JP6840658B2 - Power system - Google Patents

Description

The present disclosure relates to an electric power system.

A power system is known that can generate DC power, convert DC power into AC power with an inverter, reverse power flow to the grid power supply, and supply it to a load. For example, Patent Document 1 describes such a power system.

JP-A-2017-117673

When a fuel cell power generation system is applied to the above power system and DC power is supplied from the fuel cell power generation system to the inverter, it is necessary to avoid reverse power flow from the fuel cell power generation system to the grid power source. Patent Document 1 does not fully examine this point.

This disclosure is
It is a power system that is connected to the grid power supply.
A fuel cell power generation system having a fuel cell and an AC load,
Inverters that convert DC power to AC power,
A current detector with a current sensor and
A first distribution board having a first branch portion including a plurality of branch breakers, a secondary interconnection breaker, and the like.
A second distribution board with a second branch that includes multiple branch breakers,
A power switching unit that has a plurality of input units including a grid power input unit and an independent power input unit, a power output unit, and switches which of the plurality of input units is connected to the power output unit. Prepare,
A system power supply path that guides AC power from the system power supply to the system power input unit via the connection point, the current detection unit, and the first branch unit in this order.
A reverse power flow path that guides AC power from the inverter to the system power supply via the connection point, and
A path for independent operation that guides AC power from the inverter to the independent power input unit,
A DC output path that guides DC power from the fuel cell power generation system to the inverter,
An AC output path that guides AC power from the fuel cell power generation system to the first branch via the secondary circuit breaker.
A load-bound path that guides AC power from the power output unit to the AC load via the second branch is formed.
The electric power system is configured so that DC electric power is supplied to the inverter from other than the fuel cell power generation system.
The electric power system has (A) the first condition that the measured value of the current detection unit is a value indicating that the system power supply is out of order, and (B) the AC output path to the fuel cell power generation system. The second condition that the input voltage is a value indicating that the system power supply is out of power, and (C) the voltage input to the fuel cell power generation system by the load going path is the operating voltage of the AC load. The third condition is that (D) the measured value of the current detection unit is maintained at a value indicating that the system power supply is out of power even if the power is consumed by the AC load. , Is satisfied, and then provides a power system that supplies DC power from the fuel cell power generation system to the inverter via the DC output path.

The technique according to the present disclosure is suitable for avoiding reverse power flow from the fuel cell power generation system to the grid power source.

FIG. 1 is a block diagram of an electric power system at the time of grid connection. FIG. 2 is a block diagram of an electric power system at the time of a power failure. FIG. 3 is a diagram for explaining the VP characteristic obtained by the characteristic conversion circuit. FIG. 4 is a diagram showing an example of a characteristic conversion circuit. FIG. 5 is a flowchart for explaining a specific example of control for avoiding reverse power flow of the generated power of the fuel cell power generation system. FIG. 6 is a diagram showing a specific example of the characteristic conversion circuit. FIG. 7 is a diagram showing another example of the characteristic conversion circuit. FIG. 8 is a diagram showing another specific example of the characteristic conversion circuit.

(Summary of one aspect relating to this disclosure)
The electric power system according to the first aspect of the present disclosure is
It is a power system that is connected to the grid power supply.
A fuel cell power generation system having a fuel cell and an AC load,
Inverters that convert DC power to AC power,
A current detector with a current sensor and
A first distribution board having a first branch portion including a plurality of branch breakers, a secondary interconnection breaker, and the like.
A second distribution board with a second branch that includes multiple branch breakers,
A power switching unit that has a plurality of input units including a grid power input unit and an independent power input unit, a power output unit, and switches which of the plurality of input units is connected to the power output unit. Prepare,
A system power supply path that guides AC power from the system power supply to the system power input unit via the connection point, the current detection unit, and the first branch unit in this order.
A reverse power flow path that guides AC power from the inverter to the system power supply via the connection point, and
A path for independent operation that guides AC power from the inverter to the independent power input unit,
A DC output path that guides DC power from the fuel cell power generation system to the inverter,
An AC output path that guides AC power from the fuel cell power generation system to the first branch via the secondary circuit breaker.
A load-bound path that guides AC power from the power output unit to the AC load via the second branch is formed.
The electric power system is configured so that DC electric power is supplied to the inverter from other than the fuel cell power generation system.
The electric power system has (A) the first condition that the measured value of the current detection unit is a value indicating that the system power supply is out of order, and (B) the AC output path to the fuel cell power generation system. The second condition that the input voltage is a value indicating that the system power supply is out of power, and (C) the voltage input to the fuel cell power generation system by the load going path is the operating voltage of the AC load. The third condition is that (D) the measured value of the current detection unit is maintained at a value indicating that the system power supply is out of power even if the power is consumed by the AC load. After determining that, is satisfied, DC power is supplied from the fuel cell power generation system to the inverter via the DC output path.

The technique according to the first aspect is suitable for avoiding reverse power flow from the fuel cell power generation system to the grid power source.

In the second aspect of the present disclosure, for example, the power system according to the first aspect further includes a photovoltaic power generation system having a photovoltaic power generation panel, and a path for guiding DC power from the photovoltaic power generation system to the inverter is formed. ing.

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

In the third aspect of the present disclosure, for example, the electric power system according to the first or second aspect further includes a power storage device, and a path for guiding DC power from the power storage device to the inverter is formed.

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

In the fourth aspect of the present disclosure, for example, the electric power system according to any one of the first to third aspects further includes a photovoltaic power generation system having a photovoltaic power generation panel, a power storage device, and the solar power. A path for guiding DC power from the power generation system to the power storage device and a path for guiding DC power from the fuel cell power generation system to the power storage device are formed.

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

In the fifth aspect of the present disclosure, for example, the electric power system according to any one of the first to fourth aspects further includes a solar power generation system having a solar power generation panel, a power storage device, and an outlet. A path for guiding electric power from the solar power generation system to the outlet via the inverter, the path for self-sustaining operation, the power switching unit and the second branch portion in this order, and the inverter from the fuel cell power generation system. A path for self-sustaining operation, a path for guiding power to the outlet through the power switching unit and the second branch in this order, and a path from the power storage device to the inverter, the path for self-sustaining operation, the power switching unit, and the said. A path for guiding electric power to the outlet through the second branch portion in this order is formed.

