JP2022120406A - Power supply system - Google Patents

Abstract

To provide a power supply system that enables switching supply of DC power and AC power using a plurality of cell strings.SOLUTION: A sweep controller 500 is configured to turn off each of relays RU, RV, and RW and turn on at least one of relays R21, 22, and R23 when supplying DC power from a DC power supply 200 to at least one of cell strings St1 to St3. The sweep controller 500 is configured to turn off each of the relays R21, R22, and R23 and turn on each of the relays RU, RV, and RW when outputting AC power from the cell strings St1, St2, and St3 to AC output terminals Tu, Tv, and Tw, respectively.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to power systems.

Japanese Patent Laying-Open No. 2018-074709 (Patent Document 1) discloses a control circuit that controls a battery string. A battery string includes a plurality of battery circuit modules connected together. Each battery circuit module included in the battery string includes a battery, a first switch connected in parallel with the battery, a second switch connected in series with the battery, and a first switch in an OFF state and a second switch in an ON state. It has a first output terminal and a second output terminal to which the voltage of the battery is applied when in the state. The control circuit can adjust the output voltage of the battery string to a desired level by controlling the first switch and the second switch of each battery circuit module included in the battery string.

JP 2018-074709 A

Patent Literature 1 discloses a power supply system that outputs DC power using the battery string as described above. However, Patent Literature 1 does not consider a power supply system that outputs AC power using a battery string. If a power supply system that outputs alternating current power using battery strings can be realized, the range of applications for battery strings will be broadened, and cost reduction of battery strings can be expected.

The present disclosure has been made to solve the above problems, and an object thereof is to provide a power supply system that can switch between DC power and AC power using a plurality of battery strings. is.

A power supply system according to the present disclosure includes a Y-connected first battery string, a second battery string, and a third battery string, and first to third DC lines that connect the DC power supply and the first to third battery strings, respectively. and first to third DC relays respectively provided on the first to third DC lines, first to third AC lines for connecting the first to third AC output terminals and the first to third battery strings, respectively; First to third AC relays provided on the first to third AC lines, respectively; and a control device for controlling each of the first to third DC relays and the first to third AC relays. Each of the first to third battery strings includes a plurality of mutually connected battery circuit modules. Each of the plurality of battery circuit modules includes a battery, a first switch connected in parallel to the battery, a second switch connected in series to the battery, and when the first switch is in an OFF state and the second switch is in an ON state. It has a first output terminal and a second output terminal to which the voltage of the battery is applied at one time. When DC power is supplied from the DC power supply to at least one of the first to third battery strings, the control device turns off each of the first to third AC relays and turns off at least one of the first to third DC relays. It is configured to turn one on. Further, when the AC power is output from the first to third battery strings to the first to third AC output terminals, respectively, the control device turns off each of the first to third DC relays to turn off the first to third DC relays. It is configured to turn on each of the 3 AC relays.

In the above power supply system, the batteries included in the first to third battery strings can be charged with DC power supplied from the DC power supply. Further, in the above power supply system, the AC power (for example, three-phase AC power) output from the first to third battery strings can be output to the first to third AC output terminals. The power supply system can switch between DC power and AC power by using a plurality of battery strings. Hereinafter, each of the first to third battery strings will be referred to as a "battery string" unless otherwise specified.

The control device may be configured to control the first switch and the second switch of each battery circuit module included in the battery string so that the voltage of the battery string reaches the target value. The control device may control the first switch and the second switch of each battery circuit module included in the battery string so that AC power is output from the battery string. According to such a configuration, there is no need to separately provide an inverter for converting DC power of the battery into AC power.

Each of the first switch and the second switch may be a semiconductor relay such as an SSR (Solid State Relay). Examples of semiconductor relays include field effect transistors. By adopting a semiconductor relay with a fast response speed as each of the first switch and the second switch, the control device can easily control the AC power output from the target string to a desired waveform (including frequency and amplitude). Become.

Each of the first to third DC relays and the first to third AC relays may be an electromagnetic mechanical relay. The first through third DC lines may have a common portion. The first to third DC relays may be arranged outside the common portion.

The battery circuit modules included in the battery string may be connected by connecting the second output terminal of the battery circuit module to the first output terminal of the adjacent battery circuit module.

According to the present disclosure, it is possible to provide a power supply system capable of switching and supplying DC power and AC power using a plurality of battery strings.

1 is a diagram showing a configuration of a power supply system according to an embodiment of the present disclosure; FIG. FIG. 2 is a diagram showing the configuration of a battery string shown in FIG. 1; 4 is a time chart showing an example of operation of a battery circuit module controlled by a control device according to an embodiment of the present disclosure; FIG. 4 is a diagram showing the battery circuit module in a driving state; FIG. 10 is a diagram showing the state of the battery circuit module during the delay period; FIG. 10 is a diagram showing the state of the battery circuit module during the suspension period; FIG. 3 is a diagram for explaining three-phase AC power output from first to third battery strings according to the embodiment of the present disclosure; FIG. FIG. 2 is a schematic diagram showing an example of a connection mode between a sweep regulator including first to third battery strings shown in FIG. 1, a DC power supply, and an electric power system; 2 is a graph showing transitions in power consumption in general households and transitions in typical PV-generated power. It is a figure which shows an example of mode switching control. FIG. 2 is a diagram showing a first modification of the power supply system shown in FIG. 1; 2 is a diagram showing a second modification of the power supply system shown in FIG. 1; FIG. 2 is a diagram showing an example of a control circuit included in the control device shown in FIG. 1; FIG.

Embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

FIG. 1 is a diagram showing the configuration of a power supply system according to this embodiment. Referring to FIG. 1 , power supply system 1 includes sweep regulator 100 , LCL filter 110 , transformer 120 , DC power supply 200 , sweep controller 500 and energy controller 600 . Each of sweep controller 500 and energy controller 600 may be a computer. Each of sweep controller 500 and energy controller 600 includes, for example, a processor, a storage device, and a communication I/F (interface). The storage device stores, for example, programs executed by the processor and information (eg, maps, formulas, and various parameters) used by the programs.

