Power storage system

Abstract

To provide a power storage system capable of efficiently charging according to a voltage state of charging equipment and keeping manufacturing costs down.SOLUTION: A power storage system 1 includes: a battery 2 including first to third semiconductor switches S / C_A, S / C_B, and S / C_C that can switch between a first voltage state, in which a first storage unit 21 and a second storage unit 22 are connected in series and can be charged with a first voltage, and a second voltage state, in which the first storage unit 21 and the second storage unit 22 are connected in parallel and can be charged with a second voltage; a three-phase motor 3; an inverter 5 and a first smooth capacitor C1 connected on power supply circuits 11P and 11N between the battery 2 and the three-phase motor 3; and DC power supply circuits 13P and 13N connected to the power supply circuits 11P and 11N between the inverter 5 and the battery 2. The DC power supply circuit 13P on the positive electrode side has a branch circuit 14 connected to either of one-phase coils 32U, 32V, and 32W from the three-phase motor 3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electricity storage system. [Background technology]

[0002] In recent years, research and development has been conducted into charging mobility vehicles equipped with secondary batteries that contribute to energy efficiency, in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] Regarding charging and supplying power to mobility vehicles equipped with secondary batteries, there are two types of charging equipment such as charging stations that support 400V class and 800V class. If a mobility vehicle is only compatible with 400V class charging equipment, it cannot enjoy the rapid charging performance of 800V class charging equipment.

[0004] When a mobility vehicle is compatible with 400V-class and 800V-class charging equipment, typically, the voltage is boosted to 800V using a voltage converter when charging with 400V-class charging equipment, or stepped down to 400V using a voltage converter when charging with 800V-class charging equipment. However, efficiency decreases when the voltage converter is used during charging.

[0005] In response to this, there is also known a mobility that can be charged at both 400V-class compatible charging equipment and 800V-class compatible charging equipment without using a voltage converter for charging by switching the connection method of the battery module (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-080474 A [Patent Document 2] JP 2020-150618 A Summary of the Invention [Problem to be solved by the invention]

[0007] On the other hand, there are two types of accessories used in mobility: those that are driven by 400V class and those that are driven by 800V class. In mobility that switches the connection method of the battery module, voltage conversion is generally performed using a voltage converter for the accessories, such as when driving a 400V class accessory while charging with a charging facility that supports the 800V class, or when driving an 800V class accessory while charging with a charging facility that supports the 400V class. However, voltage converters for accessories are expensive, which increases manufacturing costs.

[0008] The present invention provides a power storage system that can efficiently charge in accordance with the voltage state of a charging facility while keeping manufacturing costs down. [Means for solving the problem]

[0009] The power storage system of the present invention comprises: a battery including a first power storage unit, a second power storage unit, and a first switch unit capable of switching between a first voltage state in which the first power storage unit and the second power storage unit are connected in series and can be charged at a first voltage and a second voltage state in which the first power storage unit and the second power storage unit are connected in parallel and can be charged at a second voltage; a three-phase motor having three-phase coils connected at a neutral point and driven by power supplied from the battery; an inverter connected on a power transmission path between the battery and the three-phase motor; a DC power supply circuit connected to a first connection portion located on a power transmission path between the inverter and the battery; a capacitor provided on the power transmission path between the battery and the three-phase motor; a branch circuit that branches off from the DC power supply circuit on the positive electrode side and is connected to one of the three-phase coils; The first switch section includes a semiconductor switch. Effect of the Invention

[0010] According to the present invention, efficient charging is possible according to the voltage state of the charging facility while manufacturing costs can be reduced. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram showing a configuration of a power storage system 1 of a first embodiment. [Diagram 2] FIG. 4 is a diagram showing a first voltage state (800 V start) of the battery 2. [Diagram 3] FIG. 13 is a diagram showing a second voltage state of the battery 2 (started at 400 V). [Figure 4] 2 is a diagram showing a current flow during running of an electric vehicle equipped with the power storage system 1 of the first embodiment. FIG. [Diagram 5] FIG. 2 is a diagram showing a current flow during charging at a first voltage (800 V) in an electrically powered vehicle equipped with the power storage system 1 of the first embodiment. [Figure 6] FIG. 4 is a diagram showing a current flow during charging at a second voltage (400 V) in an electrically powered vehicle equipped with the power storage system 1 of the first embodiment. [Figure 7] 2 is a diagram showing an operation sequence during running of an electric vehicle equipped with the power storage system 1 of the first embodiment. FIG. [Figure 8] FIG. 2 is a diagram showing an operation sequence during charging with a first voltage (800 V) of an electrically powered vehicle equipped with the power storage system 1 of the first embodiment. [Figure 9] FIG. 4 is a diagram showing an operation sequence during charging with a second voltage (400 V) of an electrically powered vehicle equipped with the power storage system 1 of the first embodiment. [Figure 10] FIG. 11 is a diagram showing a current flow during a precharge operation in a first voltage state (started at 800 V) of a battery 2 in a comparative example. [Figure 11] 11A and 11B are diagrams illustrating an operation sequence during a precharge operation in a comparative example. [Figure 12] FIG. 4 is a diagram showing a current flow during a precharge operation in a first voltage state (started at 800 V) of the battery 2 in the first embodiment. [Figure 13]5A to 5C are diagrams illustrating an operation sequence during a precharge operation in the first embodiment. [Figure 14] FIG. 11 is a diagram showing a configuration of an electric vehicle equipped with a power storage system 1 according to a second embodiment. [Figure 15] FIG. 11 is a diagram showing a current flow during running of an electric vehicle equipped with an electricity storage system 1 according to a second embodiment. [Figure 16] FIG. 11 is a diagram showing a current flow during charging at a first voltage (800 V) in an electrically powered vehicle equipped with the power storage system 1 of the second embodiment. [Figure 17] FIG. 11 is a diagram showing a current flow during charging at a second voltage (400 V) in an electrically powered vehicle equipped with the power storage system 1 of the second embodiment. [Figure 18] FIG. 11 is a diagram showing an operation sequence during running of an electric vehicle equipped with the electricity storage system 1 of the second embodiment. [Figure 19] FIG. 11 is a diagram showing an operation sequence during charging with a first voltage (800 V) of an electrically powered vehicle equipped with the power storage system 1 of the second embodiment. [Figure 20] FIG. 11 is a diagram showing an operation sequence during charging with a second voltage (400 V) of an electric vehicle equipped with the power storage system 1 of the second embodiment. [Figure 21] FIG. 4 is a diagram showing a configuration of a modified example of the power storage system 1 of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. First, a first embodiment of the present invention will be described with reference to Figs.