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

In the sixth aspect of the present disclosure, for example, in the electric power system according to the fifth aspect, the fuel from the power storage device via the inverter, the path for independent operation, the power switching unit, and the second branch portion in this order. A path is formed to guide electric power to the battery power generation system.

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

In the seventh aspect of the present disclosure, for example, the electric power system according to any one of the first to sixth aspects further includes a substrate provided on the DC output path, and the electric power system is the first condition. After determining that the second condition, the third condition, and the fourth condition are satisfied, the substrate starts to output DC power.

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

In the present specification, the ordinal numbers such as first, second, third ... May be used. As a reminder, if an element has an ordinal number, it is not essential that a younger element of the same type exists. For example, the term third connection point is not used to mean that the first connection point and the second connection point always exist together with the third connection point.

Also, in the present specification, the term route may be used. As a reminder, a route can have multiple tracks. The same applies to connection points and the like. For example, a single-phase three-wire path has two ungrounded lines and one grounded line. In addition, it should be understood that the connection point between single-phase, three-wire routes is used to indicate a range of regions including the points where the lines are connected in the route.

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

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

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

[Power Station 10]
The power station 10 includes a DC power converter 20, a first DC bus 11, a fourth DCDC converter 12, a first inverter 13, and a first disconnection relay 14.

The DC power converter 20 is designed so that maximum power point tracking control (hereinafter, may be referred to as MPPT control) can be executed for the assumed system. Here, the assumed system is a system that generates electricity using a photovoltaic power generation panel. Further, the assumed system is a system in which the output power of the assumed system peaks when the output voltage of the assumed system is within a predetermined range.

DC power is input to the DC power converter 20 from the photovoltaic power generation systems 31 and 32 and the fuel cell power generation system 40. The DC power output from the DC power converter 20 is supplied to the first DC bus 11.

Specifically, the DC power converter 20 includes a first DCDC converter 21, a second DCDC converter 22, and a third DCDC converter 23. DC power is input to the first DCDC converter 21 from the fuel cell power generation system 40. DC power is input to the second DCDC converter 22 from the first photovoltaic power generation system 31. DC power is input to the third DCDC converter 23 from the second photovoltaic power generation system 32. The DC power output from these DCDC converters 21, 22, and 23 is supplied to the first DC bus 11.

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

The first inverter 13 converts DC power into AC power. Specifically, the first inverter 13 converts the DC power input from the first DC bus 11 into AC power having a voltage V _AC1 or a voltage V _AC2 . _{When AC power of voltage V AC1} is obtained by the first inverter 13, the power is supplied to the power switching unit 28. _{When AC power of voltage V AC2} is obtained by the first inverter 13, the power is supplied to the main distribution board 80 via the first disconnection relay 14.

The first inverter 13 can also convert the AC power of _{the voltage V AC2} input from the system power supply 200 via the main distribution board 80 and the first disconnection relay 14 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.

The first disconnection relay 14 is provided on a path connecting the first inverter 13 and the main distribution board 80, specifically, on a path connecting the first inverter 13 and the interconnection breaker 81. .. The first disconnection relay 14 disconnects the electrical connection between the first inverter 13 and the main distribution board 80 when a power failure of the system power supply 200 is detected.

[Solar power generation systems 31 and 32]
The photovoltaic power generation systems 31 and 32 correspond to the above assumed system. That is, the first photovoltaic power generation system 31 has at least one photovoltaic power generation panel 36. The first photovoltaic power generation system 31 generates electricity using the at least one photovoltaic power generation panel 36. The second photovoltaic power generation system 32 has at least one photovoltaic power generation panel 37. The second photovoltaic power generation system 32 generates electricity using the at least one photovoltaic power generation panel 37. The DC power generated by the photovoltaic power generation systems 31 and 32 is supplied to the DC power converter 20.

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

The fuel cell power generation system 40 includes a fuel cell 41, a fifth DCDC converter 42, a second DC bus 43, a second inverter 44, a second disconnection relay 48, a sixth DCDC converter 45, a heater 46, and a hot water storage unit. It has 47, a micro control unit (hereinafter, may be referred to as MCU) 51, a low-voltage power supply 52, an auxiliary power supply (hereinafter, may be referred to as D1 power supply) 55, and an AC load 56.

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

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

The second inverter 44 converts the DC power input from the second DC bus 43 into AC power having a voltage V _AC2 . The AC power obtained by the second inverter 44 is supplied to the main distribution board 80 via the second disconnection relay 48.

The second disconnection relay 48 is provided on the path connecting the second inverter 44 and the main distribution board 80, specifically, on the path connecting the second inverter 44 and the secondary interconnection breaker 83. ing. The second disconnection relay 48 disconnects the electrical connection between the second inverter 44 and the main distribution board 80 when a power failure of the system power supply 200 is detected.

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

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

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

The AC load 56 is a load driven by _{an AC voltage V AC1.} In this example, the AC load 56 is an auxiliary machine of the fuel cell power generation system 40, specifically a heater.

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

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

As is clear from the above description, the characteristic conversion circuit 100 exists on the path connecting the fuel cell power generation system 40 and the DC power conversion device 20, specifically on the DC power path. The characteristic conversion circuit 100 includes a first feedback circuit 110 and a second feedback circuit 120. The first feedback circuit 110 is used to define an upper limit target value of the output voltage of the characteristic conversion circuit 100. The second feedback circuit 120 adjusts the output voltage of the characteristic conversion circuit 100 (hereinafter, may be referred to as the output voltage at the maximum power point) to a value within a predetermined range when the output power of the characteristic conversion circuit 100 reaches its peak. Used to do. Specifically, this peak is a single peak.