The transformer 120 is a YY-connected three-phase transformer, and includes a Y-connected battery-side three-phase coil Y1 and a Y-connected system-side three-phase coil Y2. The three-phase coil Y1 includes a U-phase coil, a V-phase coil, and a W-phase coil. One ends of the U-phase coil, the V-phase coil, and the W-phase coil are connected to AC output terminals Tu, Tv, and Tw, respectively, and the other end of each coil is commonly connected to a neutral point. The AC output terminals Tu, Tv, and Tw are connected to a U-phase electric wire UL, a V-phase electric wire VL, and a W-phase electric wire WL, respectively. The three-phase coil Y2 is connected to a power grid provided by an electric utility company (for example, a power company). A power system is, for example, a power network that supplies electric power to each consumer under contract with an electric power company. A power supply system 1 according to this embodiment is used in a house that receives power supply from the power system.

The power supply system 1 can perform grid interconnection control. That is, the power supply system 1 can adjust the power of the power system by controlling the three-phase AC power output from the three-phase coil Y1 to the three-phase coil Y2 while being connected to the power system. In the power supply system 1 according to this embodiment, when three-phase AC power with a phase difference of 120° is sent to the three-phase coil Y1 through three wires (wires UL, VL, and WL), the transformer 120 performs three-phase AC power is transformed as it is in three phases. Then, the transformed three-phase AC power is output to the three-phase coil Y2. Although the details will be described later, the power supply system 1 according to this embodiment is configured to supply three-phase AC power generated by a sweep regulator 100 to a house via an LCL filter 110 and a transformer 120 (Fig. 8). LCL filter 110 reduces noise components of the three-phase AC power, and transformer 120 converts the three-phase AC power into a predetermined voltage (eg, 200 V).

The object to which the power supply system 1 supplies power (hereinafter, also simply referred to as “supply object”) is not limited to a house and is arbitrary. For example, the supply target may be a commercial facility. Also, the power supply system 1 may be mounted on a moving object such as an automobile, a ship, a drone, or a space probe, and used as a power source for movement.

Sweep regulator 100 is a chargeable/dischargeable power supply device. The sweep regulator 100 includes three battery strings St1-St3. A negative terminal of each of the battery strings St1 to St3 is connected to the neutral point N1. Battery strings St1, St2, and St3 according to this embodiment correspond to examples of the “first battery string,” “second battery string,” and “third battery string,” respectively, according to the present disclosure.

DC power supply 200 is a stationary power supply that outputs DC power. In this embodiment, PV power generation equipment (for example, solar panels installed on the roof) is employed as DC power supply 200 . PV power generation means photovoltaic power generation. A PV power generation facility corresponds to a naturally fluctuating power supply. The power output of variable renewable energy sources fluctuates depending on weather conditions. A positive terminal and a negative terminal of DC power supply 200 are connected to electric wires DL1 and DL2, respectively. Electric power generated by DC power supply 200 is output to electric wires DL1 and DL2. A capacitor Cd for smoothing the voltage is provided between the wires DL1 and DL2. The power supply system 1 also includes a current sensor Id and a voltage sensor Vr. Current sensor Id and voltage sensor Vr are configured to detect the current and voltage in wires DL<b>1 and DL<b>2 , respectively, and output the detected values to sweep controller 500 .

Each of battery strings St 1 to St 3 is configured to be supplied with DC power from DC power supply 200 . Specifically, the neutral point N1 to which the negative terminals of the battery strings St1, St2, and St3 are connected is connected to the electric wire NL1. The electric wire NL1 connects the neutral point N1 and the electric wire DL2. A relay R2 is provided on the electric wire NL1. Relay R2 is, for example, an electromagnetic mechanical relay. The sweep controller 500 is configured to switch connection/disconnection of the electric wire NL1 by controlling ON/OFF of the relay R2.

Positive terminals of the battery strings St1, St2, and St3 are connected to electric wires PL1, PL2, and PL3, respectively. Electric wires PL1, PL2, and PL3 connect battery strings St1, St2, and St3 to branch points D1, D2, and D3, respectively. The electric wires PL1, PL2 and PL3 are branched into the electric wires DL11, DL12 and DL13 and the electric wires UL, VL and WL at branch points D1, D2 and D3.

Each of electric wires DL11, DL12, and DL13 is connected to electric wire DL1. The electric wires DL11, DL12 and DL13 are provided with relays R21, R22 and R23, respectively. Each of relays R21, R22, and R23 is, for example, an electromagnetic mechanical relay. The sweep controller 500 is configured to switch connection/disconnection of the wires DL11, DL12, and DL13 by ON/OFF-controlling the relays R21, R22, and R23.

In this embodiment, electric wires NL1, DL11, DL1, and DL2 correspond to an example of the “first DC line” according to the present disclosure, and connect DC power supply 200 and battery string St1. Battery string St1 is connected to DC power supply 200 when both relays R2 and R21 are in the ON state. Also, the electric wires NL1, DL12, DL1, and DL2 correspond to an example of the “second DC line” according to the present disclosure, and connect the DC power supply 200 and the battery string St2. Battery string St2 is connected to DC power supply 200 when both relays R2 and R22 are in the ON state. Also, the electric wires NL1, DL13, DL1, and DL2 correspond to an example of the “third DC line” according to the present disclosure, and connect the DC power supply 200 and the battery string St3. Battery string St3 is connected to DC power supply 200 when both relays R2 and R23 are in the ON state. Relays R21, R22, and R23 according to this embodiment correspond to examples of "first DC relay," "second DC relay," and "third DC relay," respectively, according to the present disclosure.

Each of the battery strings St1 to St3 is configured to be capable of outputting AC power (eg, three-phase AC power) to AC output terminals Tu, Tv, and Tw. Specifically, electric wires UL, VL, and WL connect AC output terminals Tu, Tv, and Tw to branch points D1, D2, and D3, respectively. LCL filters 110 are provided on the wires UL, VL, and WL. LCL filter 110 is configured to attenuate current ripple components in each of wires UL, VL, and WL. The details of the configuration of the LCL filter 110 will be described later (see FIG. 7).

The electric wires UL, VL, and WL are provided with relays RU, RV, and RW, respectively. Each of relays RU, RV, and RW is, for example, an electromagnetic mechanical relay. The sweep controller 500 is configured to switch connection/disconnection of the wires UL, VL, and WL by controlling ON/OFF of the relays RU, RV, and RW. Connection/disconnection of each power supply path from the battery strings St1, St2, and St3 to the three-phase coil Y1 is switched by relays RU, RV, and RW, respectively. In this embodiment, the AC output terminals Tu, Tv, and Tw correspond to examples of a "first AC output terminal," a "second AC output terminal," and a "third AC output terminal," respectively.

