second terminal 127b outputs the adjustment current i 3.
In the example of fig. 20, the adjustment current output transistor 127 is a bipolar transistor, specifically, a PNP transistor. The control terminal 127c is a base. The first terminal 127a is an emitter. The second terminal 127b is a collector.
The first sensor voltage V1, the second sensor voltage V2, the adjustment current i3 and the output voltage V of the second circuit 620 are further described by using equations out 。
Fig. 22 shows a current sensor 128 according to the present embodiment. The current sensor 128 includes a shunt resistor 128r and a current sense amplifier 128 s. The shunt resistor 128R has a resistance value of R sense . When current I load When the voltage is applied to the shunt resistor 128R, the voltage R is applied to the shunt resistor 128R sense I load . The current sense amplifier 128s will be coupled to the voltage R sense I load Voltage multiplied by gain G and bias voltage V bias Is output as the first sensor voltage V1. That is, the first sensor voltage V1 generated by the current sensor 128 of the present embodiment is given by equation 4. However, another current sensor such as a hall element type current sensor may be used as the current sensor 128, and the output of the current sensor may be used as the first sensor voltage V1. In addition, the current I load Corresponding to the output current of the characteristic conversion circuit 600. "" is a symbol representing a multiplication operation. As can be understood from fig. 5 and 22, the current sensor 128 of fig. 22 has the same structure as that of the current sensor of fig. 5.
The numerical formula 4: v1 ═ R sense *I load *G+V bias
The sensor voltage adjustment circuit 620a generates the second sensor voltage V2 by differential amplification using the sensor voltage adjustment operational amplifier 124. The second sensor voltage V2 is given by equation 5 below. Here, R1 is the resistance value of the input resistor R1. R2 is the resistance value of the feedback resistor R2.
The numerical formula 5: v2 ═ V4+ (V4-V1) × R2/R1
In the voltage-to-current conversion circuit 620b, when V2< V3, the transistor driving operational amplifier 126 drives the adjustment current output transistor 127 so that the voltage of the power supply input terminal 126a tracks the voltage of the second sensor voltage input terminal 126b due to a virtual short. Specifically, when V2< V3, the transistor drives the operational amplifier 126 to drive the control terminal 127c so that the voltage of the power supply input terminal 126a becomes the second sensor voltage V2, a voltage difference V3-V2 between the threshold voltage V3 and the second sensor voltage V2 is applied to the intermediate resistor R3, and a current (V3-V2)/R3 flows from the intermediate resistor R3 to the first terminal 127 a. More specifically, during this driving, a current flows between the control voltage output terminal 126c and the control terminal 127 c. Here, R3 is the resistance value of the intermediate resistor R3. At V2< V3, the adjustment current i3 is given by equation 6 below. When V2 ≧ V3, the adjustment current i3 is given by the following equation 7. In equation 6, the current flowing between the control voltage output terminal 126c and the control terminal 127c, i.e., the base current in the example of fig. 20, is ignored as a very small current.
Number 6: i3 ═ V3-V2)/R3
The numerical formula 7: i3 ═ 0
In the illustrated example, the transistor drive operational amplifier 126 suppresses the variation in the adjustment current i3 due to temperature-induced variations in the voltage across the terminals 127c-127a of the adjustment current output transistor 127. Specifically, it is assumed that if the second sensor voltage V2 is directly supplied to the control terminal 127c of the transistor 127, the voltage of the first terminal 127a becomes a value obtained by adding the voltage between the terminals 127c to 127a to the second sensor voltage V2. Thus, the voltage at the first terminal 127a is affected by the voltage between terminals 127c-127 a. In contrast, in the present embodiment, since the terminal 126a and the terminal 126b of the operational amplifier 126 are virtually short-circuited, the voltage of the first terminal 127a is substantially the same as the second sensor voltage V2, and the adjustment current i3 is substantially not affected by the voltage between the terminals 127c to 127 a. As described above, the control terminal 127c is specifically a base. The first terminal 127a is an emitter. The second terminal 127b is a collector. The voltage between terminals 127c-127a is the base-emitter voltage.
As can be understood from the above description using fig. 21, the first reference voltage V is adjusted by the first shunt regulator 625 ref1 Tracking a constant first reference voltage V s1 . Output voltage V out This is given by the following numerical expression 8. Here, R621 is a resistance value of the first resistor 621. R622 is the resistance value of the second resistor 622. Equation 8 shows: the larger the adjustment current i3 is, the larger the output voltage V of the characteristic conversion circuit 600 is out The smaller.
The numerical formula 8: v out ＝(V ref1 /R622-i3)*R621+V ref1
As can be understood from equation 8 and fig. 19, if the adjustment current i3 flows, the output voltage V is output out And becomes smaller. Thus, the adjustment current i3 acts to adjust the output voltage V out The function of (1). The adjustment current i3 can be referred to as an output voltage adjustment current i 3.
As can be understood from the above description, in the present embodiment, the second feedback control is realized by adjusting the first feedback control. Specifically, the adjustment is performed by the second circuit 620. The second circuit 620 can be referred to as a regulation circuit.
In the present embodiment, the conversion of the output characteristics of the fuel cell power generation system 40 is performed using the first circuit 610 and the second circuit 620. From the viewpoints of simplification of a control structure, cost, and the like, a circuit has many advantages of playing a role that a software can play. In addition, this can avoid the design of software and the risk of a failure occurring in the software.
In addition, the system for performing characteristic conversion using an electric circuit has good compatibility with a fuel cell power generation system. Specifically, the output voltage and output power of the fuel cell power generation system are easy to be maintained constant unlike the wind power generation system and the like. In one embodiment, the output voltage and output power of the fuel cell power generation system are maintained constant during rated power generation. Therefore, when the power generation system connected to the characteristic conversion circuit is a fuel cell power generation system, the necessity of changing the characteristic of the characteristic conversion according to the output voltage and/or the output power of the power generation system is low, and the system of performing the characteristic conversion using the circuit is easily adopted.
[ Individual bias of Current sensor 128 and suppression thereof ]
As described above, the current sensor 128 sometimes has an individual deviation. The influence of the individual deviation is explained in detail with reference to fig. 23 and 24.
In the present embodiment, the current sensor 128 has the structure shown in fig. 22. Ideally, the resistance value R of the shunt resistor 128R sense Gain G and bias voltage V bias Is a reference value. However, the resistance value R sense Gain G and/or bias voltage V bias There may be errors within the tolerance range. In the present embodiment, the current sensor 128 is configured to: when the resistance value of the shunt resistance 128r is larger than the reference value, the current sensor 128 outputs a first sensor voltage V1 larger than when the resistance value of the shunt resistance 128r is the reference value. The current sensor 128 is configured to: when the gain G is larger than the reference value, the current sensor 128 outputs a first sensor voltage V1 larger than when the gain G is the reference value. The current sensor 128 is configured to: at a bias voltage V bias Above the reference value, the current sensor 128 outputs a voltage compared to the bias voltage V bias The first sensor voltage V1, which is larger for the reference value.
In fig. 23, the horizontal axis represents the output voltage of the characteristic conversion circuit 600. In FIG. 23, the gain G and the bias voltage V are shown bias At the reference value, the resistance value R is set sense The output characteristic of the characteristic conversion circuit 600 in the case where the change has occurred.
Specifically, in fig. 23, "output current (0) of the characteristic conversion circuit" indicates a resistance value R of the shunt resistor 128R sense The output current of the characteristic conversion circuit 600 when at the reference value. "output current (+)" of the characteristic conversion circuit represents resistance value R sense The output current is larger than the reference value. "output current (-) of characteristic conversion circuit" represents resistance value R sense The output current is smaller than the reference value. "output power (0) of characteristic conversion circuit" represents resistance value R sense The output power of the characteristic conversion circuit 600 when at the reference value. "output power (+)" of the characteristic conversion circuit represents the resistance value R sense The output power is larger than a reference value. "output power (-) of characteristic conversion circuit" represents resistance value R sense The output power when less than a reference value.
In fig. 24, the horizontal axis represents the output current of the characteristic conversion circuit 600. Shown in FIG. 24 are the gain G and the bias voltage V bias At the reference value, the resistance value R is set sense The output characteristic of the characteristic conversion circuit 600 in the case where the change has occurred.
Specifically, in fig. 24, "output voltage (0) of the characteristic conversion circuit" indicates a resistance value R of the shunt resistor 128R sense The output voltage of the characteristic conversion circuit 600 at the reference value. "output voltage (+)" of the characteristic conversion circuit represents resistance value R sense The output voltage is larger than the reference value. "output voltage (-) of characteristic conversion circuit" represents resistance value R sense The output voltage is less than the reference value. "adjustment current i3 (0)" represents the resistance value R of the shunt resistor 128R sense The adjustment current i3 at the reference value. "adjustment current i3 (+)" represents resistance value R sense The adjustment current i3 when greater than the reference value. "adjustment current i3 (-)" represents resistance value R sense The adjustment current i3 when less than the reference value. "output power (0) of characteristic conversion circuit" represents resistance value R sense The output power of the characteristic conversion circuit 600 when at the reference value. "output power (+)" of the characteristic conversion circuit indicates the resistance value R sense The output power is larger than the reference value. "output power (-) of characteristic conversion circuit" represents resistance value R sense The output power when less than the reference value. "switching Current i sw (0) "represents the resistance value R sense Switching current i at reference value sw . "switching Current i sw (+) "represents the resistance value R sense Switching current i above a reference value sw . "switching Current i sw (-) - "represents the resistance value R sense Switching current i less than a reference value sw . As described above, the current i is switched sw Is the output current of the characteristic conversion circuit 600 when switching between the first feedback control and the second feedback control.
At a resistance value R sense At the reference value, the maximum power point is at the target point. The situation is as followsAs shown in fig. 18 and 19.
