Power conversion device and program

Abstract

A power conversion device comprises: a transformer circuit (11, 20, 73, 111, 120A, 120B, 240) that transforms a DC output voltage of a supply source power storage unit and supplies the transformed DC voltage to a supply destination power storage unit, said supply source power storage unit being one of a first power storage unit (31, 131, 231) and a second power storage unit (32, 132, 232), and said supply destination power storage unit being the other power storage unit; a command value calculation unit that calculates a command value (Ich1, Ich2, Idis1, Idis2) for a current flowing to at least one of the supply source power storage unit and the supply destination power storage unit; and a circuit control unit that performs switching control of the transformer circuit on the basis of the calculated command value. The command value calculation unit calculates the command value on the basis of an output upper limit value, which is either the upper limit output power or the upper limit output current of the supply source power storage unit, and an input upper limit value, which is either the upper limit input power or the upper limit input current of the supply destination power storage unit.

Description

Power conversion device and program CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2023-099577, filed on June 16, 2023, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a power conversion device and a program.

[0003] A power conversion device applied to a system including a first power storage unit and a second power storage unit has been known. The power conversion device includes a transformer circuit that transforms a DC output voltage of a source power storage unit, which is one of the first power storage unit and the second power storage unit, and supplies the transformed DC voltage to a destination power storage unit, which is the other power storage unit. An example of such a power conversion device is described in Patent Document 1.

[0004] JP 2011-18532 A

[0005] In the power conversion device, a technique is desired that can prevent the power of at least one of the first and second power storage units from exceeding the upper limit power.

[0006] A primary object of the present disclosure is to provide a power conversion device and a program that can prevent the power of at least one of a first and a second power storage unit from exceeding an upper limit power.

[0007] The present disclosure relates to a power conversion device applied to a system including a first power storage unit and a second power storage unit, the power conversion device including: a transformer circuit that transforms a DC output voltage of a source power storage unit that is one of the first power storage unit and the second power storage unit, and supplies the transformed DC voltage to a destination power storage unit that is the other power storage unit; a command value calculation unit that calculates a command value for a current flowing in at least one of the source power storage unit and the destination power storage unit; and a circuit control unit that performs switching control of the transformer circuit based on the calculated command value.

[0008] The command value calculation unit calculates the command value based on an output upper limit value, which is either an upper limit output power or an upper limit output current of the supply source power storage unit, and an input upper limit value, which is either an upper limit input power or an upper limit input current of the supply destination power storage unit.

[0009] According to the power conversion device of the present disclosure in which such a method for calculating a command value is employed, it is possible to prevent the power of at least one of the first and second power storage units from exceeding the upper limit power.

[0010] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. 11 is a diagram showing the control state of the switches during high-voltage power supply according to the third embodiment, FIG. 12 is a diagram showing the control state of the switches during low-voltage power supply, FIG. 13 is a functional block diagram of the battery ECU and the EVECU, FIG. 14 is a flowchart showing the procedure of the external power supply control process, and FIG. 15 is a flowchart showing the procedure of the external power supply control process according to the fourth embodiment. 16 is a flowchart showing the procedure of the ratio setting process, FIG. 17 is a diagram showing the control state of the switches during equalization control according to the fifth embodiment, FIG. 18 is a flowchart showing the procedure of the equalization control process, FIG. 19 is an overall configuration diagram of the system according to the sixth embodiment, FIG. 20 is a diagram showing the control state of the switches during high-voltage charging, FIG. 21 is a diagram showing the control state of the switches during low-voltage charging, FIG. 22 is a flowchart showing the procedure of the external charging control process, FIG. 23 is a flowchart showing the procedure of the external charging control process according to the seventh embodiment, FIG. 24 is a flowchart showing the procedure of the ratio setting process, FIG. 25 is a diagram showing the control state of the switches during high-voltage power feeding according to the eighth embodiment, FIG. 26 is a diagram showing the control state of the switches during low-voltage power feeding, FIG. 27 is a flowchart showing the procedure of the external power feeding control process, FIG. 28 is a flowchart showing the procedure of the external power feeding control process according to the ninth embodiment, FIG. 29 is a flowchart showing the procedure of the ratio setting process, and FIG.FIG. 31 is a diagram showing the control state of switches during equalization control according to the tenth embodiment, FIG. 31 is a flowchart showing the procedure of equalization control processing, FIG. 32 is a functional block diagram of a battery ECU and an EVECU according to another embodiment, FIG. 33 is a functional block diagram of a battery ECU and an EVECU according to another embodiment, FIG. 34 is an overall configuration diagram of a system according to another embodiment, FIG. 35 is an overall configuration diagram of a system according to another embodiment, and FIG. 36 is an overall configuration diagram of a system according to another embodiment.

[0011] Several embodiments will be described with reference to the drawings. In several embodiments, functionally and / or structurally corresponding and / or associated parts may be designated by the same reference numerals or reference numerals that differ in the hundredth or more digit. For corresponding and / or associated parts, reference may be made to the descriptions of other embodiments.

[0012] A first embodiment of a power conversion device according to the present disclosure will now be described with reference to the drawings. The power conversion device of this embodiment is mounted on a vehicle such as an electric vehicle or a hybrid vehicle, and forms an in-vehicle system.

[0013] As shown in FIG. 1 , the power conversion device includes a motor 10, an inverter 20, a high-potential side path 22H, and a low-potential side path 22L. The motor 10 is a three-phase synchronous machine that includes star-connected armature windings 11 of U, V, and W phases, and a rotor (not shown). The armature windings 11 of each phase are arranged with an electrical angle offset of 120°. The motor 10 is, for example, a permanent magnet synchronous machine. The rotor is capable of transmitting power to the drive wheels of the vehicle. Therefore, the motor 10 serves as a source of torque for propelling the vehicle.

[0014] The inverter 20 includes three phases of series-connected upper-arm switches SWH and lower-arm switches SWL. An upper-arm diode DH, which is a freewheeling diode, is connected in antiparallel to the upper-arm switch SWH, and a lower-arm diode DL, which is also a freewheeling diode, is connected in antiparallel to the lower-arm switch SWL. In this embodiment, each of the switches SWH and SWL is an IGBT.

[0015] The inverter 20 includes a smoothing capacitor 21. A long high-potential side path 22H is connected to a high-potential side terminal of the smoothing capacitor 21. A long low-potential side path 22L is connected to a low-potential side terminal of the smoothing capacitor 21. The high-potential side path 22H and the low-potential side path 22L are, for example, electrical paths such as bus bars. The smoothing capacitor 21 may be provided outside the inverter 20.

[0016] In each phase, a first end of the armature winding 11 is connected to a connection point between an emitter serving as a low potential terminal of the upper arm switch SWH and a collector serving as a high potential terminal of the lower arm switch SWL via a conductive member 23 such as a bus bar. Second ends of the armature windings 11 of each phase are connected to each other at a neutral point O. In this embodiment, the armature windings 11 of each phase are set to have the same number of turns. As a result, the armature windings 11 of each phase are set to have the same inductance, for example.

[0017] A high potential side path 22H is connected to the collector of the upper arm switch SWH of each phase, and a low potential side path 22L is connected to the emitter of the lower arm switch SWL of each phase.

[0018] The system includes a first storage battery 31 (corresponding to the "first power storage unit") and a second storage battery 32 (corresponding to the "second power storage unit"). Each storage battery 31, 32 serves as a power supply source for rotating the rotor of the motor 10. Each storage battery 31, 32 is an assembled battery including a series connection of multiple unit batteries. A unit battery is a single battery cell, which is a single cell, or a series connection of multiple battery cells. In this embodiment, the unit batteries constituting the first storage battery 31 and the second storage battery 32 have the same full charge capacity (specifically, for example, rated full charge capacity) [Ah]. The positive terminal of the first storage battery 31 is connected to the high-potential side path 22H via a first fuse 41, and the negative terminal of the second storage battery 32 is connected to the low-potential side path 22L via a second fuse 42. The terminal voltages (e.g., rated voltages) of the battery cells constituting the assembled battery are set to be the same, for example. The battery cells are, for example, secondary batteries such as lithium-ion batteries. In this embodiment, the terminal voltage (e.g., rated voltage) of the first storage battery 31 is higher than the terminal voltage (e.g., rated voltage) of the second storage battery 32. This configuration can be realized, for example, by making the number of unit batteries constituting the first storage battery 31 greater than the number of unit batteries constituting the second storage battery 32.

[0019] The power conversion device includes main switches for electrically connecting or disconnecting the first and second storage batteries 31, 32 from the inverter 20. Specifically, the main switches include a high-side main switch SMRH, a low-side main switch SMRL, and a pre-charge main switch SMRP. In this embodiment, the main switches SMRH, SMRL, and SMRP are mechanical relays. When turned off, the main switches SMRH, SMRL, and SMRP block bidirectional current flow, and when turned on, allow bidirectional current flow. The high-side main switch SMRH is provided in the high-side path 22H, and the low-side main switch SMRL is provided in the low-side path 22L. A series connection of the pre-charge main switch SMRP and a pre-charge resistor 40 is connected in parallel to the low-side main switch SMRL. The main switches SMRH, SMRL, and SMRP are not limited to mechanical relays, and may be semiconductor switching elements, for example.

[0020] Each of the storage batteries 31 and 32 can be charged by an external charger provided outside the vehicle through external charging control. The external charger is, for example, a stationary charger.

[0021] Each of the storage batteries 31, 32 can supply power to a power supply target outside the vehicle through external power supply control. When the power supply target is a grid power supply, the external power supply control is also called V2G (Vehicle to Grid). When the power supply target is an electrical device in a building such as a residence, the external power supply control is also called V2H (Vehicle to Home).

[0022] The power conversion device includes a high-potential-side connection switch DCRH and a low-potential-side connection switch DCRL for electrically connecting or disconnecting an external charger or a power supply target unit to or from the first and second storage batteries 31, 32. In this embodiment, each of the connection switches DCRH and DCRL is a mechanical relay. When turned off, each of the connection switches DCRH and DCRL blocks bidirectional current flow, and when turned on, allows bidirectional current flow. The high-potential-side connection switch DCRH is provided in a portion of the high-potential-side path 22H closer to the inverter 20 than the high-potential-side main switch SMRH. The low-potential-side connection switch DCRL is provided in a portion of the low-potential-side path 22L closer to the inverter 20 than the low-potential-side main switch SMRL. Note that each of the connection switches DCRH and DCRL is not limited to a mechanical relay, and may be, for example, a semiconductor switching element.

[0023] The power conversion device includes an inter-battery switch 50 (corresponding to an "inter-power storage unit switch"), a bypass switch 60, a first motor-side switch 71, a second motor-side switch 72, and a connection path 73 as components for switching the connection state of the first storage battery 31 and the second storage battery 32. In this embodiment, the inter-battery switch 50, the bypass switch 60, and the motor-side switches 71 and 72 are mechanical relays. When turned off, the inter-battery switch 50, the bypass switch 60, and the motor-side switches 71 and 72 block bidirectional current flow, and when turned on, allow bidirectional current flow. Note that the inter-battery switch 50, the bypass switch 60, and the motor-side switches 71 and 72 are not limited to mechanical relays and may be, for example, semiconductor switching elements.

[0024] The inter-battery switch 50 connects the negative terminal of the first storage battery 31 and the positive terminal of the second storage battery 32. When the inter-battery switch 50 is turned on, the negative terminal of the first storage battery 31 and the positive terminal of the second storage battery 32 are electrically connected. When the inter-battery switch 50 is turned off, the negative terminal of the first storage battery 31 and the positive terminal of the second storage battery 32 are electrically disconnected.

[0025] The bypass switch 60 connects the negative terminal of the first storage battery 31 and the low potential side path 22L. When the bypass switch 60 is turned on, the negative terminal of the first storage battery 31 and the negative terminal of the second storage battery 32 are electrically connected. When the bypass switch 60 is turned off, the negative terminal of the first storage battery 31 and the negative terminal of the second storage battery 32 are electrically disconnected.

[0026] In this embodiment, the first storage battery 31 and the second storage battery 32 constitute a battery unit 30 .

[0027] The connection path 73 is an electrical path that connects the positive terminal of the second storage battery 32 and the neutral point O. The connection path 73 is provided with a first motor-side switch 71 and a second motor-side switch 72 in this order from the second storage battery 32.

[0028] The power conversion device includes a neutral point capacitor 74 that is a capacitor that connects the connection path 73 and the low potential side path 22L. A first end of the neutral point capacitor 74 is connected to a portion of the connection path 73 between the first motor side switch 71 and the second motor side switch 72. A second end of the neutral point capacitor 74 is connected to a portion of the low potential side path 22L that is closer to the inverter 20 than the low potential side main switch SMRL and the pre-charge main switch SMRP.

[0029] When the first motor-side switch 71 is turned on, the first end of the neutral point capacitor 74 is electrically connected to the positive terminal of the second storage battery 32. On the other hand, when the first motor-side switch 71 is turned off, the first end of the neutral point capacitor 74 is electrically disconnected from the positive terminal of the second storage battery 32. When the second motor-side switch 72 is turned on, the neutral point O of the armature winding 11 is electrically connected to the first end of the neutral point capacitor 74. On the other hand, when the second motor-side switch 72 is turned off, the neutral point O is electrically disconnected from the first end of the neutral point capacitor 74.

[0030] The power conversion device includes current sensors that detect the current flowing through each part of the power conversion device itself, including a first current sensor 81, a second current sensor 82, a phase current sensor 83, and a motor current sensor 84. The first current sensor 81 detects the current flowing through the first storage battery 31, and the second current sensor 82 detects the current flowing through the second storage battery 32. The phase current sensor 83 detects the current flowing through the armature winding 11 of each phase. The motor current sensor 84 detects the current flowing through the connection path 73, and in this embodiment, detects the current flowing through a portion of the connection path 73 that is closer to the neutral point O than the connection point with the neutral point capacitor 74.

[0031] The power conversion device includes a capacitor voltage sensor 85 that detects the terminal voltage of the neutral point capacitor 74, a first voltage sensor 86 that detects the terminal voltage of the first storage battery 31, and a second voltage sensor 87 that detects the terminal voltage of the second storage battery 32. The first voltage sensor 86 detects, for example, the terminal voltage of each unit battery that constitutes the first storage battery 31, and the second voltage sensor 87 detects, for example, the terminal voltage of each unit battery that constitutes the second storage battery 32. The power conversion device also includes a power supply voltage sensor 89 that detects the terminal voltage of the smoothing capacitor 21.

[0032] The power conversion device includes a temperature sensor 88 that detects the temperatures of the first storage battery 31 and the second storage battery 32. The temperature sensor 88 detects, for example, the temperature of each unit battery that constitutes the first storage battery 31 and the temperature of each unit battery that constitutes the second storage battery 32. The power conversion device also includes, as another sensor, a rotation angle sensor (not shown) that detects the rotation angle (electrical angle) of the rotor.

[0033] The system includes a battery ECU 90 that controls the battery unit 30, and an EVECU 100 that controls the inverter 20. The battery ECU 90 is an electronic control unit that mainly comprises a microcomputer 91. The EVECU 100 is an electronic control unit that mainly comprises a microcomputer 101. The battery ECU 90 and the EVECU 100 can exchange information via a communication unit such as CAN communication.