In this embodiment, the electric wire UL corresponds to an example of the "first AC line" according to the present disclosure, and connects the AC output terminal Tu and the battery string St1. The battery string St1 is connected to the AC output terminal Tu when the relay RU is in the ON state. Also, the electric wire VL corresponds to an example of the “second AC line” according to the present disclosure, and connects the AC output terminal Tv and the battery string St2. The battery string St2 is connected to the AC output terminal Tv when the relay RV is in the ON state. Also, the electric wire WL corresponds to an example of the "third AC line" according to the present disclosure, and connects the AC output terminal Tw and the battery string St3. The battery string St3 is connected to the AC output terminal Tw when the relay RW is in the ON state. Relays RU, RV, and RW according to this embodiment correspond to examples of a "first AC relay," a "second AC relay," and a "third AC relay," respectively, according to the present disclosure.

Current sensors Ia, Ib, and Ic are provided on the electric wires PL1, PL2, and PL3, respectively. Current sensors Ia, Ib, and Ic are configured to detect currents output from battery strings St1, St2, and St3, respectively, and output the detected values to sweep controller 500 .

The sweep controller 500 can detect the U-phase, V-phase, and W-phase AC currents output from the battery strings St1, St2, and St3 based on the outputs of the current sensors Ia, Ib, and Ic, respectively. Note that the sweep controller 500 may detect only two phase currents of the three phase currents with a current sensor, and calculate the remaining one phase from the detected two phase currents. For example, in a form in which the current sensor Ic is omitted, the sweep controller 500 uses the U-phase current Iu detected by the current sensor Ia and the V-phase current Iv detected by the current sensor Ib to calculate the expression " Iw=−Iu−Iv” to calculate the W-phase current Iw.

The battery strings St1 to St3 may have different configurations, but in this embodiment, the battery strings St1 to St3 have the same configuration. Hereinafter, each of the battery strings St1 to St3 will be referred to as a "battery string St" and each of the electric wires PL1 to PL3 will be referred to as a "electric wire PL", unless otherwise specified.

FIG. 2 is a diagram showing the configuration of the battery string St. Referring to FIG. 2, the battery string St includes a plurality of battery circuit modules (only battery circuit modules M1 to M3 are shown in FIG. 2) and a monitoring module 20. As shown in FIG. Each of the battery circuit modules M1, M2, M3, . The number of battery circuit modules M included in the battery string St is arbitrary, and may be 5 to 50, or may be 100 or more. In this embodiment, each battery string St includes the same number of battery circuit modules M, but the number of battery circuit modules M may be different for each battery string St.

A plurality of battery circuit modules M (including battery circuit modules M1 to M3) included in the battery string St are connected by a common electric wire PL. The electric wire PL includes output terminals OT1 and OT2 of each battery circuit module M included in the battery string St. The battery circuit modules M included in the battery string St are connected to each other by connecting the output terminal OT2 of the battery circuit module to the output terminal OT1 of the adjacent battery circuit module. For example, the output terminal OT2 of the battery circuit module M1 is electrically connected to the output terminal OT1 of the battery circuit module M2 adjacent to the battery circuit module M1. The output terminals OT1 and OT2 according to this embodiment correspond to examples of the "first output terminal" and the "second output terminal" according to the present disclosure, respectively.

The battery circuit module M includes a battery 10, a first switching element 11 (hereinafter referred to as "SW11"), a second switching element 12 (hereinafter referred to as "SW12"), a first diode 13, A second diode 14 , a choke coil 15 and a capacitor 16 are provided. Each of SW11 and SW12 is controlled by sweep controller 500 . SW11 and SW12 according to this embodiment correspond to examples of a “first switch” and a “second switch” according to the present disclosure, respectively.

The monitoring module 20 includes a voltage sensor that detects the voltage of each battery 10 included in the battery string St, a current sensor that detects the current flowing through the battery string St, and a temperature sensor that detects the temperature of the battery string St, A detection result is output to the sweep controller 500 . In addition to the sensor function, the monitoring module 20 is a BMS (Battery Management System) having an SOC (State Of Charge) estimation function, an SOH (State of Health) estimation function, a cell voltage equalization function, a diagnosis function, and a communication function. System). The sweep controller 500 can acquire the state (for example, temperature, current, voltage, SOC, and internal resistance) of each battery 10 included in the battery string St based on the output of the monitoring module 20 .

Between output terminals OT1 and OT2 of battery circuit module M, SW11, capacitor 16, and battery 10 are connected in parallel. The SW11 is positioned on the electric wire PL and configured to switch the connection state (conducting/disconnecting) between the output terminal OT1 and the output terminal OT2. The output terminal OT1 is connected to the positive electrode of the battery 10 via the wire BL1, and the output terminal OT2 is connected to the negative electrode of the battery 10 via the wire BL2. A wire BL1 that connects the output terminal OT1 and the battery 10 is provided with a SW12 and a choke coil 15 . When the SW12 connected in series with the battery 10 is in the ON state (connected state) and the SW11 connected in parallel with the battery 10 is in the OFF state (disconnected state), the battery is connected between the output terminals OT1 and OT2. 10 voltages are applied.

Between the output terminals OT1, OT2 and the battery 10, a capacitor 16 is provided that is connected to each of the wires BL1 and BL2. One end of capacitor 16 is connected to wire BL1 between SW12 and choke coil 15 . The capacitor 16 smoothes the voltage of the battery 10 and outputs it between the output terminals OT1 and OT2.

The first diode 13 and the second diode 14 are connected in parallel to SW11 and SW12, respectively. SW12 is positioned between output terminal OT1 and choke coil 15 . Choke coil 15 is positioned between SW 12 and the positive electrode of battery 10 . The battery 10, choke coil 15 and capacitor 16 form an RCL filter. The current is leveled by this RCL filter.

The battery 10 is an assembled battery configured by electrically connecting a plurality of secondary batteries (hereinafter also referred to as “cells”) to each other. In this embodiment, a lithium ion secondary battery is adopted as the cell. However, the cells may be secondary batteries other than lithium-ion secondary batteries (for example, nickel-metal hydride batteries). The cell may be a liquid secondary battery or an all-solid secondary battery. Also, the battery 10 may be a secondary battery (single battery) that is not an assembled battery.