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

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

The characteristic conversion circuit 100 of this example will be further described with reference to FIG. In FIG. 3, the solid line represents the relationship between the output voltage of the characteristic conversion circuit 100 and the output power of the characteristic conversion circuit 100, that is, the VP characteristic. The dotted line represents the relationship between the output voltage of the characteristic conversion circuit 100 and the output current of the characteristic conversion circuit 100, that is, the VI characteristic. The alternate long and short dash line represents the contribution of the first feedback circuit 110. The alternate long and short dash line represents the contribution of the second feedback circuit 120.

As can be understood from FIG. 3, by the first feedback circuit 110, the VI characteristic of the characteristic conversion circuit 100 is such that the output voltage follows the target value in the region where the output current is small. According to the second feedback circuit 120, the VI characteristic of the characteristic conversion circuit 100 is such that the output voltage decreases as the output current increases in the region where the output current is large. Combined with the actions of these circuits 110 and 120, the VI characteristics of the characteristic conversion circuit 100 are shown by the dotted line in FIG. As a result, the VP characteristic of the characteristic conversion circuit 100 has a single peak and is convex as shown by the solid line in FIG. Therefore, MPPT control of the characteristic conversion circuit 100 becomes possible.

The value within the above predetermined range is lower than the target value. Therefore, the output voltage at the maximum power point of the characteristic conversion circuit 100 is lower than the target value. Further, in this example, the input voltage of the characteristic conversion circuit 100 (the voltage in the second DC bus 43 in this example) is larger than the target value. However, even when the input voltage is smaller than the target value, it is possible to obtain the VP characteristic shown in FIG.

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

In this example, the DC power converter 20 includes a first DCDC converter 21, a second DCDC converter 22, and a third DCDC converter 23. The first DCDC converter 21 adjusts the output voltage of the characteristic conversion circuit 100 by MPPT control. The second DCDC converter 22 adjusts the output voltage of the first photovoltaic power generation system 31 by MPPT control. The third DCDC converter 23 adjusts the output voltage of the second photovoltaic power generation system 32 by MPPT control. As described above, in this example, the multi-string type DC power conversion device 20 that individually MPPT controls the output voltage of the photovoltaic power generation systems 31 and 32 and the output voltage of the characteristic conversion circuit 100 is realized. However, the DC power converter may be a centralized type that collectively controls these output voltages by MPPT.

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

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

In the first feedback circuit 110, the output voltage of the characteristic conversion circuit 100 is divided by the first resistor 111 and the second resistor 112. The divided voltage appears at the connection point p1 of the first resistor 111 and the second resistor 112. The voltage at the connection point p1 is input to the reference voltage terminal of the first shunt regulator 115. The larger the voltage input to the reference voltage terminal, the larger the current flowing through the constant voltage source 131, the sixth resistor 132, the first shunt regulator 115, and the reference potential in this order (hereinafter, may be referred to as the first current). Become. In FIG. 4, this current is the current flowing downward in the drawing through the first shunt regulator 115.

In the second feedback circuit 120, the output voltage of the characteristic conversion circuit 100 is divided by the third resistor 121 and the fourth resistor 122. Further, the current sensor 128 generates a sensor voltage that increases as the output current of the characteristic conversion circuit 100 increases. This sensor voltage is divided by the fifth resistor 123 and the fourth resistor 122. A voltage obtained by adding the voltage dividing voltage derived from the resistors 123 and 122 to the voltage dividing voltage derived from the resistors 121 and 122 appears at the connection point p2 of the three resistors 121, 122 and 123. The voltage at the connection point p2 is input to the reference voltage terminal of the second shunt regulator 125. The larger the voltage input to the reference voltage terminal, the larger the current flowing through the constant voltage source 131, the sixth resistor 132, the second shunt regulator 125, and the reference potential in this order (hereinafter, may be referred to as the second current). Become. In FIG. 4, this current is the current flowing downward in the drawing through the second shunt regulator 125. In this embodiment, the current sensor 128 is a current transformer.

In the region where the output current of the characteristic conversion circuit 100 is small, the first current occupies most of the current flowing out from the constant voltage source 131. On the other hand, in the region where the output current of the characteristic conversion circuit 100 is large, the second current occupies most of the current flowing out from the constant voltage source 131. That is, the operation of the first feedback circuit 110 is dominant in the region where the output current of the characteristic conversion circuit 100 is small, and the operation of the second feedback circuit 120 is dominant in the region where the output current of the characteristic conversion circuit 100 is large. The parameters of the resistors 111, 112, 121, 122 and 123 and the shunt regulators 115 and 125 are selected so that the circuits 110 and 120 operate in this way.

The voltage-current control circuit 160 functions as a DCDC converter. The voltage-current control circuit 160 reduces the ratio of the output voltage to the input voltage of the voltage-current control circuit 160 as the current flowing out from the constant voltage source 131 increases. In this way, the characteristic conversion circuit 100 is adapted to adjust the above ratio according to the current flowing out from the constant voltage source 131. Such a characteristic conversion circuit 100 can be appropriately designed.

Returning to FIGS. 1 and 2, the output power of the characteristic conversion circuit 100 is supplied to the DC power conversion device 20, specifically to the first DCDC converter 21, via the LC filter 61 and the protection relay 62.

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

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

[Current detector 27]
The current detection unit 27 has at least one current sensor. Specifically, the current detection unit 27 is composed of at least one current sensor. The current sensor is, for example, a current transformer. The current detection unit 27 is used for detecting a power failure of the system power supply 200.

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

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

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

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

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

In this example, AC power of _{voltage V AC2} can be supplied from the system power supply 200 to the main breaker 82 via the third connection point p3. AC power of _{voltage V AC2} can be supplied from the system power supply 200 to the first inverter 13 via the third connection point p3 and the interconnection breaker 81 in this order. _{AC power of voltage V AC2} can be reverse-flowed from the first inverter 13 to the system power supply 200 via the interconnection breaker 81 and the third connection point p3 in this order. AC power of _{voltage V AC2} can be supplied from the first inverter 13 to the main breaker 82 via the interconnection breaker 81 and the third connection point p3 in this order. _{AC power of voltage V AC2} can be supplied to the secondary interconnection breaker 83 from the second inverter 44. AC power of _{voltage V AC1} can be supplied from the branch breaker 85a to the power switching unit 28. AC power of _{voltage V AC1} can be supplied from the branch breaker 85b to the second load 252. AC power of _{voltage V AC2} can be supplied from the branch breaker 85c to the third load 253.