[0034] Each microcomputer 91, 101 includes a central processing unit (CPU). The functions of each microcomputer 91, 101 can be provided by software stored in a physical memory device and a computer executing the software, software alone, hardware alone, or a combination thereof. For example, when each microcomputer 91, 101 is provided by a hardware electronic circuit, the function can be provided by a digital circuit including multiple logic circuits or an analog circuit. For example, each microcomputer 91, 101 executes a program stored in a non-transitory tangible storage medium serving as its own storage unit. The program includes, for example, a program for the process shown in FIG. 5 (described later). A set of instructions constituting the program is executed to perform a method corresponding to the program. The storage unit is, for example, a non-volatile memory. The program stored in the storage unit can be updated via a communication network such as the Internet, for example, via OTA (Over the Air).

[0035] The battery ECU 90 receives detection values ​​from the first current sensor 81, the second current sensor 82, the first voltage sensor 86, the second voltage sensor 87, and the temperature sensor 88. The battery ECU 90 calculates the SOC of each unit battery that constitutes the first storage battery 31 based on the detection values ​​of the first voltage sensor 86, the first current sensor 81, and the temperature sensor 88. The battery ECU 90 calculates the SOC of each unit battery that constitutes the second storage battery 32 based on the detection values ​​of the second voltage sensor 87, the second current sensor 82, and the temperature sensor 88.

[0036] The EVECU 100 receives detection values ​​from a phase current sensor 83, a motor current sensor 84, a capacitor voltage sensor 85, a power supply voltage sensor 89, and a rotation angle sensor. Based on the detection values ​​received from each sensor, the EVECU 100 performs switching control of the switches SWH and SWL constituting the inverter 20 to feedback control the control variable of the motor 10 to a command value. The control variable is, for example, torque. In each phase, the upper arm switch SWH and the lower arm switch SWL are alternately turned on. As a result, the rotational power of the rotor of the motor 10 is transmitted to the drive wheels, causing the vehicle to run.

[0037] The main switches SMRH, SMRL, SMRP, the connection switches DCRH, DCRL, the inter-battery switch 50, the bypass switch 60, and the motor-side switches 71, 72 may be controlled by either the battery ECU 90 or the EVECU 100. In this embodiment, for convenience, it is assumed that the main switches SMRH, SMRL, SMRP, the connection switches DCRH, DCRL, the inter-battery switch 50, the bypass switch 60, the first motor-side switch 71, and the second motor-side switch 72 are controlled by the EVECU 100.

[0038] Next, the external charging control will be described.

[0039] In this embodiment, the external charger is a high-voltage charger 200 or a low-voltage charger 210, as shown in FIGS. 2 and 3 . The charging voltage of the high-voltage charger 200 is higher than the inter-terminal voltage (specifically, the rated voltage) of the series-connected first and second storage batteries 31, 32, e.g., 800 V. The charging voltage of the low-voltage charger 210 is lower than the inter-terminal voltage of the series-connected first and second storage batteries 31, 32 and higher than the inter-terminal voltage (specifically, the rated voltage) of the first storage battery 31, e.g., 400 V. When the first and second storage batteries 31, 32 are being charged by the external charger, the high-potential-side connection switch DCRH and the low-potential-side connection switch DCRL are switched on. On the other hand, when charging by the external charger is not being performed or the external charger is not connected to the power conversion device, the high-potential-side connection switch DCRH and the low-potential-side connection switch DCRL are switched off.

[0040] 2 shows the control state of each switch during external charging control using the high-voltage charger 200. The vehicle user electrically connects the charging plug of the high-voltage charger 200 to the connection switches DCRH and DCRL, thereby electrically connecting the high-voltage charger 200 to the power conversion device. When the EVECU 100 determines that the external charger connected to the power conversion device is the high-voltage charger 200, it turns off the pre-charge main switch SMRP, the bypass switch 60, the first motor-side switch 71, the second motor-side switch 72, and the upper and lower arm switches SWH and SWL of all phases of the inverter 20, and turns on the high-potential-side main switch SMRH, the low-potential-side main switch SMRL, and the inter-battery switch 50. This results in the first storage battery 31 and the second storage battery 32 being connected in series to the high-voltage charger 200. As a result, current flows through a closed circuit including the high-voltage charger 200, the high-potential side path 22H, the first storage battery 31, the inter-battery switch 50, the second storage battery 32, and the low-potential side path 22L, and the first storage battery 31 and the second storage battery 32 are charged in a series-connected state. At this time, because the upper arm switch SWH of the inverter 20 and the second motor-side switch 72 are turned off, it is possible to prevent the charging current of the high-voltage charger 200 from flowing to the inverter 20 and the armature winding 11.

[0041] 3 shows the control state of each switch during external charging control using the low-voltage charger 210. When the vehicle user electrically connects the charging plug of the low-voltage charger 210 to each connection switch DCRH, DCRL, the low-voltage charger 210 and the power conversion device are electrically connected. When the EVECU 100 determines that the external charger connected to the power conversion device is the low-voltage charger 210, it turns off the pre-charge main switch SMRP and the inter-battery switch 50 and turns on the high-potential-side main switch SMRH, the low-potential-side main switch SMRL, the bypass switch 60, the first motor-side switch 71, and the second motor-side switch 72. As a result, current flows through a closed circuit including the low-voltage charger 210, the high-potential-side path 22H, the first storage battery 31, the bypass switch 60, and the low-potential-side path 22L, and the first storage battery 31 is charged.

[0042] In the external charging control by the low-voltage charger 210, the EVECU 100 performs switching control to alternately turn on the upper and lower arm switches SWH, SWL of at least one phase, or performs switching control to switch on the upper arm switch SWH of at least one phase while keeping the lower arm switches SWL of all phases of the inverter 20 off, thereby stepping down the output voltage of the low-voltage charger 210 and supplying it to the second storage battery 32. More specifically, the EVECU 100 performs step-down control, which is the switching control described above, to control the voltage detected by the capacitor voltage sensor 85 (hereinafter referred to as the neutral point capacitor voltage VN) to a target charging voltage. As a result, a current flows through a closed circuit including the low-voltage charger 210, the high-potential side path 22H, the upper arm switch SWH of the inverter 20, the armature winding 11, the neutral point O, the second motor-side switch 72, the first motor-side switch 71, the second storage battery 32, and the low-potential side path 22L, and the second storage battery 32 is charged. Since the terminal voltage of the second storage battery 32 is lower than the terminal voltage of the first storage battery 31 , the target charging voltage of the second storage battery 32 is lower than the target charging voltage of the first storage battery 31 .

[0043] In this embodiment, the first storage battery 31 corresponds to the “source power storage unit,” and the second storage battery 32 corresponds to the “destination power storage unit.” The armature winding 11, the inverter 20, and the connection path 73 correspond to the “transformer circuit.”

[0044] During external charging control by the low-voltage charger 210, the external charging control may suddenly stop due to some factor. For example, the external charging control may suddenly stop if a failure occurs in a component of the low-voltage charger 210 or a power conversion device related to the external charging control, or if the charging plug is unplugged by a user during external charging control. In this case, current continues to flow from the first storage battery 31 to the second storage battery 32 via the inverter 20, the armature winding 11, and the connection path 73 until the switching control of the inverter 20 stops, thereby drawing power from the first storage battery 31. As a result, the discharge power of the first storage battery 31 increases, which may cause over-discharge of the first storage battery 31 and result in failure of the first storage battery 31. Therefore, in this embodiment, the charging current of the second storage battery 32 is set so as to prevent over-discharge of the first storage battery 31. The setting method is described below.

[0045] FIG. 4 is a functional block diagram of the battery ECU 90 and the EVECU 100.

[0046] The battery ECU 90 is equipped with a first input power calculation unit 92A, a first output power calculation unit 92B, a second input power calculation unit 93A, and a second output power calculation unit 93B as processing units that calculate parameters related to the charging and discharging of the first storage battery 31 and the second storage battery 32.

[0047] The first input power calculation unit 92A calculates the first upper limit input power Win1 based on the battery state of the first storage battery 31. The first upper limit input power Win1 is the maximum value of power that can be input to the first storage battery 31. The battery state of the first storage battery 31 includes, for example, the temperature of the first storage battery 31 detected by the temperature sensor 88 and the SOC of the first storage battery 31. For example, the first input power calculation unit 92A calculates a smaller first upper limit input power Win1 as the SOC of the first storage battery 31 increases or the temperature of the first storage battery 31 decreases. The SOC used in calculating the first upper limit input power Win1 may be, for example, the maximum value of the SOC of each unit battery constituting the first storage battery 31 or the average value of the SOC of each unit battery.

[0048] The first output power calculation unit 92B calculates the first upper limit output power Wout1 based on the battery state of the first storage battery 31. The first upper limit output power Wout1 is the maximum value of power that can be output from the first storage battery 31. For example, the first output power calculation unit 92B calculates a larger first upper limit output power Wout1 the higher the SOC of the first storage battery 31 or the higher the temperature of the first storage battery 31 detected by the temperature sensor 88. The SOC used in calculating the first upper limit output power Wout1 may be, for example, the minimum value of the SOC of the unit batteries that make up the first storage battery 31 or the average value of the SOC of the unit batteries.

[0049] The second input power calculation unit 93A calculates the second upper limit input power Win2 based on the battery state of the second storage battery 32. The second upper limit input power Win2 is the maximum value of power that can be input to the second storage battery 32. The battery state of the second storage battery 32 includes, for example, the temperature of the second storage battery 32 detected by the temperature sensor 88 and the SOC of the second storage battery 32. For example, the second input power calculation unit 93A calculates a smaller second upper limit input power Win2 as the SOC of the second storage battery 32 increases or the temperature of the second storage battery 32 decreases. The SOC used in calculating the second upper limit input power Win2 may be, for example, the maximum value of the SOC of each unit battery constituting the second storage battery 32 or the average value of the SOC of each unit battery.

[0050] The second output power calculation unit 93B calculates the second upper limit output power Wout2 based on the battery state of the second storage battery 32. The second upper limit output power Wout2 is the maximum value of power that can be output from the second storage battery 32. For example, the second output power calculation unit 93B calculates a larger second upper limit output power Wout2 as the SOC of the second storage battery 32 increases or the temperature of the second storage battery 32 detected by the temperature sensor 88 increases. The SOC used in calculating the second upper limit output power Wout2 may be, for example, the minimum value of the SOC of the unit batteries that make up the second storage battery 32 or the average value of the SOC of the unit batteries.

[0051] The EVECU 100 includes a first charging current calculation unit 102A, a second charging current calculation unit 102B, an inverter instruction unit 103, and an external charger instruction unit 104.

[0052] The first charging current calculation unit 102A calculates a first command charging current Ich1, which is a command value for the charging current of the first storage battery 31, based on the calculated first upper limit input power Win1 and the first detected voltage VH, which is the voltage detected by the first voltage sensor 86. In this embodiment, the first charging current calculation unit 102A calculates the first command charging current Ich1 (=Win1 / VH) by dividing the first upper limit input power Win1 by the first detected voltage VH. For example, if the first upper limit input power Win1 is 20 kW and the first detected voltage VH is 400 V, the first command charging current Ich1 is 50 A.

[0053] The second charging current calculation unit 102B calculates a second command charging current Ich2, which is a command value for the charging current of the second storage battery 32, based on the calculated second upper limit input power Win2, the second detected voltage VL, which is the voltage detected by the second voltage sensor 87, and the calculated first upper limit output power Wout1. In this embodiment, the second command charging current Ich2 corresponds to the "destination command charging current." The reason why the first upper limit output power Wout1 of the first storage battery 31 is used to calculate the charging current of the second storage battery 32 is to prevent the output power of the first storage battery 31 from exceeding the first upper limit output power Wout1 even when external charging control is suddenly stopped, thereby preventing over-discharge of the first storage battery 31.

[0054] The second charging current calculation unit 102B first selects the second upper limit input power Win2 (corresponding to the "input upper limit") or the first upper limit output power Wout1 (corresponding to the "output upper limit"), whichever has the smaller absolute value, as the reference power Wstd. The second charging current calculation unit 102B then divides the selected reference power Wstd by the second detected voltage VL to calculate the second command charging current Ich2 (=Wstd / VL). For example, if the first upper limit output power Wout1 is 5 kW, the second upper limit input power Win2 is 10 kW, and the second detected voltage VL is 200 V, the reference power Wstd is 5 kW, and the second command charging current Ich2 is 25 A (=5 kW / 200 V).

[0055] The inverter command unit 103 performs step-down control of the inverter 20 to control the current flowing through the second storage battery 32 to the calculated second command charging current Ich2. Specifically, for example, the inverter command unit 103 performs step-down control of the inverter 20 to control the motor current IN, which is the current detected by the second current sensor 82 or the current detected by the motor current sensor 84, to the second command charging current Ich2.

[0056] Based on the calculated first and second command charging currents Ich1 and Ich2 and the first and second detected voltages VH and VL, the external charger instructing unit 104 calculates the external command charging current Icht, which is a command value for the charging current output from the low-voltage charger 210. The first and second detected voltages VH and VL are used in order to take into account the voltage drop due to the step-down control.

[0057] The external charger instructing unit 104 first calculates the first command conversion current Ichc1 based on the second command charging current Ich2 and the first and second detected voltages VH and VL. Specifically, the external charger instructing unit 104 calculates the first command conversion current Ichc1 based on "Ichc1 = Ich2 × VL / VH." For example, if the first detected voltage VH is 400 V, the second detected voltage VL is 200 V, and the second command charging current Ich2 is 25 A, the first command conversion current Ichc1 is 12.5 A (= 25 A × 200 V / 400 V).

[0058] The external charger instructing unit 104 calculates an external command charging current Icht (e.g., 62.5 A) by adding the calculated first command conversion current Ichc1 (e.g., 12.5 A) to the first command charging current Ich1 (e.g., 50 A). The external charger instructing unit 104 transmits the calculated external command charging current Icht to the low-voltage charger 210. As a result, the low-voltage charger 210 is controlled so that the output current of the low-voltage charger 210 becomes the external command charging current Icht.

[0059] 5 is a flowchart showing the procedure of the external charging control process of the low-voltage charger 210. This process is executed repeatedly, for example, at a predetermined control period, by cooperation between the EVECU 100 and the battery ECU 90.

[0060] In step S10 , the battery ECU 90 calculates a first upper limit input power Win1 , a first upper limit output power Wout1 , a second upper limit input power Win2 , and a second upper limit output power Wout2 , and transmits these to the EVECU 100 .

[0061] In step S11, the EVECU 100 calculates a first command charging current Ich1 and a second command charging current Ich2. In this embodiment, the process of step S11 corresponds to a "command value calculation unit."

[0062] The EVECU 100 calculates the external command charging current Icht in step S12, and transmits the external command charging current Icht to the low-voltage charger 210 in step S13. In this embodiment, the process of step S12 corresponds to an "external command value calculation unit."

