JP7439971B2 - Distributed power supply system and its operation method - Google Patents

Description

The present disclosure relates to a distributed power supply system and a method of operating the same.

Low-voltage distribution lines that supply electricity to consumers such as residences in Japan are mainly single-phase three-wire systems of 200 VAC/100 VAC. On the other hand, distributed power supply systems such as solar power generation devices, power storage devices, and fuel cell systems for residential use, which have become popular in recent years, require only two of the voltage lines, excluding the neutral line, of the three single-phase three-wire electrical circuits. AC 200V is output between the lines (for example, see Patent Document 1).

Japanese Patent Application Publication No. 2018-11476

In a residential solar power generation device, a string that outputs a DC voltage of about 200V to 300V is configured by connecting a large number of power generation cells in series. Then, this DC voltage is boosted to, for example, 350V (an example of a value with a margin above the peak value of AC 200V) using a DC/DC converter, and then converted to AC 200V using a single-phase inverter and connected to a commercial power grid. In this case, since the DC voltage of the string is 200V or more, the step-up width is relatively small. Therefore, highly efficient power conversion can be performed with an inexpensive power conversion device.

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 solar power generation string described above, and is often 100V or less. It is difficult to convert a low DC voltage of 100V or less into a DC voltage of 350V using only a single stage DC/DC converter. Therefore, we decided to connect non-isolated DC/DC converters in multiple stages and increase the voltage step by step, or to make the DC/DC converter a high frequency isolated type and increase the voltage by changing the turns ratio of the transformer. Become. However, in that case, problems arise such as an increase in the size of the device, an increase in cost, and a decrease in power conversion efficiency.

Therefore, it is considered that the voltage output by the power storage device or fuel cell system is AC100V, and the output is provided between one of the two voltage wires excluding the neutral wire of a single-phase three-wire electric circuit and the neutral wire. It will be done. In this case, the DC side voltage of the single-phase inverter only needs to be about 175V, so it is possible to boost the voltage even with a single-stage non-isolated DC/DC converter, realizing smaller devices, lower costs, and higher power conversion efficiency. It becomes possible to do so.

However, in a distributed power supply system with an output AC of 100 V, power is supplied only to one phase of a single-phase three-wire electric circuit, and power cannot be supplied to the other phase. Therefore, if the power consumption of the load differs significantly 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, the amount of electricity purchased and sold increases, and the purchase price of the electricity sold decreases, which may not lead to savings in electricity costs for consumers.

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

This disclosure includes the following inventions. However, the present invention is defined by the scope of the claims.

A distributed power supply system of the present disclosure includes a power storage device connected to a single-phase three-wire electric line having a first voltage line, a neutral line, and a second voltage line, When defining the space between the first voltage line and the neutral line as the U phase, and the space between the second voltage line and the neutral line as the W phase, the power storage device
A DC power supply section including a storage battery,
A first leg that is connected to the DC power supply unit and has an intermediate connection point of a pair of switching elements in series connected to the first voltage line, and an intermediate connection point of the pair of switching elements in series is connected to the second voltage line. an inverter having a second leg connected to the neutral line, and a third leg whose intermediate connection point of a pair of series 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 operated to switch, 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 operated, the second switch is closed, and the first switch is opened is defined as the power at the U-phase power receiving point, and a control unit that selectively switches based on the power at the W-phase power receiving point;
It is equipped with

A distributed power system according to another expression is a distributed power system that includes two sets of power 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 the space between the first voltage line and the neutral line as the U phase, and the space between the second voltage line and the neutral line as the W phase,
comprising a solar power generation device connected to supply an output between the first voltage line and the second voltage line of the single-phase three-wire electric circuit,
Each of the two sets of power storage devices is
A DC power supply section including a storage battery,
A first leg that is connected to the DC power supply unit and has an intermediate connection point of a pair of switching elements in series connected to the first voltage line, and an intermediate connection point of the pair of switching elements in series is connected to the second voltage line. an inverter having a second leg connected to the neutral line, and a third leg whose intermediate connection point of the pair of series 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 operated to switch, 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 operated, the second switch is closed, and the first switch is opened is defined as the power at the U-phase power receiving point, and a control unit that selectively switches based on the power at the W-phase power receiving point;
It is equipped with

