JP7234852B2 - Distributed power supply system and its operation method - Google Patents

Description

The present disclosure relates to a distributed power supply system and its operation method.

In Japan, low-voltage distribution lines that supply electric power to consumers such as houses are mainly AC200V/AC100V single-phase three-wire systems. On the other hand, distributed power supply systems such as residential solar power generation devices, power storage devices, and fuel cell systems, which have become popular in recent years, have two voltage lines, excluding the neutral line, out of the three single-phase three-wire lines. AC200V is output between lines (see, for example, Patent Document 1).

JP 2018-11476 A

In a residential photovoltaic power generation device, a string that outputs a DC voltage of about 200V to 300V is configured by connecting a large number of cells for power generation in series. After this DC voltage is boosted to, for example, 350 V (an example of a value with a margin for the peak value of AC 200 V) by a DC/DC converter, it is converted to AC 200 V by a single-phase inverter and connected to the commercial power system. In this case, since the DC voltage of the string is 200 V or higher, the boost width is relatively small. Therefore, an inexpensive power conversion device can perform power conversion with high efficiency.

On the other hand, the DC voltage of a storage battery or fuel cell used in a residential power storage device or fuel cell system is generally lower than that of the photovoltaic string, and is often 100 V or less. It is impossible to convert a low DC voltage of 100V or less to a DC voltage of as high as 350V using only a single-stage DC/DC converter. Therefore, it is possible to increase the voltage step by step by connecting non-isolated DC/DC converters in multiple stages, or to make the DC/DC converter a high-frequency isolated type and increase the voltage according to the winding ratio of the transformer. Become. However, in that case, there arise problems of an increase in size of the device, an increase in cost, and a decrease in power conversion efficiency.

Therefore, it is conceivable to set the voltage output by the power storage device or the fuel cell system to AC 100V, and provide an output between one of the two voltage lines excluding the neutral line of the single-phase three-wire system and the neutral line. be done. In this case, the DC side voltage of the single-phase inverter can be about 175V, so even a single-stage non-isolated DC/DC converter can boost the voltage, and the size and cost of the device can be reduced, and high power conversion efficiency can be achieved. It becomes possible to

However, in a distributed power supply system with an output of AC 100V, it is not possible to supply power to only one phase of a single-phase three-wire electric circuit and power to the other phase. Therefore, when the power consumption of the load differs greatly between one phase and the other phase, the power supply and power storage functions of the distributed power supply system cannot be fully utilized. As a result, if the amount of power to be purchased and sold increases and the purchase price of the power to be sold decreases, there is a possibility that it will not lead to savings in power costs for consumers.

In view of such problems, an object of the present disclosure is to make it possible to fully utilize the function of a distributed power supply system connected to one phase of a single-phase three-wire electric circuit.

The present disclosure includes the following inventions. However, the present invention is defined by the claims.

A distributed power supply system of the present disclosure is a distributed power supply system including a power storage device connected to a single-phase three-wire electric circuit having a first voltage line, a neutral line, and a second voltage line, When a U-phase is defined between the first voltage line and the neutral line, and a W-phase is defined between the second voltage line and the neutral line, the power storage device:
a DC power supply unit including a storage battery;
A first leg connected to the DC power supply unit and having an intermediate connection point of the series body of a pair of switching elements connected to the first voltage line, and an intermediate connection point of the series body of the pair of switching elements being the second voltage line. and an inverter having a third leg in which an intermediate connection point of a series body of a pair of switching elements is connected to the neutral wire;
a first switch provided between the inverter and the first voltage line;
a second switch provided between the inverter and the second voltage line;
a U-phase operating state in which the second leg is opened, the first leg and the third leg are switched, the first switch is closed, and the second switch is opened; a W-phase operating state in which the circuit is opened, the second leg and the third leg are switched, the second switch is closed, and the first switch is opened; and a control unit that alternatively switches based on the power at the W-phase power receiving point;
It has

Another expression of the distributed power system is a distributed power system that includes two sets of electrical storage devices connected to a single-phase three-wire electrical circuit having a first voltage line, a neutral line, and a second voltage line. When defining a U phase between the first voltage line and the neutral line and a W phase between the second voltage line and the neutral line,
a photovoltaic generator connected to provide output between the first voltage line and the second voltage line of the single-phase three-wire electrical circuit;
Each of the two sets of power storage devices,
a DC power supply unit including a storage battery;
A first leg connected to the DC power supply unit and having an intermediate connection point of the series body of a pair of switching elements connected to the first voltage line, and an intermediate connection point of the series body of the pair of switching elements being the second voltage line. and an inverter having a third leg in which an intermediate connection point of a series body of a pair of switching elements is connected to the neutral wire;
a first switch provided between the inverter and the first voltage line;
a second switch provided between the inverter and the second voltage line;
a U-phase operating state in which the second leg is opened, the first leg and the third leg are switched, the first switch is closed, and the second switch is opened; a W-phase operating state in which the circuit is opened, the second leg and the third leg are switched, the second switch is closed, and the first switch is opened; and a control unit that alternatively switches based on the power at the W-phase power receiving point;
It has

From a method point of view, a power storage device connected to a single-phase three-wire electric circuit having a first voltage line, a neutral line, and a second voltage line, the DC power supply section including a storage battery, and the DC power supply. A first leg connected to a pair of switching elements connected to the first leg connected to the second voltage line and having an intermediate connection point of the series body of the pair of switching elements connected to the first voltage line, and an intermediate connection point of the series body of the pair of switching elements being connected to the second voltage line and an inverter having a third leg in which an intermediate connection point of a series body of a pair of switching elements is connected to the neutral line. There is
a U-phase operating state in which the second leg is opened, the first leg and the third leg are switched, and the inverter is connected to the U phase and disconnected from the W phase;
A W-phase operating state in which the first leg is opened, the second leg and the third leg are switched, and the inverter is connected to the W phase and disconnected from the U phase,
The method of operating a distributed power supply system selectively switches based on the power at the U-phase power receiving point and the power at the W-phase power receiving point.

According to the present disclosure, it is possible to fully utilize the functionality of a distributed power supply system that connects to one phase of a single-phase, three-wire electrical circuit.

FIG. 1 is a circuit diagram of a distributed power supply system according to the first embodiment. FIG. 2 is an example of an internal circuit diagram of a power storage device. FIG. 3 is a flowchart illustrating an example of processing executed by a control unit; FIG. 4 is a circuit diagram of a distributed power supply system according to the second embodiment. FIG. 5 is a circuit diagram showing a reference example of a distributed power supply system. FIG. 6 is a circuit diagram considering an example of a specific state in the distributed power supply system shown in FIG. FIG. 7 is a circuit diagram in which another example of a specific state is applied to the distributed power supply system shown in FIG.