[0013] [First embodiment] The power storage system 1 of the first embodiment shown in Fig. 1 is mounted on an electric vehicle such as an electric car. The electric vehicle on which the power storage system 1 is mounted is compatible with 400V-class and 800V-class charging equipment, and can not only rapidly charge the battery 2 at a charging voltage of 400V and 800V, but also efficiently drive the three-phase motor 3 and auxiliary equipment 4 at a base voltage of 800V.

[0014] Specifically, as shown in FIG. 1, the energy storage system 1 includes a battery 2, a three-phase motor 3, an auxiliary device 4, an inverter 5 (INV), a DC-DC converter 6, power supply circuits 11P, 11N, auxiliary device drive circuits 12P, 12N, DC power supply circuits 13P, 13N, a branch circuit 14, and a control unit 10.

[0015] As shown in Figures 1 to 3, the battery 2 includes a first power storage unit 21, a second power storage unit 22, a first contactor M / C, first to third semiconductor switches S / C_A, S / C_B, S / C_C, first and second reactors L1, L2, a current sensor IS, and a current breaker FUSE.

[0016] First power storage unit 21 and second power storage unit 22 are each a battery module capable of charging and discharging 400V.

[0017] The first contactor M / C is disposed at the end of the positive electrode side of the battery 2, and functions as a main switch that turns on / off the connection of the battery 2 with the outside (power supply circuit 11P).

[0018] The first to third semiconductor switches S / C_A, S / C_B, and S / C_C are composed of a MOSFET, a bipolar transistor, an IGBT, or the like, and switch the connection state between the first power storage unit 21 and the second power storage unit 22. For example, as shown in FIG. 2, when the first semiconductor switch S / C_A is turned ON and the second semiconductor switch S / C_B and the third semiconductor switch S / C_C are turned OFF, the battery 2 is in a first voltage state (800V start) in which the first power storage unit 21 and the second power storage unit 22 are connected in series, and charging and discharging at 800V becomes possible. Also, as shown in FIG. 3, when the first semiconductor switch S / C_A is turned OFF and the second semiconductor switch S / C_B and the third semiconductor switch S / C_C are turned ON, the battery 2 is in a second voltage state (400V start) in which the first power storage unit 21 and the second power storage unit 22 are connected in parallel, and charging and discharging at 400V becomes possible. The concept of startup includes driving the electric vehicle equipped with the power storage system 1 while it is traveling and charging the electric vehicle while it is stopped. The first to third semiconductor switches S / C_A, S / C_B, S / C_C are an example of a first switch unit capable of switching between a first voltage state (800V startup) and a second voltage state (400V startup).

[0019] The first and second reactors L1, L2 are arranged in series with the first, second and third semiconductor switches S / C_A, S / C_B and S / C_C, and prevent short circuits when the first, second and third semiconductor switches S / C_A, S / C_B and S / C_C are turned ON.

[0020] Specifically, as shown in Fig. 2 and Fig. 3, the battery 2 includes a positive electrode side node N1, a negative electrode side node N2, a negative electrode side connection node N3, and a positive electrode side connection node N4. The positive electrode side node N1 is connected in parallel to the positive electrode side path K1 of the first power storage unit 21 and the positive electrode side path K2 of the second power storage unit 22. The negative electrode side node N2 is connected in parallel to the negative electrode side path K3 of the first power storage unit 21 and the negative electrode side path K4 of the second power storage unit 22. The negative electrode side connection node N3 is connected to the series connection path K5 that connects the negative electrode side path K3 of the first power storage unit 21 and the positive electrode side path K2 of the second power storage unit 22, and the negative electrode side path K3 of the first power storage unit 21. The positive electrode side connection node N4 is connected to the series connection path K5 and the positive electrode side path K2 of the second power storage unit 22.

[0021] The first semiconductor switch S / C_A is disposed on the series connection path K5, the second semiconductor switch S / C_B is disposed between the positive electrode side node N1 and the positive electrode side connection node N4, and the third semiconductor switch S / C_C is disposed between the negative electrode side node N2 and the negative electrode side connection node N3. The first reactor L1 is disposed between the positive electrode side connection node N4 and the positive electrode of the second power storage unit 22, and the second reactor L2 is disposed between the negative electrode side connection node N3 and the negative electrode of the first power storage unit 21. As a result, when starting up with the first voltage (800V), two reactors L1 and L2 are connected in series, and when starting up with the second voltage (400V), one reactor L1 and one reactor L2 are connected to each path, and the reactors L1 and L2 are appropriately disposed according to the voltage. The number and arrangement of the reactors are not limited to the above example. At least one reactor needs to be arranged in the circuit in each of the first voltage state (800V start-up) and the second voltage state (400V start-up). Therefore, even if there is a single reactor arranged between the first contactor M / C and the current sensor IS, it is possible to prevent a short circuit when the first to third semiconductor switches S / C_A, S / C_B, S / C_C are turned ON.

[0022] According to such a battery 2, the first to third semiconductor switches S / C_A, S / C_B, and S / C_C are used to switch between a first voltage state (800V start) and a second voltage state (400V start), and therefore, by controlling the first to third semiconductor switches S / C_A, S / C_B, and S / C_C with PWM (Pulse Width Modulation), it is possible to precharge the first smoothing capacitor C1, which will be described later. This eliminates the need for a precharge circuit, as compared to a case in which the first voltage state (800V start) and the second voltage state (400V start) are switched using a mechanical switch (such as a contactor) that cannot be switched at high frequency, and therefore the volume and weight of the circuit of the battery 2 can be reduced. The PWM control of the first to third semiconductor switches S / C_A, S / C_B, and S / C_C will be described later.

[0023] The current sensor IS is disposed between the first contactor M / C and the power storage units 21 and 22, and measures the current.

[0024] The current breaker FUSE is disposed at the end of the negative electrode side of the battery 2, and cuts off the connection of the battery 2 with the outside (power supply circuit 11N) when an abnormality occurs. In the power storage system 1 of this embodiment, the current breaker FUSE is configured with a pyro fuse that can intentionally cut off the current in response to an electric signal, and when an abnormality occurs (such as a vehicle collision or a short circuit in the battery 2), the current breaker FUSE is cut off and all contactors and semiconductor switches in the battery 2 are turned OFF (open).