[0063] In step S14, the EVECU 100 performs step-down control of the inverter 20 to control the current flowing through the second storage battery 32 to the second command charging current Ich2. In this embodiment, the process of step S14 corresponds to the "circuit control unit".

[0064] In step S15, the EVECU 100 determines whether the external charging control has ended. If the EVECU 100 determines that the external charging control has not ended, the EVECU 100 determines in step S16 whether the direction of the current flowing to the first storage battery 31 is a direction that charges the first storage battery 31. This determination process is a process for determining whether the external charging control has been suddenly stopped. If the external charging control is suddenly stopped, the direction of the current flowing to the first storage battery 31 switches from a direction that charges the first storage battery 31 to a direction that discharges the first storage battery 31. The EVECU 100 may determine the direction of the current flowing to the first storage battery 31 based on, for example, the current detected by the first current sensor 81.

[0065] The EVECU 100 continues the external charging control when it determines that the direction of the current flowing through the first storage battery 31 is the direction that charges the first storage battery 31. On the other hand, when it determines that the direction of the current flowing through the first storage battery 31 is the direction that discharges the first storage battery 31, the EVECU 100 determines in step S17 that an abnormality that causes the external charging control to suddenly stop has occurred.

[0066] In step S18, the EVECU 100 performs fail-safe processing. In this embodiment, as the fail-safe processing, the EVECU 100 stops the step-down control (switching control) of the inverter 20, and after the current flowing through the high-potential side main switch SMRH and the low-potential side main switch SMRL becomes zero, performs processing to switch off each of the main switches SMRH and SMRL. This makes it possible to prevent welding of each of the main switches SMRH and SMRL.

[0067] In step S19, the EVECU 100 identifies that a failure has occurred in any of the components of the power conversion device, including the connection switches DCRH and DCRL, or the components from the connection switches DCRH and DCRL to the charging plug. This identification information is stored in the memory of the EVECU 100. As a result, when the vehicle is subsequently repaired, for example, at a repair shop, the location of the failure in the power conversion device can be quickly identified using a diagnostic tool, and the failed part can be quickly replaced. After completing the processing of step S19, the EVECU 100 ends the external charging control.

[0068] In this embodiment, the processes in steps S16 to S19 correspond to an "abnormality processing unit."

[0069] Fig. 6 shows an example of each waveform when external charging control of the low-voltage charger 210 is executed. In Fig. 6, SOC1 is the SOC of the unit battery that constitutes the first storage battery 31, and SOC2 is the SOC of the unit battery that constitutes the second storage battery 32. Wr1 is the actual charge / discharge power of the first storage battery 31, and Wr2 is the actual charge / discharge power of the second storage battery 32. In Fig. 6, the sign of each power is positive on the discharge side and negative on the charge side.

[0070] When external charging control is started, a first command charging current Ich1 is calculated based on the first upper limit input power Win1 and the first detected voltage VH, and the charging current of the first storage battery 31 is controlled to the first command charging current Ich1. As the first storage battery 31 is charged, the SOC1 gradually increases, and the terminal voltage of the first storage battery 31 gradually increases. As the SOC1 gradually increases, the magnitude of the first upper limit input power Win1 gradually decreases, and the magnitude of the first upper limit output power Wout1 gradually increases.

[0071] Meanwhile, the second command charging current Ich2 is calculated based on the second upper limit input power Win2, the second detected voltage VL, and the first upper limit output power Wout1. As the second storage battery 32 is charged, the SOC2 gradually increases, and the voltage across the terminals of the second storage battery 32 gradually increases. As the SOC2 gradually increases, the magnitude of the second upper limit input power Win2 gradually decreases, and the magnitude of the second upper limit output power Wout2 gradually increases.

[0072] At time t1, external charging control is suddenly stopped for some reason, and power supply from the low-voltage charger 210 to the first storage battery 31 is stopped. Here, the second command charging current Ich2 of the second storage battery 32 is calculated based on the second upper limit input power Win2 or the first upper limit output power Wout1, whichever has the smaller absolute value. Therefore, the discharge current of the first storage battery 31 does not become excessively large due to charging of the second storage battery 32, and it is possible to prevent the discharge power Wr1 of the first storage battery 31 from exceeding the first upper limit output power Wout1. This makes it possible to prevent the first storage battery 31 from malfunctioning.

[0073] Then, the fail-safe process is started, the step-down control of the inverter 20 is stopped at time t2, and the high-side main switch SMRH and the low-side main switch SMRL are switched off at time t3. In the example shown in Fig. 6, during the period from when the external charging control is suddenly stopped until when the step-down control of the inverter 20 is stopped, the discharge power Wr1 of the first storage battery 31 does not exceed the first upper-limit output power Wout1.

[0074] 7 shows an example of waveforms when external charging control according to a comparative example is executed. Unlike the present embodiment, the comparative example does not use the first upper limit output power Wout1 to calculate the second command charging current Ich2. That is, the second command charging current Ich2 is calculated as "Win2 / VL." In this case, if the external charging control is suddenly stopped at time t1, the discharge power Wr1 of the first storage battery 31 may greatly exceed the first upper limit output power Wout1, potentially causing a malfunction of the first storage battery 31.

[0075] 5, the EVECU 100 may stop the step-down control of the inverter 20 after switching off the high-side main switch SMRH and the low-side main switch SMRL. This allows the discharge of the first storage battery 31 to be stopped quickly.

[0076] The second command charging current Ich2 may be calculated as a value smaller than "Wstd / VL." The first command charging current Ich1 may be calculated as a value smaller than "Win1 / VH."

[0077] Second Embodiment Hereinafter, a second embodiment will be described with reference to the drawings, focusing on differences from the first embodiment. In this embodiment, the distribution ratio of the output current of the low-voltage charger 210 to the first and second storage batteries 31, 32 is adjusted based on the first upper limit output power Wout1 of the first storage battery 31, the second upper limit input power Win2 of the second storage battery 32, and the SOCs of the first and second storage batteries 31, 32.

[0078] 8 is a flowchart showing the procedure of the external charging control process of the low-voltage charger 210. This process is executed repeatedly, for example, at a predetermined control period, by cooperation between the EVECU 100 and the battery ECU 90.

[0079] After step S10, the EVECU 100 performs a ratio setting process in step S20. Fig. 9 is a flowchart showing the procedure of the ratio setting process. In this embodiment, the process in step S20 corresponds to the "command value calculation unit."

[0080] In step S21, the EVECU 100 determines whether the absolute value of the first upper limit output power Wout1 is smaller than the absolute value of the second upper limit input power Win2.

[0081] If the EVECU 100 determines that the absolute value of the first upper limit output power Wout1 is smaller than the absolute value of the second upper limit input power Win2, the EVECU 100 proceeds to step S22. In step S22, the EVECU 100 imposes the conditions that the charging power of the first storage battery 31 is set to be equal to or less than the first upper limit input power Win1 and the charging power of the second storage battery 32 is set to be equal to or less than the second upper limit input power Win2, and calculates the first command charging current Ich1 to be greater than the second command charging current Ich2. As a result, the charging power of the first storage battery 31 becomes greater than the charging power of the second storage battery 32. In this embodiment, the first command charging current Ich1 corresponds to the "supply source command charging current."

[0082] Over-discharge due to a sudden stop of external charging control occurs in the first storage battery 31, not the second storage battery 32. To prevent over-discharge of the first storage battery 31, it is necessary to increase the first upper limit output power Wout1 of the first storage battery 31 as quickly as possible. In consideration of this, the process of step S22 is provided to prioritize charging of the first storage battery 31 over the second storage battery 32. In this embodiment, the EVECU 100 calculates the first command charging current Ich1 based on the first upper limit input power Win1 and the first detected voltage VH. Specifically, for example, the first command charging current Ich1 may be set to "Win1 / VH." Furthermore, the EVECU 100 sets the second command charging current Ich2 to zero.

[0083] When the EVECU 100 determines that the absolute value of the first upper limit output power Wout1 is equal to or greater than the absolute value of the second upper limit input power Win2, the EVECU 100 calculates a charging rate difference ΔSOC and determines whether the calculated charging rate difference ΔSOC is greater than a determination threshold value Sth in step S23. The charging rate difference ΔSOC is a value obtained by subtracting the SOC2 of the unit battery constituting the second storage battery 32 from the SOC1 of the unit battery constituting the first storage battery 31.

[0084] If the EVECU 100 determines that the difference in the charging rates ΔSOC is greater than the determination threshold value Sth, the EVECU 100 proceeds to step S24. In step S24, the EVECU 100 imposes the conditions that the charging power of the first storage battery 31 is set to be equal to or less than the first upper limit input power Win1 and the charging power of the second storage battery 32 is set to be equal to or less than the second upper limit input power Win2, and calculates the second command charging current Ich2 to be greater than the first command charging current Ich1. As a result, the charging power of the second storage battery 32 becomes greater than the charging power of the first storage battery 31. The processing of step S24 is processing for reducing the difference between the SOC of each unit battery constituting the first storage battery 31 and the SOC of each unit battery constituting the second storage battery 32 as quickly as possible. In this embodiment, the EVECU 100 calculates the second command charging current Ich2 based on the second upper limit input power Win2 and the second detected voltage VL, and specifically, for example, the second command charging current Ich2 may be set to "Win2 / VL".

[0085] When the EVECU 100 determines that the difference in the charging rates ΔSOC is equal to or less than the determination threshold value Sth, the EVECU 100 sets the first command charging current Ich1 and the second command charging current Ich2 to the same value by imposing the conditions that the charging power of the first storage battery 31 is equal to or less than the first upper limit input power Win1 and the charging power of the second storage battery 32 is equal to or less than the second upper limit input power Win2 in step S25. This prevents the difference between the SOC of each unit battery constituting the first storage battery 31 and the SOC of each unit battery constituting the second storage battery 32 from becoming too large.

[0086] After the processing of step S22, S24, or S25, returning to the description of Fig. 8 , in step S12, the EVECU 100 calculates the external command charging current Icht by adding the first command charging current Ich1 and the second command charging current Ich2 calculated in the processing of Fig. 9. In step S13, the EVECU 100 transmits the external command charging current Icht to the low-voltage charger 210. In step S14, the second command charging current Ich2 calculated in the processing of Fig. 9 is used for voltage step-down control of the inverter 20.

[0087] FIG. 10 shows an example of each waveform when external charging control of the low-voltage charger 210 is executed.

[0088] After the external charging control is started, the EVECU 100 determines that the absolute value of the first upper limit output power Wout1 is smaller than the absolute value of the second upper limit input power Win2. As a result, the EVECU 100 calculates the first command charging current Ich1 to be greater than the second command charging current Ich2. At time t1, the EVECU 100 determines that the absolute value of the first upper limit output power Wout1 is equal to or greater than the absolute value of the second upper limit input power Win2. Then, the EVECU 100 determines that the difference ΔSOC in the charging rates is greater than the determination threshold Sth. As a result, the EVECU 100 calculates the second command charging current Ich2 to be greater than the first command charging current Ich1.

[0089] At time t2, the EVECU 100 determines that the difference ΔSOC in the charging rates is equal to or less than the determination threshold value Sth, and thereby sets the first command charging current Ich1 and the second command charging current Ich2 to the same value.

[0090] According to the present embodiment described above, it is possible to reduce the risk of over-discharging of the first storage battery 31 due to a sudden stop of external charging control, while shortening the charging period of the first and second storage batteries 31, 32.

[0091] <Modification of Second Embodiment> In step S22 of FIG. 9, the second command charging current Ich2 may be set to a value greater than zero.

[0092] Third Embodiment Hereinafter, a third embodiment will be described with reference to the drawings, focusing on differences from the first embodiment. In this embodiment, during external power supply control, overcharging of the first storage battery 31 due to a sudden stop of the external power supply control is suppressed.

[0093] 11 shows the control state of each switch during external power supply control in which power is supplied from the first and second storage batteries 31, 32 to the high-voltage power supply target unit 220. When the EVECU 100 determines that the power supply target unit connected to the power conversion device is the high-voltage power supply target unit 220, it turns off the pre-charge main switch SMRP, the bypass switch 60, the first motor-side switch 71, the second motor-side switch 72, and the upper and lower arm switches SWH, SWL of all phases of the inverter 20, and turns on the connection switches DCRH, DCRL, the high-potential-side main switch SMRH, the low-potential-side main switch SMRL, and the inter-battery switch 50. This results in the first storage battery 31 and the second storage battery 32 being connected in series to the high-voltage power supply target unit 220. Therefore, current flows through a closed circuit including the first storage battery 31, the high-voltage side path 22H, the high-voltage power supply target portion 220, the low-voltage side path 22L, and the second storage battery 32, and power is supplied from the first storage battery 31 and the second storage battery 32 to the high-voltage power supply target portion 220.

[0094] 12 shows the control states of each switch during external power supply control in which power is supplied from the first and second storage batteries 31, 32 to the low-voltage power supply target unit 230. The rated voltage of the low-voltage power supply target unit 230 is lower than the rated voltage of the high-voltage power supply target unit 220. When the EVECU 100 determines that the power supply target unit connected to the power conversion device is the low-voltage power supply target unit 230, it turns off the pre-charge main switch SMRP and the inter-battery switch 50 and turns on the connection switches DCRH, DCRL, the high-potential-side main switch SMRH, the low-potential-side main switch SMRL, the bypass switch 60, the first motor-side switch 71, and the second motor-side switch 72. As a result, current flows through a closed circuit including the first storage battery 31, the high-potential-side path 22H, the low-voltage power supply target unit 230, the low-potential-side path 22L, and the bypass switch 60, and power is supplied from the first storage battery 31 to the low-voltage power supply target unit 230.

[0095] In the external power supply control for the low-voltage power supply target 230, the EVECU 100 performs switching control to alternately turn on the upper and lower arm switches SWH, SWL of at least one phase, or performs switching control to switch on the lower arm switch SWL of at least one phase while keeping the upper arm switches SWH of all phases of the inverter 20 off, thereby boosting the output voltage of the second storage battery 32 and supplying it to the low-voltage power supply target 230. More specifically, the EVECU 100 performs boost control, which is the switching control for controlling the power supply voltage VB, which is the voltage detected by the power supply voltage sensor 89, to a target power supply voltage. As a result, a current flows through a closed circuit including the second storage battery 32, the connection path 73, the armature winding 11, the inverter 20, the high-potential-side path 22H, the low-voltage power supply target 230, and the low-potential-side path 22L, and power is supplied from the second storage battery 32 to the low-voltage power supply target 230.

[0096] In this embodiment, the second storage battery 32 corresponds to the "source power storage unit," and the first storage battery 31 corresponds to the "destination power storage unit."

[0097] However, during the external power supply control for the low-voltage power supply target unit 230, the external power supply control may suddenly stop due to some factor. In this case, current continues to be output from the second storage battery 32 to the first storage battery 31 via the inverter 20 until the switching control of the inverter 20 stops. As a result, the first storage battery 31 may be overcharged, causing a breakdown of the first storage battery 31. Therefore, in this embodiment, the discharge current of the second storage battery 32 is set so as not to cause the first storage battery 31 to be overcharged. A method for setting this current will be described below.