At a resistance value R sense At a reference value, the current i is switched sw In agreement with the target current. "switching Current i sw (0) "corresponds to the target current. When the resistance value R is sense Greater than a reference value, as compared with the resistance value R sense At the reference value, the switching current i sw Is relatively small. On the contrary, when the resistance value R is sense Less than the reference value, compared with the resistance value R sense At the reference value, the switching current i sw Is relatively large.
At a resistance value R sense At the reference value, the maximum power of the characteristic conversion circuit 600 coincides with the target power. The output current of the characteristic conversion circuit 600 is the switching current i sw (0) The output power (0) of the characteristic conversion circuit at "time" corresponds to the target power. When the resistance value R is sense Greater than a reference value, as compared with the resistance value R sense At the reference value, the maximum power is small. On the contrary, when the resistance value R is sense Less than the reference value, compared with the resistance value R sense At the reference value, the maximum power is large.
As shown in fig. 23 and 24, the resistance value R of the shunt resistor 128R sense Causes a deviation of the maximum power point of the characteristic conversion circuit 600. The deviation of the maximum power point results in a switching current i sw And deviation from maximum power.
In this regard, in the present embodiment, the switching current i of the characteristic conversion circuit 600 can be adjusted by adjusting the variable voltage V4 sw Thereby enabling adjustment of the maximum power.
For example, consider the following case: at a resistance value R sense Less than the reference value, compared with the resistance value R sense At the reference value, the switching current i sw And the maximum power is larger. In this case, the variable voltage V4 is compared with the resistance value R sense Decreases at the reference value, the switching current i can be reduced sw And maximum power. Thereby, the switching current i can be switched sw And the maximum power is close to the target current and the target power.
Conversely, consider the following: at a resistance value R sense Greater than a reference value, as compared with the resistance value R sense At the reference value, the switching current i sw And the maximum power is small. In this case, the variable voltage V4 is compared with the resistance value R sense Increases at the reference value, and increases the switching current i sw And maximum power. Thereby, the switching current i can be switched sw And the maximum power is close to the target current and the target power.
The case where the adjustment variable voltage V4 can vary the adjustment current i3 and the maximum power is further explained with reference to fig. 25.
The first sensor voltage V1 is shown in fig. 25 (a). However, the first sensor voltage V1 may have an error due to an individual deviation of the current sensor 128.
Fig. 25 (b) shows the second sensor voltage V2. The voltage V2a is the second sensor voltage V2 before the variable voltage V4 is adjusted. The variable voltage V4 before adjustment may be 0V or may not be 0V. As can be understood from equation 5, if the variable voltage V4 is increased, the second sensor voltage V2 becomes larger. The voltage V2b is the second sensor voltage V2 that has become larger in this way. Conversely, if the variable voltage V4 is decreased, the second sensor voltage V2 becomes smaller. The voltage V2c is the second sensor voltage V2 that becomes small in this way. Arrow AR1 indicates that the second sensor voltage V2 can be adjusted by adjusting the variable voltage V4.
Fig. 25 (c) shows an adjustment current i3 and a switching current i sw . The current i3a is the adjusted current i3 before adjusting the variable voltage V4 and the second sensor voltage V2. Current i sw a is the switching current i at this time sw . If the second sensor voltage V2 is increased to become the voltage V2b, the adjustment current i3 starts to flow when the output current of the characteristic conversion circuit 600 is larger. The current i3b is the adjustment current i3 after the timing at which the flow starts in this manner is changed. Current i sw b is the switching current i at this time sw . Conversely, if the second sensor voltage V2 is decreased to become the voltage V2c, thenWhen the output current of the characteristic conversion circuit 600 is smaller, the adjustment current i3 starts to flow. The current i3c is the adjustment current i3 after the timing at which the flow starts in this manner is changed. Current i sw c is the switching current i at this time sw . Arrow AR2 indicates: the switching current i can be adjusted by adjusting the second sensor voltage V2 by adjusting the variable voltage V4 sw . By this adjustment, the maximum power can be adjusted.
By adjusting the variable voltage V4, the current i can be switched sw And maximum power approaching resistance value R sense The value at the reference value. That is, the switching current i can be made to be sw And the maximum power is close to the target current and the target power.
In the case where the current sensor 128 has the structure shown in fig. 22, it is possible to bias the voltage V bias Also causes a deviation of the maximum power point of the characteristic conversion circuit 600. It is possible that the individual deviation of the gain G also causes the deviation of the maximum power point of the characteristic conversion circuit 600. Even in the case where the current sensor 128 is another sensor such as a hall element type current sensor, an error caused by an individual deviation of the current sensor 128 may cause a deviation of the maximum power point of the characteristic conversion circuit 600. However, in these cases, the resistance value R is equal to the resistance value R of the shunt resistor 128R sense Similarly, when there is a deviation, the maximum power point of the characteristic conversion circuit 600 can be brought close to the target point by adjusting the variable voltage V4, and the switching current i can be set sw And the maximum power is close to the target current and the target power.
[ example of adjustment mode of variable Voltage V4 ]
Hereinafter, a first adjustment example and a second adjustment example of the variable voltage V4 will be described.
Taking into account the presence of a switching current i sw Target value of (2), i.e. target current. In the first and second adjustment examples, the variable voltage V4 is adjusted to correct the characteristic conversion circuit 600 so that the output voltage is the target voltage, the output power is the maximum power, and the target power when the output current is the target current. Specifically, in the first and second adjustment examplesThe target current is "switching current i" of FIG. 24 sw (0)". The target voltage is the output current in FIG. 24 as "switching current i sw (0) "output voltage (0) of the characteristic conversion circuit" at "time". The maximum power and the target power are the output current in FIG. 24 as "switching current i sw (0) "output power (0) of the characteristic conversion circuit" at "time".
In the first adjustment example, the variable voltage V4 is adjusted as follows. First, the first DCDC converter 21 is caused to perform constant current control while supplying dc power from the fuel cell power generation system 40 to the characteristic conversion circuit 600 so that the output current of the characteristic conversion circuit 600 is fixed to the target current. Next, the variable voltage V4 is adjusted so that the output voltage of the characteristic conversion circuit 600 becomes the target voltage.
Specifically, in the first modification example, the characteristic conversion circuit 600 is assumed to have the output current-output voltage characteristic shown by "output voltage (+)" of the characteristic conversion circuit in fig. 24. In this case, when the output current is "switching current i sw (0) "the output voltage is lower than the target voltage. Accordingly, the variable voltage V4 is increased. Then, the output current-output voltage characteristic changes, and the output voltage approaches the target voltage. By increasing the variable voltage V4 appropriately, the output voltage can be made to match the target voltage. By setting the variable voltage V4, the current i is switched sw In accordance with the target current, the output power is the maximum power and is the target power. Thereby, the above-described correction is realized.
In the first modification example, the characteristic conversion circuit 600 is assumed to have the output current-output voltage characteristic shown by "output voltage (-) of characteristic conversion circuit" in fig. 24. In this case, when the output current is "switching current i sw (0) "the output voltage is the same as the target voltage. Here, the variable voltage V4 is reduced. When the magnitude of the decrease of the variable voltage V4 reaches a certain degree, the output voltage starts to decrease from the target voltage. By setting the variable voltage V4 to the value at which the output voltage starts to decrease, the output voltage can be made to coincide with the target voltage, and the switching current i can be made to coincide with the target voltage sw In accordance with the target current, the output power can be made to beThe maximum power is the target power. Thereby, the above correction is realized.
In the second adjustment example, the variable voltage V4 is adjusted as follows. First, the first DCDC converter 21 is caused to perform constant current control while supplying dc power from the fuel cell power generation system 40 to the characteristic conversion circuit 600 so that the output current of the characteristic conversion circuit 600 is fixed to the target current. Next, the variable voltage V4 is adjusted so that the output power of the characteristic conversion circuit 600 becomes the target power. The output power of the characteristic conversion circuit 600 can be measured using a power meter or the like.
Specifically, in the second modification example, the characteristic conversion circuit 600 is assumed to have the output current-output power characteristic shown by "output power (+)" of the characteristic conversion circuit in fig. 24. In this case, when the output current is "switching current i sw (0) "the output power is lower than the target power. Accordingly, the variable voltage V4 is increased. Then, the output current-output power characteristic changes, and the output power approaches the target power. By increasing the variable voltage V4 appropriately, the output power can be made the maximum power and the target power. By setting the variable voltage V4, the current i is switched sw The output voltage is consistent with the target voltage. Thereby, the above-described correction is realized.
In the second modification example, the characteristic conversion circuit 600 is assumed to have the output current-output power characteristic shown in "output power (-) of characteristic conversion circuit" in fig. 24. In this case, when the output current is "switching current i sw (0) "the output power is not the maximum power, but is the same as the target power. Here, the variable voltage V4 is reduced. When the magnitude of the decrease of the variable voltage V4 reaches a certain degree, the output power starts to decrease from the target power. By setting the variable voltage V4 to a value at which the output power starts to decrease, the output power can be made the maximum power and the target power, and the switching current i can be made the switching current i sw The output voltage can be made to coincide with the target voltage in accordance with the target current. Thereby, the above correction is realized.
[ adjustment of maximum Power of characteristic conversion Circuit 600 according to situation ]
By adjusting the variable parameter, the maximum power of the characteristic conversion circuit 600 can also be adjusted according to the situation. In one example, the variable parameter is adjusted according to the power generation condition of the solar power generation system connected to the dc power conversion device 20. Hereinafter, such an example will be described.
The power system 500 of the present embodiment includes a controller 51. In the present embodiment, specifically, the fuel cell power generation system 40 includes the controller 51. However, the controller 51 may not be included in the fuel cell power generation system 40.
In one embodiment, the controller 51 varies the variable parameter based on the power generation output of at least one solar power generation system. In this way, the output power of the characteristic conversion circuit 600 can be adjusted according to the power generation output of the solar power generation system.