[Description of Embodiments of the Present Disclosure]
Embodiments of the present disclosure include at least the following as gists thereof.

(1) This is a distributed power supply system including power storage devices connected to a single-phase three-wire electric circuit having a first voltage line, a neutral line, and a second voltage line, wherein the first voltage line and the neutral wire is defined as a U phase, and between the second voltage line and the neutral wire is defined as a W phase. A first leg connected to a pair of switching elements connected to the first leg connected to the second voltage line and having an intermediate connection point of the series body of the pair of switching elements connected to the first voltage line, and an intermediate connection point of the series body of the pair of switching elements being connected to the second voltage line and an inverter having a third leg in which an intermediate connection point of a series body of a pair of switching elements is connected to the neutral line; A first switch, a second switch provided between the inverter and the second voltage line, and the second leg are opened, the first leg and the third leg are switched, and the first switch is switched. a U-phase operating state in which a switch is closed and the second switch is opened, the first leg is opened, the second leg and the third leg are switched, and the second switch is closed; and a control unit that selectively switches between a W-phase operating state in which the first switch is opened, based on the power at the U-phase power receiving point and the power at the W-phase power receiving point. ing.

In the distributed power supply system configured as described above, power can only be transferred between either one of the U phase and W phase and the inverter at the same time. By switching the two legs to be used and switching the connection state with a switch, power can be transferred between the other phase and the inverter as well. As a result, the power supply and power storage functions of the power storage device in the distributed power supply system can be fully utilized.

(2) In the distributed power supply system of (1) above, when discharging the storage battery, the control unit connects, for example, the U-phase load and the W-phase load, which consumes more power. Connect the inverter to the phase that is connected.
In this case, of the loads connected to the U-phase and W-phase, by supplying power from the storage battery to the phase to which the load that consumes more power is connected, It is possible to suppress the power to be supplied.

(3) The distributed power supply system of (1) or (2) is a solar system connected to supply output between the first voltage line and the second voltage line of the single-phase three-wire electric circuit. A photovoltaic device may be provided. In such a distributed power supply system, when the storage battery is charged using the power generated by the photovoltaic power generation device, the control unit selects, for example, the U-phase load or the W-phase load, whichever consumes less power. The inverter is connected to the phase to which the load of is connected.
In this case, of the loads connected to the U-phase and W-phase, the surplus power of the phase to which the load with lower power consumption is connected is used to charge the storage battery, thereby making the surplus power of the solar power generation effective. can be used.

(4) The distributed power supply system of (1) or (2) is a solar system connected to supply output between the first voltage line and the second voltage line of the single-phase three-wire electric circuit. A photovoltaic device may be provided. In such a distributed power supply system, when the storage battery is charged using the power generated by the photovoltaic power generation device, the control unit, for example, transfers the Connect the inverter.
In this case, the surplus power of the photovoltaic power generation can be effectively used by charging the storage battery with the surplus power of the phase with the larger surplus power of the U-phase and the W-phase.

(5) Also, this is a distributed power supply system including two sets of power storage devices connected to a single-phase three-wire electric circuit having a first voltage line, a neutral line, and a second voltage line, When the U phase is defined between the first voltage line and the neutral line, and the W phase is defined between the second voltage line and the neutral line, the first a solar power generation device connected to supply output between a voltage line and the second voltage line, wherein each of the two sets of power storage devices includes a DC power supply unit including a storage battery; A first leg in which an intermediate connection point of the series bodies of a pair of switching elements is connected to the first voltage line, and a second leg in which an intermediate connection point of the series bodies of the pair of switching elements is connected to the second voltage line. an inverter having two legs and a third leg in which an intermediate connection point of a series body of a pair of switching elements is connected to the neutral line; and a first voltage line provided between the inverter and the first voltage line. 1 switch, a second switch provided between the inverter and the second voltage line, and the second leg are opened, the first leg and the third leg are switched, and the first switch is switched. and open the second switch, open the first leg, switch the second leg and the third leg, close the second switch, and and a W-phase operating state in which the first switch is opened, based on the power at the U-phase power receiving point and the power at the W-phase power receiving point. there is

In the distributed power supply system configured as in (5) above, two sets of power storage devices can be connected to phases different from each other, and can also be connected to the same phase. Therefore, according to the power consumption situation and the surplus power situation, the power supply and power storage functions of the distributed power supply system including the two power storage devices can be fully utilized, and the surplus power generated by the photovoltaic power generation can be used. can be effectively utilized.

(6) In the distributed power supply system according to any one of (1) to (5), when switching from the U-phase operating state to the W-phase operating state, the control unit controls the first leg and the third leg. After stopping the switching operation of the leg, the first switch is opened, and then the second switch is closed, the switching operation of the second leg and the third leg is started, and the W-phase operation state is changed. When switching to the U-phase operating state, the control unit stops the switching operations of the second leg and the third leg, opens the second switch, and then closes the first switch. , the switching operations of the first leg and the third leg are started.
In this case, since the first switch and the second switch are not directly involved in cutting off or turning on the current, the life of the contacts can be lengthened.

(7) from a method point of view, an electrical storage device connected to a single-phase three-wire electrical circuit having a first voltage line, a neutral line, and a second voltage line, the DC power supply section including a storage battery; A first leg connected to the DC power supply unit and having an intermediate connection point of the series body of the pair of switching elements connected to the first voltage line, and an intermediate connection point of the series body of the pair of switching elements being the second voltage line. and an inverter having a third leg in which an intermediate connection point of a series body of a pair of switching elements is connected to the neutral line. wherein the second leg is opened, the first leg and the third leg are switched, and the inverter is connected to the U phase and disconnected from the W phase. A phase operating state, and W-phase operation in which the first leg is opened, the second leg and the third leg are switched, and the inverter is connected to the W phase and disconnected from the U phase. state is alternatively switched based on the power at the U-phase power receiving point and the power at the W-phase power receiving point.

According to such a method of operating a distributed power supply system, using a power storage device that outputs a voltage (for example, AC 100 V) between one voltage line and a neutral line, between both the U phase and the W phase It is possible to realize the delivery of electric power in As a result, the power supply and power storage functions of the power storage device in the distributed power supply system can be fully utilized.

[Details of the embodiment of the present disclosure]
Hereinafter, specific examples of the distributed power supply system of the present disclosure and its operation method will be described with reference to the drawings.