[0098] FIG. 13 is a functional block diagram of the battery ECU 90 and the EVECU 100.

[0099] The EVECU 100 includes a first discharge current calculation unit 105A and a second discharge current calculation unit 105B. The first discharge current calculation unit 105A calculates a first command discharge current Idis1, which is a command value for the discharge current of the first storage battery 31, based on the first upper limit output power Wout1 and the first detected voltage VH. In this embodiment, the first discharge current calculation unit 105A calculates the first command discharge current Idis1 (=Wout1 / VH) by dividing the first upper limit output power Wout1 by the first detected voltage VH.

[0100] The second discharge current calculation unit 105B calculates a second command discharge current Idis2, which is a command value for the discharge current of the second storage battery 32, based on the first upper limit input power Win1 in addition to the second upper limit output power Wout2 and the second detected voltage VL. In this embodiment, the second command discharge current Idis2 corresponds to the "supply source command discharge current." The reason why the first upper limit input power Win1 of the first storage battery 31 is used to calculate the discharge current of the second storage battery 32 is to prevent the input power of the first storage battery 31 from exceeding the first upper limit input power Win1 even when the external power supply control is suddenly stopped, thereby preventing overcharging of the first storage battery 31.

[0101] The second discharge current calculation unit 105B first selects the second upper limit output power Wout2 (corresponding to the "output upper limit value") or the first upper limit input power Win1 (corresponding to the "input upper limit value"), whichever has the smaller absolute value, as the reference power Wstd. The second discharge current calculation unit 105B then divides the selected reference power Wstd by the second detection voltage VL to calculate the second command discharge current Idis2 (=Wstd / VL).

[0102] The inverter instruction unit 103 performs boost control of the inverter 20 to control the current flowing through the second storage battery 32 (for example, the detected current of the second current sensor 81B or the motor current IN) to the calculated second command discharge current Idis2.

[0103] The external power supply instructing unit 104D calculates the external command discharge current Idist, which is a command value of the discharge current to be supplied from each of the storage batteries 31 and 32 to the low-voltage power supply target unit 230, based on the calculated first and second command discharge currents Idis1 and Idis2 and the first and second detected voltages VH and VL. The first and second detected voltages VH and VL are used in order to take into account the voltage increase due to the voltage step-up control.

[0104] The external power supply instructing unit 104D first calculates the first command conversion current Idisc1 based on the second command discharge current Idis2 and the first and second detected voltages VH and VL. Specifically, the external power supply instructing unit 104D calculates the first command conversion current Idisc1 based on "Idisc1 = Idis2 × VL / VH". The external power supply instructing unit 104D calculates the external command discharge current Idist by adding the first command discharge current Idis1 to the calculated first command conversion current Idisc1. The external power supply instructing unit 104D transmits the calculated external command discharge current Idist to the low-voltage power supply target unit 230. As a result, the low-voltage power supply target unit 230 is controlled so that the input current of the low-voltage power supply target unit 230 becomes the external command discharge current Idist.

[0105] 14 is a flowchart showing the procedure of the external power supply control process for the low-voltage power supply target unit 230. This process is executed repeatedly, for example, at a predetermined control period by cooperation between the EVECU 100 and the battery ECU 90.

[0106] In step S30, the battery ECU 90 calculates the first upper limit input power Win1, the first upper limit output power Wout1, the second upper limit input power Win2, and the second upper limit output power Wout2, and transmits them to the EVECU 100.

[0107] In step S31, the EVECU 100 calculates a first command discharge current Idis1 and a second command discharge current Idis2. In this embodiment, the process of step S31 corresponds to a "command value calculation unit."

[0108] The EVECU 100 calculates the external command discharge current Idist in step S32, and transmits the external command discharge current Idist to the low-voltage power supply target unit 230 in step S33. In this embodiment, the process of step S32 corresponds to an "external command value calculation unit."

[0109] In step S34, the EVECU 100 performs boost control of the inverter 20 to control the current flowing through the second storage battery 32 to the second command discharge current Idis2. In this embodiment, the process of step S34 corresponds to the "circuit control unit".

[0110] In step S35, the EVECU 100 determines whether the external power supply control has ended. If the EVECU 100 determines that the external power supply control has not ended, the EVECU 100 determines in step S36 whether the direction of the current flowing to the first storage battery 31 is a direction in which the first storage battery 31 is discharging. This determination process is a process for determining whether the external power supply control has been suddenly stopped. If the external power supply control has been suddenly stopped, the direction of the current flowing to the first storage battery 31 switches from a direction in which the first storage battery 31 is discharging to a direction in which the first storage battery 31 is charging. The EVECU 100 may determine the direction of the current flowing to the first storage battery 31 based on, for example, the current detected by the first current sensor 81.

[0111] The EVECU 100 continues the external power supply control when it determines that the direction of the current flowing through the first storage battery 31 is a direction discharging the first storage battery 31. On the other hand, when it determines that the direction of the current flowing through the first storage battery 31 is a direction charging the first storage battery 31, it determines in step S37 that an abnormality has occurred that causes the external power supply control to suddenly stop.

[0112] In step S38, the EVECU 100 performs a fail-safe process. In this embodiment, the EVECU 100 stops the voltage step-up control (switching control) of the inverter 20, and after the current flowing through the high-potential side main switch SMRH and the low-potential side main switch SMRL becomes zero, the EVECU 100 performs a process of switching off the main switches SMRH and SMRL.

[0113] In step S39, the EVECU 100 identifies that a failure has occurred in any of the components of the power conversion device, including the connection switches DCRH and DCRL, and the components extending from the connection switches DCRH and DCRL to the low-voltage power supply target unit 230. This identification information is stored in the memory of the EVECU 100. As a result, when the vehicle is subsequently repaired, for example, at a repair shop, the location of the failure in the power conversion device can be quickly identified using a diagnostic tool, and the failed part can be quickly replaced. After completing the processing of step S39, the EVECU 100 ends the external power supply control.

[0114] In this embodiment, the processes of steps S36 to S39 correspond to an "abnormality processing unit."

[0115] According to the present embodiment described above, even if the external power supply control is suddenly stopped, the charging power of the first storage battery 31 can be prevented from exceeding the first upper limit input power Win1, thereby preventing overcharging of the first storage battery 31.

[0116] 14 , the EVECU 100 may stop the boost control of the inverter 20 after switching off the high potential side main switch SMRH and the low potential side main switch SMRL. This allows the charging of the first storage battery 31 to be stopped quickly.

[0117] The second commanded discharge current Idis2 may be calculated as a value smaller than "Wstd / VL." The first commanded discharge current Idis1 may be calculated as a value smaller than "Wout1 / VH."

[0118] Fourth Embodiment Hereinafter, a fourth embodiment will be described with reference to the drawings, focusing on differences from the third embodiment. In this embodiment, the distribution ratio of the currents supplied from the first and second storage batteries 31 and 32 to the low-voltage power supply target section 230 is adjusted.

[0119] 15 is a flowchart showing the procedure of the external power supply control process for the low-voltage power supply target unit 230. This process is executed repeatedly, for example, at a predetermined control period by cooperation between the EVECU 100 and the battery ECU 90.

[0120] After step S30, the EVECU 100 performs a ratio setting process in step S40. Fig. 16 is a flowchart showing the procedure of the ratio setting process. In this embodiment, the process in step S40 corresponds to the "command value calculation unit."

[0121] In step S41, the EVECU 100 determines whether the absolute value of the first upper limit input power Win1 is smaller than the absolute value of the second upper limit output power Wout2.

[0122] If the EVECU 100 determines that the absolute value of the first upper limit input power Win1 is smaller than the absolute value of the second upper limit output power Wout2, the EVECU 100 proceeds to step S42. In step S42, the EVECU 100 imposes the conditions that the discharge power of the first storage battery 31 is equal to or less than the first upper limit output power Wout1 and the discharge power of the second storage battery 32 is equal to or less than the second upper limit output power Wout2, and calculates the first command discharge current Idis1 to be greater than the second command discharge current Idis2. In this embodiment, the first command discharge current Idis1 corresponds to the "destination command discharge current."

[0123] Overcharging due to a sudden stop of external power supply control occurs in the first storage battery 31, not the second storage battery 32. To prevent overcharging of the first storage battery 31, it is necessary to increase the first upper limit input power Win1 of the first storage battery 31 as quickly as possible. In consideration of this, the process of step S42 is provided to prioritize discharging of the first storage battery 31 over the second storage battery 32. In this embodiment, the EVECU 100 calculates the first commanded discharge current Idis1 based on the first upper limit output power Wout1 and the first detected voltage VH. Specifically, for example, the first commanded discharge current Idis1 may be set to "Wout1 / VH." Furthermore, the EVECU 100 sets the second commanded discharge current Idis2 to zero.

[0124] When the EVECU 100 determines that the absolute value of the first upper limit input power Win1 is equal to or greater than the absolute value of the second upper limit output power Wout2, the EVECU 100 calculates the charging rate difference ΔSOC and determines whether the calculated charging rate difference ΔSOC is greater than the determination threshold value Sth in step S43. The charging rate difference ΔSOC is a value obtained by subtracting the SOC1 of the unit battery constituting the first storage battery 31 from the SOC2 of the unit battery constituting the second storage battery 32.

[0125] If the EVECU 100 determines that the difference in the charging rates ΔSOC is greater than the determination threshold value Sth, the EVECU 100 proceeds to step S44. In step S44, the EVECU 100 imposes the conditions that the discharge power of the first storage battery 31 is set to be equal to or less than the first upper limit output power Wout1 and the discharge power of the second storage battery 32 is set to be equal to or less than the second upper limit output power Wout2, and calculates the second command discharge current Idis2 to be greater than the first command discharge current Idis1. As a result, the discharge power of the second storage battery 32 is greater than the discharge power of the first storage battery 31. The processing of step S44 is processing for suppressing an increase in the difference between the SOC of each unit battery constituting the first storage battery 31 and the SOC of each unit battery constituting the second storage battery 32. In this embodiment, the EVECU 100 calculates the second command discharge current Idis2 based on the second upper limit output power Wout2 and the second detected voltage VL, and specifically, for example, the second command discharge current Idis2 may be set to "Wout2 / VL".

[0126] When the EVECU 100 determines that the difference ΔSOC in the charging rates is equal to or less than the determination threshold value Sth, the EVECU 100 sets the first command discharge current Idis1 and the second command discharge current Idis2 to the same value by imposing the conditions that the discharge power of the first storage battery 31 is equal to or less than the first upper limit output power Wout1 and the discharge power of the second storage battery 32 is equal to or less than the second upper limit output power Wout2 in step S45. This prevents the difference between the SOC of each unit battery constituting the first storage battery 31 and the SOC of each unit battery constituting the second storage battery 32 from becoming too large.

[0127] After the processing of step S42, S44, or S45, returning to the description of Fig. 15 , in step S32, the EVECU 100 calculates the external command discharge current Idist by adding together the first command discharge current Idis1 and the second command discharge current Idis2 calculated in the processing of Fig. 16. In step S33, the EVECU 100 transmits the external command discharge current Idist to the low-voltage power supply target unit 230. In step S34, the second command discharge current Idis2 calculated in the processing of Fig. 16 is used for boost control of the inverter 20.

[0128] According to the present embodiment described above, it is possible to reduce the risk of overcharging of the first storage battery 31 due to a sudden stop of the external power supply control.

[0129] <Modification of Fourth Embodiment> In step S42 of FIG. 16, the second command discharge current Idis2 may be set to a value greater than zero.

[0130] Fifth Embodiment A fifth embodiment will be described below with reference to the drawings, focusing on differences from the above-described embodiments. In this embodiment, the EVECU 100 performs power transmission control (specifically, for example, equalization control) for transmitting power from one of the first storage battery 31 and the second storage battery 32 to the other by performing switching control of the inverter 20.

[0131] 17 shows the control state of each switch during equalization control. During equalization control, each of the connection switches DCRH and DCRL is controlled to be OFF.

[0132] The EVECU 100 turns on the high-potential-side main switch SMRH, the low-potential-side main switch SMRL, the inter-battery switch 50, the first motor-side switch 71, and the second motor-side switch 72, and turns off the pre-charge main switch SMRP and the bypass switch 60. The EVECU 100 also controls the switching of at least one phase of the inverter 20 to transfer power from one of the first storage battery 31 and the second storage battery 32 to the other.

[0133] Specifically, the EVECU 100 performs a first control to supply current from the first storage battery 31 to the second storage battery 32 via the inverter 20, the armature winding 11, and the connection path 73 by performing a step-down control for at least one phase. The EVECU 100 also performs a second control to supply current to the first storage battery 31 via the second storage battery 32, the connection path 73, the armature winding 11, and the inverter 20 by performing a step-up control for at least one phase.

[0134] By the equalization control, for example, it is possible to make the SOC of each unit battery constituting the first storage battery 31 and the SOC of each unit battery constituting the second storage battery 32 equal to each other.

[0135] 18 is a flowchart showing the procedure of the equalization control process. This process is repeatedly executed, for example, at a predetermined control interval, by the cooperation of the EVECU 100 and the battery ECU 90.

[0136] In step S50, the battery ECU 90 calculates the first upper limit input power Win1, the first upper limit output power Wout1, the second upper limit input power Win2, and the second upper limit output power Wout2, and transmits them to the EVECU 100.

[0137] In step S51, the EVECU 100 determines whether the first control is being executed, which supplies power from the first storage battery 31, which is the "source storage unit," to the second storage battery 32, which is the "destination storage unit," or the second control is being executed, which supplies power from the second storage battery 32, which is the "source storage unit," to the first storage battery 31, which is the "destination storage unit."

[0138] If the EVECU 100 determines that the first control is being executed, the EVECU 100 proceeds to step S52. In step S52, the EVECU 100 calculates a first commanded discharge current Idis1 based on the second upper limit input power Win2, the first upper limit output power Wout1, and the first detected voltage VH. Specifically, the EVECU 100 first selects, as the first reference power Wstd1, the second upper limit input power Win2 (corresponding to the "input upper limit") or the first upper limit output power Wout1 (corresponding to the "output upper limit"), whichever has the smaller absolute value. The EVECU 100 then calculates, as the first commanded discharge current Idis1, a value obtained by dividing the selected first reference power Wstd1 by the first detected voltage VH (=Wstd1 / VH), or a value smaller than this divided value.

[0139] In step S53, the EVECU 100 performs step-down control of the inverter 20 to control the current flowing through the first storage battery 31 (for example, the current detected by the first current sensor 81) to the calculated first command discharge current Idis1. This allows power to be supplied from the first storage battery 31 to the second storage battery 32 while preventing the discharge power of the first storage battery 31 from exceeding the first upper limit output power Wout1, thereby preventing over-discharge of the first storage battery 31.

[0140] On the other hand, if the EVECU 100 determines that the second control is being executed, the EVECU 100 proceeds to step S54. In step S54, the EVECU 100 calculates a second commanded discharge current Idis2 based on the first upper limit input power Win1, the second upper limit output power Wout2, and the second detected voltage VL. Specifically, the EVECU 100 first selects, as the second reference power Wstd2, the first upper limit input power Win1 (corresponding to the "input upper limit") or the second upper limit output power Wout2 (corresponding to the "output upper limit"), whichever has the smaller absolute value. The EVECU 100 then divides the selected second reference power Wstd2 by the second detected voltage VL (=Wstd2 / VL), or calculates a value smaller than this divided value, as the second commanded discharge current Idis2.