The generated output is, for example, a generated voltage, generated power, generated current, or the like. The power generation output of the at least one solar power generation system may be a power generation output of one solar power generation system included in the at least one solar power generation system, a value determined based on power generation outputs of a plurality of solar power generation systems included in the at least one solar power generation system, or a value determined based on power generation outputs of all solar power generation systems included in the at least one solar power generation system. The value determined from the power generation outputs of a plurality or all of the solar power generation systems can be a sum value or an average value. Specifically, the power generation output of at least one solar power generation system may be the power generation output of one of the solar power generation systems 31 and 32, or the sum or average of the power generation outputs of the solar power generation systems 31 and 32.
In one embodiment, the generated power output is a generated voltage of at least one solar power generation system. The controller 51 varies the variable parameter so that the switching current i becomes larger when (a) the generated voltage becomes larger so as to cross the threshold generated voltage sw Becomes smaller or the controller 51 changes the variable parameter so that (b) the larger the generated voltage is, the larger the switching current i sw The smaller. Typically, the generated voltage in a solar power generation system is largeIn the case of (2), the generated power of the solar power generation system is large. In this specific example, in such a case, the variable parameter is varied so that the current i is switched sw And becomes smaller. If so, the maximum power of the characteristic conversion circuit 600 becomes small. In this way, the power taken out from the characteristic conversion circuit 600 to the dc power conversion device 20 by MPPT control is reduced. For the above reasons, according to this specific example, not much power can be supplied to the dc power conversion device 20.
In one specific example, the controller 51 changes the variable parameter using a control signal indicating the power generation output. Thus, the adjustment of the variable parameter corresponding to the power generation output can be easily performed. The control signal is generated by the dc power conversion device 20, for example. Alternatively, power system 500 may include an output sensor for generating a control signal indicating a power generation output.
Note that the description of "adjustment of the maximum power of the characteristic conversion circuit 600 according to the situation" can also be applied to the second embodiment and the fourth embodiment.
Fig. 26 shows a characteristic conversion circuit 600X as a specific example of the characteristic conversion circuit 600. As can be understood from fig. 26, the characteristic conversion circuit 600X can be configured in accordance with the characteristic conversion circuit 100X of fig. 8 of the first embodiment. Therefore, a detailed description of the characteristic conversion circuit 600X is omitted.
(fourth embodiment)
The characteristic conversion circuit according to the fourth embodiment can also be adopted. The characteristic conversion circuit according to the fourth embodiment will be described below. Hereinafter, the same portions as those of the third embodiment are denoted by the same reference numerals, and description thereof is omitted.
Fig. 27 and 28 are block diagrams of a power system 700 according to the fourth embodiment. Specifically, fig. 27 shows an example of the flow of electric power when the system is connected. Fig. 28 shows an example of the flow of power at the time of power failure.
As shown in fig. 27 and 28, the power system 700 has a base plate 760. The base plate 760 is provided on a path connecting the fuel cell power generation system 40 and the power plant 10. DC power is supplied from the fuel cell power generation system 40, specifically, from the second DC bus 43 to the substrate 760. The substrate 760 includes the characteristic conversion circuit 800, the LC filter 61, and the protective relay 62.
The characteristic conversion circuit 800 is provided on a path connecting the fuel cell power generation system 40 and the dc power conversion device 20, specifically, on a path of dc power. The characteristic conversion circuit 800 performs characteristic conversion control.
Fig. 29A and 30 show output characteristics of the characteristic conversion circuit 800 according to the fourth embodiment. Fig. 31 shows a characteristic conversion circuit 800 according to the fourth embodiment.
In the fourth embodiment, the first circuit 810 performs the first feedback control in cooperation with the voltage-current control circuit 160. The second circuit 820 performs a second feedback control in cooperation with the first circuit 810 and the voltage-current control circuit 160. The current sensor 128 is used in both the first feedback control and the second feedback control.
In the characteristic conversion circuit 800, in order to bring about the output voltage-output power characteristic of (i) and the output current-output power characteristic of (ii) described below, the first feedback control is performed when the sensor output is relatively small, and the second feedback control is performed when the sensor output is relatively large.
The output voltage-output power characteristic of (i) of the characteristic conversion circuit 800 is an output voltage-output power characteristic in which the output power of the characteristic conversion circuit 800 is the maximum when the output voltage of the characteristic conversion circuit 800 is a certain value, as shown in fig. 29A. The output voltage-output current characteristic (i) is an output voltage-output current characteristic in which the output current of the characteristic conversion circuit 800 decreases as the output voltage of the characteristic conversion circuit 800 increases in a region where the output voltage of the characteristic conversion circuit 800 crosses a certain value, as shown in fig. 29A and 30. Here, the region in which the output voltage of the characteristic conversion circuit 800 crosses the certain value is a region from when the output voltage of the characteristic conversion circuit 800 is a first value smaller than the certain value to when the output voltage of the characteristic conversion circuit 800 is a second value larger than the certain value. Specifically, as in the first embodiment, the certain value is a value within a predetermined range.
As described above, the dc power conversion device 20 is designed to be able to execute MPPT control of the solar power generation system that maximizes the output power when the output voltage is within a predetermined range. In the present embodiment, the characteristic conversion circuit 800 has the output voltage-output power characteristic of (i) above, in which the output power is the maximum when the output voltage is a value within the predetermined range. In this embodiment, the characteristic conversion circuit 800 has an output voltage-output current characteristic in which the output current of the characteristic conversion circuit 800 decreases as the output voltage of the characteristic conversion circuit 800 increases in a region where the output voltage crosses a certain value. The output voltage-output power characteristic of the fuel cell power generation system is not necessarily suitable for extraction of electric power by MPPT control. However, the characteristic conversion circuit 800 having the output voltage-output power characteristic (i) can extract power from the fuel cell power generation system 40 to the dc power conversion device 20 by executing MPPT control using the dc power conversion device 20.
Further, according to the characteristic conversion circuit 800, it is easy to take out large electric power from the fuel cell power generation system 40 to the dc power conversion device 20 based on the MPPT control. This point will be described below with reference to fig. 29A and 29B.
As described above, in the region where the output voltage of the characteristic conversion circuit 800 crosses the certain value, the output voltage-output current characteristic is provided in which the output current of the characteristic conversion circuit 800 decreases as the output voltage of the characteristic conversion circuit 800 increases. According to the output voltage-output current characteristic, as shown in fig. 29A, the graph of the output voltage-output power characteristic of the characteristic conversion circuit 800 can be a curve in which the output power is convex with respect to the output voltage in a region that spans the above certain value. In a typical example, the graph of the output voltage-output power characteristic of the characteristic conversion circuit 800 is a single peak graph in which the output power is the maximum when the output voltage is at the certain value.
Assume that the graph of the output voltage-output power characteristic of the characteristic conversion circuit 800 is as shown in fig. 29BIs convex upward with respect to the output voltage. In this case, although the MPPT control is executed, the operating point is adjusted to a point deviated from the maximum power point. Specifically, the output voltage of the characteristic conversion circuit 800 is adjusted to the output voltage V with respect to the maximum power point target Deviated voltage V real . In this case, the output power of the characteristic conversion circuit 800 is reduced as compared with the output power in the case where the operating point is adjusted to the maximum power point. In fig. 29B, the reduction width is denoted by δ P B 。
On the other hand, also in the example of fig. 29A, if the output voltage of the characteristic conversion circuit 800 is adjusted to the output voltage V with respect to the maximum power point target Deviated voltage V real The output power of the characteristic conversion circuit 800 is reduced compared to the output power in the case where the operating point is adjusted to the maximum power point. In fig. 29A, the reduction width is denoted by δ P A 。
As described above, in the case where the graph of the output voltage-output power characteristic of the characteristic conversion circuit 800 is linear or curved, the output power of the characteristic conversion circuit 800 decreases when the operating point deviates from the maximum power point. However, the magnitude of the reduction is different. Specifically, the reduction width δ P in the case of fig. 29A A By a magnitude δ P of reduction from that of FIG. 29B B Is small. In this way, from the viewpoint of suppressing the reduction in the output power due to the above-described variation, and thus suppressing the reduction in the electric power taken out from the fuel cell power generation system 40 to the dc power conversion device 20, it is advantageous that the graph of the output voltage-output power characteristic has an upwardly convex curve shape.
As in the first embodiment, the output characteristic of the characteristic conversion circuit 800 according to the fourth embodiment has an advantage that the reduction of the output power due to the MPPT control system and the resolution can be suppressed. This output characteristic has real advantages. In addition, this output characteristic has an advantage of improving the compatibility of the characteristic conversion circuit 800 and reducing the restriction on the dc power conversion device 20 that can be used.
The output current-output power characteristic (ii) is such that the output current of the characteristic conversion circuit 800 is the switching current i as shown in fig. 29A and 30 sw The output current-output power characteristic of the time characteristic conversion circuit 800 at which the output power is maximum. In this case, the current i is switched sw Is the output current of the characteristic conversion circuit 800 when switching between the first feedback control and the second feedback control.
Switching current i sw Depends on an error of detection of the output current of the characteristic conversion circuit 800 by the current sensor 128, and switches the current i if a variable parameter is made to vary sw And (4) changing. This point is the same as that of the third embodiment, and therefore, a detailed description thereof is omitted.
As can be understood from fig. 29A, in the present embodiment, the characteristic conversion circuit 800 causes the output voltage-output current characteristic in which the output current of the characteristic conversion circuit 800 decreases as the output voltage of the characteristic conversion circuit 800 increases in a region where the output voltage of the characteristic conversion circuit 800 is greater than the certain value and less than the open circuit voltage by the first feedback control and the second feedback control. In addition, in a region where the output voltage of the characteristic conversion circuit 800 is greater than 0 and smaller than the certain value, the output voltage-output current characteristic is obtained in which the output current of the characteristic conversion circuit 800 decreases as the output voltage of the characteristic conversion circuit 800 increases. Here, the open circuit voltage is an output voltage of the characteristic conversion circuit 800 when the output current of the characteristic conversion circuit 800 is zero.