[0025] In this way, when an abnormality occurs, the connection to the outside can be cut off at both the positive and negative ends of the battery 2. Also, in both the first voltage state (800V start) and the second voltage state (400V start), by turning off the multiple contactors and semiconductor switches present on the circuit, it is possible to reliably cut off the circuit even when a failure occurs in a contactor or semiconductor switch. Furthermore, by using a pyro fuse as the current breaker FUSE, the contactor placed at the end on the negative side of the battery 2 is not required, thereby reducing the number of parts and costs.

[0026] The three-phase motor 3 includes three-phase coils 32U, 32V, and 32W, one end of which is connected at a neutral point 31, and is driven to rotate by power supplied from the battery 2 via the inverter 5. The three-phase motor 3 of this embodiment includes a U-phase terminal 33U, a V-phase terminal 33V, and a W-phase terminal 33W, which are connected to the other ends of the coils 32U, 32V, and 32W. The U-phase terminal 33U, the V-phase terminal 33V, and the W-phase terminal 33W are connected to the inverter 5. The other end of any one of the coils 32U, 32V, and 32W is connected to the branch circuit 14 at a connection portion 34. In this embodiment, the coil 32U of the three-phase coils 32U, 32V, and 32W is connected to the branch circuit 14 at a connection portion 34 located between the U-phase terminal 33U and the inverter 5.

[0027] The inverter 5 converts the DC power supplied from the battery 2 into three-phase AC power by switching a plurality of switching elements, and drives the three-phase motor 3 to rotate. When a DC current (400V) is supplied from the branch circuit 14 to the connection portion 34, the inverter 5 can function as a boost circuit that boosts the DC current (800V) by switching a plurality of switching elements using the coil connected to the branch circuit 14 and the coil of the other phase (in this embodiment, the coils 32U, 32V, or the coils 32U, 32W). That is, the coils 32U, 32V, and 32W wound around the stator core are used as a transformer. The inverter 5 allows a current to flow from the three-phase motor 3 side to the battery 2 side regardless of whether the gate is ON / OFF, and allows a current to flow from the battery 2 side to the three-phase motor 3 side only when the gate is ON.

[0028] The auxiliary device 4 is a high-voltage in-vehicle device that can be driven by DC power from the battery 2 and an external power source, and includes, for example, an electric compressor for an air conditioner and a heater. The auxiliary device 4 is connected to the battery 2 via auxiliary device drive circuits 12P, 12N, a second contactor VS / C, and power supply circuits 11P, 11N, which will be described later. The second contactor VS / C is an example of a third switch unit. The auxiliary device 4 in this embodiment operates on a base voltage of 800V.

[0029] The DC-DC converter 6 steps down the DC power from the battery 2 and an external power source to drive low-voltage in-vehicle devices. The DC-DC converter 6 is provided with an ammeter (not shown).

[0030] The power supply circuits 11P, 11N are configured as a positive / negative pair and connect the battery 2 and the inverter 5 (three-phase motor 3). The power supply circuits 11P, 11N are provided with connection parts 111P, 111N with the DC power supply circuits 13P, 13N, and connection parts 112P, 112N with the auxiliary drive circuits 12P, 12N (auxiliary 4) are provided on the inverter 5 side of the connection parts 111P, 111N. In addition, the positive power supply circuit 11P is provided with a second contactor VS / C that turns the circuit ON / OFF between the connection part 112P with the auxiliary drive circuit 12P and the connection part 111P with the DC power supply circuit 13P. In addition, a first voltage sensor V_PIN, a first smoothing capacitor C1, and a first resistor R1 are provided on the inverter 5 side of the power supply circuits 11P, 11N. The first voltage sensor V_PIN, the first smoothing capacitor C1, and the first resistor R1 are provided on a circuit connecting the positive power supply circuit 11P and the negative power supply circuit 11N. The first resistor R1 is provided to discharge the first smoothing capacitor C1 when the circuit is interrupted.

[0031] The DC power supply circuits 13P, 13N are configured as a pair of positive and negative terminals, and one end of the DC power supply circuits 13P, 131N is provided with a charging terminal 131P, 131N to which an external power source such as a charging facility can be connected, and the other end is connected to the power supply circuits 11P, 11N via the connection parts 111P, 111N. The DC power supply circuits 13P, 13N are provided with a third contactor QC / C_A and a fourth contactor QC / C_B for turning the respective circuits ON / OFF. A second voltage sensor V_BAT is provided at a position closer to the connection parts 111P, 111N side than the third contactor QC / C_A and the fourth contactor QC / C_B. A third voltage sensor V_QC is provided at a position closer to the charging terminals 131P, 131N side than the third contactor QC / C_A and the fourth contactor QC / C_B.

[0032] The branch circuit 14 branches off at a position on the positive-pole DC power supply circuit 13P closer to the connection unit 111P than the third contactor QC / C_A and the second voltage sensor V_BAT, and is connected to any one of the coils of the three-phase motor 3 via a connection unit 34. A fifth contactor QC / C_C that turns the circuit ON / OFF is provided in an intermediate portion of the branch circuit 14. The fifth contactor QC / C_C is an example of a second switch unit.

[0033] The control unit 10 is, for example, a vehicle ECU, and controls the driving and charging of the power storage system 1. More specifically, the control unit 10 performs ON / OFF control of the contactors M / C, VS / C, QC / C_A, QC / C_B, and QC / C_C, and failure detection thereof (welding detection), ON / OFF control (including PWM control) of the semiconductor switches S / C_A, S / C_B, and S / C_C, and failure detection, and controls the DC-DC converter 6 and the inverter 5.

[0034] Next, the operation of the power storage system 1 will be described with reference to FIGS.

[0035] FIG. 4 is a diagram showing the flow of current when an electric vehicle equipped with the energy storage system 1 of the first embodiment is traveling (800V drive), and FIG. 7 is a diagram showing the operation sequence when an electric vehicle equipped with the energy storage system 1 of the first embodiment is traveling (800V drive).

[0036] When an ignition switch IG of an electric vehicle is turned ON, the control unit 10 first turns ON the first contactor M / C and the second contactor VS / C, and checks the detected voltage values ​​of the first voltage sensor V_PIN and the second voltage sensor V_BAT. If the detected voltage value of the first voltage sensor V_PIN or the second voltage sensor V_BAT increases, the control unit 10 determines that any of the first to third semiconductor switches S / C_A, S / C_B, S / C_C has failed, and issues an abnormality notification.