From the viewpoint of the method, the power storage device is connected to a single-phase three-wire electric circuit having a first voltage line, a neutral line, and a second voltage line, and includes a DC power supply unit including a storage battery, and the DC power supply unit. a first leg connected to the first leg, an intermediate connection point of the series body of the pair of switching elements is connected to the first voltage line, and an intermediate connection point of the series body of the pair of switching elements is connected to the second voltage line. A method for operating a distributed power supply system for a power storage device including an inverter having a second leg connected to the neutral wire, and a third leg having an intermediate connection point of a pair of switching elements in series connected to the neutral wire. There it is,
a U-phase operating state in which the second leg is opened, the first leg and the third leg are operated for switching, 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 operated for switching, and the inverter is connected to the W-phase and disconnected from the U-phase.
This is a method of operating a distributed power supply system in which switching is performed alternatively 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 functions of a distributed power supply system connected to one phase of a single-phase three-wire electric circuit.

FIG. 1 is a circuit diagram of a distributed power supply system according to a first embodiment. FIG. 2 is an example of an internal circuit diagram of the power storage device. FIG. 3 is a flowchart illustrating an example of processing executed by the 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 a specific example of the state in the distributed power supply system shown in FIG. FIG. 7 is a circuit diagram considering another example of a specific state in the distributed power supply system shown in FIG. 5.

[Description of embodiments of the present disclosure]
The embodiment of the present disclosure includes at least the following as its gist.

(1) This 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, the first voltage line and the neutral line is defined as a U phase, and the area between the second voltage line and the neutral line is defined as a W phase, and the power storage device includes a DC power supply unit including a storage battery, and a DC power supply unit including a storage battery. a first leg connected to the first leg, an intermediate connection point of the series body of the pair of switching elements is connected to the first voltage line, and an intermediate connection point of the series body of the pair of switching elements is connected to the second voltage line. an inverter having a second leg connected to the neutral line, and a third leg having an intermediate connection point of a series body of a pair of switching elements connected to the neutral line; and an inverter provided between the inverter and the first voltage 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 operated to switch, and the first leg and the third leg are switched. a U-phase operating state in which the switch is closed and the second switch is opened, the first leg is opened, the second leg and the third leg are operated for switching, and the second switch is closed; and a control unit that selectively switches the 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 the U phase or W phase and the inverter at the same time. By switching the two legs used and switching the connection state with a switch, power can be transferred between the other phase and the inverter. Thereby, 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 the load that consumes more power among the U-phase load and the W-phase load, for example. Connect the inverter to the phase that is connected.
In this case, by supplying power from the storage battery to the phase to which the load that consumes the most power is connected among the loads connected to the U and W phases, the power can be purchased from the single-phase three-wire electric circuit. It is possible to suppress the amount of electricity used.

(3) The distributed power supply system according to (1) or (2) above includes a solar cell connected to supply output between the first voltage line and the second voltage line of the single-phase three-wire electric circuit. It may also include a photovoltaic device. In such a distributed power supply system, when charging the storage battery using the power generated by the solar power generation device, the control unit may select one of the U-phase load and the W-phase load, which consumes less power. The inverter is connected to the phase to which the load is connected.
In this case, by charging the storage battery with the surplus power of the phase to which the load with lower power consumption is connected among the loads connected to the U phase and W phase, the surplus power of solar power generation can be made effective. can be used.

(4) The distributed power supply system according to (1) or (2) above includes a solar cell connected to supply output between the first voltage line and the second voltage line of the single-phase three-wire electrical circuit. It may also include a photovoltaic device. In such a distributed power supply system, when charging the storage battery using the power generated by the solar power generation device, the control unit may, for example, charge the phase that has more surplus power based on the output of the solar power generation device. Connect the inverter.
In this case, by charging the storage battery with the surplus power of the phase with more surplus power among the U phase and W phase, the surplus power of solar power generation can be effectively used.