A value smaller than the certain value is defined as a first value. A value larger than the certain value is defined as a second value. At this time, in the example of fig. 29A, the output characteristic is the following characteristic: in both the region where the output voltage is greater than the first value and less than the certain value and the region where the output voltage is greater than the certain value and less than the second value, the output current decreases more linearly as the output voltage increases. That is, the output characteristic is a characteristic in which the output current becomes smaller as a linear function with respect to the output voltage in the above two regions. Thus, the output characteristic can be a characteristic in which the output power changes in a form of a quadratic function with respect to the output voltage in the two regions.
Specifically, in the example of fig. 29A, the output characteristic is the following characteristic: in both a region where the output voltage is greater than 0 and less than the certain value and a region from the certain value to the value where the output voltage is the open-circuit voltage, the output current linearly decreases as the output voltage increases. That is, the output characteristic is a characteristic in which the output current becomes smaller as a linear function with respect to the output voltage in the above two regions. Thus, the output characteristic can be a characteristic in which the output power changes in a form of a quadratic function with respect to the output voltage in the two regions.
In the graph of the output voltage-output power characteristic, a point at which the voltage is zero and the power is zero is defined as an origin. In the graph of the output voltage-output power characteristic, the maximum power point may be said to be a point at which the voltage is at a certain value and the power is maximum. In the graph of the output voltage-output power characteristic, a point where the voltage is an open circuit voltage and the power is zero is defined as an open circuit voltage point. In the graph of the output voltage-output power characteristic, a straight line connecting the origin and the maximum power point is defined as a first straight line. In the graph of the output voltage-output power characteristic, a straight line connecting the maximum power point and the open circuit voltage point is defined as a second straight line. In this case, in the example of fig. 29A, the region in the graph of the output voltage-output power characteristic in which the output voltage is greater than the first value and less than the certain value is on the high power side with respect to the first straight line. In the graph of the output voltage-output power characteristic, a region in which the output voltage is greater than the certain value and less than the second value is on the high power side with respect to the second straight line.
Specifically, in the example of fig. 29A, the region in the graph of the output voltage-output power characteristic in which the output voltage is greater than 0 and less than the certain value is on the high power side with respect to the first straight line. In the graph of the output voltage-output power characteristic, a region from when the output voltage is the certain value to when the output voltage is the open circuit voltage is on the high power side with respect to the second straight line.
The output voltage-output current characteristic of the characteristic conversion circuit 800 becomes a characteristic shown by a broken line in fig. 29A and fig. 30 by the combination of the first feedback control and the second feedback control. As a result, the output voltage-output power characteristic of the characteristic conversion circuit 800 becomes an upward convex characteristic having a single peak as shown by the solid line in fig. 29A.
As described above, the upwardly convex output voltage-output power characteristic of the characteristic conversion circuit 800 enables MPPT control by the dc power conversion device 20. MPPT control of the characteristic conversion circuit 800 can be performed by the dc power conversion device 20.
The structure of the characteristic conversion circuit 800 is further explained.
As shown in fig. 31, the first circuit 810 has a first resistor 621, a second resistor 622, a sixth resistor 850, the current sensor 128, and a first shunt regulator 625. The second circuit 820 includes a sixth resistor 850, a current sensor 128, a sensor voltage adjustment circuit 820a, and a voltage-to-current conversion circuit 820 b. Current sensor 128 and sixth resistor 850 are shared by first circuit 810 and second circuit 820. The feedback current supply unit 130 includes a current supply power source 131 and a third resistor 132. In the present embodiment, the current supply power source 131 is a constant voltage source.
In the voltage-current control circuit 160, the ratio of the output voltage of the voltage-current control circuit 160 to the input voltage is made larger as the current flowing from the current supply source 131 is smaller. In this way, the characteristic conversion circuit 800 adjusts the ratio in accordance with the current flowing from the current supply power source 131.
In the fourth embodiment, as in the third embodiment, the current sensor 128 has the structure shown in fig. 22. The first sensor voltage V1 generated by the current sensor 128 is given by equation 4 above. However, another current sensor such as a hall element type current sensor may be used as the current sensor 128, and the output of the current sensor may be used as the first sensor voltage V1.
In the fourth embodiment, the first shunt regulator 625 has the structure shown in fig. 21, as in the third embodiment. Through the first stepA shunt regulator 625, a first reference voltage V ref1 Tracking a constant first reference voltage V s1 。
In the first circuit 810 shown in fig. 31, the output voltage V of the characteristic conversion circuit 800 in the first feedback control out This is given by the following equation 9. Here, R621 is a resistance value of the first resistor 621, R622 is a resistance value of the second resistor 622, and R850 is a resistance value of the sixth resistor 850.
[ number 1]
The numerical expression 9:
Figure GDA0003185641750000591
as can be understood from expression 9, if the output current of the characteristic conversion circuit 800 becomes large and the first sensor voltage V1 becomes large, the output voltage V becomes large out And becomes smaller. Thus, the first sensor voltage V1 functions to regulate the output voltage V out The function of (1).
Specifically, in the first feedback control by the first circuit 810, if the first sensor voltage V1 becomes large, the current flowing from the current sensor 128 to the first connection point p1 via the sixth resistor 850 and the connection point ps in this order becomes large. A first reference voltage V via a first shunt regulator 625 ref1 Tracking a constant first reference voltage V s1 . To achieve this tracking, a constant current is passed through the second resistor 622. This means that if the current flowing to the first connection point p1 in the sixth resistor 850 increases, the current flowing to the first connection point p1 in the first resistor 621 decreases. This reduction in current means that the voltage generated in the first resistor 621 becomes small.
Based on the description with reference to fig. 31, the operation of the first circuit 810 in the first feedback control can be described as follows. If the output current of the characteristic conversion circuit 800 becomes large, the voltage at the first connection point p1 tracks the first reference voltage V ref1 The voltage generated in the first resistor 621 becomes small in the state of (3). As a result, the output voltage V of the characteristic conversion circuit 800 out And becomes smaller. Thus, by the first feedback control, as shown in fig. 29A and 30 is obtainedSimilarly, the output voltage-output current characteristic is such that the output current of the characteristic conversion circuit 800 decreases as the output voltage of the characteristic conversion circuit 800 increases.
In addition, the open circuit voltage of the characteristic conversion circuit 800 is controlled by the first feedback control. Here, the open circuit voltage is an output of the characteristic conversion circuit 800 when the output current of the characteristic conversion circuit 800 is zero. Since the output current of the characteristic conversion circuit 800 is zero, I in equation 4 load Zero, V1 and a bias voltage V bias Are equal. Thus, V defined by equation 9 out Becomes a fixed value. The fixed value corresponds to the open circuit voltage of the characteristic conversion circuit 800. In this way, in the present embodiment, the first current i1 is controlled by the operations of the first shunt regulator 625 and the voltage-current control circuit 160, so that the output voltage V of the voltage-current control circuit 160 out The open circuit voltage is set to a predetermined value by the voltage determined by equation 9.
In the fourth embodiment, the second sensor voltage V2 is given by the above equation 5, as in the third embodiment. The adjustment current i3 at V2< V3 is given by equation 6 above. The adjustment current i3 at V2 ≧ V3 is given by the above equation 7.
On the other hand, in the fourth embodiment, the output voltage V out This is given by a different expression from expression 8 described in the third embodiment. Specifically, the first reference voltage V is passed through the first shunt regulator 625 ref1 Tracking a constant first reference voltage V s1 . Output voltage V out This is given by the following equation 10. Here, R621 is a resistance value of the first resistor 621. R622 is the resistance value of the second resistor 622, and R850 is the resistance value of the sixth resistor 850. Equation 10 shows: the larger the sensor output (specifically, the first sensor voltage V1) from the current sensor 128 is, and the larger the adjustment current i3 is, the larger the output voltage V of the characteristic conversion circuit 800 is out The smaller.
[ number 2]
The numerical expression 10:
Figure GDA0003185641750000611
as can be understood from equation 10 and fig. 30, if the adjustment current i3 flows, the output voltage V is output out And becomes smaller. Thus, the adjustment current i3 acts to adjust the output voltage V out The function of (1). The adjustment current i3 can be referred to as an output voltage adjustment current i 3. The second circuit 820 can be referred to as an adjustment circuit.
[ Individual bias of Current sensor 128 and suppression thereof ]
As described in the third embodiment, the current sensor 128 may have individual variations. However, according to the fourth embodiment, adjustment for suppressing the influence of individual variation can be performed as in the third embodiment. This point will be described in detail below with reference to fig. 32 to 34. Fig. 32 shows the output characteristics of the characteristic conversion circuit 800 before adjustment for suppressing the influence of individual variations is performed. Fig. 33 is a diagram for explaining adjustment. Fig. 34 shows the output characteristics of the characteristic conversion circuit 800 after adjustment for suppressing the influence of individual variations is performed.
In the present embodiment, the current sensor 128 has the structure shown in fig. 22. Ideally, the resistance value R of the shunt resistor 128R sense Gain G and bias voltage V bias Is a reference value. However, the resistance value R sense Gain G and/or bias voltage V bias There may be errors within the tolerance range. In the present embodiment, the current sensor 128 is configured to: when the resistance value of the shunt resistance 128r is larger than the reference value, the current sensor 128 outputs a first sensor voltage V1 larger than when the resistance value of the shunt resistance 128r is the reference value. The current sensor 128 is configured to: when the gain G is larger than the reference value, the current sensor 128 outputs a first sensor voltage V1 larger than when the gain G is the reference value. The current sensor 128 is configured to: at a bias voltage V bias Above the reference value, the current sensor 128 outputs a voltage compared to the bias voltage V bias The first sensor voltage V1, which is larger for the reference value.