《Detailed analysis of the issue》
First, we will analyze the aforementioned issues in detail.
FIG. 5 is a circuit diagram showing a reference example of the distributed power supply system 200. As shown in FIG. A single-phase three-wire commercial power system 1 has a U line and a W line as voltage lines and an O line as a neutral line. AC 100V is applied between the U line and the O line, and AC 100V is applied between the O line and the W line in the opposite phase to that between the U line and the O line. AC200V is applied between the U line and the W line. A U-phase is between the U-line and the O-line, and a W-phase is between the W-line and the O-line. That is, the U-phase power supply 1U of AC 100V viewed from the neutral line O, and the W-phase power supply 1W of AC 100V, which is in the opposite phase to the U-phase viewed from the neutral line O, are present in the U-phase, respectively. It means that

A consumer's load _LUW is connected between the U line and the W line, a load _LU is connected between the U line and the O line, and a load _LW is connected between the W line and the O line. The solar power generation device 2 includes a solar power generation panel 3 and a power conditioner 4 connected thereto. The output of the photovoltaic panel 3 is converted into alternating current by the power conditioner 4, and the output is supplied between the U line and the W line.

An output end (or input end) of a power storage device 5j including a storage battery, an inverter, etc. (not shown) is connected between the U line and the O line. Assuming that the power receiving point is where the U-phase power supply 1U and the W-phase power supply 1W are located, current sensors 5iu and 5iw are provided on the power receiving point sides of the U-line and O-line, respectively. The detection outputs of current sensors 5iu and 5iw are sent to power storage device 5j. The power storage device 5j also receives a voltage detection output between the U line and the O line from an internal voltage sensor (not shown). The power storage device 5j causes the storage battery to be charged or discharged based on the detection output of the sensors and information on the storage battery.

(Power supply to load)
Here, first, consider a situation in which the photovoltaic power generation device 2 is not generating power and the power storage device 5j is discharging the charged energy and supplying it to the load Lu. The power storage device 5j controls discharge power so that the power on the power receiving point side becomes a constant forward power flow (approximately 5% of the rated power of the power storage device 5j) close to zero. The power at the receiving point can be the sum of the U-phase and W-phase active powers. In this case, even if one of them is reverse power flow, the total power of both the U phase and the W phase should be the forward power flow target value. Therefore, even if the load is connected only to the W phase and no load is connected to the U phase and between the U line and the W line, the power at the receiving point matches the forward power flow target value. It is possible to control power storage device 5j as follows.

FIG. 6 is a circuit diagram considering an example of a specific state in the distributed power supply system 200 shown in FIG. In FIG. 6, the photovoltaic power generation device 2 is in the process of stopping power generation. A load of 500 W is connected to the W phase. The forward power flow target value is 50W. In this case, power storage device 50 discharges power of 450 W to the U phase, but all of this power is reverse power flow. The discharged power of the power storage device 50 is not used for the W phase, and the 500 _W power received from the commercial power system is supplied to the W phase load LW. At this time, the purchased power is 500W and the sold power is 450W. Although power discharged from a storage battery charged with power from a commercial power system cannot be sold, a case will be considered below in which a storage battery charged with surplus power generated by photovoltaic power generation is discharged.

This situation is not a disadvantage for users under the feed-in tariff (FIT) system for the amount of electricity generated by photovoltaic power generation. However, after the end of FIT, when the purchase price becomes significantly lower than the electricity rate, the reverse flow of the power stored in the storage battery becomes economically disadvantageous. Therefore, the power storage device 5j should be controlled so that the reverse power flow does not occur in both the U-phase and the W-phase.

In the example of FIG. 5, in terms of the maximum power that can be supplied by the power storage device 5j with an output of 100 V (excluding the reduction due to the forward power flow target value), the load _Lu connected to the U phase is supplied with a maximum of 100%. can. A maximum of 50% can be supplied to the load L _UW connected between the U line and the W line. The power that can be supplied to the load _LW connected to the W phase becomes zero. If the power consumption of the load is biased toward the W phase, the discharge of the power storage device 5j will not be consumed by the load, and the amount of power purchased from the commercial power system 1 will increase accordingly. Therefore, it is assumed that the power storage device 5j is used for the purpose of self-consumption of power generated by photovoltaic power generation after the FIT is completed.

(Charging surplus electricity from solar power generation)
Next, consider a situation in which the power generated by the photovoltaic power generation device 2 is greater than the power consumption of the load, and therefore surplus power is generated, and the power storage device 5j is being charged with this surplus power. The power storage device 5j in FIG. 5 controls charging power so that the total active power of the U-phase and W-phase becomes zero.

FIG. 7 is a circuit diagram in which another example of a specific state is applied to the distributed power supply system 200 shown in FIG. In FIG. 7, the photovoltaic power generation device 2 is generating power and is generating 2000W. As for the loads, it is assumed that the U-phase load L _U and the W-phase load L _W equally consume 500 W each, for a total of 1000 W. The power storage device 5j performs control so that the surplus power of 1000 W generated at this time is charged. At this time, since the photovoltaic power generation device 2 outputs between the U line and the W line, it is not possible to supply the charging power of 1000 W only to the U phase. 500W each for a total of 1000W surplus power.

As a result, with respect to the surplus power of 1000 W of the photovoltaic power generation device 2, 500 W is used for charging in the U phase, but since control is performed to originally charge at 1000 W, the shortage of 500 W is drawn from the commercial power system 1. On the other hand, in the W phase, 500 W, which is half of the surplus power, is not used. As a result, 500 W of power is purchased in the U phase, and 500 W of reverse power flow (sold power) is obtained in the W phase. If the target value of charging control is set to 500W, the U-phase purchased power will be 0W, and waste can be prevented, but the W-phase will not change due to the reverse power flow of 500W, and the amount of power that can be originally charged and used for self-consumption will not change. Since it decreases, it becomes disadvantageous after the FIT ends.

《Analysis summary》
As described above, the 100 V output power storage device is disadvantageous for the self-consumption of photovoltaic power generation after the end of FIT, both for supplying power to loads and for charging surplus power of photovoltaic power generation. In the 100V output system, it is essential to reduce power purchase in load feeding, reduce reverse power flow of photovoltaic power generation, and increase self-consumption rate of surplus power generated by photovoltaic power generation.

<<1st Embodiment>>
Next, a distributed power supply system according to the first embodiment of the present disclosure will be described.
The basic concept is to allow the power storage device to be selectively connected to either the U phase or the W phase. By connecting the power storage device to the phase that consumes a lot of power during discharging, more power can be discharged and power purchase can be reduced. When charging surplus power generated by photovoltaic power generation, if the power storage device is connected to a phase that consumes less power and has more surplus power, more surplus power can be charged and wasteful reverse power flow can be reduced.