[0037] When the control unit 10 determines that there is no failure in the first to third semiconductor switches S / C_A, S / C_B, and S / C_C, it switches the first semiconductor switch S / C_A to a continuous ON state after an intermittent ON period by PWM control, and connects the circuit in the battery 2 to a first voltage state (800V). This causes the first smoothing capacitor C1 to be precharged, and the detected voltage values ​​of the first voltage sensor V_PIN and the second voltage sensor V_BAT gradually increase. Then, when the precharging of the first smoothing capacitor C1 is completed, the electric vehicle becomes capable of running. At this time, the accessories 4 are connected to the power supply circuits 11P, 11N via the accessory drive circuits 12P, 12N, and are driven by the first voltage (800V) supplied from the battery 2.

[0038] On the other hand, when the ignition switch IG is turned OFF, the control unit 10 first turns OFF the second contactor VS / C and checks the detected voltage value of the first voltage sensor V_PIN. If the detected voltage value of the first voltage sensor V_PIN does not decrease due to the discharge of the first smoothing capacitor C1, the control unit 10 determines that the second contactor VS / C has failed and issues an abnormality notification.

[0039] When the control unit 10 determines that the second contactor VS / C is not malfunctioning, it turns off the first contactor M / C at the timing when the discharge of the first smoothing capacitor C1 is completed and checks the detected voltage value of the second voltage sensor V_BAT. When the detected voltage value of the second voltage sensor V_BAT does not decrease, the control unit 10 determines that the first contactor M / C is malfunctioning and issues an abnormality notification.

[0040] When the control unit 10 determines that there is no failure in the first contactor M / C, it turns off the first semiconductor switch S / C_A and ends the operating sequence during running.

[0041] FIG. 5 is a diagram showing the current flow during first voltage charging (800 V charging) of an electric vehicle equipped with the energy storage system 1 of the first embodiment, and FIG. 8 is a diagram showing the operation sequence during first voltage charging (800 V charging) of an electric vehicle equipped with the energy storage system 1 of the first embodiment.

[0042] When a charging plug is connected to the charging terminals 131P, 131N, the control unit 10 performs CAN communication with the charging equipment to identify the charging voltage. When the charging voltage is the first voltage (800V), the control unit 10 first turns on the first contactor M / C and the second contactor VS / C, and checks the detected voltage values ​​of the first voltage sensor V_PIN and the second voltage sensor V_BAT. When the detected voltage value of the first voltage sensor V_PIN or the second voltage sensor V_BAT increases, the control unit 10 determines that one of the first to third semiconductor switches S / C_A, S / C_B, S / C_C has failed, and issues an abnormality alert.

[0043] When the control unit 10 determines that there is no failure in the first to third semiconductor switches S / C_A, S / C_B, and S / C_C, it switches the first semiconductor switch S / C_A to a continuous ON state after an intermittent ON period by PWM control, and connects the circuit in the battery 2 to a first voltage state (800V). This causes the first smoothing capacitor C1 to be precharged, and the detected voltage values ​​of the first voltage sensor V_PIN and the second voltage sensor V_BAT gradually increase. Then, when the precharging of the first smoothing capacitor C1 is completed, the battery 2 is in a state in which charging with the first voltage (800V) can start.

[0044] After that, the control unit 10 turns on the third contactor QC / C_A and the fourth contactor QC / C_B to start charging the battery 2 with the first voltage (800 V). At this time, the accessories 4 are connected to the DC power supply circuits 13P, 13N via the accessory drive circuits 12P, 12N and the second contactor VS / C, and are driven by the first voltage (800 V) supplied from the charging facility.

[0045] On the other hand, when the control unit 10 determines that a charging stop signal has been input, it turns off the third contactor QC / C_A and the fourth contactor QC / C_B and checks the detected voltage value of the third voltage sensor V_QC. If the detected voltage value of the third voltage sensor V_QC does not decrease, the control unit 10 determines that the third contactor QC / C_A and the fourth contactor QC / C_B are faulty and issues an abnormality notification.

[0046] If the control unit 10 determines that the third contactor QC / C_A and the fourth contactor QC / C_B are not malfunctioning, it turns off the second contactor VS / C and checks the detected voltage value of the first voltage sensor V_PIN. If the detected voltage value of the first voltage sensor V_PIN does not decrease due to the discharge of the first smoothing capacitor C1, the control unit 10 determines that the second contactor VS / C is malfunctioning and issues an abnormality notification.

[0047] When the control unit 10 determines that the second contactor VS / C is not malfunctioning, it turns off the first contactor M / C at the timing when the discharge of the first smoothing capacitor C1 is completed and checks the detected voltage value of the second voltage sensor V_BAT. When the detected voltage value of the second voltage sensor V_BAT does not decrease, the control unit 10 determines that the first contactor M / C is malfunctioning and issues an abnormality notification.

[0048] When the control unit 10 determines that there is no failure in the first contactor M / C, it turns off the first semiconductor switch S / C_A and ends the operation sequence during charging with the first voltage (800 V).

[0049] FIG. 6 is a diagram showing the current flow during second voltage charging (400 V charging) of an electric vehicle equipped with the energy storage system 1 of the first embodiment, and FIG. 9 is a diagram showing the operation sequence during second voltage charging (400 V charging) of an electric vehicle equipped with the energy storage system 1 of the first embodiment.

[0050] When a charging plug is connected to the charging terminals 131P, 131N, the control unit 10 performs CAN communication with the charging equipment to identify the charging voltage. When the charging voltage is the second voltage (400V), the control unit 10 first turns on the first contactor M / C and the fifth contactor QC / C_C, and checks the detected voltage values ​​of the first voltage sensor V_PIN and the second voltage sensor V_BAT. When the detected voltage value of the first voltage sensor V_PIN or the second voltage sensor V_BAT increases, the control unit 10 determines that one of the first to third semiconductor switches S / C_A, S / C_B, S / C_C has failed, and issues an abnormality alert.

[0051] When the control unit 10 determines that there is no failure in the first to third semiconductor switches S / C_A, S / C_B, and S / C_C, it switches the second semiconductor switch S / C_B and the third semiconductor switch S / C_C to a continuous ON state after an intermittent ON period by PWM control, and connects the circuit in the battery 2 to the second voltage state (400 V). This precharges the first smoothing capacitor C1, and the detected voltage values ​​of the first voltage sensor V_PIN and the second voltage sensor V_BAT gradually increase.

[0052] In addition, the control unit 10 enables the boost circuit formed by the three-phase motor 3 and the inverter 5, and then turns on the third contactor QC / C_A and the fourth contactor QC / C_B. This puts the battery 2 in a state in which charging with the second voltage (400V) can begin. In addition, the three-phase motor 3 and the inverter 5 connected to the DC power supply circuits 13P and 13N via the branch circuit 14 can boost the second voltage (400V) supplied from the charging facility to the first voltage (800V) to drive the auxiliary equipment 4.