[0141] In step S53, the EVECU 100 performs step-down control of the inverter 20 to control the current flowing through the second storage battery 32 (for example, the current detected by the second current sensor 82) to the calculated second command discharge current Idis2. This allows power to be supplied from the second storage battery 32 to the first storage battery 31 while preventing the discharge power of the second storage battery 32 from exceeding the second upper limit output power Wout2, thereby preventing over-discharge of the second storage battery 32.

[0142] In this embodiment, the processes of steps S52 and S54 correspond to a "command value calculation unit," and the process of step S53 corresponds to a "circuit control unit."

[0143] Sixth Embodiment The sixth embodiment will be described below with reference to the drawings, focusing on differences from the first embodiment. In this embodiment, as shown in Fig. 19 , a connection path 73 electrically connects the neutral point O of the armature winding 11 to the negative terminal of the first storage battery 31. A bypass switch 61 connects the positive terminal of the second storage battery 32 to the high-potential-side path 22H. A first end of a neutral-point capacitor 75 is connected to a portion of the connection path 73 between the first motor-side switch 71 and the second motor-side switch 72. A second end of the neutral-point capacitor 75 is connected to a portion of the high-potential-side path 22H closer to the inverter 20 than the high-potential-side main switch SMRH.

[0144] In this embodiment, the terminal voltage (for example, rated voltage) of the first storage battery 31 is lower than the terminal voltage (for example, rated voltage) of the second storage battery 32 .

[0145] Next, the external charging control of this embodiment will be described. Figure 20 shows the control state of each switch during external charging control using the high-voltage charger 200. When the EVECU 100 determines that the external charger connected to the power conversion device is the high-voltage charger 200, it turns off the pre-charge main switch SMRP, the bypass switch 61, the first motor-side switch 71, the second motor-side switch 72, and the upper and lower arm switches SWH, SWL of all phases of the inverter 20, and turns on the high-potential side main switch SMRH, the low-potential side main switch SMRL, and the inter-battery switch 50. As a result, the first storage battery 31 and the second storage battery 32 are charged while connected in series to the high-voltage charger 200.

[0146] 21 shows the control state of each switch during external charging control using the low-voltage charger 210. When the EVECU 100 determines that the external charger connected to the power conversion device is the low-voltage charger 210, it turns off the pre-charge main switch SMRP and the inter-battery switch 50, and turns on the high-potential side main switch SMRH, the low-potential side main switch SMRL, the bypass switch 61, the first motor-side switch 71, and the second motor-side switch 72. This causes the second storage battery 32 to be charged.

[0147] In the external charging control by the low-voltage charger 210, the EVECU 100 performs switching control to alternately turn on the upper and lower arm switches SWH, SWL of at least one phase, or performs switching control to switch on the lower arm switch SWL of at least one phase while keeping the upper arm switches SWH of all phases of the inverter 20 off, thereby stepping down the output voltage of the low-voltage charger 210 and supplying it to the first storage battery 31. More specifically, the EVECU 100 performs step-down control, which is the switching control described above, to control the neutral point capacitor voltage VN to a target charging voltage. This charges the first storage battery 31. Because the terminal voltage of the first storage battery 31 is lower than the terminal voltage of the second storage battery 32, the target charging voltage of the first storage battery 31 is lower than the target charging voltage of the second storage battery 32.

[0148] In this embodiment, the second storage battery 32 corresponds to the "source power storage unit," and the first storage battery 31 corresponds to the "destination power storage unit."

[0149] However, during external charging control by the low-voltage charger 210, the external charging control may suddenly stop due to some factor. In this case, current continues to flow from the second storage battery 32 to the first storage battery 31 until the switching control of the inverter 20 stops. As a result, the discharge power of the second storage battery 32 increases, which may cause over-discharge of the second storage battery 32 and result in failure of the second storage battery 32. Therefore, in this embodiment, the charging current of the first storage battery 31 is set so as to prevent over-discharge of the second storage battery 32 from occurring.

[0150] 22 is a flowchart showing the procedure of the external charging control process of the low-voltage charger 210. This process is executed repeatedly, for example, at a predetermined control period, by cooperation between the EVECU 100 and the battery ECU 90.

[0151] In step S60, the battery ECU 90 calculates the first upper limit input power Win1, the first upper limit output power Wout1, the second upper limit input power Win2, and the second upper limit output power Wout2, and transmits them to the EVECU 100.

[0152] In step S61, the EVECU 100 calculates a first command charging current Ich1 and a second command charging current Ich2. In this embodiment, the process of step S61 corresponds to a "command value calculation unit."

[0153] Specifically, the EVECU 100 calculates the second command charging current Ich2 based on the second upper limit input power Win2 and the second detected voltage VL, and specifically sets the second command charging current Ich2 to "Win2 / VL."

[0154] The EVECU 100 calculates the first command charging current Ich1 based on the second upper limit output power Wout2 in addition to the first upper limit input power Win1 and the first detected voltage VH. In this embodiment, the first command charging current Ich1 corresponds to the "destination command charging current." Specifically, the EVECU 100 first selects the first upper limit input power Win1 (corresponding to the "input upper limit") or the second upper limit output power Wout2 (corresponding to the "output upper limit"), whichever has the smaller absolute value, as the reference power Wstd. The EVECU 100 then divides the selected reference power Wstd by the first detected voltage VH to calculate the first command charging current Ich1 (=Wstd / VH).

[0155] In step S62, the EVECU 100 calculates the external command charging current Icht based on the first and second command charging currents Ich1 and Ich2 and the first and second detected voltages VH and VL. Specifically, the EVECU 100 first calculates the second command conversion current Ichc2 based on the first command charging current Ich1 and the first and second detected voltages VH and VL. Specifically, the EVECU 100 calculates the second command conversion current Ichc2 based on the equation "Ichc2 = Ich1 × VH / VL." The EVECU 100 then adds the calculated second command conversion current Ichc2 and the second command charging current Ich2 to calculate the external command charging current Icht. In this embodiment, the process of step S62 corresponds to an "external command value calculation unit."

[0156] In step S63 , the EVECU 100 transmits the calculated external command charging current Icht to the low-voltage charger 210 .

[0157] In step S64, the EVECU 100 performs step-down control of the inverter 20 to control the charging current of the first storage battery 31 to the first command charging current Ich1. Specifically, for example, the EVECU 100 performs step-down control of the inverter 20 to control the current detected by the first current sensor 81 or the motor current IN to the first command charging current Ich1. In this embodiment, the process of step S64 corresponds to the "circuit control unit."

[0158] In step S65, the EVECU 100 determines whether the external charging control has ended. If the EVECU 100 determines that the external charging control has not ended, the EVECU 100 determines in step S66 whether the direction of the current flowing through the second storage battery 32 is a direction that charges the second storage battery 32. This determination process is a process for determining whether the external charging control has been suddenly stopped. The EVECU 100 may determine the direction of the current flowing through the second storage battery 32 based on, for example, the current detected by the second current sensor 82.

[0159] If the EVECU 100 determines that the direction of the current flowing through the second storage battery 32 is a direction that charges the second storage battery 32, the EVECU 100 continues the external charging control. On the other hand, if the EVECU 100 determines that the direction of the current flowing through the second storage battery 32 is a direction that discharges the second storage battery 32, the EVECU 100 determines in step S67 that an abnormality has occurred that causes the external charging control to suddenly stop. Thereafter, in steps S68 and S69, the EVECU 100 performs fail-safe processing and fault location identification processing, similar to steps S18 and S19 in FIG. 5 of the first embodiment. In this embodiment, the processing in steps S66 to S69 corresponds to an "abnormality processing unit."

[0160] According to the present embodiment described above, even if the external charging control is suddenly stopped, the occurrence of over-discharge of the second storage battery 32 can be suppressed.

[0161] 22 , the EVECU 100 may stop the step-down control of the inverter 20 after switching off the high-side main switch SMRH and the low-side main switch SMRL. This allows the discharge of the second storage battery 32 to be stopped quickly.

[0162] The first command charging current Ich1 may be calculated as a value smaller than "Wstd / VH." The second command charging current Ich2 may be calculated as a value smaller than "Win2 / VL."

[0163] Seventh Embodiment Hereinafter, a seventh embodiment will be described with reference to the drawings, focusing on differences from the sixth embodiment. In this embodiment, the distribution ratio of the output current of the low-voltage charger 210 to the first and second storage batteries 31, 32 is adjusted based on the second upper limit output power Wout2 of the second storage battery 32, the first upper limit input power Win1 of the first storage battery 31, and the SOCs of the first and second storage batteries 31, 32.

[0164] 23 is a flowchart showing the procedure of the external charging control process of the low-voltage charger 210. This process is executed repeatedly, for example, at a predetermined control period, by cooperation between the EVECU 100 and the battery ECU 90.

[0165] After step S60, the EVECU 100 performs a ratio setting process in step S70. Fig. 24 is a flowchart showing the procedure of the ratio setting process. In this embodiment, the process in step S70 corresponds to the "command value calculation unit."

[0166] In step S71, the EVECU 100 determines whether the absolute value of the second upper limit output power Wout2 is smaller than the absolute value of the first upper limit input power Win1.

[0167] If the EVECU 100 determines that the absolute value of the second upper limit output power Wout2 is smaller than the absolute value of the first upper limit input power Win1, the EVECU 100 proceeds to step S72. In step S72, the EVECU 100 imposes the conditions that the charging power of the first storage battery 31 is set to be equal to or less than the first upper limit input power Win1 and the charging power of the second storage battery 32 is set to be equal to or less than the second upper limit input power Win2, and calculates the second command charging current Ich2 to be larger than the first command charging current Ich1. As a result, the charging power of the second storage battery 32 becomes larger than the charging power of the first storage battery 31. In this embodiment, the second command charging current Ich2 corresponds to the "supply source command charging current."

[0168] Over-discharge due to a sudden stop of external charging control occurs in the second storage battery 32, not the first storage battery 31. To prevent over-discharge of the second storage battery 32, it is necessary to increase the second upper limit output power Wout2 of the second storage battery 32 as quickly as possible. In consideration of this, the process of step S72 is provided to prioritize charging of the second storage battery 32 over the first storage battery 31. In this embodiment, the EVECU 100 calculates the second command charging current Ich2 based on the second upper limit input power Win2 and the second detected voltage VL. Specifically, for example, the second command charging current Ich2 may be set to "Win2 / VL." Furthermore, the EVECU 100 sets the first command charging current Ich1 to zero.

[0169] When the EVECU 100 determines that the absolute value of the second upper limit output power Wout2 is equal to or greater than the absolute value of the first upper limit input power Win1, the EVECU 100 calculates the charging rate difference ΔSOC and determines whether the calculated charging rate difference ΔSOC is greater than the determination threshold value Sth in step S73. The charging rate difference ΔSOC is a value obtained by subtracting the SOC1 of the unit battery constituting the first storage battery 31 from the SOC2 of the unit battery constituting the second storage battery 32.

[0170] If the EVECU 100 determines that the difference in the state of charge ΔSOC is greater than the determination threshold Sth, the EVECU 100 proceeds to step S74. In step S74, the EVECU 100 imposes the conditions that the charging power of the first storage battery 31 is equal to or less than the first upper limit input power Win1 and the charging power of the second storage battery 32 is equal to or less than the second upper limit input power Win2, and calculates the first command charging current Ich1 to be greater than the second command charging current Ich2. As a result, the charging power of the first storage battery 31 becomes greater than the charging power of the second storage battery 32. The processing of step S74 is performed for the same purpose as the processing of step S24 in the first embodiment. In this embodiment, the EVECU 100 calculates the first command charging current Ich1 based on the first upper limit input power Win1 and the first detected voltage VH. Specifically, the first command charging current Ich1 may be set to "Win1 / VH," for example.

[0171] When the EVECU 100 determines that the difference in charging rate ΔSOC is equal to or less than the determination threshold value Sth, the EVECU 100 sets the first command charging current Ich1 and the second command charging current Ich2 to the same value by imposing the conditions that the charging power of the first storage battery 31 is equal to or less than the first upper limit input power Win1 and the charging power of the second storage battery 32 is equal to or less than the second upper limit input power Win2 in step S75. This prevents the difference between the SOC of each unit battery constituting the first storage battery 31 and the SOC of each unit battery constituting the second storage battery 32 from becoming too large.

[0172] After the processing of step S72, S74, or S75, returning to the description of Fig. 23 , in step S62, the EVECU 100 calculates the external command charging current Icht by adding the first command charging current Ich1 and the second command charging current Ich2 calculated in the processing of Fig. 24. In step S63, the EVECU 100 transmits the external command charging current Icht to the low-voltage charger 210. In step S64, the first command charging current Ich1 calculated in the processing of Fig. 24 is used for voltage step-down control of the inverter 20.

[0173] According to the present embodiment described above, it is possible to reduce the risk of over-discharging of the second storage battery 32 due to a sudden stop of external charging control, while shortening the charging period of the first and second storage batteries 31, 32.

[0174] <Modification of Seventh Embodiment> In step S72 of FIG. 24, the first command charging current Ich1 may be set to a value greater than zero.

[0175] Eighth Embodiment An eighth embodiment will be described below with reference to the drawings, focusing on differences from the sixth embodiment. In this embodiment, during external power supply control, overcharging of the second storage battery 32 due to a sudden stop of the external power supply control is suppressed.

[0176] 25 shows the control state of each switch during external power supply control in which power is supplied from the first and second storage batteries 31, 32 to the high-voltage power supply target unit 220. When the EVECU 100 determines that the power supply target unit connected to the power conversion device is the high-voltage power supply target unit 220, it turns off the pre-charge main switch SMRP, the bypass switch 61, the first motor-side switch 71, the second motor-side switch 72, and the upper and lower arm switches SWH, SWL of all phases of the inverter 20, and turns on the connection switches DCRH, DCRL, the high-potential-side main switch SMRH, the low-potential-side main switch SMRL, and the inter-battery switch 50. As a result, power is supplied from the first storage battery 31 and the second storage battery 32 to the high-voltage power supply target unit 220.

[0177] 26 shows the control state of each switch during external power supply control in which power is supplied from the first and second storage batteries 31, 32 to the low-voltage power supply target unit 230. When the EVECU 100 determines that the power supply target unit connected to the power conversion device is the low-voltage power supply target unit 230, it turns off the pre-charge main switch SMRP and the inter-battery switch 50 and turns on the connection switches DCRH, DCRL, the high-potential side main switch SMRH, the low-potential side main switch SMRL, the bypass switch 61, the first motor-side switch 71, and the second motor-side switch 72. As a result, power is supplied from the second storage battery 32 to the low-voltage power supply target unit 230.