(5) This is also a distributed power supply system including two sets of power 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 wire and a W phase between the second voltage line and the neutral wire, the first The solar power generation device is connected to supply an output between a voltage line and the second voltage line, and each of the two sets of power storage devices includes a DC power supply unit including a storage battery, and a DC power supply unit connected to the DC power supply unit. a first leg whose intermediate connection point of a pair of series bodies of switching elements is connected to the first voltage line; and a first leg whose intermediate connection point of a pair of series bodies of switching elements is connected to the second voltage line. an inverter having two legs, and a third leg whose intermediate connection point of a pair of switching elements in series is connected to the neutral wire; and a third leg provided between the inverter and the first voltage line. a second switch provided between the inverter and the second voltage line, the second leg is opened, the first leg and the third leg are operated for switching, and the first switch a U-phase operating state in which the circuit is closed and the second switch is opened, the first leg is opened, the second leg and the third leg are operated to switch, and the second switch is closed, and , a control unit that selectively switches the 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 described in (5) above, two sets of power storage devices can be connected to mutually different phases, and can also be connected to the same phase. Therefore, it is possible to fully utilize the power supply and power storage functions of the distributed power supply system including two sets of power storage devices according to the power consumption situation and surplus power situation, and also to fully utilize the power supply and power storage functions of the distributed power generation system including two sets of power storage devices. can be used effectively.

(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 After stopping the switching operation of the leg, the first switch is opened, and then, after the second switch is closed, the switching operation of the second leg and the third leg is started, and the W-phase operating state is changed from the W-phase operating state. 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 operation of the first leg and the third leg is started from.
In this case, since the first switch and the second switch are not directly involved in cutting off or turning on current, the life of the contacts can be extended.

(7) From the viewpoint of the method, 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 that is connected to the DC power supply unit and has an intermediate connection point of a pair of switching elements connected in series with the first voltage line, and an intermediate connection point of the pair of switching elements connected in series is connected to the second voltage line. a second leg connected to the neutral line, and an inverter having a third leg whose intermediate connection point of a pair of series switching elements is connected to the neutral line. In the operation method, the second leg is opened, the first leg and the third leg are operated for switching, and the inverter is connected to the U phase and disconnected from the W phase. phase operation state, and W-phase operation in which the first leg is opened, the second leg and the third leg are operated for switching, and the inverter is connected to the W-phase and disconnected from the U-phase. This is a method of operating a distributed power supply system in which the state is selectively switched based on the power at the U-phase power receiving point and the power at the W-phase power receiving point.

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

[Details of embodiments of the present disclosure]
Hereinafter, specific examples of the distributed power supply system of the present disclosure and its operating 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. 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 O line, and AC 100V is applied between the O line and W line, the phase of which is opposite to that between the U line and O line. AC 200V is applied between the U line and the W line. The space between the U line and the O line is called the U phase, and the space between the W line and the O line is called the W phase. In other words, the U-phase has a 1U AC 100V power supply when viewed from the neutral wire O, and the W-phase has an AC 100V W-phase power supply 1W, which has the opposite phase to the U-phase when viewed from the neutral wire O. This means that

A consumer load _LUW is connected between the U line and the W line, a load _LUW 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 to the solar power generation panel 3. The output of the solar power generation 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.

The output end (or input end) of 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 source 1U and the W-phase power source 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. Power storage device 5j also receives a detection output of the voltage between line U and line O from an internal voltage sensor (not shown). The power storage device 5j charges or discharges the storage battery based on detection outputs of sensors and information on the storage battery.

(Power supply to load)
First, consider a situation where the solar 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. Power storage device 5j controls the discharge power so that the power on the power receiving point side is a constant forward flow close to 0 (approximately 5% of the rated power of power storage device 5j). The power at the power receiving point can be the sum of the active powers of the U phase and W phase. In this case, even if one side is a reverse power flow, it suffices if the total power of both the U phase and the W phase is the forward flow target value. Therefore, even if a load is connected only to the W phase and no load is connected to the U phase or between the U line and the W line, the power at the receiving point will match the forward flow target value. It is possible to control power storage device 5j in this manner.