Each of SW11 and SW12 is, for example, an FET (field effect transistor). Each of SW11 and SW12 is ON/OFF controlled by a gate signal from the sweep controller 500. FIG. Note that each of SW11 and SW12 is not limited to an FET, and may be a switch other than an FET.

FIG. 3 is a time chart showing an example of the operation of the battery circuit module M controlled by the sweep controller 500. FIG. "Low" and "High" of the gate signal shown in FIG. 3 mean L level and H level of the gate signal (rectangular wave signal), respectively. Also, "output voltage" means a voltage output between the output terminals OT1 and OT2. "SW11" and "SW12" in FIG. 3 mean SW11 and SW12 shown in FIG. 2, respectively.

Referring to FIG. 3 together with FIG. 2, in the initial state of battery circuit module M, no gate signal is output from sweep controller 500 (gate signal=L level), and SW11 and SW12 are in the ON state and the OFF state, respectively. It's becoming In this embodiment, a rectangular wave signal is used as the gate signal for driving the battery circuit module M. FIG. The sweep controller 500 may include a control circuit (gate circuit) that generates gate signals according to instructions from the processor. The sweep controller 500 controls SW11 and SW12 using this gate signal. As described below, the states (ON/OFF) of SW11 and SW12 are switched according to the rise/fall of the gate signal. Therefore, the sweep controller 500 can perform PWM (Pulse Width Modulation) control using the gate signal.

When the gate signal rises from the L level to the H level at timing t1, SW11 switches from the ON state to the OFF state simultaneously with the rise of the gate signal. Then, at timing t2, which is delayed by a predetermined delay time (hereinafter referred to as "dt1") from the rise of the gate signal, SW12 switches from the OFF state to the ON state. As a result, the battery circuit module M is driven. Hereinafter, the period from the rise of the gate signal to the elapse of dt1 is also referred to as "first delay period".

FIG. 4 is a diagram showing the battery circuit module M in a driven state. Referring to FIG. 4, in the battery circuit module M in the driving state, the voltage of the battery 10 is applied between the output terminals OT1 and OT2 by turning off SW11 and turning on SW12. When the voltage of the battery 10 is applied between the output terminals OT1 and OT2 via the capacitor 16, the voltage Vm is output between the output terminals OT1 and OT2.

Again referring to FIG. 3 together with FIG. 2, when the gate signal falls from H level to L level at timing t3, SW12 switches from ON state to OFF state simultaneously with the fall of the gate signal. As a result, the battery circuit module M is stopped. In the battery circuit module M in the stopped state, the voltage of the battery 10 is not applied between the output terminals OT1 and OT2 by turning off the SW12. After that, at timing t4, which is delayed by a predetermined delay time (hereinafter referred to as "dt2") from the fall of the gate signal, SW11 switches from the OFF state to the ON state. dt1 and dt2 may be the same or different. In this embodiment, each of dt1 and dt2 is 100 ns. However, each of dt1 and dt2 can be set arbitrarily.

Hereinafter, the period from the fall of the gate signal to the elapse of dt2 is also referred to as the "second delay period". Also, the period from the end of the second delay period until the battery circuit module M enters the driving state is also referred to as the "suspension period".

FIG. 5 is a diagram showing the state of the battery circuit module M during the delay period. As shown in FIG. 5, both SW11 and SW12 are in the OFF state during each of the first delay period and the second delay period.

FIG. 6 is a diagram showing the state of the battery circuit module M during the suspension period. As shown in FIG. 6, during the stop period, SW11 is in the ON state and SW12 is in the OFF state, as in the initial state.

The battery circuit module M is in a stopped state during both the delay period and the stop period. In the battery circuit module M in the stopped state, no voltage is applied between the output terminals OT1 and OT2.

Each battery circuit module M included in the battery string St is controlled as described above (see FIGS. 3 to 6). In the control described above, since the first delay period and the second delay period are provided, it is suppressed that SW11 and SW12 are turned ON at the same time (that is, the battery circuit module M is short-circuited). . In this embodiment, a plurality of battery circuit modules M (including battery circuit modules M1 to M3) included in the battery string St have the same configuration (see FIG. 2). However, the plurality of battery circuit modules M included in the battery string St may have different configurations.

FIG. 7 is a diagram for explaining the three-phase AC power output from the battery strings St1 to St3. Referring to FIG. 7 together with FIGS. 1 and 2, battery strings St1 to St3 are Y-connected. In this embodiment, the negative terminal of each of the battery strings St1-St3 is connected to the neutral point N1. Neutral point N1 may be grounded. Note that the positive terminal of each battery string St may be connected to the neutral point N1 instead of the negative terminal.

The sweep controller 500 is configured to switch parallel (connection)/disconnection (disconnection) between the power supply system 1 and the power system by controlling relays RU, RV, and RW.

The sweep controller 500 can adjust the number of battery circuit modules M in the driving state in the battery string St by controlling SW11 and SW12 of each battery circuit module M included in the battery string St. Furthermore, the sweep controller 500 can control the voltage output from the battery string St (hereinafter also referred to as "string voltage") based on the number of battery circuit modules M in the driving state. The battery string St is configured to be capable of outputting a voltage from 0V to the sum of the voltages of the batteries 10 included in the battery string St. Further, when an abnormality occurs in any of the batteries 10 included in the battery string St, the sweep controller 500 sets the corresponding SW11 and SW12 to the state of the suspension period (FIG. 6), may be disconnected from the circuit. Although the maximum string voltage drops due to battery disconnection, the battery string St can continue to operate.

Each string voltage generated by the battery strings St1 to St3 has a voltage waveform of 0V or more with an offset, for example. Lines L11, L12, and L13 in FIG. 7 indicate examples of string voltages of the battery strings St1, St2, and St3, respectively. The frequency of the string voltage according to this example is 60 Hz.

Each string voltage generated by the battery strings St1-St3 passes through the LCL filter 110 and is output to the wires UL, VL, and WL. Hereinafter, the line voltage between the wires UL and VL is also referred to as “Vuv”, the line voltage between the wires WL and UL is also referred to as “Vwu”, and the line voltage between the wires VL and WL is also referred to as “Vvw”. Each line voltage has an AC voltage waveform whose polarity (positive/negative) changes periodically. Lines L21, L22, and L23 in FIG. 7 indicate examples of Vuv, Vwu, and Vvw, respectively. The frequency of each line voltage according to this example is 60 Hz.