[0178] In the external power supply control for the low-voltage power supply target portion 230, the EVECU 100 performs switching control to alternately turn on the upper and lower arm switches SWH, SWL of at least one phase, or performs switching control of the upper arm switch SWH of at least one phase while keeping the lower arm switches SWL of all phases of the inverter 20 off, thereby boosting the output voltage of the first storage battery 31 and supplying it to the low-voltage power supply target portion 230. More specifically, the EVECU 100 performs boost control, which is the switching control for controlling the power supply voltage VB to the target power supply voltage. As a result, power is supplied from the first storage battery 31 to the low-voltage power supply target portion 230.

[0179] In this embodiment, the first storage battery 31 corresponds to the "source power storage unit" and the second storage battery 32 corresponds to the "destination power storage unit."

[0180] Incidentally, during the external power supply control for the low-voltage power supply target unit 230, the external power supply control may suddenly stop due to some factor. In this case, current continues to be output from the first storage battery 31 to the second storage battery 32 via the inverter 20 until the switching control of the inverter 20 stops. As a result, the second storage battery 32 may be overcharged, causing a breakdown of the second storage battery 32. Therefore, in this embodiment, the discharge current of the first storage battery 31 is set so as to prevent the second storage battery 32 from being overcharged.

[0181] 27 is a flowchart showing the procedure of the external power supply control process for the low-voltage power supply target unit 230. This process is executed repeatedly, for example, at a predetermined control period by cooperation between the EVECU 100 and the battery ECU 90.

[0182] In step S80, the battery ECU 90 calculates the first upper limit input power Win1, the first upper limit output power Wout1, the second upper limit input power Win2, and the second upper limit output power Wout2, and transmits them to the EVECU 100.

[0183] In step S81, the EVECU 100 calculates a first command discharge current Idis1 and a second command discharge current Idis2. In this embodiment, the process of step S81 corresponds to a "command value calculation unit."

[0184] The EVECU 100 calculates the second commanded discharge current Idis2 based on the second upper limit output power Wout2 and the second detected voltage VL. In this embodiment, the EVECU 100 divides the second upper limit output power Wout2 by the second detected voltage VL to calculate the second commanded discharge current Idis2 (=Wout2 / VL).

[0185] The EVECU 100 calculates the first command discharge current Idis1 based on the first upper limit output power Wout1, the first detected voltage VH, and the second upper limit input power Win2. Specifically, the EVECU 100 first selects the first upper limit output power Wout1 (corresponding to the "output upper limit value") or the second upper limit input power Win2 (corresponding to the "input upper limit value"), whichever has the smaller absolute value, as the reference power Wstd. The EVECU 100 then divides the selected reference power Wstd by the first detected voltage VH to calculate the first command discharge current Idis1 (=Wstd / VH). In this embodiment, the first command discharge current Idis1 corresponds to the "supply source command discharge current."

[0186] In step S82, the EVECU 100 calculates the external command discharge current Idist based on the calculated first and second command discharge currents Idis1 and Idis2 and the first and second detected voltages VH and VL. In this embodiment, the process of step S82 corresponds to the "external command value calculation unit."

[0187] Specifically, the EVECU 100 first calculates the second command conversion current Idisc2 based on the first command discharge current Idis1 and the first and second detected voltages VH and VL. Specifically, the EVECU 100 calculates the second command conversion current Idisc2 based on "Idisc2 = Idis1 × VH / VL." The EVECU 100 adds the calculated second command conversion current Idisc2 to the second command discharge current Idis2 to calculate the external command discharge current Idist.

[0188] In step S83 , the EVECU 100 transmits the calculated external command discharge current Idist to the low-voltage power supply target unit 230 .

[0189] In step S84, the EVECU 100 performs boost control of the inverter 20 to control the current flowing through the first storage battery 31 (for example, the current detected by the first current sensor 81) to the first command discharge current Idis1. In this embodiment, the process of step S84 corresponds to the "circuit control unit."

[0190] In step S85, the EVECU 100 determines whether the external power supply control has ended. If the EVECU 100 determines that the external power supply control has not ended, the EVECU 100 determines in step S86 whether the direction of the current flowing to the second storage battery 32 is a direction in which the second storage battery 32 is discharging. This determination process is a process for determining whether the external power supply control has been suddenly stopped. The EVECU 100 may determine the direction of the current flowing to the second storage battery 32 based on, for example, the current detected by the second current sensor 82.

[0191] If the EVECU 100 determines that the direction of the current flowing through the second storage battery 32 is a direction discharging the second storage battery 32, the EVECU 100 continues the external power supply control. On the other hand, if the EVECU 100 determines that the direction of the current flowing through the second storage battery 32 is a direction charging the second storage battery 32, the EVECU 100 determines in step S87 that an abnormality has occurred that causes the external power supply control to suddenly stop. Thereafter, in steps S88 and S89, the EVECU 100 performs fail-safe processing and fault location identification processing, similar to steps S38 and S39 in FIG. 14 of the third embodiment. In this embodiment, the processing in steps S86 to S89 corresponds to an "abnormality processing unit."

[0192] According to the present embodiment described above, even if the external power supply control is suddenly stopped, it is possible to prevent the second storage battery 32 from being overcharged.

[0193] 27 , the EVECU 100 may stop the boost control of the inverter 20 after switching off the high potential side main switch SMRH and the low potential side main switch SMRL. This allows the charging of the second storage battery 32 to be stopped quickly.

[0194] The first commanded discharge current Idis1 may be calculated as a value smaller than "Wstd / VH." The second commanded discharge current Idis2 may be calculated as a value smaller than "Wout2 / VL."

[0195] Ninth Embodiment A ninth embodiment will be described below with reference to the drawings, focusing on differences from the eighth embodiment. In this embodiment, the distribution ratio of the currents supplied from the first and second storage batteries 31 and 32 to the low-voltage power supply target section 230 is adjusted.

[0196] 28 is a flowchart showing the procedure of the external power supply control process for the low-voltage power supply target unit 230. This process is executed repeatedly, for example, at a predetermined control period by cooperation between the EVECU 100 and the battery ECU 90.

[0197] After step S80, the EVECU 100 performs a ratio setting process in step S90. Fig. 29 is a flowchart showing the procedure of the ratio setting process. In this embodiment, the process in step S90 corresponds to the "command value calculation unit."

[0198] In step S91, the EVECU 100 determines whether the absolute value of the second upper limit input power Win2 is smaller than the absolute value of the first upper limit output power Wout1.

[0199] If the EVECU 100 determines that the absolute value of the second upper limit input power Win2 is smaller than the absolute value of the first upper limit output power Wout1, the EVECU 100 proceeds to step S92. In step S92, the EVECU 100 imposes the conditions that the discharge power of the first storage battery 31 is equal to or less than the first upper limit output power Wout1 and the discharge power of the second storage battery 32 is equal to or less than the second upper limit output power Wout2, and calculates the second command discharge current Idis2 to be larger than the first command discharge current Idis1. In this embodiment, the second command discharge current Idis2 corresponds to the "destination command discharge current."

[0200] Overcharging due to a sudden stop of external power supply control occurs in the second storage battery 32, not the first storage battery 31. To prevent overcharging of the second storage battery 32, it is necessary to increase the second upper limit input power Win2 of the second storage battery 32 as quickly as possible. In consideration of this, the process of step S92 is provided to prioritize discharging of the second storage battery 32 over the first storage battery 31. In this embodiment, the EVECU 100 calculates the second command discharge current Idis2 based on the second upper limit output power Wout2 and the second detected voltage VL. Specifically, for example, the second command discharge current Idis2 may be set to "Wout2 / VL." Furthermore, the EVECU 100 sets the first command discharge current Idis1 to zero.

[0201] When the EVECU 100 determines that the absolute value of the second upper limit input power Win2 is equal to or greater than the absolute value of the first upper limit output power Wout1, the EVECU 100 calculates the charging rate difference ΔSOC and determines whether the calculated charging rate difference ΔSOC is greater than the determination threshold value Sth in step S93. The charging rate difference ΔSOC is a value obtained by subtracting the SOC2 of the unit battery constituting the second storage battery 32 from the SOC1 of the unit battery constituting the first storage battery 31.

[0202] If the EVECU 100 determines that the difference in the charging rates ΔSOC is greater than the determination threshold value Sth, the EVECU 100 proceeds to step S94. In step S94, the EVECU 100 imposes the conditions that the discharge power of the first storage battery 31 is set to be equal to or less than the first upper limit output power Wout1 and the discharge power of the second storage battery 32 is set to be equal to or less than the second upper limit output power Wout2, and calculates the first command discharge current Idis1 to be greater than the second command discharge current Idis2. As a result, the discharge power of the first storage battery 31 becomes greater than the discharge power of the second storage battery 32. The processing of step S94 is performed for the same purpose as step S44 of FIG. 16 in the fourth embodiment. In this embodiment, the EVECU 100 calculates the first command discharge current Idis1 based on the first upper limit output power Wout1 and the first detected voltage VH, and specifically, for example, the first command discharge current Idis1 may be set to "Wout1 / VH".

[0203] When the EVECU 100 determines that the difference ΔSOC in the charging rates is equal to or less than the determination threshold value Sth, the EVECU 100 sets the first command discharge current Idis1 and the second command discharge current Idis2 to the same value by imposing the conditions that the discharge power of the first storage battery 31 is equal to or less than the first upper limit output power Wout1 and the discharge power of the second storage battery 32 is equal to or less than the second upper limit output power Wout2 in step S95. This prevents the difference between the SOC of each unit battery constituting the first storage battery 31 and the SOC of each unit battery constituting the second storage battery 32 from becoming too large.

[0204] After the processing of step S92, S94, or S95, returning to the description of Fig. 28 , in step S82, the EVECU 100 calculates the external command discharge current Idist by adding together the first command discharge current Idis1 and the second command discharge current Idis2 calculated in the processing of Fig. 29. In step S83, the EVECU 100 transmits the external command discharge current Idist to the low-voltage power supply target unit 230. In step S84, the first command discharge current Idis1 calculated in the processing of Fig. 29 is used for boost control of the inverter 20.

[0205] According to the present embodiment described above, it is possible to reduce the risk of overcharging of the first storage battery 31 due to a sudden stop of the external power supply control.

[0206] <Modification of the Ninth Embodiment> In step S92 of FIG. 29, the first command discharge current Idis1 may be set to a value greater than zero.

[0207] Tenth Embodiment A tenth embodiment will be described below with reference to the drawings, focusing on differences from the sixth to ninth embodiments. In this embodiment, the EVECU 100 performs power transmission control (specifically, for example, equalization control) for transmitting power from one of the first storage battery 31 and the second storage battery 32 to the other by performing switching control of the inverter 20.

[0208] 30 shows the control state of each switch during equalization control. During equalization control, each of the connection switches DCRH and DCRL is controlled to be turned off.

[0209] The EVECU 100 turns on the high-potential-side main switch SMRH, the low-potential-side main switch SMRL, the inter-battery switch 50, the first motor-side switch 71, and the second motor-side switch 72, and turns off the pre-charge main switch SMRP and the bypass switch 61. The EVECU 100 also controls the switching of at least one phase of the inverter 20 to transfer power from one of the first storage battery 31 and the second storage battery 32 to the other.

[0210] Specifically, the EVECU 100 performs a first control to supply current from the second storage battery 32 to the first storage battery 31 by performing a step-down control for at least one phase. The EVECU 100 also performs a second control to supply current from the first storage battery 31 to the second storage battery 32 by performing a step-up control for at least one phase.

[0211] By the equalization control, for example, it is possible to make the SOC of each unit battery constituting the first storage battery 31 and the SOC of each unit battery constituting the second storage battery 32 equal to each other.

[0212] 31 is a flowchart showing the procedure of the equalization control process. This process is repeatedly executed, for example, at a predetermined control interval, by the cooperation of the EVECU 100 and the battery ECU 90.

[0213] In step S100, the battery ECU 90 calculates a first upper limit input power Win1, a first upper limit output power Wout1, a second upper limit input power Win2, and a second upper limit output power Wout2, and transmits these to the EVECU 100.

[0214] In step S101, the EVECU 100 determines whether the first control is being executed, which supplies power from the second storage battery 32, which is the "source storage unit," to the first storage battery 31, which is the "destination storage unit," or the second control is being executed, which supplies power from the first storage battery 31, which is the "source storage unit," to the second storage battery 32, which is the "destination storage unit."

[0215] If the EVECU 100 determines that the first control is being executed, the process proceeds to step S102. In step S102, the EVECU 100 calculates a second commanded discharge current Idis2 based on the first upper limit input power Win1, the second upper limit output power Wout2, and the second detected voltage VL. Specifically, the EVECU 100 first selects, as the second reference power Wstd2, the first upper limit input power Win1 (corresponding to the "input upper limit") or the second upper limit output power Wout2 (corresponding to the "output upper limit"), whichever has the smaller absolute value. The EVECU 100 then divides the selected second reference power Wstd2 by the second detected voltage VL (=Wstd2 / VL), or calculates a value smaller than this divided value, as the second commanded discharge current Idis2.

[0216] In step S103, the EVECU 100 performs step-down control of the inverter 20 to control the current flowing through the second storage battery 32 (for example, the current detected by the second current sensor 82) to the calculated second command discharge current Idis2. This allows power to be supplied from the second storage battery 32 to the first storage battery 31 while preventing the discharge power of the second storage battery 32 from exceeding the second upper limit output power Wout2, thereby preventing over-discharge of the second storage battery 32.

[0217] On the other hand, if the EVECU 100 determines that the second control is being executed, the EVECU 100 proceeds to step S104. In step S104, the EVECU 100 calculates a first commanded discharge current Idis1 based on the second upper limit input power Win2, the first upper limit output power Wout1, and the first detected voltage VH. Specifically, the EVECU 100 first selects, as the first reference power Wstd1, the second upper limit input power Win2 (corresponding to the "input upper limit") or the first upper limit output power Wout1 (corresponding to the "output upper limit"), whichever has the smaller absolute value. The EVECU 100 then calculates, as the first commanded discharge current Idis1, a value obtained by dividing the selected first reference power Wstd1 by the first detected voltage VH (=Wstd1 / VH), or a value smaller than this divided value.

[0218] In step S103, the EVECU 100 performs boost control of the inverter 20 to control the current flowing through the first storage battery 31 (for example, the current detected by the first current sensor 81) to the calculated first command discharge current Idis1. This allows power to be supplied from the first storage battery 31 to the second storage battery 32 while preventing the discharge power of the first storage battery 31 from exceeding the first upper limit output power Wout1, thereby preventing over-discharge of the first storage battery 31.

[0219] In this embodiment, the processes of steps S102 and S104 correspond to a "command value calculation unit," and the process of step S103 corresponds to a "circuit control unit."

[0220] Other Embodiments The above-described embodiments may be modified as follows.

[0221] A configuration may be adopted in which some of the functions of the EVECU 100 are provided in the battery ECU 90, rather than in the EVECU 100. For example, as shown in FIG. 32 , a first charging current calculation unit 102A and a second charging current calculation unit 102B may be provided in the battery ECU 90.

[0222] The output upper limit value and the input upper limit value calculated by the battery ECU 90 are not limited to the upper limit power, but may be the upper limit current. FIG. 33 is a functional block diagram of the battery ECU 90 and the EVECU 100.