[0053] On the other hand, when the control unit 10 determines that a charging stop signal has been input, it turns off the third contactor QC / C_A and the fourth contactor QC / C_B and checks the detected voltage value of the third voltage sensor V_QC. If the detected voltage value of the third voltage sensor V_QC does not decrease, the control unit 10 determines that the third contactor QC / C_A and the fourth contactor QC / C_B are faulty and issues an abnormality notification.

[0054] If the control unit 10 determines that the third contactor QC / C_A and the fourth contactor QC / C_B are not faulty, it stops boosting the voltage by the three-phase motor 3 and the inverter 5, turns off the fifth contactor QC / C_C, and checks the detected voltage value of the first voltage sensor V_PIN. If the detected voltage value of the first voltage sensor V_PIN does not decrease, the control unit 10 determines that the fifth contactor QC / C_C is faulty and issues an abnormality alert.

[0055] If the control unit 10 determines that the fifth contactor QC / C_C is not broken, it turns off the first contactor M / C and checks the detected voltage value of the second voltage sensor V_BAT. If the detected voltage value of the second voltage sensor V_BAT does not decrease, the control unit 10 determines that the first contactor M / C is broken and issues an abnormality notification.

[0056] If the control unit 10 determines that there is no failure in the first contactor M / C, it turns off the second semiconductor switch S / C_B and the third semiconductor switch S / C_C, and ends the operation sequence for charging with the second voltage (400 V).

[0057] Next, the precharge operation will be described with reference to FIGS.

[0058] FIG. 10 is a diagram showing the first voltage state (800V start) of the battery 2 of the comparative example, and FIG. 11 is a diagram showing an operation sequence during a pre-charge operation of the comparative example.

[0059] As in the comparative example shown in Fig. 10, when the first switch section (S / C_A, S / C_B, S / C_C) that switches between the first voltage state (started at 800V) and the second voltage state (started at 400V) is configured using a mechanical switch (contactor or the like) that cannot be switched at high frequency, a precharge circuit is provided to precharge the first smoothing capacitor C1. The precharge circuit is provided, for example, in parallel with the first contactor M / C. In the precharge circuit, a precharge contactor P / C and a precharge resistor R are arranged in series.

[0060] 11, when starting the battery 2 in the first voltage state (800V start), the control unit 10 turns on the pre-charge contactor P / C and the second contactor VS / C (see FIG. 1) before the first contactor M / C, and then turns on the mechanical switch S / C_A (mechanical switch S / C_B and mechanical switch S / C_C in the second voltage state). As a result, a current (I_C1) determined by the pre-charge resistor R flows to the first smoothing capacitor C1, and the first smoothing capacitor C1 is pre-charged (V_C1).

[0061] FIG. 12 is a diagram showing the first voltage state (800V start) of the battery 2 in the first embodiment, and FIG. 13 is a diagram showing an operation sequence during a pre-charge operation in the first embodiment.

[0062] As shown in Fig. 12, in this embodiment, the first switch section is composed of semiconductor switches S / C_A, S / C_B, and S / C_C. As shown in Fig. 13, when starting up the battery 2 in the first voltage state (800V start-up), the control section 10 turns on the first contactor M / C and the second contactor VS / C (see Fig. 1) and then turns on the first semiconductor switch S / C_A (the second semiconductor switch S / C_B and the third semiconductor switch S / C_C in the second voltage state). At this time, the control section 10 controls the current flowing through the first smoothing capacitor C1 by intermittently turning on the first semiconductor switch S / C_A by PWM control, thereby precharging the first smoothing capacitor C1.

[0063] The gradient of the current value I_C1 flowing through the first smoothing capacitor C1 is determined by the inductance of the reactors L1 and L2. In addition, if the initial ON time of the first semiconductor switch S / C_A (or the second semiconductor switch S / C_B and the third semiconductor switch S / C_C) is long, the reactors L1 and L2 may saturate and become a short-circuit current. Therefore, the control unit 10 determines an upper limit current that will not saturate and switches the first semiconductor switch S / C_A (or the second semiconductor switch S / C_B and the third semiconductor switch S / C_C). In this way, the first switch unit is composed of the semiconductor switches S / C_A, S / C_B, and S / C_C, and the first smoothing capacitor C1 is precharged by PWM control of the first switch unit, so that the precharge circuit described in FIG. 10 can be omitted.

[0064] [Second embodiment] Next, a power storage system 1 according to a second embodiment will be described with reference to Fig. 14 to Fig. 20. However, for configurations common to the first embodiment, the same reference numerals as in the first embodiment are used, and the description of the first embodiment may be used.

[0065] In the energy storage system 1 of the first embodiment described above, the third contactor QC / C_A, which is the main switch for charging, is connected in series with the first contactor M / C, which is the main switch for the battery 2. However, in the energy storage system 1 of the second embodiment, as shown in FIG. 14, the third contactor QC / C_A is connected in parallel with the first contactor M / C.

[0066] Even in the energy storage system 1 of the second embodiment, the same effect as the energy storage system 1 of the first embodiment can be obtained based on the operation according to the operation sequence described later. Furthermore, in the energy storage system 1 of the second embodiment, in charging the second voltage (400 V), the first contactor M / C can be used to separate the battery 2 charged with the second voltage (400 V) from the first voltage (800 V) boosted by the three-phase motor 3 and the inverter 5, eliminating the need for a switch component equivalent to the second contactor VS / C of the first embodiment.

[0067] In the second embodiment, the first to third semiconductor switches S / C_A, S / C_B, and S / C_C are an example of a first switch section, and the fifth contactor QC / C_C is an example of a second switch section, which is similar to the first embodiment, but differs from the first embodiment in that the first contactor M / C is an example of a third switch section.

[0068] In the power storage system 1 of the second embodiment, the third contactor QC / C_A, the fourth contactor QC / C_B, the fifth contactor QC / C_C, the second voltage sensor V_BAT, and the third voltage sensor V_QC are disposed in the battery 2.

[0069] Next, the operation of the power storage system 1 of the second embodiment will be described with reference to FIGS.

[0070] FIG. 15 is a diagram showing the current flow when an electric vehicle equipped with the energy storage system 1 of the second embodiment is traveling (800V drive), and FIG. 18 is a diagram showing the operation sequence when an electric vehicle equipped with the energy storage system 1 of the second embodiment is traveling (800V drive).