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

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

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

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

In this example, AC power of _{voltage V AC1} can be supplied from the power switching unit 28 to the downstream electric circuit 99 via the main breaker 92. AC power of _{voltage V AC1} can be supplied from the branch breaker 95a to the D1 power supply 55 and the AC load 56. AC power of _{voltage V AC1} can be supplied from the branch breaker 95b to the hot water storage unit 47. AC power of _{voltage V AC1} can be supplied from the branch breaker 95c to the first load 251 via the outlet 260.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[Route formed by the power system 300]
As can be seen from the above description and FIGS. 1 and 2, in the power system 300, the system power supply path 351 and the reverse power flow path 352, the self-sustained operation path 353, the DC output path 354, and the AC output A route 355 and a load-bound route 356 are formed. The system power supply path 351 is a path for guiding AC power from the system power supply 200 to the system power input unit 28a of the power switching unit 28 via the third connection point p3, the current detection unit 27, and the first branch unit 85 in this order. Is. The reverse power flow path 352 is a path for guiding AC power from the inverter 13 to the system power supply 200 via the third connection point p3. The path 353 for self-sustaining operation is a path for guiding AC power from the inverter 13 to the self-sustaining power input unit 28b of the power switching unit 28. The DC output path 354 is a path for guiding DC power from the fuel cell power generation system 40 to the inverter 13. The AC output path 355 is a path for guiding AC power from the fuel cell power generation system 40 to the first branch portion 85 via the secondary interconnection breaker 83. The load-bound path 356 is a path that guides AC power from the power output unit 28c of the power switching unit 28 to the AC load 56 of the fuel cell power generation system 40 via the second branch portion 95. In this example, the system power supply path 351 and the reverse power flow path 352 overlap at the portion on the system power supply 200 side when viewed from the third connection point p3.

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

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

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

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

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

In the electric power system 300 of this example, a path for guiding electric power from the power storage device 25 to the fuel cell power generation system 40 is formed through the inverter 13, the path 353 for independent operation, the electric power switching unit 28, and the second branch portion 95 in this order. ing. Specifically, in this way, a path for guiding electric power to the D1 power source 55 and the AC load 56 of the fuel cell power generation system 40 is formed. Further, specifically, the same connection as the above connection to the outlet 260 is also made in the fuel cell power generation system 40. As can be understood from the above description, the power storage device 25 of this example functions as an emergency power source capable of supplying power to the outlet 260 in the event of a power failure. In this example, the power storage device 25 also functions as an emergency power source capable of supplying electric power to the fuel cell power generation system 40 in the event of a power failure. In this way, a dedicated power source for starting the fuel cell power generation system 40 in the event of a power failure, for example, a dedicated power source for supplying power to the auxiliary equipment of the system 40 can be omitted.

[About avoiding reverse power flow of generated power of fuel cell power generation system]
The electric power system 300 is a system capable of generating DC electric power, converting the DC electric power into AC electric power by the inverter 13, backfeeding the AC electric power to the system power supply 200, and supplying the AC electric power to the load. Further, in the electric power system 300, a fuel cell power generation system 40 is applied, and DC power is supplied from the fuel cell power generation system 40 to the inverter 13. In such an electric power system 300, it is necessary to pay attention to the following points in order to avoid reverse power flow of electric power from the fuel cell power generation system 40 to the grid power source 200.

First, in the electric power system 300, reverse power flow of electric power from a power source different from the fuel cell power generation system 40 to the system power source 200 is performed at the time of grid connection. In this example, the other power sources are photovoltaic systems 31 and 32. In order to prevent the power generated by the fuel cell power generation system 40 from being mixed with the reverse power flow power, it is conceivable to limit the DC power supply from the fuel cell power generation system 40 to the inverter 13 during a power failure of the system power supply 200. .. For that purpose, it is necessary to confirm with sufficient accuracy that the system power supply 200 is out of power. Hereinafter, this task may be referred to as a first task.

Further, it is not always possible to start supplying DC power from the fuel cell power generation system 40 to the inverter 13 as soon as it is confirmed that the system power supply 200 has a power failure. In order to prevent the generated power of the fuel cell power generation system 40 from flowing back to the system power supply 200, the power supplied to the inverter 13 can be supplied to the load before the start of the power supply. It is necessary to confirm with sufficient accuracy that the system power supply 200 cannot be supplied. Hereinafter, this task may be referred to as a second task.

In this respect, the power system 300 can detect a power failure of the system power supply 200. In one example of the power system 300, power failure detection is realized by using a known method such as an active method. When a power failure is detected, the power system 300 changes the electrical connection state from the state shown in FIG. Specifically, first, the first disconnection relay 14 and the second disconnection relay 48 are disconnected and opened. Next, the power switching unit 28 is switched so that the inverter 13 and the self-supporting distribution board 90 are electrically connected via the power switching unit 28. Hereinafter, the above-mentioned power failure detection that triggers the disconnection of the disconnection relays 14 and 48 and the switching of the power switching unit 28 may be referred to as a first power failure detection.

By doing so, it means that the power failure of the system power supply 200 has been confirmed for the time being. Further, in the electrically connected state obtained as described above, power is not reverse power flowed from the inverter 13 to the system power supply 200 via the reverse power flow path 352. On the other hand, in this electrically connected state, the inverter 13 passes through the path 352 for independent operation, the power switching unit 28, and the second branch 95, and the D1 power supply 55, the AC load 56, the hot water storage unit 47, and the first load. Power can be supplied to 251. That is, in this electrically connected state, the electric power supplied to the inverter 13 can be supplied to the load, while it is not reverse power flowed to the system power supply 200.