[0223] The battery ECU 90 includes a first input current calculation unit 94A, a first output current calculation unit 94B, a second input current calculation unit 95A, and a second output current calculation unit 95B.

[0224] The first input current calculation unit 94A calculates a first upper limit input current Iin1, which is the maximum value of current that can be input to the first storage battery 31, based on the battery state of the first storage battery 31. For example, the first input current calculation unit 94A calculates a smaller first upper limit input current Iin1 as the SOC of the first storage battery 31 increases or the temperature of the first storage battery 31 detected by the temperature sensor 88 decreases.

[0225] The first output current calculation unit 94B calculates a first upper limit output current Iout1, which is the maximum value of the current that can be output from the first storage battery 31, based on the battery state of the first storage battery 31. For example, the first output current calculation unit 94B calculates a larger first upper limit output current Iout1 as the SOC of the first storage battery 31 increases or the temperature of the first storage battery 31 detected by the temperature sensor 88 increases.

[0226] The second input current calculation unit 95A calculates the second upper limit input current Iin2, which is the maximum value of the current that can be input to the second storage battery 32, based on the battery state of the second storage battery 32. For example, the second input current calculation unit 95A calculates the second upper limit input current Iin2 to be smaller as the SOC of the second storage battery 32 is higher or the temperature of the second storage battery 32 detected by the temperature sensor 88 is lower.

[0227] The second output current calculation unit 95B calculates a second upper limit output current Iout2, which is the maximum value of the current that can be output from the second storage battery 32, based on the battery state of the second storage battery 32. For example, the second output current calculation unit 95B calculates a larger second upper limit output current Iout2 as the SOC of the second storage battery 32 increases or the temperature of the second storage battery 32 detected by the temperature sensor 88 increases.

[0228] In each of the above embodiments, instead of the first upper limit input power Win1, the first upper limit output power Wout1, the second upper limit input power Win2, and the second upper limit output power Wout2, the first upper limit input current Iin1, the first upper limit output current Iout1, the second upper limit input current Iin2, and the second upper limit output current Iout2 may be used.

[0229] Taking the first embodiment as an example, the first charging current calculation unit 102A may calculate the calculated first upper limit input current Iin1 or a value smaller than the first upper limit input current Iin1 as the first command charging current Ich1.

[0230] In addition, the second charging current calculation unit 102B may calculate the second command charging current Ich2 as a reference current which is the smaller absolute value of the calculated second upper limit input current Iin2 and first upper limit output current Iout1, or a value smaller than the reference current.

[0231] In each of the above embodiments, the power conversion device does not necessarily have to include either the first or second motor-side switch 71, 72. Furthermore, the power conversion device does not necessarily have to include both the first and second motor-side switches 71, 72.

[0232] The switches of the inverter 20 are not limited to IGBTs and may be, for example, N-channel MOSFETs having body diodes. In this case, the high-potential terminal of the N-channel MOSFET serves as the drain, and the low-potential terminal serves as the source.

[0233] The high-potential side main switch SMRH does not have to be provided.

[0234] Instead of the low-potential side main switch SMRL, a series connection of the pre-charge main switch SMRP and the pre-charge resistor 40 may be connected in parallel to the high-potential side main switch SMRH. In this case, the low-potential side main switch SMRL does not have to be provided.

[0235] The fuses 41 and 42 do not have to be provided.

[0236] The motor is not limited to a star-connected motor, but may be a delta-connected motor. The motor and inverter are not limited to a three-phase motor, but may be a two-phase motor, or a four-phase or more phase motor. The motor is not limited to a permanent magnet synchronous machine having a permanent magnet as a field pole on the rotor, but may be a wound field synchronous machine having a field winding as a field pole on the rotor. In this case, the rotor may be provided with both a field winding and a permanent magnet. The motor is not limited to a synchronous machine, but may be an induction machine.

[0237] The system including the power conversion device is not limited to the systems shown in Fig. 1 and Fig. 19, but may be, for example, the systems shown in Fig. 34 to Fig. 36. Note that in Fig. 34 to Fig. 36, the pre-charge main switch, pre-charge resistor, control device, etc. are not shown.

[0238] 34 shows a system including two storage batteries and two inverters. The system includes a first storage battery 131, a second storage battery 132, and a first inverter 120A and a second inverter 120B that constitute a power conversion device. The first storage battery 131 is an assembled battery similar to the first storage battery 31 in FIG. 1 etc., and the second storage battery 132 is an assembled battery similar to the second storage battery 32 in FIG. 1 etc. A positive terminal of the first storage battery 131 is electrically connected to a positive terminal of an external charger 240 via a high-side connection switch DCRH, and a negative terminal of the first storage battery 131 is electrically connected to a negative terminal of the external charger 240 via a low-side connection switch DCRL.

[0239] The first inverter 120A includes three phases of a series connection of a first upper-arm switch SWHA and a first lower-arm switch SWLA. A first upper-arm diode DHA, which is a freewheeling diode, is connected in anti-parallel to the first upper-arm switch SWHA, and a first lower-arm diode DLA, which is also a freewheeling diode, is connected in anti-parallel to the first lower-arm switch SWLA. In this embodiment, each of the switches SWHA and SWLA is an IGBT. Like the first inverter 120A, the second inverter 120B also includes a second upper-arm switch SWHB, a second lower-arm switch SWLB, a second upper-arm diode DHB, and a second lower-arm diode DLB.

[0240] The power conversion device includes a motor 110, and the motor 110 includes three-phase armature windings 111. In each phase, a connection point between the emitter of the second upper arm switch SWHB and the collector of the second lower arm switch SWLB is connected via the armature winding 111 to a connection point between the emitter, which is the low potential terminal of the first upper arm switch SWHA, and the collector, which is the high potential terminal of the first lower arm switch SWLA.

[0241] The collector of the first upper arm switch SWHA of each phase is connected to the positive terminal of the first storage battery 131 via the first high-side main switch SRH1. The emitter of the first lower arm switch SWLA of each phase is connected to the negative terminal of the first storage battery 131 via the first low-side main switch SRL1. The collector of the second upper arm switch SWHB of each phase is connected to the positive terminal of the second storage battery 132 via the second high-side main switch SRH2. The emitter of the second lower arm switch SWLB of each phase is connected to the negative terminal of the second storage battery 132 via the second low-side main switch SRL2.

[0242] During external charging control using the external charger 240, a control device (not shown) of the power conversion device charges the first storage battery 131 from the external charger 240 while keeping the switches DCRH, DCRL, SRH1, SRL1, SRH2, and SRL2 on. At the same time, the control device controls the switching of the switches of the first inverter 120A and the second inverter 120B, thereby also charging the second storage battery 132 from the external charger 240 via the inverters 120A and 120B. In this case, if the external charging control is suddenly stopped, over-discharge of the second storage battery 132 may occur. Therefore, to prevent over-discharge from occurring, the control device may perform processing similar to that described in FIG. 5 of the first embodiment or FIGS. 8 and 9 of the second embodiment.

[0243] In external power supply control in which an external power supply target component, which is a system power supply or an electrical load, is electrically connected to the first storage battery 131 instead of the external charger 240, power is supplied from the second storage battery 132 to the external power supply target component via the inverters 120A and 120B by switching control of the inverters 120A and 120B. In this case, if the external power supply control is suddenly stopped, overcharging of the first storage battery 131 may occur. Therefore, in order to suppress overcharging, the control device may perform processing similar to the processing described in FIG. 14 of the third embodiment or FIGS. 15 and 16 of the fourth embodiment.

[0244] Furthermore, when the control device performs power transmission control (specifically, for example, equalization control) to supply power from one of the first storage battery 131 and the second storage battery 132 to the other by switching control of each inverter 120A, 120B, it may perform processing similar to that shown in Figure 18 of the fifth embodiment.

[0245] 35 shows a system including two storage batteries and one inverter. The system includes a first storage battery 231 and a second storage battery 232, an inverter 121 constituting a power conversion device, a motor 310, and a DCDC converter 340. The first storage battery 231 is an assembled battery similar to the first storage battery 31 shown in FIG. 1 , etc., and the second storage battery 232 is an assembled battery similar to the second storage battery 32 shown in FIG. 1 , etc. A positive terminal of the first storage battery 231 is electrically connected to a positive terminal of an external charger 240 via a high-potential side connection switch DCRH, and a negative terminal of the first storage battery 231 is electrically connected to a negative terminal of the external charger 240 via a low-potential side connection switch DCRL. The motor 310 includes a three-phase armature winding 311 and a smoothing capacitor 321.

[0246] The DCDC converter 340 and the first storage battery 231 are connected via a high-side main switch SRH and a low-side main switch SRL. The DCDC converter 340 has a boost function that boosts the DC output voltage of the first storage battery 231 and outputs it to the inverter 121 side through its own switching control, and a buck function that lowers the DC input voltage from the inverter 121 side and outputs it to the first storage battery 231. The smoothing capacitor 321 and the second storage battery 232 are connected via a main switch SRS.

[0247] During external charging control using the external charger 240, a control device (not shown) of the power conversion device charges the first storage battery 231 from the external charger 240 while keeping the switches DCRH, DCRL, SRH, SRL, and SRS on, while also charging the second storage battery 232 from the external charger 240 by controlling the switching of the DCDC converter 340. In this case, if the external charging control is suddenly stopped, over-discharge of the second storage battery 232 may occur. Therefore, in order to prevent over-discharge from occurring, the control device may perform processing similar to that described in FIG. 5 of the first embodiment or FIGS. 8 and 9 of the second embodiment. Note that the same processing is also performed during external power feeding control and equalization control as in the case shown in FIG. 34 .

[0248] Fig. 36 shows a system including two storage batteries and one inverter. In the configuration shown in Fig. 36, the DCDC converter 340 will be referred to as the first DCDC converter 340. The system also includes a second DCDC converter 350 provided between the smoothing capacitor 321 and the second storage battery 232. The second DCDC converter 350 has a boost function that boosts the DC output voltage of the second storage battery 232 and outputs it to the inverter 121 side, and a buck function that lowers the DC input voltage from the inverter 121 side and outputs it to the second storage battery 232, through its own switching control.

[0249] In external charging control using the external charger 240, a control device (not shown) of the power conversion device turns on each of the switches DCRH, DCRL, SRH, SRL, and SRS, and charges the second storage battery 232 from the external charger 240 via the second DC-DC converter 350 by switching control of the second DC-DC converter 350, while also charging the first storage battery 231 from the external charger 240 via the first DC-DC converter 340 by switching control of the first DC-DC converter 340. If the power transmitted from the first DC-DC converter 340 to the first storage battery 231 is greater than the power transmitted from the second DC-DC converter 350 to the second storage battery 232, and the external charging control is suddenly stopped, over-discharge of the second storage battery 232 may occur. On the other hand, if the power transmitted from the second DC-DC converter 350 to the second storage battery 232 is greater than the power transmitted from the first DC-DC converter 340 to the first storage battery 231, a sudden stop of the external charging control may cause over-discharge of the first storage battery 231. In such a case, in order to suppress the occurrence of over-discharge, the same processing as that described in the configuration of Fig. 35 may be performed. Furthermore, the same processing as that described in the configuration of Fig. 35 may be performed during external power feeding control and equalization control.

[0250] The control devices that perform external charging, power supply control, and equalization control are not limited to the battery ECU 90 and the EVECU 100. For example, each control may be performed by cooperation between the battery ECU 90 and the EVECU 100 and a control device other than the battery ECU 90 and the EVECU 100, or by cooperation between a plurality of control devices other than the battery ECU 90 and the EVECU 100, or by a single control device (for example, the EVECU 100).

[0251] The power storage unit to be charged by the external charger is not limited to a storage battery. For example, it may be a large-capacity electric double layer capacitor, or a unit including both a storage battery and an electric double layer capacitor.

[0252] The mobile body on which the power conversion device is mounted is not limited to a vehicle, but may be, for example, an aircraft or a ship.Furthermore, the power conversion device is not limited to a mobile body, but may be a stationary device.

[0253] The control device and method described herein may be implemented by a special-purpose computer configured with a processor and memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control device and method described herein may be implemented by a special-purpose computer configured with a processor comprising one or more dedicated hardware logic circuits. Alternatively, the control device and method described herein may be implemented by one or more special-purpose computers configured with a combination of a processor and memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer.