FIG. 1 is a circuit diagram of a distributed power supply system 100 according to the first embodiment. A single-phase three-wire commercial power system 1 has a U line and a W line as voltage lines and an O line as a neutral line. AC 100V is applied between the U line and the O line, and AC 100V is applied between the O line and the W line in the opposite phase to that between the U line and the O line. AC200V is applied between the U line and the W line. A U-phase is between the U-line and the O-line, and a W-phase is between the W-line and the O-line. That is, the U-phase power supply 1U of AC 100V viewed from the neutral line O, and the W-phase power supply 1W of AC 100V, which is in the opposite phase to the U-phase viewed from the neutral line O, are present in the U-phase, respectively. It means that

A consumer's load _LUW is connected between the U line and the W line, a load _LU is connected between the U line and the O line, and a load _LW is connected between the W line and the O line. The solar power generation device 2 includes a solar power generation panel 3 and a power conditioner 4 connected thereto. The power conditioner 4 includes a power conversion device (including a control unit) 41 that converts direct current to alternating current, and an interconnection relay 42 . The interconnection relay 42 is closed during system interconnection, and is opened only when the power conditioner 4 is disconnected. The output of the photovoltaic power generation device 2 is supplied between the U line and the W line.

The power storage device 5 is connected to three lines of U line, O line and W line.
Assuming that the power receiving point is where the U-phase power supply 1U and the W-phase power supply 1W are located, current sensors 50iu and 50iw are provided on the power receiving point sides of the U line and W line, respectively. The detection outputs of current sensors 50iu and 50iw are sent to control unit 50 ( FIG. 2 ) in power storage device 5 .

FIG. 2 is an example of an internal circuit diagram of the power storage device 5. As shown in FIG. In the figure, the power storage device 5 has a DC power supply section 5A including a storage battery 51 . The rated voltage of the storage battery 51 is, for example, 100 V or less. A capacitor 52 is connected across the storage battery 51 . A DC/DC converter 5B is connected to the storage battery 51 . The DC/DC converter 5B includes a DC reactor 53, a low-side switching element QL, and a high-side switching element QH. The switching elements QL and QH are controlled by the controller 50 .

The DC/DC converter 5B boosts the voltage of the storage battery 51 from 100V or less to about 175V and outputs it to the DC bus 5D. 175 V is a value obtained by adding some margin to the peak value (approximately 141 V) of AC 100 V, which is the output voltage of power storage device 5 . Since the voltage of the DC bus 5D is approximately 175V, the voltage is low compared to the case where the voltage is boosted to approximately 350V, so insulation is easy. In addition, the electric parts used have half the withstand voltage, and the cost is accordingly reduced. A current sensor 50 id detects the current flowing through the DC/DC converter 5 B, and the detection output is sent to the control unit 50 . A smoothing capacitor 54 and a voltage sensor 50vd are provided between the two lines of the DC bus 5D. A detection output of the voltage sensor 50vd is sent to the control section 50 .

The inverter 5C is connected to the DC power supply section 5A via a DC bus 5D. The inverter 5C constitutes a 3-leg bridge. The left side is the first leg, the right side is the second leg, and the middle is the third leg. An intermediate connection point of the series body of the pair of switching elements Q21 and Q22 forming the second leg is connected to the W line. An intermediate connection point of the series body of the pair of switching elements Q31 and Q32 forming the third leg is connected to the O line. Each switching element Q11, Q12, Q21, Q22, Q31, Q32 is controlled by the controller 50. FIG.

On the AC side of the inverter 5C, AC reactors 55u, 55o and 55w are provided on each line, and capacitors 56u and 56w are provided between the lines of UO and WO as filters. A current sensor 50io is provided in series with the O-line AC reactor 55o. A detection output of the current sensor 50io is sent to the control unit 50 .

Switches 57u, 57o, and 57w that can be individually opened and closed by the control unit 50 are provided on the commercial power system 1 side when viewed from the capacitors 56u and 56w. During operation of the power storage device 5, the switch 57o is always closed. The switches 57u and 57w are closed alternatively and are not closed at the same time. The switches 57u, 57o, and 57w also serve as interconnection relays for disconnecting the power storage device 5 from interconnection with the commercial power system 1 . All the switches 57u, 57o, 57w are opened when parallel-off.

Voltage sensors 50vu and 50vw are provided on the commercial power system 1 side of the switches 57u, 57o and 57w to detect the voltages between the U-O lines and between the WO lines, respectively. The circuits outside the power storage device 5 are the same as those described with reference to FIG. The control unit 50 can obtain the power at the U-phase power receiving point based on the current value detected by the current sensor 50iu and the voltage value detected by the voltage sensor 50vu. Further, the control unit 50 can obtain the power at the W-phase power receiving point based on the current value detected by the current sensor 50iw and the voltage value detected by the voltage sensor 50vw.

In the power storage device 5 configured as described above, when the storage battery 51 is discharged, the output voltage of the storage battery 51 is boosted to about 175V by the DC/DC converter 5B. In the 3-leg inverter 5C, either the first leg or the second leg is open, and the switch 57u or 57w corresponding to the open leg is also open. For example, when the first leg (Q11, Q12) and the third leg (Q31, Q32) perform switching operations, and the second leg (Q21, Q22) and the switch 57w are open (switch 57u is closed), AC100V is output to the U phase. When the second leg (Q21, Q22) and the third leg (Q31, Q32) perform switching operations, and the first leg (Q11, Q12) and the switch 57u are open (switch 57w is closed), AC 100V is W phase.

When charging the storage battery 51, a voltage of AC 100V (either U phase or W phase) externally applied to the storage device 5 is rectified by the body diode of the inverter 5C or by synchronous rectification by switching, and smoothed by the capacitor 54. be done. Furthermore, the DC/DC converter 5B operates as a step-down chopper, and the storage battery 51 is charged with the DC voltage smoothed by the capacitor 52 .

The switching elements QL, QH, Q11, Q12, Q21, Q22, Q31, and Q32 in FIG. 2 are examples of MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). ) can also be used.

The control unit 50 can also acquire information about the state of charge of the storage battery 51 . Each sensor 50id, 50vd, 50iu, 50io, 50iw, 50vu, 50vw is also part of the control unit 50 in a broad sense.
The control unit 50 includes, for example, a computer, and the computer executes software (computer program) to implement necessary control functions. The software is stored in a storage device (not shown) of control unit 50 .