[0071] When the ignition switch IG of the electric vehicle is turned ON, the control unit 10 turns ON the first contactor M / C, and then turns the first semiconductor switch S / C_A to a continuous ON state after an intermittent ON period by PWM control, and connects the circuit in the battery 2 to a first voltage state (800V). This precharges the first smoothing capacitor C1, and the detected voltage values ​​of the first voltage sensor V_PIN and the second voltage sensor V_BAT gradually increase. Then, when the precharge of the first smoothing capacitor C1 is completed, the electric vehicle becomes capable of running. At this time, the accessories 4 are connected to the power supply circuits 11P, 11N via the accessory drive circuits 12P, 12N, and are driven by the first voltage (800V) supplied from the battery 2.

[0072] On the other hand, when the ignition switch IG is turned OFF, the control unit 10 first turns OFF the first contactor M / C and checks the detected voltage value of the first voltage sensor V_PIN. If the detected voltage value of the first voltage sensor V_PIN does not decrease due to the discharge of the first smoothing capacitor C1, the control unit 10 determines that the first contactor M / C has failed and issues an abnormality notification.

[0073] If the control unit 10 determines that the first contactor M / C is not faulty, it turns off the first semiconductor switch S / C_A at the timing when the discharge of the first smoothing capacitor C1 is completed and checks the detected voltage value of the second voltage sensor V_BAT. If the detected voltage value of the second voltage sensor V_BAT does not decrease, the control unit 10 determines that any of the first to third semiconductor switches S / C_A, S / C_B, S / C_C is faulty and issues an abnormality notification.

[0074] When the control unit 10 determines that there is no failure in the first to third semiconductor switches S / C_A, S / C_B, and S / C_C, it ends the operating sequence during running.

[0075] FIG. 16 is a diagram showing the current flow during first voltage charging (800 V charging) of an electric vehicle equipped with the energy storage system 1 of the second embodiment, and FIG. 19 is a diagram showing the operation sequence during first voltage charging (800 V charging) of an electric vehicle equipped with the energy storage system 1 of the second embodiment.

[0076] When a charging plug is connected to the charging terminals 131P, 131N, the control unit 10 performs CAN communication with the charging equipment to identify the charging voltage. When the charging voltage is the first voltage (800V), the control unit 10 turns on the first contactor M / C, and then turns on the first semiconductor switch S / C_A through an intermittent ON period by PWM control, and then turns it to a continuous ON state, connecting the circuit in the battery 2 to the first voltage state (800V). This causes the first smoothing capacitor C1 to be precharged, and the detected voltage values ​​of the first voltage sensor V_PIN and the second voltage sensor V_BAT gradually increase. Then, when the precharging of the first smoothing capacitor C1 is completed, the battery 2 is in a state in which charging with the first voltage (800V) can be started.

[0077] After that, the control unit 10 turns on the third contactor QC / C_A and the fourth contactor QC / C_B to start charging the battery 2 with the first voltage (800 V). At this time, the accessories 4 are connected to the DC power supply circuits 13P, 13N via the accessory drive circuits 12P, 12N and the first contactor M / C, and are driven by the first voltage (800 V) supplied from the charging facility.

[0078] On the other hand, when the control unit 10 determines that a charging stop signal has been input, it turns off the third contactor QC / C_A and the fourth contactor QC / C_B and checks the detected voltage value of the third voltage sensor V_QC. If the detected voltage value of the third voltage sensor V_QC does not decrease, the control unit 10 determines that the third contactor QC / C_A and the fourth contactor QC / C_B are faulty and issues an abnormality notification.

[0079] If the control unit 10 determines that the third contactor QC / C_A and the fourth contactor QC / C_B are not malfunctioning, it turns off the first contactor M / C and checks the detected voltage value of the first voltage sensor V_PIN. If the detected voltage value of the first voltage sensor V_PIN does not decrease due to the discharge of the first smoothing capacitor C1, the control unit 10 determines that the first contactor M / C is malfunctioning and issues an abnormality notification.

[0080] If the control unit 10 determines that the first contactor M / C is not faulty, it turns off the first semiconductor switch S / C_A at the timing when the discharge of the first smoothing capacitor C1 is completed and checks the detected voltage value of the second voltage sensor V_BAT. If the detected voltage value of the second voltage sensor V_BAT does not decrease, the control unit 10 determines that any of the first to third semiconductor switches S / C_A, S / C_B, S / C_C is faulty and issues an abnormality notification.

[0081] When the control unit 10 determines that there is no failure in the first to third semiconductor switches S / C_A, S / C_B, and S / C_C, it ends the operation sequence during charging with the first voltage (800V).

[0082] FIG. 17 is a diagram showing the current flow during second voltage charging (400 V charging) of an electric vehicle equipped with the energy storage system 1 of the second embodiment, and FIG. 20 is a diagram showing the operation sequence during second voltage charging (400 V charging) of an electric vehicle equipped with the energy storage system 1 of the second embodiment.

[0083] When a charging plug is connected to the charging terminals 131P, 131N, the control unit 10 performs CAN communication with the charging equipment to identify the charging voltage. When the charging voltage is the second voltage (400V), the control unit 10 turns on the fifth contactor QC / C_C, and then turns on the second semiconductor switch S / C_B and the third semiconductor switch S / C_C through an intermittent ON period by PWM control, and then turns them to a continuous ON state, connecting the circuit in the battery 2 to the second voltage state (400V). This precharges the first smoothing capacitor C1, and the detected voltage values ​​of the first voltage sensor V_PIN and the second voltage sensor V_BAT gradually increase.

[0084] In addition, the control unit 10 enables the boost circuit formed by the three-phase motor 3 and the inverter 5, and then turns on the third contactor QC / C_A and the fourth contactor QC / C_B. This puts the battery 2 in a state in which charging with the second voltage (400V) can begin. In addition, the three-phase motor 3 and the inverter 5 connected to the DC power supply circuits 13P and 13N via the branch circuit 14 can boost the second voltage (400V) supplied from the charging facility to the first voltage (800V) to drive the auxiliary equipment 4.

[0085] On the other hand, when the control unit 10 determines that a charging stop signal has been input, it turns off the third contactor QC / C_A and the fourth contactor QC / C_B and checks the detected voltage value of the third voltage sensor V_QC. If the detected voltage value of the third voltage sensor V_QC does not decrease, the control unit 10 determines that the third contactor QC / C_A and the fourth contactor QC / C_B are faulty and issues an abnormality notification.