[0254] Characteristic configurations extracted from the above-described embodiments will be described below. [Configuration 1] A power conversion device applied to a system including a first power storage unit (31, 131, 231) and a second power storage unit (32, 132, 232), comprising: a transformer circuit (11, 20, 73, 111, 120A, 120B, 240) that transforms a DC output voltage of a source power storage unit that is one of the first power storage unit and the second power storage unit, and supplies the transformed DC voltage to a destination power storage unit that is the other power storage unit, a command value calculation unit that calculates a command value (Ich1, Ich2, Idis1, Idis2) of a current flowing through at least one of the source power storage unit and the destination power storage unit, and a circuit control unit that performs switching control of the transformer circuit based on the calculated command value, the command value calculation unit calculates the command value based on an output upper limit value that is either an upper limit output power or an upper limit output current of the supply source power storage unit, and an input upper limit value that is either an upper limit input power or an upper limit input current of the supply destination power storage unit. [Configuration 2] The power conversion device according to Configuration 1, wherein the supply source power storage unit is a power storage unit to which an external charger (210, 240) is electrically connected, the command value is a supply destination command charging current (Ich1, Ich2) that is a command value for a charging current to be supplied from the transformer circuit to the supply destination power storage unit, the command value calculation unit calculates the supply destination command charging current based on the output upper limit value and the input upper limit value in external charging control in which the charging current output from the external charger is supplied to the supply source power storage unit, and the circuit control unit performs switching control of the transformer circuit to control the charging current of the supply destination power storage unit to the supply destination command charging current. [Configuration 3] The power conversion device according to Configuration 2, wherein the command value calculation unit calculates the supply destination command charging current based on the smaller of the absolute value of the output upper limit value and the absolute value of the input upper limit value. [Configuration 4] The power conversion device according to Configuration 2, wherein the command value calculation unit makes a supply source command charging current, which is a command value for a charging current of the supply source power storage unit, larger than the supply destination command charging current when the absolute value of the output upper limit value is smaller than the absolute value of the input upper limit value.[Configuration 5] The power conversion device according to Configuration 4, wherein the command value calculation unit makes the supply source command charging current smaller than the supply destination command charging current when the absolute value of the output upper limit value is equal to or greater than the absolute value of the input upper limit value and the SOC of the supply source power storage unit is greater than the SOC of the supply destination power storage unit by more than a threshold value (Sth). [Configuration 6] The power conversion device according to Configuration 4 or 5, further comprising an external command value calculation unit that calculates a command value (Icht) of a charging current output from the external charger based on the supply source command charging current, the supply destination command charging current, the voltage of the supply source power storage unit, and the voltage of the supply destination power storage unit. [Configuration 7] The power conversion device according to any one of Configurations 2 to 6, further comprising an abnormality processing unit that determines whether a direction of a current flowing in the supply source power storage unit has changed from a charging direction of the supply source power storage unit to a discharging direction of the supply source power storage unit during execution of the external charging control, and the abnormality processing unit determines that an abnormality has occurred in the external charging control when it determines that the direction of the current flowing in the supply source power storage unit has changed to the discharging direction. [Configuration 8] The power conversion device according to Configuration 7, wherein the abnormality processing unit determines that an abnormality has occurred in the electrical path from the supply destination power storage unit to the external charger as the abnormality in the external charging control. [Configuration 9] The power conversion device according to Configuration 7 or 8, wherein the abnormality processing unit stops switching control of the transformer circuit when it determines that an abnormality has occurred in the external charging control. [Configuration 10] The power conversion device according to Configuration 1, wherein the destination power storage unit is a power storage unit electrically connected to an external power supply target unit (230), the command value is a supply source command discharge current (Idis1, Idis2) that is a command value for a discharge current supplied from the supply source power storage unit to the transformer circuit, the command value calculation unit calculates the supply source command discharge current based on the output upper limit value and the input upper limit value in external power supply control in which an output current of the destination power storage unit is supplied to the external power supply target unit, and the circuit control unit performs switching control of the transformer circuit to control the discharge current of the supply source power storage unit to the supply source command discharge current.[Configuration 11] The power conversion device according to configuration 10, wherein the command value calculation unit calculates the supply source command discharge current based on the smaller of the absolute value of the output upper limit value and the absolute value of the input upper limit value. [Configuration 12] The power conversion device according to configuration 10, wherein the command value calculation unit makes the supply destination command discharge current, which is a command value for the discharge current of the supply destination power storage unit, larger than the supply source command discharge current when the absolute value of the input upper limit value is smaller than the absolute value of the output upper limit value. [Configuration 13] The power conversion device according to configuration 12, wherein the command value calculation unit makes the supply destination command discharge current smaller than the supply source command discharge current when the absolute value of the output upper limit value is equal to or larger than the absolute value of the input upper limit value and the SOC of the supply source power storage unit is larger than the SOC of the supply destination power storage unit by more than a threshold (Sth). [Configuration 14] The power conversion device according to configuration 12 or 13, further comprising an external command value calculation unit that calculates a command value (Idist) for an output current of the external power supply target unit based on the supply source command discharge current, the supply destination command discharge current, the voltage of the supply source power storage unit, and the voltage of the supply destination power storage unit. [Configuration 15] The power conversion device according to any one of configurations 10 to 14, further comprising an abnormality processing unit that determines whether a direction of a current flowing in the supply destination power storage unit has changed from a discharging direction of the supply destination power storage unit to a charging direction of the supply destination power storage unit during execution of the external power supply control, and the abnormality processing unit determines that an abnormality has occurred in the external power supply control when it is determined that the direction of the current flowing in the supply destination power storage unit has changed to the charging direction. [Configuration 16] The power conversion device according to configuration 15, further comprising an abnormality processing unit that determines that an abnormality has occurred in an electrical path from the supply destination power storage unit to the external power supply target unit, as the abnormality in the external power supply control. [Configuration 17] The power conversion device according to configuration 15 or 16, wherein the abnormality processing unit stops switching control of the transformer circuit when it determines that an abnormality has occurred in the external power supply control.[Configuration 18] The power conversion device according to Configuration 1, wherein the command value calculation unit calculates, as the command value, a command discharge current (Idis1, Idis2) to be supplied from the supply source power storage unit to the transformer circuit during switching control of the transformer circuit for supplying power from the supply source power storage unit to the supply destination power storage unit via the transformer circuit, the circuit control unit performs switching control of the transformer circuit to control the discharge current to be supplied from the supply source power storage unit to the command discharge current, and the command value calculation unit calculates the command discharge current based on the smaller of the absolute value of the output upper limit value and the absolute value of the input upper limit value. [Configuration 19] An inverter (20) having an upper arm switch (SWH) and a lower arm switch (SWL); a motor (10) having an armature winding (11) electrically connected to a low potential side terminal of the upper arm switch and a high potential side terminal of the lower arm switch; a high potential side path (22H) electrically connecting a positive terminal of the first power storage unit (31) and the high potential side terminal of the upper arm switch; a low potential side path (22L) electrically connecting a negative terminal of the second power storage unit (32) and the low potential side terminal of the lower arm switch; a connection path (73) electrically connecting the positive terminal of the second power storage unit and the armature winding; and an inter-power storage unit switch (50) that, when turned on, electrically connects the negative terminal of the first power storage unit and the positive terminal of the second power storage unit, and, when turned off, electrically disconnects the negative terminal of the first power storage unit and the positive terminal of the second power storage unit. a bypass switch (60) that, when turned on, electrically connects the negative terminal of the first power storage unit and the negative terminal of the second power storage unit, and that, when turned off, electrically disconnects the negative terminal of the first power storage unit and the negative terminal of the second power storage unit, wherein the armature winding, the inverter, and the connection path form the transformer circuit.[Configuration 20] An inverter (20) having an upper arm switch (SWH) and a lower arm switch (SWL); a motor (10) having an armature winding (11) electrically connected to a low potential side terminal of the upper arm switch and a high potential side terminal of the lower arm switch; a high potential side path (22H) electrically connecting a positive terminal of the first power storage unit (31) and a high potential side terminal of the upper arm switch; a low potential side path (22L) electrically connecting a negative terminal of the second power storage unit (32) and a low potential side terminal of the lower arm switch; a connection path (73) electrically connecting the negative terminal of the first power storage unit and the armature winding; and an inter-power storage unit switch (50) that, when turned on, electrically connects the negative terminal of the first power storage unit and the positive terminal of the second power storage unit, and, when turned off, electrically disconnects the negative terminal of the first power storage unit and the positive terminal of the second power storage unit. a bypass switch (61) that, when turned on, electrically connects the positive terminal of the first power storage unit and the positive terminal of the second power storage unit, and that, when turned off, electrically disconnects the positive terminal of the first power storage unit and the positive terminal of the second power storage unit, wherein the armature winding, the inverter, and the connection path form the transformer circuit.

[0255] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A power conversion device applied to a system including a first power storage unit (31, 131, 231) and a second power storage unit (32, 132, 232), comprising: a transformer circuit (11, 20, 73, 111, 120A, 120B, 240) that transforms a DC output voltage of a source power storage unit that is one of the first power storage unit and the second power storage unit, and supplies the transformed DC voltage to a destination power storage unit that is the other power storage unit; a command value calculation unit that calculates a command value (Ich1, Ich2, Idis1, Idis2) of a current flowing through at least one of the source power storage unit and the destination power storage unit; and a circuit control unit that performs switching control of the transformer circuit based on the calculated command value, The command value calculation unit calculates the command value based on an output upper limit value, which is either an upper limit output power or an upper limit output current of the supply source power storage unit, and an input upper limit value, which is either an upper limit input power or an upper limit input current of the supply destination power storage unit.

2. The power conversion device according to claim 1, wherein the source storage unit is a storage unit to which an external charger (210, 240) is electrically connected, the command value is a destination command charging current (Ich1, Ich2) that is a command value for a charging current supplied from the transformer circuit to the destination storage unit, the command value calculation unit calculates the destination command charging current based on the output upper limit value and the input upper limit value in external charging control in which the charging current output from the external charger is supplied to the source storage unit, and the circuit control unit performs switching control of the transformer circuit to control the charging current of the destination storage unit to the destination command charging current.

3. The power conversion device according to claim 2, wherein the command value calculation unit calculates the destination command charging current based on the smaller of the absolute value of the output upper limit value and the absolute value of the input upper limit value.

4. The power conversion device according to claim 2, wherein the command value calculation unit makes a supply source command charging current, which is a command value for the charging current of the supply source power storage unit, larger than the supply destination command charging current when the absolute value of the output upper limit value is smaller than the absolute value of the input upper limit value.

5. The power conversion device according to claim 4, wherein the command value calculation unit makes the supply source command charging current smaller than the supply destination command charging current when the absolute value of the output upper limit value is equal to or greater than the absolute value of the input upper limit value and the SOC of the supply source power storage unit is greater than the SOC of the supply destination power storage unit by more than a threshold value (Sth).

6. The power conversion device according to claim 4 or 5, further comprising an external command value calculation unit that calculates a command value (Icht) of the charging current output from the external charger based on the supply source command charging current, the supply destination command charging current, the voltage of the supply source power storage unit, and the voltage of the supply destination power storage unit.

7. The power conversion device according to any one of claims 2 to 5, further comprising an abnormality processing unit that determines whether or not a direction of current flowing into the supply source storage unit has changed from a charging direction of the supply source storage unit to a discharging direction of the supply source storage unit during execution of the external charging control, wherein the abnormality processing unit determines that an abnormality has occurred in the external charging control when it determines that the direction of current flowing into the supply source storage unit has changed to the discharging direction.

8. The power conversion device according to claim 7, wherein the abnormality processing unit determines that an abnormality has occurred in the electrical path from the supply destination power storage unit to the external charger as the abnormality in the external charging control.

9. The power conversion device according to claim 7, wherein the abnormality processing unit stops switching control of the transformer circuit when it determines that an abnormality has occurred in the external charging control.

10. The power conversion device according to claim 1, wherein the destination storage unit is a storage unit electrically connected to an external power supply target unit (230), the command value is a source command discharge current (Idis1, Idis2) that is a command value for a discharge current supplied from the source storage unit to the transformer circuit, the command value calculation unit calculates the source command discharge current based on the output upper limit value and the input upper limit value in external power supply control in which the output current of the destination storage unit is supplied to the external power supply target unit, and the circuit control unit performs switching control of the transformer circuit to control the discharge current of the source storage unit to the source command discharge current.

11. The power conversion device according to claim 10, wherein the command value calculation unit calculates the supply source command discharge current based on the smaller of the absolute value of the output upper limit value and the absolute value of the input upper limit value.

12. The power conversion device according to claim 10, wherein the command value calculation unit makes a destination command discharge current, which is a command value for the discharge current of the destination storage unit, larger than the source command discharge current when the absolute value of the input upper limit value is smaller than the absolute value of the output upper limit value.

13. The power conversion device according to claim 12, wherein the command value calculation unit makes the destination command discharge current smaller than the supply source command discharge current when the absolute value of the output upper limit value is equal to or greater than the absolute value of the input upper limit value and the SOC of the supply source power storage unit is greater than the SOC of the supply destination power storage unit by more than a threshold value (Sth).

14. The power conversion device according to claim 12 or 13, further comprising an external command value calculation unit that calculates a command value (Idist) of the output current of the external power supply target unit based on the supply source command discharge current, the supply destination command discharge current, the voltage of the supply source power storage unit, and the voltage of the supply destination power storage unit.

15. A power conversion device according to any one of claims 10 to 13, further comprising an abnormality processing unit that determines whether or not a direction of current flowing into the destination power storage unit has changed from a discharging direction of the destination power storage unit to a charging direction of the destination power storage unit during execution of the external power supply control, wherein the abnormality processing unit determines that an abnormality has occurred in the external power supply control when it determines that the direction of current flowing into the destination power storage unit has changed to the charging direction.

16. The power conversion device according to claim 15, wherein the abnormality processing unit determines that an abnormality has occurred in the electrical path from the supply destination power storage unit to the external power supply target unit as the abnormality in the external power supply control.

17. The power conversion device according to claim 15, wherein the abnormality processing section stops switching control of the transformer circuit when it determines that an abnormality has occurred in the external power supply control.

18. The power conversion device according to claim 1, wherein in switching control of the transformer circuit for supplying power from the supply source storage unit to the destination storage unit via the transformer circuit, the command value calculation unit calculates, as the command value, a command discharge current (Idis1, Idis2) supplied from the supply source storage unit to the transformer circuit, the circuit control unit performs switching control of the transformer circuit to control the discharge current supplied from the supply source storage unit to the transformer circuit to the command discharge current, and the command value calculation unit calculates the command discharge current based on the smaller of the absolute value of the output upper limit value and the absolute value of the input upper limit value.

19. An inverter (20) having an upper arm switch (SWH) and a lower arm switch (SWL); a motor (10) having an armature winding (11) electrically connected to a low potential side terminal of the upper arm switch and a high potential side terminal of the lower arm switch; a high potential side path (22H) electrically connecting a positive terminal of the first power storage unit (31) and a high potential side terminal of the upper arm switch; a low potential side path (22L) electrically connecting a negative terminal of the second power storage unit (32) and a low potential side terminal of the lower arm switch; a connection path (73) electrically connecting the positive terminal of the second power storage unit and the armature winding; and an inter-power storage unit switch (50) which, when turned on, electrically connects the negative terminal of the first power storage unit and the positive terminal of the second power storage unit and, when turned off, electrically cuts off the negative terminal of the first power storage unit and the positive terminal of the second power storage unit; a bypass switch (60) that, when turned to an on state, electrically connects the negative terminal of the first power storage unit and the negative terminal of the second power storage unit, and that, when turned to an off state, electrically disconnects the negative terminal of the first power storage unit and the negative terminal of the second power storage unit, wherein the armature winding, the inverter, and the connection path form the transformer circuit.

20. An inverter (20) having an upper arm switch (SWH) and a lower arm switch (SWL); a motor (10) having an armature winding (11) electrically connected to a low potential side terminal of the upper arm switch and a high potential side terminal of the lower arm switch; a high potential side path (22H) electrically connecting a positive terminal of the first power storage unit (31) and a high potential side terminal of the upper arm switch; a low potential side path (22L) electrically connecting a negative terminal of the second power storage unit (32) and a low potential side terminal of the lower arm switch; a connection path (73) electrically connecting the negative terminal of the first power storage unit and the armature winding; and an inter-power storage unit switch (50) which, when turned on, electrically connects the negative terminal of the first power storage unit and the positive terminal of the second power storage unit and, when turned off, electrically cuts off the negative terminal of the first power storage unit and the positive terminal of the second power storage unit. a bypass switch (61) that, when turned on, electrically connects the positive terminal of the first power storage unit and the positive terminal of the second power storage unit, and that, when turned off, electrically cuts off the positive terminal of the first power storage unit and the positive terminal of the second power storage unit, wherein the armature winding, the inverter, and the connection path form the transformer circuit.

21. A program applied to a system including a first power storage unit (31, 131, 231), a second power storage unit (32, 132, 232), a power conversion device, and a computer (91, 101), wherein the power conversion device includes a transformer circuit (11, 20, 73, 111, 120A, 120B, 240) that transforms a DC output voltage of a source power storage unit that is one of the first power storage unit and the second power storage unit, and supplies the transformed DC voltage to a destination power storage unit that is the other power storage unit, and causes the computer to execute a command value calculation process that calculates a command value (Ich1, Ich2, Idis1, Idis2) of a current flowing through at least one of the source power storage unit and the destination power storage unit, and a circuit control process that performs switching control of the transformer circuit based on the calculated command value, the command value calculation process is a process of calculating the command value based on an output upper limit value, which is either an upper limit output power or an upper limit output current of the supply source power storage unit, and an input upper limit value, which is either an upper limit input power or an upper limit input current of the supply destination power storage unit.