FIG. 6 is a circuit diagram considering a specific example of the state in the distributed power supply system 200 shown in FIG. In FIG. 6, the solar power generation device 2 is not generating power. A load of 500 W is connected to the W phase. The forward current target value is 50W. In this case, power storage device 50 discharges 450 W of power to the U phase, but all of this power becomes a reverse flow. The discharged power of the power storage device 50 is not used for the W phase, and the W phase load _LW is supplied with 500 W of power received from the commercial power system. At this time, the purchased power is 500W, and the sold power is 450W. Electric power discharged from a storage battery charged with electricity from a commercial power grid cannot be sold, but below we will consider the case where surplus power from solar power generation is discharged from a charged storage battery.

This situation is not disadvantageous to users under the feed-in tariff (FIT) scheme for solar power generation. However, after the FIT ends, when the purchase price becomes significantly lower than the electricity rate, it becomes economically disadvantageous to reverse the flow of electricity stored in storage batteries. Therefore, power storage device 5j should be controlled so that the discharged power does not flow in reverse in both the U-phase and W-phase.

In the example of FIG. 5, the maximum power that can be supplied by the power storage device 5j with a 100V output (excluding the loss due to the normal power flow target value) is 100% at the maximum supplied to the load L _u connected to the U phase. can. A maximum of 50% can be supplied to the load _LUW connected between the U line and the W line. The power that can be supplied to the load LW connected to the _W phase is zero. If the power consumption of the load is biased toward the W phase, the discharge of power storage device 5j will not be consumed by the load, and the amount of power purchased from commercial power system 1 will increase accordingly. Therefore, it is assumed that the power storage device 5j is used for the purpose of self-consuming the power generated by solar power generation after the FIT ends.

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

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

As a result, regarding the surplus power of 1000 W of the solar power generation device 2, 500 W is used for charging in the U phase, but since charging is originally controlled 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, cannot be used. As a result, there is a reverse power flow (power sale) of 500 W in the U phase and 500 W in the W phase. If the charging control target value is set to 500W, the power purchased in the U phase will be 0W and waste will be prevented, but the W phase will still have a reverse power flow of 500W, and the amount of power that could normally be used for charging and self-consumption will be reduced. Since it will decrease, you will be at a disadvantage after the FIT ends.

《Summary of analysis》
As described above, a power storage device with an output of 100 V is disadvantageous for both supplying power to a load and charging surplus power from solar power generation, and for self-consumption of solar power generation after the FIT ends. In a 100V output system, it is important to reduce power purchase in load power supply, reduce reverse power flow of solar power generation, and increase the self-consumption rate of surplus power generated by solar power generation.

《First embodiment》
Next, a distributed power supply system according to a first embodiment of the present disclosure will be described.
The basic concept is to enable the power storage device to be selectively connected to either the U phase or the W phase. If a power storage device is connected to a phase that consumes a lot of power during discharging, more power can be discharged and electricity purchased can be reduced. When charging surplus power from solar power generation, by connecting a power storage device to a phase that consumes less power and has more surplus power, more surplus power can be charged and unnecessary 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 O line, and AC 100V is applied between the O line and W line, the phase of which is opposite to that between the U line and O line. AC 200V is applied between the U line and the W line. The space between the U line and the O line is called the U phase, and the space between the W line and the O line is called the W phase. In other words, the U-phase has a 1U AC 100V power supply when viewed from the neutral wire O, and the W-phase has an AC 100V W-phase power supply 1W, which has the opposite phase to the U-phase when viewed from the neutral wire O. This means that

A consumer load _LUW is connected between the U line and the W line, a load _LUW 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 to the solar power generation panel 3. The power conditioner 4 includes a power conversion device (including a control unit) 41 that converts direct current to alternating current, and a grid interconnection relay 42. The interconnection relay 42 is closed when connected to the grid, and opens only when the power conditioner 4 is disconnected from the grid. The output of the solar power generation device 2 is supplied between the U line and the W line.

The power storage device 5 is connected to three wires: a U line, an O line, and a W line.
Assuming that the power receiving point is where the U-phase power source 1U and the W-phase power source 1W are located, current sensors 50iu and 50iw are provided on the power receiving point sides of the U and W lines, 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 power storage device 5. As shown in FIG. In the figure, power storage device 5 has a DC power supply unit 5A including a storage battery 51. The rated voltage of the storage battery 51 is, for example, 100V or less. A capacitor 52 is connected to both ends of 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. Switching elements QL and QH are controlled by control section 50.