[0086] If the control unit 10 determines that the third contactor QC / C_A and the fourth contactor QC / C_B are not faulty, it stops boosting the voltage by the three-phase motor 3 and the inverter 5, turns off the fifth contactor QC / C_C, and checks the detected voltage value of the first voltage sensor V_PIN. If the detected voltage value of the first voltage sensor V_PIN does not decrease, the control unit 10 determines that the fifth contactor QC / C_C is faulty and issues an abnormality alert.

[0087] If the control unit 10 determines that the fifth contactor QC / C_C is not faulty, it turns off the second semiconductor switch S / C_B and the third semiconductor switch S / C_C and checks the detected voltage value of the second voltage sensor V_BAT. If the detected voltage value of the second voltage sensor V_BAT does not decrease, the control unit 10 determines that one of the first to third semiconductor switches S / C_A, S / C_B, S / C_C is faulty and issues an abnormality alert.

[0088] When the control unit 10 determines that there is no failure in the first to third semiconductor switches S / C_A, S / C_B, and S / C_C, it ends the operation sequence during charging with the second voltage (400V).

[0089] Next, a modified example of the power storage system 1 of the first embodiment will be described. Note that the same reference numerals as in the first embodiment are used for configurations common to the first embodiment, and descriptions are omitted, and only changes will be described.

[0090] FIG. 21 is a diagram showing the configuration of a modified example of the power storage system 1 of the first embodiment. In the power storage system 1 of the first embodiment shown in Fig. 1, the first contactor M / C is disposed at the end on the positive electrode side of the battery 2, and the current breaker FUSE is disposed at the end on the negative electrode side of the battery 2, but in this modification, as shown in Fig. 21, the first contactor M / C is disposed on the negative electrode side of the battery 2, and the current breaker FUSE is disposed on the positive electrode side of the battery 2. Furthermore, as a configuration of the battery 2, a second contactor VS / C, a third contactor QC / C_A, a fourth contactor QC / C_B, a fifth contactor QC / C_C, a third voltage sensor V_QC, and a second voltage sensor V_BAT are disposed on the end side of the first contactor M / C and the current breaker FUSE.

[0091] 1, when the power supply to the battery 2 is to be cut off in the event of a failure of the battery 2, in other words, when cutting off the supply of power to the outside of the battery 2, it is necessary to turn off the first contactor M / C arranged at the end on the positive electrode side of the battery 2 and to cut off the current breaker FUSE arranged at the end on the negative electrode side of the battery 2. Once the current breaker FUSE is cut off, it must be replaced.

[0092] In this modification, when cutting off the power supply to the battery 2, the second contactor VS / C and the third contactor QC / C_A, which are arranged on the positive electrode side of the battery 2 and closer to the end than the current breaker FUSE, are turned OFF, and the first contactor M / C, which is arranged on the negative electrode side of the battery 2, is turned OFF, thereby making it possible to cut off the power supply to the battery 2 without cutting off the current breaker FUSE. Thus, according to this modification, when cutting off the power supply to the battery 2, it is sufficient to control the contactors ON / OFF, so that the control can be simplified and replacement of the current breaker FUSE can be eliminated.

[0093] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present invention. Furthermore, the components in the above-mentioned embodiments may be arbitrarily combined within the scope of the invention.

[0094] For example, in the above embodiment, the control unit 10 performs CAN communication with the charging equipment, but the communication method is not limited to CAN communication, and any communication method can be adopted.

[0095] This specification describes at least the following items. Note that, in parentheses, components corresponding to those in the above-mentioned embodiment are shown, but the present invention is not limited to these.

[0096] (1) a battery (battery 2) including a first power storage unit (first power storage unit 21), a second power storage unit (second power storage unit 22), and a first switch unit capable of switching between a first voltage state in which the first power storage unit and the second power storage unit are connected in series and can be charged at a first voltage and a second voltage state in which the first power storage unit and the second power storage unit are connected in parallel and can be charged at a second voltage; a three-phase motor (three-phase motor 3) in which three-phase coils (coils 32U, 32V, 32W) are connected at a neutral point (neutral point 31) and driven by power supplied from the battery; an inverter (inverter 5) connected on a power transmission path (power supply circuits 11P, 11N) between the battery and the three-phase motor; a DC power supply circuit (DC power supply circuits 13P, 13N) connected to a first connection portion (connection portion 111P, 111N) located on a power transmission path between the inverter and the battery; a capacitor (first smoothing capacitor C1) provided on the power transmission path between the battery and the three-phase motor; a branch circuit (branch circuit 14) that branches off from the DC power supply circuit on the positive electrode side and is connected to one of the three-phase coils; The first switch unit is a power storage system including semiconductor switches (a first semiconductor switch S / C_A, a second semiconductor switch S / C_B, and a third semiconductor switch S / C_C).

[0097] According to (1), whether the external charging equipment is a system that charges at a first voltage or a system that charges at a second voltage, by switching the connection mode of the first power storage unit and the second power storage unit with the first switch unit, it is possible to appropriately charge according to the voltage state of the charging equipment. In other words, since charging can be performed without passing through a voltage converter, it is possible to avoid efficiency degradation due to a voltage converter and to make a voltage converter for charging unnecessary. In addition, the positive-side DC power supply circuit connected to the connection part located on the power transmission path between the inverter and the battery has a branch circuit connected to the coil of one of the three-phase motor phases, so voltage conversion can be performed using the three-phase motor and the inverter. This makes it possible to eliminate the need for a dedicated voltage converter even if the voltage state of the charging equipment and the operating voltage of the auxiliary equipment, etc. are different, and reduces manufacturing costs. Furthermore, by configuring the first switch section to include a semiconductor switch, a precharge circuit can be eliminated, compared to a configuration including a contactor, and the volume and weight of the battery circuit can be reduced.

[0098] (2) The storage system according to (1), A control unit (control unit 10) is provided to control the first switch unit, The control unit performs PWM control on the first switch unit when precharging the capacitor.

[0099] According to (2), the capacitor can be precharged by PWM controlling the semiconductor switch.