In fig. 32, the horizontal axis represents the output current of the characteristic conversion circuit 800. Shown in FIG. 32Gain G and bias voltage V bias At the reference value, the resistance value R is set sense The output characteristic of the characteristic conversion circuit 800 in the case where the change has occurred.
Specifically, in fig. 32, "output voltage (0) of the characteristic conversion circuit" indicates a resistance value R of the shunt resistor 128R sense The output voltage of the characteristic conversion circuit 800 when it is at the reference value. "output voltage (+)" of the characteristic conversion circuit represents resistance value R sense The output voltage is greater than a reference value. "output voltage (-) of characteristic conversion circuit" represents resistance value R sense The output voltage is less than the reference value. "adjustment current i3 (0)" represents the resistance value R of the shunt resistor 128R sense The adjustment current i3 at the reference value. "adjustment current i3 (+)" represents resistance value R sense The adjustment current i3 when greater than the reference value. "adjustment current i3 (-)" represents resistance value R sense The adjustment current i3 when less than the reference value. "output power (0) of characteristic conversion circuit" represents resistance value R sense The output power of the characteristic conversion circuit 800 when at the reference value. "output power (+)" of the characteristic conversion circuit represents the resistance value R sense The output power is larger than a reference value. "output power (-) of characteristic conversion circuit" represents resistance value R sense The output power when less than the reference value. "switching Current i sw (0) "represents the resistance value R sense Switching current i at reference value sw . "switching Current i sw (+) "represents the resistance value R sense Switching current i above a reference value sw . "switching Current i sw (-) - "represents the resistance value R sense Switching current i less than a reference value sw . As described above, the current i is switched sw Is the output current of the characteristic conversion circuit 800 when switching between the first feedback control and the second feedback control.
At a resistance value R sense At the reference value, the maximum power point is at the target point. This state is as shown in fig. 29A and 30.
At a resistance value R sense At a reference value, the current i is switched sw In agreement with the target current. "Switching current i sw (0) "corresponds to the target current. As shown in fig. 32, if the resistance value R is set sense Greater than the reference value, then R is compared with the resistance value sense At a reference value, the switching current i sw Is smaller. On the contrary, if the resistance value R is sense Less than the reference value, is compared with the resistance value R sense At the reference value, the switching current i sw Is relatively large.
At a resistance value R sense At the reference value, the maximum power of the characteristic conversion circuit 800 coincides with the target power. The output current of the characteristic conversion circuit 800 is a switching current i sw (0) The output power (0) of the characteristic conversion circuit at "time" corresponds to the target power. If the resistance value R is sense Greater than the reference value, then R is compared with the resistance value sense At the reference value, the maximum power is small. On the contrary, if the resistance value R is sense Less than the reference value, is compared with the resistance value R sense At the reference value, the maximum power is large.
[ example of adjustment mode of variable Voltage V4 ]
As shown in fig. 32, the resistance value R of the shunt resistor 128R sense Causes a deviation of the maximum power point of the characteristic conversion circuit 800. The deviation of the maximum power point results in a switching current i sw And the deviation from maximum power.
In this regard, in the present embodiment, the switching current i of the characteristic conversion circuit 800 can be adjusted by adjusting the variable voltage V4 sw Thereby adjusting the maximum power.
For example, in the resistance value R sense When the voltage is less than the reference value, the variable voltage V4 is compared with the resistance value R sense Decreases at the reference value to adjust the switching current i sw Thereby enabling the maximum power to approach the target power.
On the contrary, at the resistance value R sense When the voltage is larger than the reference value, the variable voltage V4 is compared with the resistance value R sense Increases at a reference value to adjust the switching current i sw Thereby enabling the maximum power to approach the target power.
As can be understood from equation 5, if the variable voltage V4 is increased, the second sensor voltage V2 increases. Conversely, if the variable voltage V4 is decreased, the second sensor voltage V2 becomes smaller.
If the second sensor voltage V2 is increased, the adjustment current i3 starts to flow when the output current of the characteristic conversion circuit 800 is larger. On the contrary, if the second sensor voltage V2 is decreased, the adjustment current i3 starts to flow when the output current of the characteristic conversion circuit 800 is smaller. The following is shown: the switching current i can be adjusted by adjusting the second sensor voltage V2 by adjusting the variable voltage V4 sw . By this adjustment, the maximum power can be adjusted.
Next, a case where the adjustment variable voltage V4 can change the adjustment current i3 and the maximum power will be further described with reference to fig. 33.
In adjusting the variable voltage V4, a power meter for measuring output power and an electronic load device as a load are connected to an output unit of the characteristic conversion circuit 800, for example.
In this adjustment example, the initial value of the variable voltage V4 is set to a sufficiently large voltage. In this adjustment example, the value of the variable voltage V4 adjusted appropriately is set to be smaller than the initial value. In addition, as shown in fig. 32, strictly speaking, the output current-output power characteristic of the characteristic conversion circuit 800 in the first feedback control is due to the resistance value R sense The influence of the individual variation of (2) varies, but in the following description with reference to fig. 33, the variation is sufficiently small and can be ignored.
The characteristic conversion circuit 800 operates as shown in fig. 33 (a). The output current from the characteristic conversion circuit 800 is gradually increased to adjust the output power of the characteristic conversion circuit 800 to a target value. The target value is a value corresponding to the adjusted maximum power point. Subsequently, the variable voltage V4 is gradually decreased. Thereby, the current i is switched sw When the variable voltage V4 becomes a certain value, the output power starts to decrease from the target value as the maximum power decreases. The operating point of the characteristic conversion circuit 800 is set to the operating point at the time of the start of the lowering. In this way it is possible to obtain,the output voltage of the characteristic conversion circuit 800 is adjusted to the maximum power point (target value).
As the electronic load device, a known device can be used. In one example, the electronic load device has a Constant Current (CC) mode. When the CC mode is used, the output current from the characteristic conversion circuit 800 can be gradually increased by gradually increasing the set value of the load current, which is the current flowing through the electronic load device. In another example, the electronic load device has a Constant Resistance (CR) mode. When the CR mode is used, the output current from the characteristic conversion circuit 800 can be gradually increased by gradually decreasing the set value of the load resistance, which is the resistance of the electronic load device. The electronic load device may have both the CC mode and the CR mode, or may have one of them.
Fig. 33 (b) shows an adjustment current i3a and a switching current i swa . The current i3a is the adjusted current i3 after the variable voltage V4 and the second sensor voltage V2 are adjusted. Current i swa Is the switching current i at this time sw . For easy understanding of the description, the switching current i is also shown in fig. 33 (a) swa 。
Adjusting the switching current i by adjusting the variable voltage V4 sw Thereby enabling the maximum power point to approach the resistance value R sense The operating point at the reference value.
In addition, according to the numerical expression 4, the numerical expression 5 and the numerical expression 6, the resistance value R sense The relationship with the adjustment current i3 is given by equation 11.
[ number 3]
The numerical expression 11:
Figure GDA0003185641750000651
as can be understood from equation 11, if the resistance value R is as shown in fig. 32 sense If it is large, the slope of the adjustment current i3 becomes large, whereas if the resistance value R is large sense When the value is small, the slope of the adjustment current i3 becomes small. This tendency is also shown in fig. 34.
In addition, in current sensingIn the case where the device 128 has the structure shown in fig. 22, it is possible to bias the voltage V bias And the individual deviation of the gain G also causes the deviation of the maximum power point of the characteristic conversion circuit 800. Also in the case where the current sensor 128 is another sensor such as a hall element type current sensor, an error caused by individual variation of the current sensor 128 may cause variation of the maximum power point of the characteristic conversion circuit 800. However, in these cases, the resistance value R is equal to the resistance value R of the shunt resistor 128R sense Similarly, when there is a deviation, the maximum power point of the characteristic conversion circuit 800 can be brought close to the target point by adjusting the variable voltage V4, and the switching current i can be set to be equal to or lower than the target point sw And the maximum power is close to the target current and the target power.
Fig. 35 shows a characteristic conversion circuit 800X as a specific example of the characteristic conversion circuit 800. As can be understood from fig. 35, the characteristic conversion circuit 800X can be configured in accordance with the characteristic conversion circuit 100X of fig. 8 of the first embodiment. Therefore, detailed description of the characteristic conversion circuit 800X is omitted.
The descriptions related to the respective embodiments can be applied to each other as long as they are not technically contradictory. The embodiments can be combined with each other as long as there is no technical contradiction. For example, the configuration of the secondary connection breaker 83 of fig. 27 and 28 can be applied not only to the fourth embodiment but also to the first to third embodiments.
In addition, in the fourth embodiment, the fuel cell power generation system 40 includes a voltage detection circuit 57 and a current detection circuit 58. The voltage detection circuit 57 detects a voltage in a path through which the ac power is guided from the fuel cell power generation system 40 to the first branch portion 85 via the secondary connection breaker 83. The current detection circuit 58 cooperates with a current sensor provided at a position between the third connection point p3 at the upstream side circuit 88 and the main breaker 82 to detect a current flowing through the position. The detection values obtained by these detection circuits 57 and 58 can be used for controlling the power system 700. For example, the controller 51 switches the protection relay 62 between the open state and the closed state based on the detection values obtained by these detection circuits 57 and 58. The detection circuits 57 and 58 and the control using them can also be applied to the first to third embodiments.
Various modifications can be applied to the embodiments. For example, the number of solar power generation systems in the power system may be one, or may be three or more. The power system may not have a solar power generation system. The dc power conversion device may not be incorporated in the power plant. The power system may not include a part of the elements shown in the drawings such as the power storage device and the hot water storage unit. The connection path between the power generation unit and the load is not limited to the illustrated path. For example, the outlet 260 may be omitted and power may be supplied to the first load 251.