However, for some reason, it is possible that a power failure of the system power supply 200 is erroneously detected even though the system power supply 200 is not actually out of power. Further, for some reason, the above-mentioned electrical connection state may not be reached. Therefore, it is desired to adopt a configuration that can more reliably solve the above-mentioned first problem and the second problem.

Therefore, the power system 300 determines that the first condition, the second condition, the third condition, and the fourth condition are satisfied, and then supplies DC power from the fuel cell power generation system 40 to the inverter 13 via the DC output path 354. To supply.

The first condition is that the measured value of the current detection unit 27 is a value indicating that the system power supply 200 is out of power. The second condition is that the voltage input to the fuel cell power generation system 40 by the AC output path 355 is a value indicating that the system power supply 200 is out of power. The third condition is that the voltage input to the fuel cell power generation system 40 by the load route 356 is the operating voltage of the AC load 56 of the fuel cell power generation system 40. The fourth condition is that the measured value of the current detection unit 27 is maintained at a value indicating that the system power supply 200 is out of power even if the AC load 56 consumes power.

In this example, the power system 300 determines that the first condition is satisfied when the measured value of the current detection unit 27 is equal to or less than the first threshold current. Here, the measured value of the current detection unit 27 refers to the measured value of the current sensor when the current detection unit 27 is composed of one current sensor. When the current detection unit 27 is composed of a plurality of current sensors, the measured value of the current detection unit 27 may be the sum of the measured values of the plurality of current sensors. Further, as the measured value, an average value over a predetermined period can be adopted. In short, the measured value of the current detection unit 27 may be such that it can be determined whether or not the system power supply 200 has a power failure.

More specifically, in this example, the portion of the system power supply path 351 provided with the current detection unit 27 is composed of a single-phase three-wire system. The current detection unit 27 includes a first current sensor provided on the single-phase three-wire first ungrounded line, a second current sensor provided on the single-phase three-wire second ungrounded line, and the like. It is composed of. Then, the power system 300 determines that the first condition is satisfied when the sum of the measured value of the first current sensor and the measured value of the second current sensor is equal to or less than the first threshold current.

In the first example, the electric power system 300 determines that the second condition is satisfied when the voltage input to the fuel cell power generation system 40 by the AC output path 355 does not cross zero. Here, zero crossing of the voltage means that the instantaneous value of the voltage changes over 0V.

In the second example, the power system 300 converts the voltage input to the fuel cell power generation system 40 by the AC output path 355 into a pulse wave. If an AC voltage is applied to the AC output path 355, the resulting pulse wave constitutes a repeating waveform. On the other hand, if no voltage is applied to the AC output path 355, the waveform obtained by this conversion is fixed at a constant level. In the second example, the power system 300 determines that the second condition is not satisfied if the repeated waveforms for a plurality of cycles are detected. On the other hand, the power system 300 determines that the second condition is satisfied when the repeated waveforms for a plurality of cycles are not detected and the waveforms obtained over a predetermined period are fixed at a constant level. .. The second example may constitute a specific example of the first example.

The electric power system 300 is configured so that DC electric power is supplied to the inverter 13 from other than the fuel cell power generation system 40. In this example, this DC power supply is provided by the photovoltaic power generation system 36, the photovoltaic power generation system 37 and / or the power storage device 25. The voltage input to the fuel cell power generation system 40 by the load going path 356 in the third condition is generated by the power supply.

In this example, the fourth condition is that the measured value of the current detection unit 27 is maintained below the first threshold current even when the AC load 56 consumes power. More specifically, in this example, even if the AC load 56 consumes power, the total of the measured values of the first current sensor and the measured values of the second current sensor is maintained below the first threshold current. It is a condition.

In this example, the substrate 60 is provided on the DC output path 354. Then, after the power system 300 determines that the first condition, the second condition, the third condition, and the fourth condition are satisfied, the substrate 60 starts to output the DC power. Specifically, the start-up of the substrate 60 is started after the power system 300 determines that the first condition and the second condition are satisfied. Here, the state in which the substrate 60 is activated refers to a state in which the characteristic conversion circuit 100 is operated to specify the ratio of the output voltage to the input voltage of the voltage / current control circuit 160. Then, during the startup of the substrate 60, after the power system 300 determines that the third condition and the fourth condition are satisfied, the substrate 60 starts outputting DC power based on the specified ratio.

If the first condition is not satisfied, it is suspected that the system power supply 200 is not out of power and current is being supplied from the system power supply 200 to the current measuring unit 27 via the third connection point p3. If the second condition is not satisfied, the system power supply 200 is not out of power and voltage is supplied from the system power supply 200 to the AC output path 355 via the third connection point p3 and the secondary interconnection breaker 83 in this order. Suspected to be. If the first condition and the second condition are satisfied but the third condition is not satisfied, the system power supply 200 is out of power, but the load from the inverter 13 via the self-sustained operation path 353 and the power switching unit 28 is in this order. It is suspected that the voltage is not supplied to the route 356. If the fourth condition is not satisfied, the system power supply 200 is not out of power, and the system power supply 200 connects to the third connection point p3, the current measurement unit 27, the first branch unit 85, the power switching unit 28, and the load route 356. It is suspected that power is being supplied to the AC load 56 through this order.

By confirming that the first condition and the second condition are satisfied, it is reconfirmed that the system power supply 200 is out of power. In the present embodiment, if it is not determined that the first condition and the second condition are satisfied, the DC power is not supplied from the fuel cell power generation system 40 to the inverter 13 via the DC output path 354. Such a configuration is suitable for avoiding a situation in which DC power is supplied from the fuel cell power generation system 40 to the inverter 13 when the system power supply 200 does not have a power failure.