LCL filter 110 includes interconnection reactors Lmu, Lmv, Lmw, filter capacitors Cfu, Cfv, Cfw, and filter reactors Lfu, Lfv, Lfw provided for electric wires UL, VL, and WL, respectively. The interconnection reactors Lmu, Lmv, and Lmw form an LC filter together with the filter capacitors Cfu, Cfv, and Cfw, respectively. Filter reactors Lfu, Lfv, and Lfw are connected after the LC filter (on the system side) in order to prevent current ripple components from flowing to the system side. One end of each of the filter capacitors Cfu, Cfv, and Cfw is connected to the neutral point N2.

Filter capacitors Cfu, Cfv, and Cfw are provided with voltage sensors Vu, Vv, and Vw (FIG. 1), respectively. The voltage sensors Vu, Vv, Vw are configured to detect the voltages of the filter capacitors Cfu, Cfv, Cfw, respectively, and output the detected values to the sweep controller 500 (FIG. 1).

In this embodiment, the sweep controller 500 is configured to switch between multiple control modes. The multiple control modes include an AC operating mode and a DC operating mode.

In the AC mode of operation, the sweep controller 500 turns off all DC relays and turns on all AC relays. Such relay states are also referred to below as "AC operating states". A DC relay is a relay located between sweep regulator 100 and DC power supply 200, and in this embodiment, each of relays R2, R21, R22, and R23 corresponds to a DC relay. AC relays are relays located between sweep regulator 100 and AC output terminals Tu, Tv, and Tw, and in this embodiment, each of relays RU, RV, and RW corresponds to an AC relay. Note that if there is an AC/DC relay that functions as both a DC relay and an AC relay (eg, a relay located between sweep regulator 100 and branch points D1, D2, or D3), AC/DC The relay remains ON in both AC and DC modes of operation.

In the AC mode of operation, the sweep controller 500 puts each relay into AC operation and then the string phase currents sensed by current sensors Ia, Ib and Ic and the system currents sensed by voltage sensors Vu, Vv and Vw. A string voltage command value (hereinafter referred to as "St command value") for each of the battery strings St1 to St3 is determined based on the phase voltage. The sweep controller 500 then generates a gate signal (FIG. 3) for each battery string St so that each battery string St outputs a voltage corresponding to the St command value (target value). The gate signal is a signal that drives SW11 and SW12 (FIG. 2) of each battery circuit module M included in the battery string St. The sweep controller 500 controls each battery string St using the gate signals thus generated, whereby the string phase power (that is, the three-phase AC power output from the sweep regulator 100) is supplied to the AC output terminals Tu, Tv, and Tw. supplied. The string phase power supplied to the AC output terminals Tu, Tv, and Tw is transformed (for example, stepped up) by the transformer 120 and then supplied to a house (supply target).

The sweep controller 500 controls string phase power while the AC lines (wires UL, VL, and WL) of the power system 1 are connected to the power system. The sweep controller 500 can adjust the three-phase AC power of the power system with the string phase power to supply the desired power to the home (target). For example, sweep controller 500 may supply three-phase AC power from sweep regulator 100 to a house (supply target) in order to reduce the power consumption of the power system (and thus reduce the electricity bill). Sweep controller 500 may also compensate for power shortages with string phase power. The sweep controller 500 may supply three-phase AC power from the sweep regulator 100 to a house (supply target) during a power failure in the power system. Sweep controller 500 may also use the string phase power to perform frequency adjustment of the power supplied to the home (supply target).

When the sweep controller 500 switches the control mode from the AC operation mode to the DC operation mode, it stops outputting the gate signal to each battery string St before starting the DC operation mode. In the DC mode of operation, sweep controller 500 turns off all AC relays and turns on at least one of relays R21, R22, and R23 and relay R2. At least one of the battery strings St 1 to St 3 is thereby connected to the DC power supply 200 . After that, the sweep controller 500 raises the output voltage of the sweep regulator 100 from 0V to precharge the capacitor Cd between the wires DL1 and DL2. This suppresses the inrush current.

After precharging the capacitor Cd, the sweep controller 500 starts charging the battery 10 ( FIG. 2 ) included in the battery string St connected to the DC power supply 200 . The sweep controller 500 controls SW11 and SW12 of each battery circuit module M included in the battery string St to connect the battery 10 to be charged to the DC power supply 200 . Battery 10 connected to DC power supply 200 is charged with DC power supplied from DC power supply 200 . Sweep controller 500 monitors the SOC of battery 10 being charged based on the output of monitoring module 20 , and disconnects battery 10 that has reached a predetermined SOC (for example, the SOC indicating full charge) from DC power supply 200 . The sweep controller 500 simultaneously connects a plurality of battery strings St (for example, all of the battery strings St1 to St3) to the DC power supply 200, and simultaneously connects the plurality of battery strings St (for example, all of the battery strings St1 to St3). Ten charges may be performed. Alternatively, the battery strings St1 to St3 may be sequentially connected to the DC power supply 200 one by one, and the battery 10 may be charged sequentially by one battery string St connected to the DC power supply 200. FIG. Then, when the charging is completed, the sweep controller 500 stops outputting the gate signal to each battery string St, and then turns off all the DC relays. This disconnects sweep regulator 100 from DC power supply 200 . Sweep controller 500 may determine that charging is completed when all batteries 10 included in sweep regulator 100 reach a predetermined SOC.

Sweep controller 500 switches between an AC operation mode and a DC operation mode, for example, according to an instruction from energy controller 600 . Mode switching control (that is, switching control between the AC operation mode and the DC operation mode) will be described below with reference to FIGS. 8 to 10. FIG. Hereinafter, switching of the control mode from the AC operation mode to the DC operation mode is referred to as "AC/DC switching", and switching of the control mode from the DC operation mode to the AC operation mode is referred to as "DC/AC switching".

FIG. 8 is a schematic diagram showing an example of a connection mode of the power system PG, the sweep regulator 100, and the DC power supply 200. As shown in FIG. Referring to FIG. 8 together with FIG. 1, in the AC operation mode, both the power system PG and the sweep regulator 100 are connected to the wiring inside the house 2 (house wiring) via the transformer 120 and the distribution board 130. . The three-phase AC power supplied from the transformer 120 to the distribution board 130 is distributed to each wiring in the house 2 by the distribution board 130 . In the DC operation mode, sweep regulator 100 is connected to DC power supply 200 via wires DL1 and DL2. The electric wires DL1 and DL2 may be connected to electrical equipment or a power storage device (neither of which is shown) inside the house 2 . Examples of electrical appliances include various domestic electrical appliances (lighting fixtures, air conditioners, cooking appliances, etc.) that can be driven by DC power.