[ Effect ]
As described above, the dc power supply system according to the 1 st aspect of the present disclosure includes:
a fuel cell power generation system; and
a characteristic conversion circuit to which the direct-current power output from the fuel cell power generation system is input, the characteristic conversion circuit being configured to execute characteristic conversion control,
wherein the characteristic conversion control brings about the following output voltage-output power characteristics: the output power of the characteristic conversion circuit is maximized when the output voltage of the characteristic conversion circuit is a certain value,
the characteristic conversion control includes a first feedback control and a second feedback control,
the first feedback control is control performed when the output current of the characteristic conversion circuit is relatively small,
the second feedback control is control performed when the output current of the characteristic conversion circuit is relatively large,
when switching between the first feedback control and the second feedback control, the output voltage of the characteristic conversion circuit is the above-described certain value.
The dc power supply system according to claim 1 includes a fuel cell power generation system. In a connected state in which the dc power supply system according to claim 1 is connected to a dc power conversion device designed to be able to execute MPPT control of the solar power generation system, the dc power conversion device can extract electric power from the fuel cell power generation system to the dc power conversion device by executing the MPPT control.
For example, in the case of the mode 1,
the output characteristic of the characteristic conversion circuit may be determined by an analog circuit included in the characteristic conversion circuit.
In the 2 nd aspect of the present disclosure, for example, in the dc power supply system according to the 1 st aspect,
the characteristic conversion control may also be performed based on an electrical output of the characteristic conversion circuit.
According to the 2 nd aspect, the accuracy of the characteristic conversion control is easily improved.
In the 3 rd aspect of the present disclosure, for example, in the dc power supply system according to the 1 st or 2 nd aspect,
the characteristic conversion circuit may also include a current sensor, a voltage-current control circuit, and at least one voltage-dividing resistor, wherein the voltage-current control circuit is a DCDC converter,
the characteristic conversion circuit may also use the current sensor to cause the output current of the characteristic conversion circuit to be reflected in the characteristic conversion control,
the characteristic conversion circuit may also cause the output voltage of the characteristic conversion circuit to be reflected in the characteristic conversion control using the at least one voltage-dividing resistance,
the characteristic conversion circuit may also adjust the transformation ratio of the voltage-current control circuit by the characteristic conversion control.
According to the 3 rd aspect, the output current and the output voltage of the characteristic conversion circuit can be reflected in the transformation ratio of the voltage-current control circuit.
In the 4 th aspect of the present disclosure, for example, in the dc power supply system according to any one of the 1 st to 3 rd aspects, the dc power supply system may be configured such that,
in the first feedback control, the first feedback control is performed,
a ratio of a decrease in output current to an increase in output voltage in the output voltage-output current characteristic is larger than that in the second feedback control; and/or
A ratio of a decrease in the output voltage to an increase in the output current in the output voltage-output current characteristic is smaller than that in the second feedback control.
According to the 4 th aspect, the output characteristic of the characteristic conversion circuit can be easily brought close to the output characteristic of the solar power generation system.
In the 5 th aspect of the present disclosure, for example, in the dc power supply system according to any one of the 1 st to 4 th aspects, the dc power supply system may be configured such that,
when the output voltage of the characteristic conversion circuit when the output current of the characteristic conversion circuit is zero is defined as an open-circuit voltage, the open-circuit voltage is controlled by the first feedback control.
The 5 th aspect is suitable for preventing the output voltage of the characteristic conversion circuit from becoming excessively large. For example, the 5 th aspect is suitable for preventing a voltage exceeding a withstand voltage from being supplied to the dc power conversion device when the output voltage of the dc power supply system is supplied to the dc power conversion device.
In the 6 th aspect of the present disclosure, for example, in the dc power supply system according to any one of the 1 st to 5 th aspects,
the first feedback control may be a control performed when the output current of the characteristic conversion circuit is relatively small and the output voltage is relatively large, and may be a control for making the output current of the characteristic conversion circuit smaller and making the output power smaller as the output voltage of the characteristic conversion circuit is larger,
the second feedback control may be control that is performed when the output current of the characteristic conversion circuit is relatively large and the output voltage is relatively small, and may be control that decreases the output current of the characteristic conversion circuit and increases the output power as the output voltage of the characteristic conversion circuit increases,
the characteristic conversion control may also bring about the following output voltage-output current characteristics: in a region where the output voltage of the characteristic conversion circuit crosses the certain value, the larger the output voltage of the characteristic conversion circuit is, the smaller the output current of the characteristic conversion circuit is.
According to the 6 th aspect, by executing the MPPT control using the dc power conversion device designed to be able to execute the MPPT control of the solar power generation system, it is easy to take out a large amount of electric power from the fuel cell power generation system to the dc power conversion device.
In the 7 th aspect of the present disclosure, for example, in the dc power supply system according to any one of the 1 st to 6 th aspects,
the characteristic conversion circuit may be provided with a voltage-current control circuit, a first feedback circuit that performs the first feedback control, and a second feedback circuit that performs the second feedback control, wherein the voltage-current control circuit is a DCDC converter,
the first feedback circuit may also have a first shunt regulator to which a first reference voltage that varies in accordance with the output current and the output voltage of the characteristic conversion circuit is input,
the second feedback circuit may also have a second shunt regulator to which a second reference voltage that varies in accordance with the output current and the output voltage of the characteristic conversion circuit is input,
in the first feedback control, the first shunt regulator may be used to adjust a transformation ratio of the voltage-current control circuit so that the first reference voltage is maintained constant,
in the second feedback control, the second shunt regulator may be used to adjust the voltage-to-current ratio of the voltage-to-current control circuit so that the second reference voltage is maintained constant.
According to the circuit configuration of claim 7, the first feedback control and the second feedback control can be realized.
In the 7 th mode, for example,
the first feedback circuit may also have a first voltage dividing resistor,
the second feedback circuit may also have a second voltage dividing resistor,
the first feedback circuit and the second feedback circuit may also share a current sensor,
the first voltage dividing resistor may be used to reflect the output voltage of the characteristic conversion circuit to the first reference voltage,
the current sensor may also be used to reflect the output current of the characteristic conversion circuit to the first reference voltage,
the output voltage of the characteristic conversion circuit may be reflected to the second reference voltage using the second voltage-dividing resistor,
the current sensor may be used to reflect the output current of the characteristic conversion circuit to the second reference voltage.
With such a circuit configuration, the first reference voltage and the second reference voltage can be obtained.
In the 8 th aspect of the present disclosure, for example, in the dc power supply system according to any one of the 1 st to 6 th aspects,
the characteristic conversion circuit may include a current sensor that detects an output current of the characteristic conversion circuit and outputs a sensor output indicating a result of the detection, and the current sensor may output the sensor output as larger as the output current of the characteristic conversion circuit is larger,
in the characteristic conversion circuit, it is preferable that,
in order to bring about the following (i) output voltage-output power characteristic and (ii) output current-output power characteristic, it is also possible to execute the first feedback control when the sensor output is relatively small and execute the second feedback control when the sensor output is relatively large,
wherein (i) the output voltage-output power characteristic is a characteristic of: when the output voltage of the characteristic conversion circuit is the certain value, the output power of the characteristic conversion circuit is maximum,
(ii) the output current-output power characteristic is the following characteristic: when the output current of the characteristic conversion circuit at the time of switching between the first feedback control and the second feedback control is defined as a switching current, the output power of the characteristic conversion circuit is maximum when the output current of the characteristic conversion circuit is the switching current,
the switching current may also depend on the detected error and vary if a variable parameter of the regulator is varied.
As described above, in a connected state in which the dc power supply system according to claim 1 is connected to the dc power conversion device designed to be able to execute MPPT control of the solar power generation system, the MPPT control is executed by the dc power conversion device, whereby electric power can be taken out from the fuel cell power generation system to the dc power conversion device. The dc power supply system according to claim 8 is adapted to adjust the extracted power.
The technique of embodiment 8 may be combined with the technique of embodiment 7.
In the 8 th mode, for example,
the sensor output may also be a first sensor voltage,
the variable output may also be a variable voltage,
the second circuit may also include a sensor voltage adjustment circuit for generating a second sensor voltage that varies in accordance with the first sensor voltage and the variable voltage,
in this way, the variable voltage can be reflected in the second sensor voltage. By using the second sensor voltage reflecting the variable voltage for control in the characteristic conversion circuit, the deviation of the switching current from the target value can be reduced, and the deviation of the maximum value of the output power from the target value can be reduced. Further, by adjusting the variable voltage to adjust the switching current, the maximum value of the output power of the characteristic conversion circuit can be adjusted according to the situation.
The current sensor may also include a sensor output for outputting the first sensor voltage,
the sensor voltage adjustment circuit may also include:
an input resistor;
a feedback resistor; and
and a sensor voltage adjusting operational amplifier including a sensor input terminal connected to the sensor output unit via the input resistor, a variable voltage input terminal to which the variable voltage is input, and a second sensor voltage output terminal connected to the sensor input terminal via the feedback resistor, wherein the sensor voltage adjusting operational amplifier generates the second sensor voltage based on a voltage difference between the sensor input terminal and the variable voltage input terminal, and outputs the second sensor voltage from the second sensor voltage output terminal.
The second circuit may also include a voltage-to-current conversion circuit in which a regulation current starts to flow when the second sensor voltage changes in a manner of crossing a threshold voltage due to the first sensor voltage becoming larger,
when the adjustment current starts to flow, the first feedback control may be switched to the second feedback control.
In such an aspect, the first feedback control is switched to the second feedback control at the time when the adjustment current starts to flow. The characteristic conversion circuit that switches control at the timing when the current starts to flow is easy to design.