The DC/DC converter 5B boosts the voltage of the storage battery 51, which is 100V or less, to about 175V and outputs it to the DC bus 5D. 175V is a value with some margin added to the peak value of 100V AC (approximately 141V), which is the output voltage of power storage device 5. Since the voltage of the DC bus 5D is approximately 175V, the voltage is lower than that in the case where the voltage is increased to approximately 350V, and therefore insulation is easy. In addition, the electrical components used are halved in voltage resistance, making them cheaper. The current flowing through the DC/DC converter 5B is detected by a current sensor 50id, 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. The detection output of the voltage sensor 50vd is sent to the control section 50.

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

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

Switches 57u, 57o, and 57w that can be opened and closed individually 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 power storage device 5, switch 57o is always closed. The switch 57u and the switch 57w are selectively closed, and are never closed at the same time. Switches 57u, 57o, and 57w also serve as interconnection relays when disconnecting power storage device 5 from interconnection with commercial power grid 1. When disconnecting, all switches 57u, 57o, and 57w are opened.

On the side closer to the commercial power system 1 than the switches 57u, 57o, and 57w, voltage sensors 50vu and 50vw are provided to detect voltages between the U-O line and the WO line, respectively. The external circuit of power storage device 5 is the same as that described in FIG. 1, and corresponding parts are denoted by the same reference numerals and description thereof will be omitted. The control unit 50 can determine 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 determine the power at the W-phase power reception 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 three-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) are in switching operation, and the second leg (Q21, Q22) and the switch 57w are open (the switch 57u is closed), the AC100V is output to the U phase. When the second leg (Q21, Q22) and the third leg (Q31, Q32) are in switching operation and the first leg (Q11, Q12) and switch 57u are open (switch 57w is closed), AC100V is output to the phase.

When charging the storage battery 51, the voltage of AC100V (either U phase or W phase) applied to the power storage device 5 from the outside is rectified by the body diode of the inverter 5C or by synchronous rectification by switching, and is 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.

Note that 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), but they may also be IGBTs (Insulated Gates). Bipolar Transistor ) can also be used.

The control unit 50 can also acquire information regarding 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 implements necessary control functions by the computer executing software (computer program). The software is stored in a storage device (not shown) of the control unit 50.

《Operation explanation including phase switching》
FIG. 3 is a flowchart illustrating an example of processing executed by the control unit 50. Upon starting the process, control unit 50 first closes switches 57u and 57o of power storage device 5 in FIG. 2, and opens 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 in accordance with the phase detected by the voltage sensor 50vu. Thereby, power storage device 5 becomes connected to the U phase (step S1). Note that 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, so the switches 57u and 57o are not directly related to the application of the starting current. , Therefore, the contact life is extended. Further, since the switch 57w is open, the voltage of 200 VAC does not enter the inverter 5C from the alternating current side.

The control unit 50 performs power measurement based on the detection outputs of the current sensors 50iu, 50iw and the voltage sensors 50vu, 50vw and information within the control unit 50 (step S2).

(When the load consumes more power than the generated power)
Specifically, the control unit 50 controls U-phase power (power at the power receiving point, hereinafter the same applies) Pu, W-phase power (power at the power receiving point, hereinafter the same) Pw, and inverter 5C to the U-phase. The electric power Px being outputted to the target is detected. In a state where the power storage device 5 is connected to the U phase, if the power consumption of the load is higher than the power generated by solar power generation and the U phase power Pu is detected as received power (purchased power), the power storage device 5 is connected to the U phase. Step 5 performs feedback control (updating the charge/discharge command value) of the power Px so that the U-phase power Pu becomes zero or a value close to zero to perform discharging (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). If 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 will be greater than the power consumption of the load connected to the W-phase. . In this case, power storage device 5 continues to be connected to the U phase (steps S2, S3, and S4 are repeated).

Conversely, when the absolute value of W-phase power Pw is greater than or equal to the absolute value of 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).