The energy controller 600 shown in FIG. 1 includes an hourly power consumption map (hereinafter, also referred to as a “power consumption map”) that predicts changes in the power consumption of a supply target (for example, a house 2) for a day, and a DC power consumption map for the day. It also holds an hourly generated power map (hereinafter also referred to as a “generated power map”) for predicting the transition of the generated power by the power source 200 . Then, energy controller 600 uses the power consumption map and the generated power map to determine mode switching timing (for example, AC/DC switching timing and DC/AC switching timing).

FIG. 9 is a graph showing changes in power consumption in general households and changes in typical PV-generated power. Referring to FIG. 9, power consumption in general households increases in the morning (for example, 6:00 to 10:00) and evening (for example, 18:00 to 22:00) hours, as indicated by line L1. It decreases during the daytime (eg, 10:00 to 18:00) and nighttime (eg, 22:00 to 6:00). Also, as indicated by line L2, in a typical example, PV power generation increases during the daytime (for example, 10:00 to 18:00).

1 and 8 together with FIG. 9, for example, when the power consumption map shows transitions similar to line L1 in FIG. 9 and the generated power map shows transitions similar to line L2 in FIG. , the energy controller 600 stores electricity in the sweep regulator 100 in the DC operation mode during the daytime, performs DC/AC switching in the evening, and supplies the stored electricity to the house 2 . Such control adjusts the supply and demand balance of electric power and achieves electric power leveling. In addition, the energy controller 600 instructs the sweep controller 500 to stop outputting the gate signal from the sweep controller 500 to each battery string St and to turn off all the DC relays and the AC relays at night. good too. Hereinafter, stopping the output of the gate signal from the sweep controller 500 to each battery string St and turning off all the DC relays and the AC relays is also referred to as "mode stop".

As described above, the energy controller 600 executes energy management in the house 2 (supply target) by performing mode switching control based on the power consumption map and the power generation map. The energy controller 600 may perform energy management based on information on energy supply and demand in the area where the power supply system 1 is installed.

Energy controller 600 determines which of the DC operation mode/AC operation mode/mode stop is to be performed for each time zone (for example, morning/daytime/evening/nighttime) based on, for example, the power consumption map and the power generation map. do. Energy controller 600 uses statistical data (for example, big data) to determine which of the DC operation mode/AC operation mode/mode stop is to be performed for each time slot by known machine learning technology or artificial intelligence. good too. The method of dividing the time zone is not limited to morning/daytime/evening/nighttime and is arbitrary. In addition, the energy controller 600 detects the power consumption peak and the generated power peak based on the power consumption map and the generated power map, executes the AC operation mode in the time zone near the power consumption peak, A DC mode of operation may be performed during the time period.

Transition of power consumption in the supply target (for example, house 2) may fluctuate depending on the season and lifestyle of the consumer. The energy controller 600 may successively detect the power consumption of the supply target and store the detected power consumption data in the storage device. Then, energy controller 600 may update the power consumption map based on the power consumption data (history information) accumulated in the storage device. Also, the energy controller 600 may have a power consumption map and a power generation map for each season (spring/summer/autumn/winter).

Energy controller 600 may acquire weather information (eg, weather, temperature, and insolation intensity) and correct at least one of the power consumption map and the power generation map based on the weather information. The energy controller 600 may obtain weather information using known weather services (eg, services provided by the Japan Meteorological Agency, information technology companies, telecommunications companies, etc.). The weather information may be measured data or forecast information. Energy controller 600 may correct the generated power map based on the weather forecast for the day.

Note that the energy controller 600 instructs the sweep controller 500 to switch AC/DC when the power generated by the DC power supply 200 is greater than a predetermined level and the power consumption in the house 2 (supply target) is less than a predetermined level. You may Also, the energy controller 600 may instruct the sweep controller 500 to switch between DC and AC when the power consumption in the house 2 (supply target) exceeds a predetermined level.

Energy controller 600 may determine the mode switching timing based on the amount of power stored in sweep regulator 100 (for example, the total amount of power stored in each battery 10 included in sweep regulator 100). Energy controller 600 may determine AC/DC switching timing based on the amount of electricity stored in sweep regulator 100 and the generated power map so that the amount of electricity stored in sweep regulator 100 does not fall below a predetermined level. Also, energy controller 600 may instruct sweep controller 500 to maintain the control mode in the AC operation mode when the amount of charge in sweep regulator 100 is sufficiently large.

FIG. 10 is a diagram showing an example of mode switching control. In FIG. 10 , the vertical axis indicates the amount of electricity stored in sweep regulator 100 . More specifically, the vertical axis represents the SOC, which represents the ratio of the current amount of charge to the amount of charge in the fully charged state of sweep regulator 100 from 0 to 100%. In FIG. 10, line L3 indicates transition of SOC of sweep regulator 100 on sunny days, and line L4 indicates transition of SOC of sweep regulator 100 on cloudy days.

Referring to FIG. 10 together with FIGS. 1 and 8, in this example, when the SOC of sweep regulator 100 reaches a predetermined lower limit (discharge lower limit), energy controller 600 instructs sweep controller 500 to switch AC/DC. . Then, when the SOC of sweep regulator 100 rises in the DC operation mode and reaches a predetermined upper limit (charge upper limit), energy controller 600 instructs sweep controller 500 to switch between DC and AC. After that, when the SOC of sweep regulator 100 reaches a predetermined reference value (reference SOC) in the AC operation mode, energy controller 600 instructs sweep controller 500 to stop the mode. On the next day, at a predetermined discharge start time (for example, 6:00), energy controller 600 instructs sweep controller 500 to start the AC operation mode. In the example shown in FIG. 10, the AC mode of operation is initiated at 6:00 and AC/DC switching occurs at 10:00 (reaching lower discharge limit), as indicated by lines L3 and L4. The energy controller 600 may determine the predetermined discharge start time based on the power consumption map and the power generation map.

The PV power generated by the DC power supply 200 may fluctuate depending on the weather conditions of the day (for example, sunny/cloudy/rainy weather). For example, sunny days are considered to have higher solar radiation intensity than cloudy days. In the example shown in FIG. 10, on a sunny day, the SOC of the sweep regulator 100 reaches the upper charge limit at 14:00, as indicated by the line L3, and on a cloudy day, the sweep regulator reaches the upper limit at 16:00, as indicated by the line L4. An SOC of 100 reaches the upper charge limit.