The advantages of confirming that both the first condition and the second condition are satisfied are as follows. The load such as loads 252 and 253 and the electric power flowing out from the first branch portion 85 to the power switching unit 28 may be small. For example, the case where the power consumption of electric appliances in the home is small corresponds to such a case. When the outflow power is small, the power system 300 determines that the first condition is satisfied even though the system power supply 200 is not out of power. However, by confirming that not only the first condition but also the second condition is satisfied, it can be confirmed that the system power supply 200 is out of power even in such a case. On the other hand, the secondary interconnection breaker 83 may be in a cutoff state due to a setting error during construction or the like. In this case, the power system 300 determines that the second condition is satisfied even though the system power supply 200 is not out of power. However, by confirming that the first condition is satisfied as well as the second condition, it can be confirmed that the system power supply 200 is out of power even in such a case.

The advantages of confirming the establishment of the third condition are as follows. For some reason, the power supplied to the inverter 13 may not be supplied to the self-sustaining operation path 353, the power switching unit 28, and the load going path 356. If a setting error occurs during construction, or if the power output mechanism to the path 353 for independent operation in the power station 10 is out of order, the main breaker 92 of the independent distribution board 90 trips due to overcurrent and is in a cutoff state. Such a case corresponds to such a case. However, in the present embodiment, it is confirmed that the third condition is satisfied. As a result, it is confirmed that the electric power supplied to the inverter 13 can be supplied to the self-sustained operation path 353, the electric power switching unit 28, and the load bound path 356.

Specifically, in the present embodiment, it is confirmed that the third condition is satisfied together with the first condition and the second condition. As a result, it is confirmed that the power supplied to the inverter 13 is not in a situation where it can be supplied to the reverse power flow path 352, but in a situation where it can be supplied to the path 353 for independent operation, the power switching unit 28, and the load going path 356. Will be done. As a result, it is confirmed that the electric power supplied to the inverter 13 is in a situation where it can be supplied to the load, while it is not in a situation where it can be supplied to the system power supply 200. In the present embodiment, if it is not determined that the first to third conditions are satisfied, the DC power is not supplied from the fuel cell power generation system 40 to the inverter 13. Such a configuration is suitable for executing the DC power supply from the fuel cell power generation system 40 to the inverter 13 in a situation where the power supplied to the inverter 13 cannot be supplied to the system power supply 200 and can be supplied to the load. There is.

Further, in the present embodiment, it is confirmed that the fourth condition is satisfied. By confirming the establishment of the fourth condition together with the first condition and the second condition, it is possible to more reliably avoid the situation where the DC power supply from the fuel cell power generation system 40 to the inverter 13 is performed when the system power supply 200 does not have a power failure. Will be done. Further, by confirming that the fourth condition is satisfied together with the first to third conditions, the DC power supply from the fuel cell power generation system 40 to the inverter 13 can be more reliably supplied to the inverter 13, and the power supplied to the inverter 13 can be systematized. It is possible to execute in a situation where the power supply 200 cannot be supplied and the load can be supplied.

Specifically, the advantages of confirming the establishment of the fourth condition are as follows. When the power flowing out from the first branch 85 is small and the secondary interconnection breaker 83 is in the cutoff state, the power system 300 has the first condition and the second condition even though the system power supply 200 is not out of power. It is judged that it is established. However, by confirming that not only the first condition and the second condition but also the fourth condition are satisfied, it can be confirmed that the system power supply 200 is out of power even in such a case.

Further, in the power system 300, it is not impossible to supply a voltage from the inverter 13 to the load going path 356 via the third connection point p3, the first branch portion 85, and the power switching unit 28 in this order. When such a voltage is supplied, even if the power system 300 determines that the third condition is satisfied, the power supplied to the inverter 13 is supplied to the inverter 13 via the reverse power flow path 352. There is a possibility that the power supply 200 is reverse power flow. The possibility that such a voltage is supplied is that the first condition and the second condition are satisfied in consideration of the case where the power flowing out from the first branch portion 85 is small and the secondary interconnection breaker 83 is in the cutoff state. Confirmation alone cannot eliminate it. However, by checking not only the first to third conditions but also the fourth condition, the possibility that the above voltage is supplied is excluded. Therefore, by confirming not only the first to third conditions but also the fourth condition, the DC power supply from the fuel cell power generation system 40 to the inverter 13 can be more reliably supplied, and the power supplied to the inverter 13 is the system power supply. It is possible to carry out in a situation where the 200 cannot be supplied and the load can be supplied.

In this example, the fuel cell power generation system 40 cooperates with the current detection unit 27 to determine whether or not the first condition and the fourth condition are satisfied. Further, the fuel cell power generation system 40 determines whether or not the second condition and the third condition are satisfied.

It is obligatory to provide the current detection unit 27 at the positions shown in FIGS. 1 and 2 by the grid interconnection regulation. Therefore, confirmation of the establishment of the first condition and the fourth condition is unlikely to cause an increase in the cost of the electric power system 300. Further, the voltage confirmation using the fuel cell power generation system 40 does not require a large cost. Therefore, confirmation of the establishment of the second condition and the third condition is unlikely to cause an increase in the cost of the electric power system 300. For the above reasons, the first to fourth conditions are excellent from the viewpoint of avoiding the reverse power flow of the generated power of the fuel cell power generation system 40 at low cost.

[Specific example of control for avoiding reverse power flow of generated power of fuel cell power generation system]
Hereinafter, a specific example of control for avoiding reverse power flow of the generated power of the fuel cell power generation system 40 will be described with reference to FIG.

The flow chart of FIG. 5 is started at the timing when the second disconnection relay 48 is disconnected and opened by the first power failure detection described above.

In step S1, the power system 300 determines whether or not the second condition is satisfied. If it is determined that the second condition is satisfied, the flow proceeds to step S2. If it is determined that the second condition is not satisfied, the flow ends without starting the DC power supply from the fuel cell power generation system 40 to the inverter 13.

In step S2, the power system 300 determines whether or not the first condition is satisfied. If it is determined that the first condition is satisfied, the flow proceeds to step S3. If it is determined that the first condition is not satisfied, the flow proceeds to step S11.

In step S11, the power system 300 determines whether or not the elapsed time from the determination that the first condition is not satisfied in step S2 is equal to or greater than the threshold time t1. When it is determined that the elapsed time is equal to or longer than the threshold time t1, the flow ends without starting the DC power supply from the fuel cell power generation system 40 to the inverter 13. If it is determined that this elapsed time is less than the threshold time t1, the flow returns to step S1.