The detailed operation sequence in step S5 will be explained. First, the control unit 50 first stops 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 three legs are temporarily opened and no current flows. Here, the control unit 50 opens the switch 57u, and then closes the switch 57w. The control unit 50 then causes the second leg (Q21, Q22) and the third leg (Q31, Q32) to perform a switching operation in accordance with the phase detected by the voltage sensor 50vw. As a result, the connection destination of the 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 within the house. Note that the switch 57o is always closed, and the switch 57w is closed first, and then the switching operations of the second and third legs are started, so the switches 57w and 57o are used to input the starting current during phase switching Therefore, the life of the contacts is extended. Further, since the switch 57u is open, the voltage of 200 VAC does not enter the inverter 5C from the AC side.

After that, the control unit 50 measures the 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 that the inverter 5C is outputting to the W-phase. In a state where the power storage device 5 is connected to the W phase, if the power consumption of the load is higher than the power generated by solar power generation and the W phase power Pw is detected as received power (purchased power), the power storage device 5 is connected to the W phase. 5, the power Px is feedback-controlled (charge/discharge command value updated) 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 and reaches a steady state (step S8). If 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 will be greater than the power consumption of the load connected to the U phase. . In this case, power storage device 5 continues to be connected to the W phase (steps S6, S7, and S8 are repeated).

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).

The detailed operation sequence in step S1 will be explained. 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 three legs are temporarily opened and no current flows. Here, the control unit 50 opens the switch 57w, and then closes the switch 57u. The control unit 50 then switches the first leg (Q11, Q12) and the third leg (Q31, Q32) in accordance with the phase detected by the voltage sensor 50vu. Thereby, the connection destination of the 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 within the house. Note that 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. Therefore, the life of the contacts is extended. Further, since the switch 57w is open, the voltage of 200 VAC does not enter the inverter 5C from the alternating current side.

(When the generated power is greater than the power consumption of the load)
Next, in a state where the power storage device 5 is connected to the U phase (step S1), if the power generated by the solar power generation is greater than the power consumption of the load and surplus power is generated, at least Reverse power flow is detected in the U-phase power Pu (step S2). At this time, the power storage device 5 performs feedback control (updates the charge/discharge command value) of the power Px so that the U-phase power Pu becomes zero or a value close to zero, and performs charging (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 and reaches a steady state (step S4). When the absolute value of power Px is larger than the absolute value of W-phase power Pw, there is more surplus power in the U-phase than in 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 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). This allows the power storage device 5 to charge more power than the surplus power generated within the house.

Furthermore, in a state where the power storage device 5 is connected to the W phase (step S5), if the power generated by the solar power generation is greater than the power consumption of the load and surplus power is generated, at least W Reverse power flow is detected in the phase power Pw (step S6). At this time, the power storage device 5 performs feedback control (updates the charge/discharge command value) of the power Px so that the W-phase power Pw becomes zero or a value close to zero, and performs charging (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 and reaches 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, there is more surplus power in the W-phase than in 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 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). This allows the power storage device 5 to charge more power than the surplus power generated within the house.

《Second embodiment》
FIG. 4 is a circuit diagram of a 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 that shown in FIG. Control unit 50 of power storage device 5, 5x executes the flowchart shown in FIG. 3. Current sensors 50iu and 50iw of power storage device 5x are located closer to commercial power system 1 than current sensors 50iu and 50iw of power storage device 5, respectively. Among the two sets of power storage devices 5 and 5x, power storage device 5 gives priority to supplying power to the load and charging 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 of the U phase and W phase.
(ii) Connect one of the two sets to the U phase and the other to the W phase.

(When the load consumes more power than the generated power)
First, consider the case where the load consumes more power than the generated power.
Power storage device 5 detects U-phase power and W-phase power (both power 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 connects to the U phase, and discharges the storage battery 51 so that the U phase power Pu becomes zero. Here, it is assumed that when power storage device 5x detects U-phase power and W-phase power, W-phase power Pw is larger than U-phase power Pu. In that case, the power storage device 5x connects 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, power storage device 5 is connected to the U phase, and power storage device 5x is connected to the W phase, as described in (ii) above.