As described above, the power supply system 1 according to this embodiment includes the Y-connected battery strings St1 to St3 (first to third battery strings), relays R21, R22, and R23 (first to third DC relay), relays RU, RV, and RW (first to third AC relays), and a sweep controller 500 (control device) that controls each of the relays R21, R22, R23, RU, RV, and RW ( See Figure 1). Relay R21 is arranged on electric wire DL11 (first DC line) for connecting DC power supply 200 and battery string St1, and relay R22 is arranged on electric wire DL12 (second DC line) for connecting DC power supply 200 and battery string St2. line), and the relay R23 is placed on a wire DL13 (third DC line) for connecting the DC power supply 200 and the battery string St3 (see FIG. 1). The relay RU is arranged on the wire UL (first AC line) for connecting the AC output terminal Tu (first AC output terminal) and the battery string St1, and the relay RV is arranged on the AC output terminal Tv (second AC output terminal). ) and the battery string St2. 3rd AC line) (see FIG. 1).

Each of the battery strings St1 to St3 includes a plurality of battery circuit modules M connected to each other (see FIG. 2). Each battery circuit module M includes a battery 10, SW11 (first switch) connected in parallel to the battery 10, SW12 (second switch) connected in series to the battery 10, SW11 in the OFF state and SW12 in the OFF state. It has output terminals OT1 and OT2 (first and second output terminals) to which the voltage of the battery 10 is applied when in the ON state (see FIG. 2).

Further, when DC power is supplied from the DC power supply 200 to at least one of the battery strings St1 to St3, the sweep controller 500 turns off the relays RU, RV, and RW to turn off the relays R21, R22, and It is configured to turn on at least one of R23 (see FIGS. 8 to 10). Further, when the AC power is output from the battery strings St1, St2, and St3 to the AC output terminals Tu, Tv, and Tw, respectively, the sweep controller 500 turns off the relays R21, R22, and R23 to turn off the relay RU. , RV, and RW are turned on (see FIGS. 8 to 10).

According to the power supply system 1 having the above configuration, the DC power supplied from the DC power supply 200 can charge the batteries 10 included in the battery strings St1 to St3. In the power supply system 1 described above, the AC power (for example, three-phase AC power) output from the battery strings St1 to St3 can be output to the AC output terminals Tu, Tv, and Tw.

In the above embodiment, the sweep controller 500 is configured to switch between the DC operating mode, the AC operating mode, and the mode stop. The AC operation mode is a control mode in which AC power generated by the battery strings St1 to St3 is output to the AC output terminals Tu, Tv, and Tw. In the above embodiment, the DC operation mode is a control mode in which the batteries 10 included in the battery strings St1 to St3 are charged with DC power supplied from the DC power supply 200 (hereinafter referred to as "first DC operation mode"). ). However, the DC operation mode is not limited to this, and the DC operation mode may be a control mode in which the DC power output from the battery strings St1 to St3 is supplied to the electric wires DL1 and DL2 (hereinafter referred to as "second DC operation mode"). . Referring to FIG. 1, in the second DC operating mode, as in the first DC operating mode, the sweep controller 500 turns all AC relays OFF and at least one of the relays R21, R22, and R23 and the relay R2 is turned on. The sweep controller 500 adjusts the DC power supplied from the DC power supply 200 to the wires DL1 and DL2 with the DC power output from the battery strings St1 to St3, and supplies desired power to the target (for example, the wires DL1 and DL2 may be supplied to an electrical device or a power storage device connected to the Further, when DC power supply 200 is out of power, DC power may be supplied from sweep regulator 100 to wires DL1 and DL2 instead of DC power supply 200 . The sweep controller 500 may be configured to switch between a first DC operating mode, a second DC operating mode, an AC operating mode, and a mode stop.

The power supply system may include multiple types of DC power supplies. Moreover, the power supply system may further include a control device that switches the DC power supply connected to the battery string. FIG. 11 is a diagram showing a first modification of power supply system 1 shown in FIG. A power supply system 1A according to a first modified example will be described below, focusing on differences from the power supply system 1 according to the above-described embodiment.

Referring to FIG. 11, power supply system 1A includes HV (hybrid vehicle) 300 in addition to DC power supply 200 (PV power generation equipment). HV 300 may function as a DC power supply. The HV 300 includes a power storage device, an engine, and an MG (motor generator) (none of which are shown), and the MG can generate power using power generated by the engine. The HV 300 can store the generated electric power in a power storage device or output the electric power to the outside of the vehicle. HV 300 can also output electric power stored in the power storage device to the outside of the vehicle.

The power supply system 1A further includes a switching device 400 and a DC controller 700 that controls the switching device 400 . DC controller 700 may be a computer. DC controller 700 includes, for example, a processor, a storage device, and a communication I/F. Switching device 400 includes, for example, an A-contact relay and a C-contact relay. The switching device 400 connects either one of the DC power supply 200 and the HV 300 to the wires DL1 and DL2 and disconnects both the DC power supply 200 and the HV 300 from the wires DL1 and DL2 in accordance with instructions from the DC controller 700. Configured. In this modification, each of current sensor Id and voltage sensor Vr is configured to output a detected value to DC controller 700 . DC controller 700 may control switching device 400 based on the current and voltage on lines DL1 and DL2. DC controller 700 may control switching device 400 to switch the DC power supply (DC power supply 200/HV 300), for example, when determining that at least one of the current and voltage in wires DL1 and DL2 is insufficient. good.

The DC controller 700 normally connects the DC power supply 200 to the wires DL1 and DL2 in the first or second DC operation mode, and in an emergency (for example, in the event of a disaster) connects the HV 300 in the first or second DC operation mode. to the wires DL1 and DL2. Further, when the energy controller 600 instructs the sweep controller 500 to switch the DC power supply, the DC controller 700 may switch the DC power supply according to the instruction from the sweep controller 500 . For example, energy controller 600 may instruct sweep controller 500 to connect HV 300 to power lines DL1 and DL2 during a time period when a shortage of PV generated power is expected. Sweep controller 500 may also charge the power storage device (battery) of HV 300 in the second DC operation mode.

