Power conversion device, program, and method for controlling power conversion device

Abstract

This power conversion device comprises: an inverter (20) having upper and lower arm switches (SUH-SWL) of a plurality of phases; a motor (10) having armature windings (11U-11W); a high-potential-side path (22H); a low-potential-side path (22L); a connection path (73); and a control device (100). The control device comprises: a switch control unit (145) that performs switching control of the upper and lower arm switches; and a threshold value determination unit (144) that determines whether or not a determination parameter (α) is equal to or less than a threshold value, said determination parameter being either the ratio of a neutral point voltage of the armature windings to the voltage difference between the high-potential-side path and the low-potential-side path or a correlation value of the ratio. When it is determined that the determination parameter is greater than the threshold value, the switch control unit performs switching control on which a condition for setting the determination parameter to be less than or equal to the threshold value is imposed.

Description

Power conversion device, program, and method for controlling power conversion device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-064152 filed on April 11, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a power conversion device, a program, and a method for controlling a power conversion device.

[0003] Conventionally, a power conversion device applied to a system including a power storage unit has been known. The power conversion device includes an inverter and a motor. A control device for the power conversion device drives the motor while controlling the temperature rise of the power storage unit. An example of such a power conversion device is described in Patent Document 1.

[0004] Japanese Patent Application Laid-Open No. 2021-093845

[0005] In the above-described power conversion device, there is a concern that problems may occur in the control of the power conversion device, such as a decrease in the efficiency of temperature rise control.

[0006] A main object of the present disclosure is to provide a power conversion device, a program, and a control method for a power conversion device that can suppress the occurrence of inconveniences in the control of the power conversion device.

[0007] The present disclosure relates to a power conversion device including an inverter having upper and lower arm switches of a plurality of phases, and a motor having an armature winding electrically connected to a low potential side terminal of the upper arm switches of each phase and a high potential side terminal of the lower arm switches of each phase, the power conversion device including: a high potential side path electrically connecting a positive terminal of a first power storage unit and a high potential side terminal of the upper arm switch; a low potential side path electrically connecting a negative terminal of a second power storage unit and a low potential side terminal of the lower arm switch; a connection path electrically connecting the negative terminal of the first power storage unit or the positive terminal of the second power storage unit and the armature winding; and a control device, wherein the control device includes: a temperature rise determination unit that determines whether or not there is a temperature rise request to flow an AC temperature rise current between the first power storage unit and the second power storage unit via the armature winding and the connection path; and an operation determination unit that determines whether or not there is an operation request to flow a DC operating current to at least one of the first power storage unit and the second power storage unit. a switch control unit that, when it is determined that there is a temperature increase request and that there is an operation request, performs switching control of the upper and lower arm switches so that the temperature increase current flows between the first power storage unit and the second power storage unit and the operation current flows to at least one of the first power storage unit and the second power storage unit; and a threshold determination unit that determines whether a determination parameter, which is either a ratio of a neutral point voltage of the armature winding to a voltage difference between the high potential side path and the low potential side path or a correlation value of the ratio, is equal to or less than a threshold, wherein, when it is determined that the determination parameter is greater than the threshold, the switch control unit performs limit control, which is the switching control, with a condition that the determination parameter be equal to or less than the threshold.

[0008] The power conversion device increases the temperatures of the first and second power storage units by flowing an AC heating current between the first and second power storage units via the armature windings and the connection path. Here, there are cases where temperature increase control of the first and second power storage units and operation control of flowing a DC operating current to at least one of the first and second power storage units are executed.

[0009] When the temperature rise control is performed, a current for causing a temperature rise current flows through the armature winding. If a current for causing a temperature rise current flows through the armature winding and operation control is also performed, there is a concern that the effect obtained by one of the temperature rise control and operation control may be smaller than expected.

[0010] Here, when the switch control unit of the present disclosure determines that the determination parameter is greater than the threshold, it performs limiting control that imposes a condition that the determination parameter be equal to or less than the threshold. This makes it possible to execute temperature rise control and operational control while maintaining the determination parameter equal to or less than the threshold. Therefore, even when temperature rise control and operational control are executed, it is possible to prevent the effect obtained by one of the temperature rise control and operational control from being smaller than expected.