《Explanation of operation including phase switching》
FIG. 3 is a flowchart showing an example of processing executed by the control unit 50. As shown in FIG. When the process starts, first, the control unit 50 closes the switches 57u and 57o of the power storage device 5 in FIG. 2 and opens the switch 57w. Then, the second leg (Q21, Q22) of the inverter 5C is opened, and the first leg (Q11, Q12) and the third leg (Q31, Q32) are switched according to the phase detected by the voltage sensor 50vu. As a result, power storage device 5 is connected to the U phase (step S1). The switch 57o is always closed, and the switch 57u is closed first, and then the switching operations of the first leg and the third leg are started. , thus prolonging contact life. Also, since the switch 57w is open, the voltage of AC 200V will not enter the inverter 5C from the AC side.

The control unit 50 measures electric power based on the detection outputs of the current sensors 50iu and 50iw and the voltage sensors 50vu and 50vw and information in the control unit 50 (step S2).

(when the power consumption of the load is greater than the generated power)
Specifically, the control unit 50 controls the U-phase power (power at the power receiving point, the same applies hereinafter) Pu, the W-phase power (power at the power receiving point, the same applies hereinafter) Pw, and the inverter 5C to the U phase. The power Px that is being output is detected. In a state where the power storage device 5 is connected to the U phase, when the power consumption of the load is greater than the power generated by the solar power generation and the U-phase power Pu is detected as the received power (purchased power), the power storage device In 5, the power Px is feedback-controlled (charge/discharge command value update) so that the U-phase power Pu becomes zero or a value close to zero, and discharge is performed (step S3).

Then, the control unit 50 compares the absolute value of the power Px with the absolute value of the W-phase power Pw when the feedback control converges to a steady state (step S4). When the absolute value of the power Px is greater than the absolute value of the W-phase power Pw, the power consumption of the load connected to the U phase is greater than the power consumption of the load connected to the W phase. . In this case, power storage device 5 continues connection to the U phase (repeating steps S2, S3, and S4).

Conversely, when the absolute value of the W-phase power Pw is greater than or equal to the absolute value of the power Px, the power consumption of the load connected to the W-phase is greater than or equal to the power consumption of the load connected to the U-phase. At this time, if the power Px has already reached the discharge power upper limit value of the power storage device 5, the connection to the U phase is continued, but if not, the connection of the power storage device 5 is switched from the U phase to the W phase. (Step S5).

A detailed operation sequence in step S5 will be described. First, the control unit 50 first stops the switching of the first leg (Q11, Q12) and the third leg (Q31, Q32) of the inverter 5C to open the circuit. As a result, all the three legs are temporarily open and no current flows. Here, the controller 50 opens the switch 57u and then closes the switch 57w. Then, the control unit 50, this time, switches the second leg (Q21, Q22) and the third leg (Q31, Q32) in accordance with the phase detected by the voltage sensor 50vw. As a result, the connection destination of power storage device 5 is completely switched from the U phase to the W phase. In this way, more power can be supplied from the power storage device 5 than the power consumed in the house. The switch 57o is normally closed, and the switch 57w is closed first, and then the switching operations of the second leg and the third leg are started. contact life is therefore prolonged. In addition, since the switch 57u is open, the AC 200V voltage will not enter the inverter 5C from the AC side.

After that, the control unit 50 measures electric power based on the detection outputs of the current sensors 50iu, 50iw and the voltage sensors 50vu, 50vw and information obtained inside the control unit 50 (step S6).

Specifically, the control unit 50 detects the U-phase power Pu, the W-phase power Pw, and the power Px output by the inverter 5C to the W-phase. In a state where the power storage device 5 is connected to the W phase, when the power consumption of the load is greater than the power generated by the solar power generation and the W-phase power Pw is detected as the received power (purchased power), the power storage device In 5, the power Px is feedback-controlled (charge/discharge command value update) so that the W-phase power Pw becomes zero or a value close to zero, and discharge is performed (step S7).

Then, the control unit 50 compares the absolute value of the power Px with the absolute value of the U-phase power Pu when the feedback control converges to a steady state (step S8). When the absolute value of the power Px is greater than the absolute value of the U-phase power Pu, the power consumption of the load connected to the W-phase is greater than the power consumption of the load connected to the U-phase. . In this case, power storage device 5 continues connection to the W phase (repeating steps S6, S7, and S8).

Conversely, when the absolute value of the U-phase power Pu is greater than or equal to the absolute value of the power Px, the power consumption of the load connected to the U phase is greater than or equal to the power consumption of the load connected to the W phase. At this time, if the power Px has already reached the discharge power upper limit value of the power storage device 5, the connection to the W phase is continued, but if not, the connection of the power storage device 5 is switched from the W phase to the U phase. (Step S1).

A detailed operation sequence in step S1 will be described. First, the control unit 50 first stops the switching of the second leg (Q21, Q22) and the third leg (Q31, Q32) of the inverter 5C to open the circuit. As a result, all the three legs are temporarily open and no current flows. Here, the controller 50 opens the switch 57w and then closes the switch 57u. Then, the control unit 50, this time, switches the first leg (Q11, Q12) and the third leg (Q31, Q32) in accordance with the phase detected by the voltage sensor 50vu. As a result, the connection destination of power storage device 5 is completely switched from the W phase to the U phase. In this way, more power can be supplied from the power storage device 5 than the power consumed in the house. The switch 57o is normally closed, and the switch 57u is closed first, and then the switching operations of the first leg and the third leg are started. contact life is therefore prolonged. Also, since the switch 57w is open, the voltage of AC 200V will not enter the inverter 5C from the AC side.

(When the generated power is greater than the power consumption of the load)
Next, in the state where the power storage device 5 is connected to the U phase (step S1), if the power generated by the photovoltaic power generation is greater than the power consumption of the load and surplus power is generated, at least A reverse power flow is detected in the U-phase power Pu (step S2). At this time, the power storage device 5 performs charging by feedback-controlling the power Px (updating the charge/discharge command value) so that the U-phase power Pu becomes zero or a value close to zero (step S3).

Then, the control unit 50 compares the absolute value of the power Px and the absolute value of the W-phase power Pw when the feedback control converges and enters a steady state (step S4). When the absolute value of the power Px is larger than the absolute value of the W-phase power Pw, the U-phase has more surplus power than the W-phase. In this case, power storage device 5 continues to be connected to the U phase. Conversely, if the W-phase power Pw is greater than or equal to the power Px, there is a possibility that the surplus power generated in the W-phase is greater than that in the U-phase. At this time, if the power Px has already reached the charging power upper limit of the power storage device 5, the connection to the U phase is continued, but if not, the connection of the power storage device 5 is switched from the U phase to the W phase. (Step S5). As a result, the power storage device 5 can be charged with more power than the surplus power generated in the house.