The voltage-current conversion circuit may also include:
a voltage supply power source that outputs the threshold voltage;
an intermediate resistance;
a transistor drive operational amplifier including a power supply input terminal connected to the voltage supply power supply via the intermediate resistor, a second sensor voltage input terminal to which the second sensor voltage is input, and a control voltage output terminal, the transistor drive operational amplifier generating a control voltage based on a voltage difference between the power supply input terminal and the second sensor voltage input terminal, and outputting the control voltage from the control voltage output terminal; and
and an adjustment current output transistor including a control terminal to which the control voltage is input, a first terminal connected to the voltage supply source via the intermediate resistor, and a second terminal outputting the adjustment current.
In the 8 th mode, for example,
the sensor output may also be a first sensor voltage,
the regulator may also be a DCDC converter transforming the first sensor voltage,
the variable parameter may be a parameter for changing a transformation ratio of the DCDC converter.
The sensor output may also be a first sensor voltage,
the regulator may also include a voltage divider circuit and an amplifier circuit,
the variable parameter may be a parameter of the voltage dividing circuit or the amplifying circuit,
the sensor output unit, the voltage divider circuit, and the amplifier circuit may be connected in this order.
The voltage divider circuit may also include a variable resistor,
the variable parameter may be a resistance value of the variable resistor.
The amplifying circuit may also comprise an operational amplifier and a feedback circuit for the operational amplifier,
the feedback circuit may also include a variable resistor,
the variable parameter may be a resistance value of the variable resistor.
In a 9 th aspect of the present disclosure, for example, in the dc power supply system according to the 8 th aspect, there may be provided:
a first circuit for performing the first feedback control in which the larger the sensor output, the larger the output power of the characteristic conversion circuit is; and
a second circuit that performs the second feedback control in which the output power of the characteristic conversion circuit is decreased as the sensor output is increased, in cooperation with the first circuit,
the variable parameter may also be a variable output,
the regulator may also be a variable output power source that outputs the variable output.
The structure according to claim 9 is a specific example of a structure capable of adjusting the extracted power.
A power system according to a 10 th aspect of the present disclosure includes:
the direct-current power supply system according to any one of claims 1 to 9; and
a DC power conversion device designed to be capable of performing MPPT control on a solar power generation system that maximizes output power when an output voltage is within a prescribed range,
wherein the direct-current power generated in the fuel cell power generation system is supplied to the direct-current power conversion device,
the characteristic conversion circuit is provided on a path connecting the fuel cell power generation system and the dc power conversion device,
the certain value is a value within the prescribed range.
The power system according to claim 10 includes a dc power conversion device designed to be able to execute MPPT control of the solar power generation system. According to the power system of claim 10, by executing MPPT control using the dc power converter, it is possible to extract power from the fuel cell power generation system to the dc power converter.
An electric power system according to claim 11 of the present disclosure includes:
the dc power supply system according to claim 8 or 9;
a direct-current power conversion device designed to be able to execute MPPT control on a solar power generation system that outputs maximum power when an output voltage is within a prescribed range;
at least one solar power generation system that outputs maximum power when an output voltage is within the prescribed range; and
a controller for controlling the operation of the electronic device,
wherein the direct-current power generated in the fuel cell power generation system is supplied to the direct-current power conversion device,
the characteristic conversion circuit is provided on a path connecting the fuel cell power generation system and the dc power conversion device,
the certain value is a value within the prescribed range,
the direct-current power generated in the at least one solar power generation system is supplied to the direct-current power conversion device,
the controller varies the variable parameter based on a power generation output of the at least one solar power generation system.
According to the 11 th aspect, the output power of the characteristic conversion circuit can be adjusted according to the generated power output of at least one solar power generation system.
In the 12 th aspect of the present disclosure, for example, in the power system according to the 11 th aspect,
the generated output may also be a generated voltage,
the controller may use a control signal indicating the generated voltage to (a) change the variable parameter so that the switching current becomes smaller when the generated voltage becomes larger so as to cross a threshold generated voltage, or (b) change the variable parameter so that the switching current becomes smaller as the generated voltage becomes larger.
The 12 th aspect is suitable for supplying not much electric power to the dc power conversion device.
In the 13 th aspect of the present disclosure, for example, the power system according to any one of the 10 th to 12 th aspects may include a first photovoltaic power generation system in which the dc power generated in the first photovoltaic power generation system is supplied to the dc power conversion device,
the direct current power conversion apparatus may also include a first DCDC converter and a second DCDC converter,
the first DCDC converter may also vary the output power of the characteristic conversion circuit through MPPT control,
the second DCDC converter may also vary the output power of the first solar power generation system by MPPT control.
According to the 13 th aspect, a multi-string dc power converter that performs MPPT control on each of the solar power generation system and the characteristic converter can be realized.
In a 14 th aspect of the present disclosure, for example, the power system according to any one of the 10 th to 13 th aspects may include:
at least one solar power generation system, the direct-current power generated in the at least one solar power generation system being supplied to the direct-current power conversion device; and
a storage means for storing the electric power supplied from the power supply,
wherein the at least one solar power generation system, the DC power conversion device, and the electrical storage device may be connected in this order,
the fuel cell power generation system, the characteristic conversion circuit, the dc power conversion device, and the power storage device may be connected in this order.
According to the 14 th aspect, the power storage device can be charged not only from the solar power generation system but also from the fuel cell power generation system.
In a 15 th aspect of the present disclosure, for example, the power system according to any one of the 10 th to 14 th aspects may include:
at least one solar power generation system, the direct-current power generated in the at least one solar power generation system being supplied to the direct-current power conversion device;
an electrical storage device;
an inverter that converts direct-current power into alternating-current power; and
a socket is provided with a plurality of sockets,
wherein the at least one solar power generation system, the DC power conversion device, the inverter, and the outlet may be connected in this order,
the fuel cell power generation system, the characteristic conversion circuit, the dc power conversion device, the inverter, and the outlet may be connected in this order,
the power storage device, the inverter, and the socket may be connected in this order.
According to the 15 th aspect, it is also possible to supply power from the fuel cell power generation system to the outlet to which the solar power generation system and the power storage device supply power.
In the 16 th aspect of the present disclosure, for example, the power system according to the 14 th or 15 th aspect may be configured to be able to supply electric power from the power storage device to the fuel cell power generation system.
According to the 16 th aspect, the fuel cell power generation system can be started up by the electric power of the power storage device at the time of power failure. According to the 16 th aspect, a dedicated power supply for starting the fuel cell power generation system at the time of power failure can be omitted.
It can also be said that the present disclosure discloses a characteristic conversion circuit. Specifically, the characteristic conversion circuit according to the present disclosure is inputted with dc power for performing characteristic conversion control,
the characteristic conversion control brings about the following output voltage-output power characteristics: the output power of the characteristic conversion circuit is maximized when the output voltage of the characteristic conversion circuit is a certain value,
the characteristic conversion control includes a first feedback control and a second feedback control,
the first feedback control is control performed when the output current of the characteristic conversion circuit is relatively small,
the second feedback control is control performed when the output current of the characteristic conversion circuit is relatively large,
when switching between the first feedback control and the second feedback control, the output voltage of the characteristic conversion circuit is the above-described certain value.
Industrial applicability
The technique according to the present disclosure can be used in a power system including a direct-current power conversion device designed to be used in a solar power generation system and a fuel cell power generation system.
Description of the reference numerals
10: a power station; 11. 43: a DC bus; 12. 21, 22, 23, 42, 45: a DCDC converter; 13. 44: an inverter; 20: a direct current power conversion device; 25: an electrical storage device; 28: a power switching unit; 28 a: a system power input section; 28 b: an independent power input section; 28 c: a power output unit; 31. 32: a solar power generation system; 36. 37: a solar power panel; 40: a fuel cell power generation system; 41: a fuel cell; 46: a heater; 47: a hot water storage unit; 51: a controller; 52: a low voltage power supply; 55: a D1 power supply; 60. 560, 760: a substrate; 61: an LC filter; 62: a protective relay; 80. 90: a switchboard; 81. 82, 83, 85a, 85b, 85c, 92, 95a, 95b, 95 c: a circuit breaker; 85. 95: a branching section; 88. 89, 98, 99: a circuit; 100. 100X, 190X, 400, 600X, 800X: a characteristic conversion circuit; 110. 120, 410, 420: a feedback circuit; 111. 112, 113, 121, 122, 123, 132, 141, 143, 191, 196, R1, R2, R3, FR1, FR2, FR3, FR4, VR1, 621, 622, 850: a resistance; 115. 125, 625: a shunt regulator; 115A, 125A, 625A: an anode; 115K, 125K, 625K: a cathode; 115a, 125a, 625 a: a reference voltage terminal; 115o, 124, 126, 125o, 175, 625 o: an operational amplifier; 115t, 125t, 127, 625 t: a transistor; 170. 180: an adjuster; 128: a current sensor; 128 a: a sensor output section; 128 r: a shunt resistor; 128 s: a current sense amplifier; 129. 131: a power source; 130. 130X, 195X: a feedback current supply unit; 135. 192: a light emitting diode; 140. 199: a current resonance control section; 142. 161, 163a, 163b, 164, 167: a capacitor; 145. 197: a phototransistor; 146: a control IC; 147: a constant current source; 148. 149a, 149 b: a terminal; 150. 198: a photoelectric coupler; 160. 160X: a voltage current control circuit; 162a, 162 b: a switching element; 165: a transformer; 165a, 165b, 165 c: a winding; 166a, 166 b: a diode; 170 a: a voltage dividing circuit; 170 b: an amplifying circuit; 200: a system power supply; 251. 252, 253: a load; 260: a socket; 300. 500, 700: an electric power system; 610. 620, 810, 820: a circuit; 620a, 820 a: a sensor voltage adjustment circuit; 620b, 820 b: a voltage-current conversion circuit; p1, p2, p3, ps: and connecting points.