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 higher than the generated power, the U-phase power Pu is larger than the W-phase power Pw, and the U-phase power Pu is the stored power. It is assumed that the output power of the device 5 is higher than the upper limit. In this case, first, the power storage device 5 is connected to the U phase, and the storage battery 51 is discharged at the output upper limit. 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 may still be higher than the W-phase power. may also become large. In that case, the power storage device 5x connects 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 power storage device 5 and 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 as a result of the power storage device 5 detecting the U-phase power and the W-phase power, the generated power is greater than the power consumption of the load, and the U-phase surplus power is larger than the W-phase surplus power. In this case, first, power storage device 5 is connected to the U phase, and storage battery 51 is charged. Here, power storage device 5x detects U-phase power and W-phase power. As a result, it is assumed that the W-phase surplus power is larger than the U-phase surplus power. 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, power storage device 5 is connected to the U phase, and power storage device 5x is connected to the W phase, as in (ii) above.

On the other hand, the process until the power storage device 5 connects to the U-phase and charges the storage battery 51 is as described above, but here, when the power storage device 5x detects the U-phase power and the W-phase power, it still , it is assumed that the surplus power of the U phase is larger than the surplus power of the W phase. In this case, power storage device 5x is connected to the U phase, and storage battery 51 is charged. That is, in this case, both power storage device 5 and power storage device 5x are connected to the U phase as in (i) above.

As described above, by connecting the two sets of power storage devices 5, 5x to the U phase or W phase depending on the situation, the power storage or discharging ability of the power storage devices 5, 5x can be effectively utilized. In particular, being able to connect two sets of power storage devices 5 and 5x to the same phase makes it easier for private solar power generators to operate than using a single power storage device with single-phase three-wire output that can control two-phase power independently. This will be 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 to the U phase and W phase each, the combined power of the two phases is a maximum of 2 kW, but the power of each phase is The upper limit is 1kW. On the other hand, if the two sets of power storage devices 5 and 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, by using two sets of power storage devices 5 and 5x with 100V output, surplus power from solar power generation can be used more effectively.

Note that the explanation regarding charging and discharging of the power storage devices 5 and 5x in the third embodiment is merely based on the assumed conditions, and if the amount of power between the U phase and the W phase is reversed, Needless to say, it works.
In addition, when the charging state of one power storage device becomes 100% or 0% during operation of two sets of power storage devices 5 and 5x and enters 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 selectively 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 between two of the three legs and control the operation of the switches based on the power at the U-phase power receiving point and the power at the W-phase power receiving point. In the distributed power supply system 100 configured in this way, power can be transferred between either the U phase or the W phase and the inverter 5C at the same time, but depending on the power usage situation, the switch 57u, By switching the connection state using 57w, power can be transferred between the other phase and inverter 5C. Thereby, 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 the U-phase or W-phase only needs to be about 175V, so the step-up (or step-down) voltage range is small, and even a single-stage non-isolated DC/DC converter can be used. Fully usable. Therefore, it is possible to reduce the size and cost of the power storage device 5 and achieve high power conversion efficiency.

In addition, when discharging the storage battery 51, the switches 57u and 57w may be operated to connect the inverter 5C to the phase to which the load that consumes more power is connected between the U-phase load and the W-phase load. can. In this way, 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 purchased from the single-phase three-wire electrical circuit.

In addition, in the distributed power supply system 100 including the solar power generation device 2, when the storage battery 51 is charged using the generated power, the load with lower power consumption among the U-phase load and the W-phase load is 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 has more surplus power) is connected, the surplus power of solar power generation can be effectively used.

Furthermore, distributed power supply system 100 may include two sets of power storage devices 5 and 5x. In this case, the two sets of power storage devices 5, 5x can be connected to mutually different phases, or can both be connected to the same phase. Therefore, the power feeding 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 in accordance with the power consumption situation and the surplus power situation. Additionally, surplus power from solar power generation can be effectively utilized.

Furthermore, 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. Then, after closing the switch 57w, 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. Then, after closing the switch 57u, the first leg (Q11, Q12) and the third leg (Q31, Q32) are started to operate.
By controlling in this way, the switch 57u and the switch 57w are not directly involved in cutting off or turning on the current, so that the life of the contacts can be extended.