Furthermore, in the state where the power storage device 5 is connected to the W phase (step S5), if the power generated by the photovoltaic power generation is greater than the power consumption of the load and surplus power is generated, at least W A reverse power flow is detected in the phase power Pw (step S6). At this time, the power storage device 5 charges by feedback-controlling the power Px (updating the charge/discharge command value) so that the W-phase power Pw becomes zero or a value close to zero (step S7).

Then, the control unit 50 compares the absolute value of the power Px and the absolute value of the U-phase power Pu with each other when the feedback control converges to a steady state (step S8). When the absolute value of the power Px is larger than the absolute value of the U-phase power Pu, the W-phase has more surplus power than the U-phase. In this case, power storage device 5 continues to be connected to the W phase. Conversely, if the U-phase power Pu is greater than or equal to the power Px, there is a possibility that the surplus power generated in the U-phase is greater than that in the W-phase. At this time, if the power Px has already reached the charging power upper limit of the power storage device 5, the connection to the W phase is continued, but if not, the connection of the power storage device 5 is switched from the W phase to the U phase. (Step S1). As a result, the power storage device 5 can be charged with more power than the surplus power generated in the house.

<<Second embodiment>>
FIG. 4 is a circuit diagram of the distributed power supply system 100 according to the second embodiment. The difference from FIG. 1 is that two sets of power storage devices 5 and 5x are provided. The internal circuits of power storage devices 5 and 5x are the same as those shown in FIG. The control units 50 of the power storage devices 5 and 5x execute the flowchart shown in FIG. The current sensors 50iu and 50iw of the power storage device 5x are closer to the commercial power system 1 than the current sensors 50iu and 50iw of the power storage device 5, respectively. Of the two sets of power storage devices 5 and 5x, the power storage device 5 is prioritized to supply power to the load and charge surplus power.

By using two sets of power storage devices 5 and 5x, the following two types of connections are possible.
(i) Both sets are connected to the same phase among the U phase and W phase.
(ii) Connect one of the two pairs to the U phase and the other to the W phase.

(when the power consumption of the load is greater than the generated power)
First, consider the case where the power consumption of the load is greater than the generated power.
The power storage device 5 detects U-phase power and W-phase power (both are receiving point power). As a result, the power consumption of the load was greater than the generated power, the U-phase power Pu was larger than the W-phase power Pw, and the U-phase power Pu was smaller than the output power upper limit of the power storage device 5. do. In this case, first, the power storage device 5 is connected to the U phase, and the storage battery 51 is discharged so that the U phase power Pu becomes zero. Here, it is assumed that when the power storage device 5x detects the U-phase power and the W-phase power, the W-phase power Pw is larger than the U-phase power Pu. In that case, the power storage device 5x is connected to the W-phase, and the power storage device 5x discharges the storage battery 51 so that the W-phase power Pw becomes zero. That is, in this case, as described in (ii) above, power storage device 5 is connected to the U phase, and power storage device 5x is connected to the W phase.

On the other hand, as a result of the power storage device 5 detecting the U-phase power and the W-phase power, the power consumption of the load is greater than the generated power, the U-phase power Pu is greater than the W-phase power Pw, and the U-phase power Pu is stored. Assume that the output power is higher than the upper limit of the output power of the device 5 . In this case, first, the power storage device 5 is connected to the U phase, and the storage battery 51 is discharged at the upper limit of the output. Here, when the power storage device 5x detects the U-phase power and the W-phase power, depending on the magnitude of the original U-phase power Pu, even if the power storage device 5 discharges to the upper limit, the U-phase power is still greater than the W-phase power. may also grow. In that case, the power storage device 5x is connected to the U phase, and the power storage device 5x discharges the storage battery 51 so that the U phase power Pu becomes zero. That is, in this case, both the power storage device 5 and the power storage device 5x are connected to the U phase as in (i) above.

(When the generated power is greater than the power consumption of the load)
Next, consider the case where the generated power is greater than the power consumption of the load. Assume that the power storage device 5 detects the U-phase power and the W-phase power, and that the generated power is greater than the power consumption of the load, and the U-phase surplus power is greater than the W-phase surplus power. In this case, first, the power storage device 5 is connected to the U phase, and the storage battery 51 is charged. Here, the power storage device 5x detects the U-phase power and the W-phase power. As a result, it is assumed that the surplus power of the W phase is larger than the surplus power of the U phase. In this case, the power storage device 5x is connected to the W phase, and the storage battery 51 is charged. That is, in this case, as described in (ii) above, power storage device 5 is connected to the U phase, and power storage device 5x is connected to the W phase.

On the other hand, the power storage device 5 is connected to the U phase and the storage battery 51 is charged as described above. , the surplus power of the U phase is greater than the surplus power of the W phase. In this case, the power storage device 5x is connected to the U phase, and the storage battery 51 is charged. That is, in this case, both the power storage device 5 and the power storage device 5x are connected to the U phase as in (i) above.

As described above, if the two power storage devices 5 and 5x are connected to the U phase or the W phase depending on the situation, the power storage or discharge capability of the power storage devices 5 and 5x can be effectively used. In particular, the fact that two sets of power storage devices 5 and 5x can be connected to the same phase is more advantageous than using a single single-phase three-wire output power storage device that can independently control two-phase power. It is advantageous in improving the consumption ratio. Specifically, for example, in a single-phase three-wire output power storage device that can charge and discharge 1 kW of power in each of the U phase and the W phase, the maximum power of the two phases is 2 kW. The upper limit is 1 kW. On the other hand, if the two power storage devices 5, 5x of the third embodiment are connected to the same phase, charging and discharging up to 2 kW is possible. Therefore, when the load is concentrated on one phase, the surplus power generated by the photovoltaic power generation can be used more effectively by using two sets of 100V output power storage devices 5 and 5x.

It should be noted that the description of charging and discharging the power storage devices 5 and 5x in the above-described third embodiment merely assumes the conditions. It goes without saying that it will work.
In addition, when the state of charge of one of the two power storage devices 5 and 5x becomes 100% or 0% during the operation of the two power storage devices 5, 5x, and a standby state in which charging or discharging is stopped, the other power storage device It is also possible to change the connection phase of the device.