Note that, instead of the HV 300, another electric vehicle (xEV) may be adopted. The combination of multiple types of DC power sources is not limited to fluctuating power sources and xEV, but may be fluctuating power sources and ESS (Energy Storage System). Also, the power supply system may include three or more types of DC power supplies.

The branch points D1, D2, and D3 may be positioned after the LCL filter 110 (system side). FIG. 12 is a diagram showing a second modification of the power supply system 1 shown in FIG. A power supply system 1B according to the second modification will be described below, focusing on differences from the power supply system 1A shown in FIG.

Referring to FIG. 12, in power supply system 1B, branch points D1, D2 and D3 are located between LCL filter 110 and relays RU, RV and RW. In the power supply system 1B, the LCL filter 110 uses the wires PL1, PL2, and PL3 (wires connecting the battery string and the branch point) instead of the wires UL, VL, and WL (wires connecting the branch point and the AC output terminal). is provided in The power supply system 1B also includes a wire NL2 that connects the neutral point N1 and the neutral point N2, and a relay R3 provided on the wire NL2. Relay R3 is, for example, an electromagnetic mechanical relay. In the first or second DC operation mode, the sweep controller 500 turns off all AC relays (relays RU, RV, and RW) and turns off at least one of relays R21, R22, and R23, relay R2, and relay R2. R3 is turned on. Like the power supply systems 1 and 1A described above, the power supply system 1B can also operate in any one of the first DC operation mode, the second DC operation mode, and the AC operation mode.

Sweep controller 500 may include control circuitry 30 described below. FIG. 13 is a diagram showing an example of a control circuit included in the sweep controller 500. As shown in FIG.

Referring to FIG. 13, control circuit 30 is configured to generate a control signal (for example, the gate signal shown in FIG. 3) for battery string St and output it to battery string St. The sweep controller 500 includes a control circuit 30 for each battery string St, for example. The control circuit 30 includes a gate circuit 31 that generates a square-wave gate signal, switch drive circuits 32a, 32b, 32c, . including. . . included in the control circuit 30 will be referred to as the "switch drive circuit 32" and the delay circuits 33a, 33b included in the control circuit 30 will be referred to as the "switch drive circuit 32" unless otherwise specified. , 33c, . . . are referred to as "delay circuits 33". A switch drive circuit 32 and a delay circuit 33 are provided for each battery circuit module M. FIG.

The gate circuit 31 outputs the generated gate signal to the delay circuit 33a through the switch drive circuit 32a. The switch drive circuit 32a drives SW11 and SW12 of the battery circuit module M1 according to the gate signal output from the gate circuit 31 (hereinafter also referred to as "first gate signal"). Further, the delay circuit 33a generates a second gate signal by delaying the first gate signal by a predetermined time (hereinafter also referred to as "first delay time"), and the second gate signal is transmitted through the switch drive circuit 32b to the delay circuit. 33b. The switch drive circuit 32b drives SW11 and SW12 of the battery circuit module M2 according to the second gate signal. Further, the delay circuit 33b generates a third gate signal by delaying the second gate signal by a predetermined time (hereinafter also referred to as "second delay time"), and delays the third gate signal through the switch driving circuit 32c. Output to circuit 33c. The switch drive circuit 32c drives SW11 and SW12 of the battery circuit module M3 according to the third gate signal. Thus, the gate signal is output from the gate circuit 31, sequentially delayed by the delay circuits 33a, 33b, 33c, . . . and transmitted to the battery circuit modules M1, M2, M3, . The control circuit 30 can sequentially bring the battery circuit modules M1, M2, M3, . The sweep controller 500 may cause the battery circuit modules M1, M2, M3, . . . to sequentially discharge, or may sequentially charge the battery circuit modules M1, M2, M3, . According to the driving method described above, it becomes easy to evenly output current from each battery 10 included in the battery string St. In addition, the SOC of each battery 10 included in the battery string St becomes easier to equalize.

The delay times (including the first and second delay times) in each delay circuit 33 may be the same or different. Also, the delay time in each delay circuit 33 may be a fixed value, or may be variable according to a predetermined parameter (for example, the current and SOC of each battery 10). The sweep controller 500 may obtain an appropriate delay time by learning and update the delay time in each delay circuit 33 as needed.

Note that the control circuit 30 may be mounted in each battery string St instead of the sweep controller 500 .

In the above embodiments and modifications, the DC power supply 200 is not limited to PV power generation equipment, and may be other generators (for example, gas turbine generators or diesel generators) or ESSs. good. DC power supply 200 may be a fuel cell.

The embodiments disclosed this time should be considered as examples and not restrictive in all respects. The scope of the present invention is indicated by the scope of the claims rather than the description of the above-described embodiments, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

1, 1A, 1B power supply system, 10 battery, 11 first switching element, 12 second switching element, 13 first diode, 14 second diode, 15 choke coil, 16 capacitor, 20 monitoring module, 30 control circuit, 31 gate circuit, 32 switch drive circuit, 33 delay circuit, 100 sweep regulator, 110 LCL filter, 120 transformer, 200 DC power supply, 300 HV, 400 switching device, 500 sweep controller, 600 energy controller, 700 DC controller, M battery circuit module, OT1, OT2 output terminals, PG power system, R21, R22, R23, RU, RV, RW relays, St, St1, St2, St3 battery strings, Tu, Tv, Tw AC output terminals.

Claims (1)

a first battery string, a second battery string, and a third battery string that are Y-connected;
first to third DC lines connecting the DC power supply and the first to third battery strings, respectively;
first to third DC relays respectively provided on the first to third DC lines;
first to third AC lines connecting the first to third AC output terminals and the first to third battery strings, respectively;
first to third AC relays respectively provided on the first to third AC lines;
a control device that controls each of the first to third DC relays and the first to third AC relays;
each of the first to third battery strings includes a plurality of battery circuit modules connected to each other;
Each of the plurality of battery circuit modules includes: a battery; a first switch connected in parallel to the battery; a second switch connected in series to the battery; a first output terminal and a second output terminal to which the voltage of the battery is applied when the switch is in an ON state;
When DC power is supplied from the DC power supply to at least one of the first to third battery strings, the control device turns off each of the first to third AC relays to turn off the first to third battery strings. configured to turn on at least one of the 3DC relays,
When outputting AC power from the first to third battery strings to the first to third AC output terminals, the control device turns off each of the first to third DC relays and turns off the first to third DC relays. A power supply system configured to turn on each of the first to third AC relays.

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