[0100] (3) The storage system according to (1) or (2), The battery includes: A positive electrode side path (positive electrode side path K1) of the first storage unit; A positive electrode side path (positive electrode side path K2) of the second storage unit; a positive electrode side node (positive electrode side node N1) to which the positive electrode side path of the first power storage unit and the positive electrode side path of the second power storage unit are connected in parallel; A negative electrode side path (negative electrode side path K3) of the first power storage unit; A negative electrode side path (negative electrode side path K4) of the second power storage unit; a negative electrode side node (negative electrode side node N2) to which the negative electrode side path of the first power storage unit and the negative electrode side path of the second power storage unit are connected in parallel; a series connection path (series connection path K5) that connects the negative electrode side path of the first power storage unit and the positive electrode side path of the second power storage unit; a negative electrode side connection node (negative electrode side connection node N3) at which the series connection path and the negative electrode side path of the first power storage unit are connected; a positive electrode side connection node (positive electrode side connection node N4) to which the series connection path and the positive electrode side path of the second power storage unit are connected, The first switch unit is a first semiconductor switch (first semiconductor switch S / C_A) disposed in the series connection path; a second semiconductor switch (second semiconductor switch S / C_B) disposed between the positive electrode side node and the positive electrode side connection node; a third semiconductor switch (third semiconductor switch S / C_C) disposed between the negative electrode side node and the negative electrode side connection node; a first reactor (first reactor L1) arranged between the positive electrode side connection node and the positive electrode of the second power storage unit; a second reactor (second reactor L2) arranged between the negative electrode side connection node and the negative electrode of the first power storage unit,

[0101] According to (3), when starting up at the first voltage, two reactors are connected in series, and when starting up at the second voltage, one reactor is connected to each path, and the reactors are appropriately arranged depending on the voltage.

[0102] (4) The storage system according to (1) or (2), The branch circuit is connected to a coil of one of the three phase coils at a second connection portion (connection portion 34) via a second switch portion (fifth contactor QC / C_C).

[0103] According to (4), when no voltage conversion is performed in the three-phase motor, that is, when the coil of the three-phase motor is not used as a transformer, the connection to the second connection part can be cut off.

[0104] (5) The storage system according to (1) or (2), an auxiliary device (auxiliary device 4) that can be driven by the battery and DC power from an external power source; an accessory drive circuit (accessory drive circuits 12P, 12N) connected on a power transmission path between the inverter and the first connection part and supplying power to the accessory; The auxiliary device operates at the first voltage.

[0105] According to (5), voltage conversion is not required when driving or charging at the first voltage.

[0106] (6) The storage system according to (5), The auxiliary device is connected to the battery via a third switch unit (the second contactor VS / C in the first embodiment, and the first contactor M / C in the second embodiment).

[0107] According to (6), when voltage conversion is performed using a three-phase motor, i.e., when the coil of a three-phase motor is used as a transformer, the third switch unit can be used to separate the parts in the first voltage state and the parts in the second voltage state.

[0108] (7) The storage system according to (1) or (2), A control unit (control unit 10) is provided to control the first switch unit and the inverter, The control unit boosts the voltage supplied from the branch circuit to the three-phase motor by the inverter to the first voltage when charging the battery with the second voltage.

[0109] According to (7), voltage conversion can be performed using a three-phase motor and an inverter, making a voltage converter for auxiliary equipment unnecessary. [Explanation of symbols]

[0110] 1. Energy storage system 2 Battery 21 First power storage unit 22 Second storage unit 3 Three-phase motor 10 Control section 31 Neutral point 32U, 32V, 32W coil 34 Connection part (second connection part) 4 Auxiliary Equipment 5. Inverter 111P, 111N Connection (first connection) 11P, 11N Power supply circuit (power transmission path) 12P, 12N Auxiliary drive circuit 13P, 13N DC power supply circuit 14 Branch Circuit S / C_A 1st semiconductor switch (1st switch section) S / C_B Second semiconductor switch (first switch section) S / C_C 3rd semiconductor switch (1st switch section) M / C 1st contactor (3rd switch section) VS / C 2nd contactor (3rd switch part) QC / C_C 5th Contactor (2nd Switch) C1 First smoothing capacitor (capacitor) L1 First reactor (first switch section) L2 Second reactor (first switch section)

Claims

1. a battery including a first power storage unit, a second power storage unit, and a first switch unit capable of switching between a first voltage state in which the first power storage unit and the second power storage unit are connected in series and can be charged at a first voltage and a second voltage state in which the first power storage unit and the second power storage unit are connected in parallel and can be charged at a second voltage; a three-phase motor having three-phase coils connected at a neutral point and driven by power supplied from the battery; an inverter connected on a power transmission path between the battery and the three-phase motor; a DC power supply circuit connected to a first connection portion located on a power transmission path between the inverter and the battery; a capacitor provided on the power transmission path between the battery and the three-phase motor; a branch circuit that branches off from the DC power supply circuit on the positive electrode side and is connected to one of the three-phase coils, The first switch unit includes a semiconductor switch.

2. The power storage system according to claim 1 , A control unit that controls the first switch unit, The control unit performs PWM control on the first switch unit when precharging the capacitor.

3. The power storage system according to claim 1 or 2, The battery includes: A positive electrode side path of the first power storage unit; A positive electrode side path of the second power storage unit; a positive electrode side node to which the positive electrode side path of the first power storage unit and the positive electrode side path of the second power storage unit are connected in parallel; A negative electrode side path of the first power storage unit; A negative electrode side path of the second power storage unit; a negative electrode side node to which the negative electrode side path of the first power storage unit and the negative electrode side path of the second power storage unit are connected in parallel; a series connection path that connects a negative electrode side path of the first power storage unit and a positive electrode side path of the second power storage unit; a negative electrode side connection node to which the series connection path and a negative electrode side path of the first power storage unit are connected; a positive electrode side connection node to which the series connection path and a positive electrode side path of the second power storage unit are connected, The first switch unit is a first semiconductor switch disposed in the series connection path; a second semiconductor switch disposed between the positive electrode side node and the positive electrode side connection node; a third semiconductor switch disposed between the negative electrode side node and the negative electrode side connection node; a first reactor arranged between the positive electrode side connection node and a positive electrode of the second power storage unit; a second reactor disposed between the negative electrode side connection node and the negative electrode of the first power storage unit.

4. The power storage system according to claim 1 or 2, the branch circuit is connected to one of the three-phase coils at a second connection section via a second switch section.

5. The power storage system according to claim 1 or 2, an auxiliary device that can be driven by DC power from the battery and an external power source; an auxiliary drive circuit connected on a power transmission path between the inverter and the first connection portion and supplying power to the auxiliary; The auxiliary device operates at the first voltage.

6. The power storage system according to claim 5, The auxiliary device is connected to the battery via a third switch unit.

7. The power storage system according to claim 1 or 2, a control unit that controls the first switch unit and the inverter, The control unit boosts the voltage supplied from the branch circuit to the three-phase motor by the inverter to the first voltage when charging the battery with the second voltage.

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