On the other hand, from a simple point of view of the operating method of a 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. The operation is such that there is a connection period. According to the operation method of such a distributed power supply system, the power storage device 5 that outputs the voltage between one voltage line and the neutral line (for example, AC 100V) is used to connect both the U phase and the W phase. It is possible to transfer power between the two. Thereby, the power supply and power storage functions of the power storage device in the distributed power supply system can be fully utilized.

《Addendum》
It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be considered restrictive. The scope of the present invention is indicated by the claims, and it is intended that all changes within the meaning and range equivalent to the claims are included.

1 Commercial power system 1U U phase power supply 1W W phase power supply 2 Solar power generation device 3 Solar power generation panel 4 Power conditioner 5, 5x, 5j Power storage device 5A DC power supply section 5B DC/DC converter 5C Inverter 5D DC bus 5iu, 5iw Current sensor 41 Power conversion device 42 Grid connection 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 (6)

A distributed power supply system including a power storage device connected to a single-phase three-wire electric line having a first voltage line, a neutral line, and a second voltage line, wherein the first voltage line and the neutral line If the period between the second voltage line and the neutral line is defined as the U phase, and the period between the second voltage line and the neutral line is defined as the W phase, the power storage device
A DC power supply section including a storage battery,
A first leg that is connected to the DC power supply unit and has an intermediate connection point of a pair of switching elements in series connected to the first voltage line, and an intermediate connection point of the pair of switching elements in series is connected to the second voltage line. an inverter having a second leg connected to the neutral line, and a third leg whose intermediate connection point of a pair of series 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 operated to switch, 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 operated, the second switch is closed, and the first switch is opened is defined as the power at the U-phase power receiving point, and a control unit that selectively switches based on the power at the W-phase power receiving point;
A distributed power system equipped with 2. When discharging the storage battery, the control unit connects the inverter to a phase to which a load with higher power consumption is connected among the U-phase load and the W-phase load. 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, the first voltage line and the middle voltage line. When defining the phase between the voltage line and the neutral wire as the U phase, and the phase between the second voltage line and the neutral wire as the W phase,
comprising a solar power generation device connected to supply an output between the first voltage line and the second voltage line of the single-phase three-wire electric circuit,
Each of the two sets of power storage devices is
A DC power supply section including a storage battery,
A first leg that is connected to the DC power supply unit and has an intermediate connection point of a pair of switching elements in series connected to the first voltage line, and an intermediate connection point of the pair of switching elements in series is connected to the second voltage line. an inverter having a second leg connected to the neutral line, and a third leg whose intermediate connection point of the pair of series 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 operated to switch, 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 operated, the second switch is closed, and the first switch is opened is defined as the power at the U-phase power receiving point, and a control unit that selectively switches based on the power at the W-phase power receiving point;
A distributed power system equipped with When switching from the U-phase operating state to the W-phase operating state, the control unit opens the first switch after stopping the switching operations of the first leg and the third leg, and then opens the first switch. after closing two switches, 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 switches the second leg to the U-phase operating state. starting the switching operation of the first leg and the third leg after closing one switch;
The distributed power supply system according to any one of claims 1 to 3. further including a third switch provided between the inverter and the neutral wire,
The distributed power supply system according to any one of claims 1 to 3, wherein the third switch is closed in both the U-phase operating state and the W-phase operating state. A power storage device connected to a single-phase three-wire electrical circuit having a first voltage line, a neutral wire, and a second voltage line, the power storage device including a DC power supply section including a storage battery, and a pair of power storage devices connected to the DC power supply section. a first leg in which a middle connection point of a series body of switching elements is connected to the first voltage line; a second leg in which a middle connection point of a pair of series body of switching elements is connected to the second voltage line; , 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 U-phase operating state in which the second leg is opened, the first leg and the third leg are operated for switching, 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 operated for switching, and the inverter is connected to the W-phase and disconnected from the U-phase.
A method for operating a distributed power supply system in which switching is performed selectively based on the power at the U-phase power receiving point and the power at the W-phase power receiving point.

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