《Summary of Disclosure》
The above disclosure can be generalized and expressed, for example, as follows.
In the distributed power supply system 100 of the present disclosure, the inverter 5C has a three-leg configuration that can alternatively switch between a U-phase operating state connected to the U-phase and a W-phase operating state connected to the W-phase, Switches 57u and 57w are provided to switch 2 legs out of 3 legs based on the power at the U-phase power receiving point and the power at the W-phase power receiving point, and to control the operation of the switches. In the distributed power supply system 100 configured in this manner, power can be transferred only between either one of the U phase and the W phase and the inverter 5C at the same time. By switching the connection state at 57w, power can be transferred between the other phase and the inverter 5C as well. As a result, the power supply and power storage functions of the power storage device 5 in the distributed power supply system 100 can be fully utilized.

In this way, the DC side voltage of the inverter connected to either one of the U-phase and W-phase can be about 175V, so the step-up (or step-down) voltage range is small, and even a single-stage non-isolated DC/DC converter fully usable. Therefore, it is possible to realize miniaturization, cost reduction, and high power conversion efficiency of the power storage device 5 .

When the storage battery 51 is to be discharged, the switches 57u and 57w can be operated so as to connect the inverter 5C to the phase to which the U-phase load or W-phase load, which consumes more power, is connected. can. In this way, by supplying power from the storage battery to the phase to which the load that consumes more power is connected, power purchased from the single-phase three-wire system can be suppressed.

Further, in the distributed power supply system 100 including the photovoltaic power generation device 2, when the storage battery 51 is charged using the generated power, the U-phase load and the W-phase load, which consumes less power, Switches 57u and 57w can be operated to connect inverter 5C to the connected phase. In this way, by charging the storage battery 51 with the surplus power of the phase to which the load that consumes less power (or the load that consumes more surplus power) is connected, the surplus power of photovoltaic power generation can be effectively used.

Furthermore, the distributed power supply system 100 may include two sets of power storage devices 5 and 5x. In this case, the two power storage devices 5 and 5x can be connected to different phases, or can be connected to the same phase. Therefore, the power supply and power storage functions of the distributed power supply system 100 including the two sets of power storage devices 5 and 5x can be fully utilized according to the power consumption situation and surplus power situation. Moreover, the surplus electric power of photovoltaic power generation can be effectively utilized.

Further, when switching from the U-phase operating state to the W-phase operating state, the control unit 50 stops the operations of the first leg (Q11, Q12) and the third leg (Q31, Q32) and then opens the switch 57u. After that, the switch 57w is closed, and then the second leg (Q21, Q22) and the third leg (Q31, Q32) are started to operate. Further, when switching from the W-phase operating state to the U-phase operating state, the control unit 50 stops the operations of the second leg (Q21, Q22) and the third leg (Q31, Q32) and then opens the switch 57w. After that, the switch 57u is closed, and then the first leg (Q11, Q12) and the third leg (Q31, Q32) are started to operate.
By controlling in this way, the switches 57u and 57w are not directly involved in cutting off or turning on the current, so the life of the contacts can be lengthened.

On the other hand, from the point of view of the operation method of the distributed power supply system, there is a period in which the AC side end of the inverter 5C connected to the storage battery 51 is connected to the U phase, and a period in which the AC side end of the inverter 5C is connected to the W phase. It becomes operation|movement which has the period which connects. According to such a method of operating a distributed power supply system, using the power storage device 5 that outputs a voltage (for example, AC 100 V) between one voltage line and the neutral line, both the U phase and the W phase It is possible to realize the transfer of electric power between them. As a result, the power supply and power storage functions of the power storage device in the distributed power supply system can be fully utilized.

《Supplement》
It should be noted that the embodiments disclosed this time should be considered as examples in all respects and not restrictive. The scope of the present invention is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope of equivalence to the scope of claims.

1 Commercial power system 1U U-phase power supply 1W W-phase power supply 2 Photovoltaic power generation device 3 Photovoltaic power generation panel 4 Power conditioner 5, 5x, 5j Power storage device 5A DC power supply unit 5B DC/DC converter 5C Inverter 5D DC bus 5iu, 5iw Current sensor 41 Power converter 42 Interconnected relay 50 Control unit 50id, 50io, 50iu, 50iw Current sensor 50vd, 50vu, 50vw Voltage sensor 51 Storage battery 52 Capacitor 53 DC reactor 54 Capacitor 55u, 55o, 55w AC reactor 56u, 56w Capacitor 57u , 57o, 57w Switch 100, 200 Distributed power supply system L _U U-phase load L _W W-phase load L _UW Load between U line and W line

Claims (8)