Claims (19)

1. A DC power supply system includes:
a fuel cell power generation system; and
a characteristic conversion circuit to which the direct-current power output from the fuel cell power generation system is input, the characteristic conversion circuit being configured to execute characteristic conversion control,
wherein the characteristic conversion control brings about the following output voltage-output power characteristics: the output power of the characteristic conversion circuit is maximized when the output voltage of the characteristic conversion circuit is a certain value,
the characteristic conversion control includes a first feedback control and a second feedback control,
the first feedback control is control performed when the output current of the characteristic conversion circuit is relatively small,
the second feedback control is control performed when the output current of the characteristic conversion circuit is relatively large,
the output voltage of the characteristic conversion circuit is the above-mentioned certain value when switching between the first feedback control and the second feedback control,
the first feedback control is control performed when the output current of the characteristic conversion circuit is relatively small and the output voltage is relatively large, and is control for making the output current of the characteristic conversion circuit smaller and making the output power smaller as the output voltage of the characteristic conversion circuit is larger,
the second feedback control is control performed when the output current of the characteristic conversion circuit is relatively large and the output voltage is relatively small, and is control for making the output current of the characteristic conversion circuit smaller and making the output power larger as the output voltage of the characteristic conversion circuit is larger,
the characteristic conversion control brings about the following output voltage-output current characteristics: in a region where the output voltage of the characteristic conversion circuit crosses the certain value, the larger the output voltage of the characteristic conversion circuit is, the smaller the output current of the characteristic conversion circuit is.
2. The direct-current power supply system according to claim 1,
the characteristic conversion control is performed based on an electrical output of the characteristic conversion circuit.
3. The direct-current power supply system according to claim 1 or 2,
the characteristic conversion circuit comprises a current sensor, a voltage-current control circuit and at least one divider resistor, wherein the voltage-current control circuit is a direct current-direct current converter,
the characteristic conversion circuit uses the current sensor to cause the output current of the characteristic conversion circuit to be reflected in the characteristic conversion control,
the characteristic conversion circuit uses the at least one voltage-dividing resistance to cause the output voltage of the characteristic conversion circuit to be reflected in the characteristic conversion control,
the characteristic conversion circuit adjusts a transformation ratio of the voltage-current control circuit by the characteristic conversion control.
4. The direct-current power supply system according to claim 1,
in the first feedback control, the first feedback control is performed,
a ratio of a decrease in output current to an increase in output voltage in the output voltage-output current characteristic is larger than that in the second feedback control; and/or
A ratio of a decrease in the output voltage to an increase in the output current in the output voltage-output current characteristic is smaller than that in the second feedback control.
5. The direct-current power supply system according to claim 1,
when the output voltage of the characteristic conversion circuit when the output current of the characteristic conversion circuit is zero is defined as an open-circuit voltage, the open-circuit voltage is controlled by the first feedback control.
6. The direct-current power supply system according to claim 1,
the characteristic conversion circuit includes a voltage/current control circuit, a first feedback circuit for performing the first feedback control, and a second feedback circuit for performing the second feedback control, wherein the voltage/current control circuit is a dc/dc converter,
the first feedback circuit has a first shunt regulator to which a first reference voltage that varies in accordance with an output current and an output voltage of the characteristic conversion circuit is input,
the second feedback circuit has a second shunt regulator to which a second reference voltage that varies in accordance with the output current and the output voltage of the characteristic conversion circuit is input,
in the first feedback control, the voltage-to-current ratio of the voltage-to-current control circuit is adjusted using the first shunt regulator such that the first reference voltage is maintained constant,
in the second feedback control, the second shunt regulator is used to adjust the transformation ratio of the voltage-current control circuit so that the second reference voltage is maintained constant.
7. The direct-current power supply system according to claim 1,
the characteristic conversion circuit includes a current sensor that detects an output current of the characteristic conversion circuit and outputs a sensor output indicating a result of the detection, and a regulator, wherein the larger the output current of the characteristic conversion circuit is, the larger the sensor output is output by the current sensor,
in the characteristic conversion circuit, a characteristic of the light emitting element is changed,
in order to bring about (i) an output voltage-output power characteristic and (ii) an output current-output power characteristic, the first feedback control is executed when the sensor output is relatively small, and the second feedback control is executed when the sensor output is relatively large,
wherein (i) the output voltage-output power characteristic is the following characteristic: when the output voltage of the characteristic conversion circuit is the certain value, the output power of the characteristic conversion circuit is maximum,
(ii) the output current-output power characteristic is the following characteristic: when the output current of the characteristic conversion circuit at the time of switching between the first feedback control and the second feedback control is defined as a switching current, the output power of the characteristic conversion circuit is maximum when the output current of the characteristic conversion circuit is the switching current,
the switching current is dependent on the detected error and varies if a variable parameter of the regulator is varied.
8. The direct-current power supply system according to claim 7, characterized in that:
a first circuit for performing the first feedback control in which the larger the sensor output, the larger the output power of the characteristic conversion circuit is; and
a second circuit that performs the second feedback control in which the output power of the characteristic conversion circuit is decreased as the sensor output increases, in cooperation with the first circuit,
the variable parameter is a variable output that is,
the regulator is a variable output power source that outputs the variable output.
9. A power system is provided with:
the direct current power supply system according to any one of claims 1 to 8; and
a direct-current power conversion device designed to be capable of performing maximum power point tracking control on a solar power generation system that has the maximum output power when the output voltage is within a prescribed range,
wherein the direct-current power generated in the fuel cell power generation system is supplied to the direct-current power conversion device,
the characteristic conversion circuit is provided on a path connecting the fuel cell power generation system and the dc power conversion device,
the certain value is a value within the prescribed range.
10. The power system of claim 9,
the power system includes a first solar power generation system in which the DC power generated is supplied to the DC power conversion device,
the DC power conversion apparatus includes a first DC-DC converter and a second DC-DC converter,
the first dc-dc converter varies the output power of the characteristic conversion circuit by maximum power point tracking control,
the second dc-dc converter varies the output power of the first solar power generation system by maximum power point tracking control.
11. The power system of claim 9,
the power system is provided with:
at least one solar power generation system, the direct-current power generated in the at least one solar power generation system being supplied to the direct-current power conversion device; and
a storage means for storing the electric power supplied from the power supply,
wherein the at least one solar power generation system, the DC power conversion device, and the electrical storage device are connected in this order,
the fuel cell power generation system, the characteristic conversion circuit, the dc power conversion device, and the power storage device are connected in this order.
12. The power system of claim 9,
the power system is provided with:
at least one solar power generation system, the direct-current power generated in the at least one solar power generation system being supplied to the direct-current power conversion device;
an electrical storage device;
an inverter that converts direct-current power into alternating-current power; and
a socket is arranged on the base plate, and a plug is arranged on the socket,
wherein the at least one solar power generation system, the DC power conversion device, the inverter, and the outlet are connected in this order,
the fuel cell power generation system, the characteristic conversion circuit, the direct current power conversion device, the inverter, and the outlet are connected in this order,
the power storage device, the inverter, and the socket are connected in this order.
13. The power system of claim 11,
the power system is configured to be able to supply electric power from the power storage device to the fuel cell power generation system.
14. A power system is provided with:
the direct-current power supply system according to claim 7 or 8;
a direct-current power conversion device designed to be able to perform maximum power point tracking control on a solar power generation system that outputs maximum power when an output voltage is within a prescribed range;
at least one solar power generation system that outputs maximum power when an output voltage is within the prescribed range; and
a controller for controlling the operation of the electronic device,
wherein the direct-current power generated in the fuel cell power generation system is supplied to the direct-current power conversion device,
the characteristic conversion circuit is provided on a path connecting the fuel cell power generation system and the dc power conversion device,
the certain value is a value within the prescribed range,
the direct-current power generated in the at least one solar power generation system is supplied to the direct-current power conversion device,
the controller varies the variable parameter based on a power generation output of the at least one solar power generation system.
15. The power system of claim 14,
the generated output is a generated voltage,
the controller uses a control signal representing the generated voltage to (a) change the variable parameter so that the switching current becomes smaller when the generated voltage becomes larger so as to cross a threshold generated voltage, or (b) change the variable parameter so that the switching current becomes smaller as the generated voltage becomes larger.
16. The power system of claim 14,
the power system includes a first solar power generation system in which the DC power generated is supplied to the DC power conversion device,
the dc power conversion apparatus includes a first dc-dc converter and a second dc-dc converter,
the first dc-dc converter varies the output power of the characteristic conversion circuit by maximum power point tracking control,
the second dc-dc converter varies the output power of the first solar power generation system by maximum power point tracking control.
17. The power system of claim 14,
the power system is provided with:
at least one solar power generation system, the direct-current power generated in the at least one solar power generation system being supplied to the direct-current power conversion device; and
an electricity storage device for storing electricity generated by the power generation device,
wherein the at least one solar power generation system, the DC power conversion device, and the electrical storage device are connected in this order,
the fuel cell power generation system, the characteristic conversion circuit, the dc power conversion device, and the power storage device are connected in this order.
18. The power system of claim 14,
the power system is provided with:
at least one solar power generation system, the direct-current power generated in the at least one solar power generation system being supplied to the direct-current power conversion device;
an electrical storage device;
an inverter that converts direct-current power into alternating-current power; and
a socket is provided with a plurality of sockets,
wherein the at least one solar power generation system, the DC power conversion device, the inverter, and the outlet are connected in this order,
the fuel cell power generation system, the characteristic conversion circuit, the direct current power conversion device, the inverter, and the outlet are connected in this order,
the power storage device, the inverter, and the socket are connected in this order.
19. The power system of claim 17,
the power system is configured to be able to supply electric power from the power storage device to the fuel cell power generation system.
CN201980090722.1A 2019-01-30 2019-06-11 DC power supply system and power system Active CN113383286B (en)

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JP2717215B2 (en) * 1988-11-04 1998-02-18 日本電信電話株式会社 Fuel cell power supply system
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