In step S3, the electric power system 300 determines whether or not the elapsed time from the determination that the first condition is satisfied in step S2 is equal to or greater than the threshold time t2. If it is determined that this elapsed time is equal to or greater than the threshold time t2, the flow proceeds to step S4. If it is determined that this elapsed time is less than the threshold time t2, the flow returns to step S1.

In step S4, the power system 300 initiates the activation of the substrate 60. After executing step S4, the flow proceeds to step S5.

In step S5, the power system 300 determines whether or not the second condition is satisfied. If it is determined that the second condition is satisfied, the flow proceeds to step S6. If it is determined that the second condition is not satisfied, the flow ends without starting the DC power supply from the fuel cell power generation system 40 to the inverter 13.

In step S6, the power system 300 determines whether or not the first condition is satisfied. If it is determined that the first condition is satisfied, the flow proceeds to step S7. If it is determined that the first condition is not satisfied, the flow proceeds to step S12.

In step S12, the power system 300 determines whether or not the elapsed time from the determination that the first condition is not satisfied in step S6 is equal to or greater than the threshold time t3. When it is determined that the elapsed time is equal to or longer than the threshold time t3, the flow ends without starting the DC power supply from the fuel cell power generation system 40 to the inverter 13. If it is determined that this elapsed time is less than the threshold time t3, the flow returns to step S5.

In step S7, the electric power system 300 determines whether or not the electric power generated by the fuel cell power generation system 40 has reached the predetermined electric power W1. If it is determined that the generated power has reached the predetermined power W1, the flow proceeds to step S8. If it is determined that the generated power has not reached the predetermined power W1, the flow returns to step S5. The predetermined power W1 is, for example, the rated power generation power of the fuel cell 41. The generated power of the fuel cell power generation system 40 is consumed by the heater 46 during the period when it is not output from the fuel cell power generation system 40.

In step S8, the power system 300 determines whether or not the third condition is satisfied. If it is determined that the third condition is satisfied, the flow proceeds to step S9. If it is determined that the third condition is not satisfied, the flow proceeds to step S13.

In step S13, the power system 300 determines whether or not the number of times (hereinafter, may be referred to as the number of retries) determined in step S8 that the third condition is not satisfied is equal to or greater than the threshold number N. When it is determined that the number of retries is equal to or greater than the threshold number N, the flow ends without starting the DC power supply from the fuel cell power generation system 40 to the inverter 13. If it is determined that the number of retries is less than the threshold number N, the flow returns to step S8.

In step S9, the power system 300 determines whether or not the fourth condition is satisfied. If it is determined that the fourth condition is satisfied, the flow proceeds to step S10. If it is determined that the fourth condition is not satisfied, the flow ends without starting the DC power supply from the fuel cell power generation system 40 to the inverter 13.

In step S10, the power system 300 causes the substrate 60 to start outputting DC power. As a result, the supply of DC power from the fuel cell power generation system 40 to the inverter 13 is started.

In this specific example, when the flow ends without starting the DC power supply from the fuel cell power generation system 40 to the inverter 13, the flow of FIG. 5 is re-executed from the beginning. This flow can be continuously repeated until step S10 is reached and the DC power supply from the fuel cell power generation system 40 to the inverter 13 is started. In this way, the DC power supply from the fuel cell power generation system 40 to the inverter 13 is started at an appropriate timing.

After the DC power supply from the fuel cell power generation system 40 to the inverter 13 is started, the power generated by the fuel cell power generation system 40 can be supplied to the second branch portion 95. In this way, in a situation where the system power supply 200 is out of power, the fuel cell power generation system 40 can supply electric power to the connection destination of the second branch portion 95 for a long time. For example, when the load 251 is an electric appliance, the electric appliance can be used for a long time.

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

The characteristic conversion circuit 100 that realizes such first and second feedback control can be appropriately designed, but the characteristic conversion circuit 100X, which is a specific example of the characteristic conversion circuit 100, will be described below with reference to FIG. To do. In the following, the elements already described with reference to FIG. 4 may be designated by the same reference numerals and the description thereof may be omitted.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

A drive pulse signal is supplied from the high-side driver output terminal 149a to the control terminal of the first switching element 162a. A drive pulse signal is supplied from the low-side driver output terminal 149b to the control terminal of the second switching element 162b. As a result, the switching elements 162a and 162b are alternately turned on and off by being supplied with drive pulse signals having opposite phases. 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. 7 shows another example of the characteristic conversion circuit. In the following, the description of the same parts as those in the example of FIG. 4 may be omitted.

The characteristic conversion circuit 190 shown in FIG. 7 has a feedback current supply unit 195 instead of the feedback current supply unit 130 of the characteristic conversion circuit 100 of FIG. The feedback current supply unit 195 has a ninth resistor 191 in addition to the constant voltage source 131 and the sixth resistor 132.

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

In the region where the output current of the characteristic conversion circuit 190 is small, the first current occupies most of the current flowing out from the constant voltage source 131. On the other hand, in the region where the output current of the characteristic conversion circuit 100 is large, the second current occupies most of the current flowing out from the constant voltage source 131. That is, the operation of the first feedback circuit 110 is dominant in the region where the output current of the characteristic conversion circuit 100 is small, and the operation of the second feedback circuit 120 is dominant in the region where the output current of the characteristic conversion circuit 100 is large. In these respects, the characteristic conversion circuit 190 is common to the characteristic conversion circuit 100. Therefore, in the characteristic conversion circuit 190, the ratio of the output voltage to the input voltage of the voltage / current control circuit 160 is adjusted in the same manner as in the characteristic conversion circuit 100.

FIG. 8 shows a characteristic conversion circuit 190X which is a specific example of the characteristic conversion circuit 190. In the following, description of the same parts as in the example of FIG. 6 may be omitted.