A distributed power supply system including power storage devices connected to a single-phase three-wire electric circuit having a first voltage line, a neutral line, and a second voltage line, wherein the first voltage line and the neutral line When the U phase is defined between and the W phase is between the second voltage line and the neutral line, the power storage device
a DC power supply unit including a storage battery;
A first leg connected to the DC power supply unit and having an intermediate connection point of the series body of a pair of switching elements connected to the first voltage line, and an intermediate connection point of the series body of the pair of switching elements being the second voltage line. and an inverter having a third leg in which an intermediate connection point of a series body of a pair of switching elements is connected to the neutral wire;
a first switch provided between the inverter and the first voltage line;
a second switch provided between the inverter and the second voltage line;
a U-phase operating state in which the second leg is opened, the first leg and the third leg are switched, the first switch is closed, and the second switch is opened; a W-phase operating state in which the circuit is opened, the second leg and the third leg are switched, the second switch is closed, and the first switch is opened; and a control unit that alternatively switches based on the power at the W-phase power receiving point;
a photovoltaic power generator connected to provide output between the first voltage line and the second voltage line of the single-phase three-wire electrical circuit;
with
When the storage battery is charged using the power generated by the photovoltaic power generation device, the control unit controls the phase to which the load that consumes less power is connected, out of the U-phase load and the W-phase load. connecting said inverter to
Distributed power system. A distributed power supply system including power storage devices connected to a single-phase three-wire electric circuit having a first voltage line, a neutral line, and a second voltage line, wherein the first voltage line and the neutral line When the U phase is defined between and the W phase is between the second voltage line and the neutral line, the power storage device
a DC power supply unit including a storage battery;
A first leg connected to the DC power supply unit and having an intermediate connection point of the series body of a pair of switching elements connected to the first voltage line, and an intermediate connection point of the series body of the pair of switching elements being the second voltage line. and an inverter having a third leg in which an intermediate connection point of a series body of a pair of switching elements is connected to the neutral wire;
a first switch provided between the inverter and the first voltage line;
a second switch provided between the inverter and the second voltage line;
a U-phase operating state in which the second leg is opened, the first leg and the third leg are switched, the first switch is closed, and the second switch is opened; a W-phase operating state in which the circuit is opened, the second leg and the third leg are switched, the second switch is closed, and the first switch is opened; and a control unit that alternatively switches based on the power at the W-phase power receiving point;
a photovoltaic power generator connected to provide output between the first voltage line and the second voltage line of the single-phase three-wire electrical circuit;
with
When the storage battery is charged using the power generated by the photovoltaic power generation device, the control unit connects the inverter to the phase with more surplus power based on the output of the photovoltaic power generation device.
Distributed power system. 2. When discharging the storage battery, the controller connects the inverter to a phase to which one of the U-phase load and the W-phase load that consumes more power is connected . Item 3. The distributed power supply system according to item 2 . A distributed power supply system including two sets of power storage devices connected to a single-phase three-wire electric circuit having a first voltage line, a neutral line, and a second voltage line, wherein the first voltage line and the medium When defining a U phase between the sex wire and a W phase between the second voltage line and the neutral wire,
a photovoltaic generator connected to provide output between the first voltage line and the second voltage line of the single-phase three-wire electrical circuit;
Each of the two sets of power storage devices,
a DC power supply unit including a storage battery;
A first leg connected to the DC power supply unit and having an intermediate connection point of the series body of a pair of switching elements connected to the first voltage line, and an intermediate connection point of the series body of the pair of switching elements being the second voltage line. and an inverter having a third leg in which an intermediate connection point of a series body of a pair of switching elements is connected to the neutral wire;
a first switch provided between the inverter and the first voltage line;
a second switch provided between the inverter and the second voltage line;
a U-phase operating state in which the second leg is opened, the first leg and the third leg are switched, the first switch is closed, and the second switch is opened; a W-phase operating state in which the circuit is opened, the second leg and the third leg are switched, the second switch is closed, and the first switch is opened; and a control unit that alternatively switches based on the power at the W-phase power receiving point;
a photovoltaic power generator connected to provide output between the first voltage line and the second voltage line of the single-phase three-wire electrical circuit;
with
When the storage battery is charged using the power generated by the photovoltaic power generation device, the control unit controls the phase to which the load that consumes less power is connected, out of the U-phase load and the W-phase load. connecting said inverter to
Distributed power system. A distributed power supply system including two sets of power storage devices connected to a single-phase three-wire electric circuit having a first voltage line, a neutral line, and a second voltage line, wherein the first voltage line and the medium When defining a U phase between the sex wire and a W phase between the second voltage line and the neutral wire,
a photovoltaic generator connected to provide output between the first voltage line and the second voltage line of the single-phase three-wire electrical circuit;
Each of the two sets of power storage devices,
a DC power supply unit including a storage battery;
A first leg connected to the DC power supply unit and having an intermediate connection point of the series body of a pair of switching elements connected to the first voltage line, and an intermediate connection point of the series body of the pair of switching elements being the second voltage line. and an inverter having a third leg in which an intermediate connection point of a series body of a pair of switching elements is connected to the neutral wire;
a first switch provided between the inverter and the first voltage line;
a second switch provided between the inverter and the second voltage line;
a U-phase operating state in which the second leg is opened, the first leg and the third leg are switched, the first switch is closed, and the second switch is opened; a W-phase operating state in which the circuit is opened, the second leg and the third leg are switched, the second switch is closed, and the first switch is opened; and a control unit that alternatively switches based on the power at the W-phase power receiving point;
a photovoltaic power generator connected to provide output between the first voltage line and the second voltage line of the single-phase three-wire electrical circuit;
with
When the storage battery is charged using the power generated by the photovoltaic power generation device, the control unit connects the inverter to the phase with more surplus power based on the output of the photovoltaic power generation device.
Distributed power system. When switching from the U-phase operating state to the W-phase operating state, the control unit stops the switching operations of the first leg and the third leg, opens the first switch, and then opens the first switch. 2 switches are closed before starting the switching operation of the second leg and the third leg;
When switching from the W-phase operating state to the U-phase operating state, the control unit stops the switching operations of the second leg and the third leg, opens the second switch, and then opens the second switch. 1 switch is closed before starting the switching operation of the first leg and the third leg;
The distributed power system according to any one of claims 1 to 5. A power storage device connected to a single-phase three-wire electric circuit having a first voltage line, a neutral line, and a second voltage line, comprising: a DC power supply unit including a storage battery; A first leg in which an intermediate connection point of the series body of the switching elements of the pair of switching elements is connected to the first voltage line, a second leg in which an intermediate connection point of the series body of the pair of switching elements is connected to the second voltage line, and and an inverter having a third leg in which an intermediate connection point of a series body of a pair of switching elements is connected to the neutral line.
a U-phase operating state in which the second leg is opened, the first leg and the third leg are switched, and the inverter is connected to the U phase and disconnected from the W phase;
A W-phase operating state in which the first leg is opened, the second leg and the third leg are switched, and the inverter is connected to the W phase and disconnected from the U phase,
alternatively switching based on the power at the U-phase power receiving point and the power at the W-phase power receiving point;
When charging the storage battery using power generated by a photovoltaic power generation device connected to supply output between the first voltage line and the second voltage line of the single-phase three-wire electric circuit, the U connecting the inverter to the phase to which the load that consumes less power is connected, out of the W-phase load and the W-phase load;
How to operate a distributed power supply system. A power storage device connected to a single-phase three-wire electric circuit having a first voltage line, a neutral line, and a second voltage line, comprising: a DC power supply unit including a storage battery; A first leg in which an intermediate connection point of the series body of the switching elements of the pair of switching elements is connected to the first voltage line, a second leg in which an intermediate connection point of the series body of the pair of switching elements is connected to the second voltage line, and and an inverter having a third leg in which an intermediate connection point of a series body of a pair of switching elements is connected to the neutral line.
a U-phase operating state in which the second leg is opened, the first leg and the third leg are switched, and the inverter is connected to the U phase and disconnected from the W phase;
A W-phase operating state in which the first leg is opened, the second leg and the third leg are switched, and the inverter is connected to the W phase and disconnected from the U phase,
alternatively switching based on the power at the U-phase power receiving point and the power at the W-phase power receiving point;
When charging the storage battery using power generated by a photovoltaic power generation device connected to supply output between the first voltage line and the second voltage line of the single-phase three-wire electric circuit, the solar connecting the inverter to the phase with the higher surplus power based on the output of the photovoltaic device;
How to operate a distributed power supply system.

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