The characteristic conversion circuit 190X shown in FIG. 8 has a feedback current supply unit 195X instead of the feedback current supply unit 130X of the characteristic conversion circuit 100X of FIG. Further, the characteristic conversion circuit 190X has a current resonance control unit 199 instead of the current resonance control unit 140 of the characteristic conversion circuit 100X.

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

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

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

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

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

It should be noted again that the specific example of the characteristic conversion circuit 100 of FIG. 4 is not limited to the characteristic conversion circuit 100X of FIG. For example, the larger the current flowing out from the constant voltage source 131, the smaller the duty ratio is defined, and a DCDC converter that operates based on the duty ratio can be configured in the characteristic conversion circuit. The same applies to the specific example of the characteristic conversion circuit 190 of FIG. 7.

Further, the configurations of the first feedback circuit 110 and the second feedback circuit 120 of FIGS. 4 and 6 are not essential. For example, the voltage sensor detects the output voltage of the voltage-current control circuit 160, the current sensor detects the output current of the voltage-current control circuit 160, and in the region where the output current is small, the output voltage is maintained at a constant voltage and the output current is reduced. In a large region, a control signal may be generated by a microcomputer so that the output current decreases as the output current increases, and the voltage-current control circuit 160 may be controlled using the control signal.

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

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

10 Power station 11,43 DC bus 12,21,22,23,42,45 DCDC converter 13,44 Inverter 14,48 Decoupling relay 20 DC power converter 25 Power storage device 27 Current detector 28 Power switching unit 28a System power Input unit 28b Independent power input unit 28c Power output unit 31, 32 Solar power generation system 36, 37 Solar power generation panel 40 Fuel cell power generation system 41 Fuel cell 46 Heater 47 Hot water storage unit 51 MCU
52 Low voltage power supply 55 D1 power supply 56, 251, 252, 253 Load 60 Board 61 LC filter 62 Protection relay 80, 90 Distribution board 81, 82, 83, 85a, 85b, 85c, 92, 95a, 95b, 95c Breaker 85, 95 Branch 88,89,98,99 Electric circuit 100,100X Characteristic conversion circuit 110,120 Feedback circuit 111,112,121,122,123,132,141,143,191,196 Resistance 115,125 Shunt regulator 128 Current sensor 130, 130X, 190, 190X Feedback current supply unit 131 Constant voltage source 135,192 Light emitting diode 140,199 Current resonance control unit 142,161,163a, 163b,164,167 Capacitor 145,197 Phototransistor 146 Control IC
147 Constant current source 148, 149a, 149b Terminal 150, 198 Optocoupler 160, 160X Voltage / current control circuit 162a, 162b Switching element 165 Transformer 165a, 165b, 165c Winding 166a, 166b Diode 200 System power supply 260 Outlet 300 Power system 351, 352,353,354,355,356 Path p1, p2, p3 Connection point

Claims (7)

It is a power system that is connected to the grid power supply.
A fuel cell power generation system having a fuel cell and an AC load,
Inverters that convert DC power to AC power,
A current detector with a current sensor and
A first distribution board having a first branch portion including a plurality of branch breakers, a secondary interconnection breaker, and the like.
A second distribution board with a second branch that includes multiple branch breakers,
A power switching unit that has a plurality of input units including a grid power input unit and an independent power input unit, a power output unit, and switches which of the plurality of input units is connected to the power output unit. Prepare,
A system power supply path that guides AC power from the system power supply to the system power input unit via the connection point, the current detection unit, and the first branch unit in this order.
A reverse power flow path that guides AC power from the inverter to the system power supply via the connection point, and
A path for independent operation that guides AC power from the inverter to the independent power input unit,
A DC output path that guides DC power from the fuel cell power generation system to the inverter,
An AC output path that guides AC power from the fuel cell power generation system to the first branch via the secondary circuit breaker.
A load-bound path that guides AC power from the power output unit to the AC load via the second branch is formed.
The electric power system is configured so that DC electric power is supplied to the inverter from other than the fuel cell power generation system.
The electric power system has (A) the first condition that the measured value of the current detection unit is a value indicating that the system power supply is out of order, and (B) the AC output path to the fuel cell power generation system. The second condition that the input voltage is a value indicating that the system power supply is out of power, and (C) the voltage input to the fuel cell power generation system by the load going path is the operating voltage of the AC load. The third condition is that (D) the measured value of the current detection unit is maintained at a value indicating that the system power supply is out of power even if the power is consumed by the AC load. A power system that supplies DC power from the fuel cell power generation system to the inverter via the DC output path after determining that. Equipped with a solar power generation system with a solar power generation panel,
The power system according to claim 1, wherein a path for guiding DC power from the photovoltaic power generation system to the inverter is formed. Equipped with a power storage device
The power system according to claim 1 or 2, wherein a path for guiding DC power from the power storage device to the inverter is formed. A photovoltaic power generation system with a photovoltaic power generation panel and
Equipped with a power storage device,
A path for guiding DC power from the photovoltaic power generation system to the power storage device,
The power system according to any one of claims 1 to 3, wherein a path for guiding DC power from the fuel cell power generation system to the power storage device is formed. A photovoltaic power generation system with a photovoltaic power generation panel and
Power storage device and
Equipped with an outlet,
A path for guiding electric power from the photovoltaic power generation system to the outlet via the inverter, the path for independent operation, the power switching unit, and the second branch portion in this order.
A route for guiding electric power from the fuel cell power generation system to the outlet via the inverter, the path for self-sustaining operation, the power switching unit, and the second branch portion in this order.
Claims 1 to 4, wherein a path for guiding electric power from the power storage device to the outlet via the inverter, the path for independent operation, the power switching unit, and the second branch portion in this order is formed. The power system according to any one item. The fifth aspect of claim 5, wherein a path for guiding electric power from the power storage device to the fuel cell power generation system via the inverter, the path for self-sustaining operation, the power switching unit, and the second branch portion in this order is formed. Power system. A substrate provided on the DC output path is provided.
Claims 1 to 6 indicate that the substrate starts to output DC power after the power system determines that the first condition, the second condition, the third condition, and the fourth condition are satisfied. The power system according to any one of the above.

Images