[0011] 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, in which Fig. 1 is an overall configuration diagram of a system according to a first embodiment, Fig. 2 is a diagram showing the control state of switches during motor driving, Fig. 3 is a diagram showing the control state of switches during high-voltage charging, Fig. 4 is a diagram showing the control state of switches during low-voltage charging, Fig. 5 is a diagram showing an equivalent circuit, Fig. 6 is a diagram showing an equivalent circuit, Fig. 7 is a functional block diagram showing processing by a microcomputer, Fig. 8 is a diagram showing the waveform of a neutral point command current, Fig. 9 is a time chart showing changes in modulation factor, Fig. 10 is a functional block diagram showing processing by a microcomputer, Fig. 11 is a flowchart showing the procedure for temperature rise control processing, Fig. 12 is an overall configuration diagram of a system according to a second embodiment, Fig. 13 is a diagram showing the control state of switches during low-voltage charging, and Fig. 14 is an overall configuration diagram of a system according to another embodiment.

[0012] 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.

[0013] 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.

[0014] 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 and includes star-connected armature windings 11 of U, V, and W phases, and a rotor 13. The armature windings 11 of each phase are arranged with an electrical angle of 120°. The motor 10 is, for example, a permanent magnet synchronous machine. The rotor 13 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.

[0015] The inverter 20 includes three phases of series-connected upper and lower arm switches. Specifically, the inverter 20 includes U-, V-, and W-phase upper arm switches SUH, SVH, and SWH and U-, V-, and W-phase lower arm switches SUL, SVL, and SWL. U-, V-, and W-phase upper arm diodes DUH, DVH, and DWH, which are freewheel diodes, are connected in antiparallel to the U-, V-, and W-phase upper arm switches SUH, SVH, and SWH, and U-, V-, and W-phase lower arm diodes DUL, DVL, and DWL, which are freewheel diodes, are connected in antiparallel to the U-, V-, and W-phase lower arm switches SUL, SVL, and SWL. In this embodiment, the switches SUH, SVH, SWH, SUL, SVL, and SWL are IGBTs.

[0016] 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.

[0017] First ends of U-, V-, and W-phase armature windings 11U, 11V, and 11W are connected to the connection points between the emitters, which are low-potential terminals of the U-, V-, and W-phase upper-arm switches SUH, SVH, and SWH, and the collectors, which are high-potential terminals of the U-, V-, and W-phase lower-arm switches SUL, SVL, and SWL, via conductive members 23 such as bus bars. Second ends of the U-, V-, and W-phase armature windings 11U, 11V, and 11W are connected to each other at a neutral point O. In this embodiment, the U-, V-, and W-phase armature windings 11U, 11V, and 11W are set to have the same number of turns. As a result, the U-, V-, and W-phase armature windings 11U, 11V, and 11W are set to have the same inductance, for example.

[0018] A high-potential-side path 22H is connected to the collectors of the U-, V-, and W-phase upper-arm switches SUH, SVH, and SWH. A low-potential-side path 22L is connected to the emitters of the U-, V-, and W-phase lower-arm switches SUL, SVL, and SWL. In this embodiment, the voltage between the high-potential-side path 22H and the low-potential-side path 22L is referred to as a power supply voltage Vbat.

[0019] 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 and driving the rotor 13 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 inter-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.

[0020] 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.

[0021] 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.

[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 the external charger and 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, 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 connecting the low potential side intermediate terminal BL and the neutral point O. The low potential side intermediate terminal BL is on a path connecting the inter-battery switch 50 and the positive terminal of the second storage battery 32. A first motor side switch 71 and a second motor side switch 72 are provided on the connection path 73 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 for detecting currents flowing through various parts thereof, including a first current sensor 81A, a second current sensor 81B, a phase current sensor 82, and a motor current sensor 83. The first current sensor 81A detects the current flowing through the first storage battery 31, and the second current sensor 81B detects the current flowing through the second storage battery 32. The phase current sensor 82 detects the currents flowing through the U-, V-, and W-phase armature windings 11U, 11V, and 11W. The motor current sensor 83 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 84 that detects the terminal voltage of the neutral point capacitor 74, a first voltage sensor 85A that detects the terminal voltage of the first storage battery 31, and a second voltage sensor 85B that detects the terminal voltage of the second storage battery 32. The power conversion device also includes a power supply voltage sensor 86 that detects the terminal voltage of the smoothing capacitor 21 (hereinafter referred to as smoothing capacitor voltage Vdc), and a rotation angle sensor 87 that detects the rotation angle (electrical angle) of the rotor 13. The power conversion device also includes a first temperature sensor 88A that detects the temperature of the first storage battery 31, and a second temperature sensor 88B that detects the temperature of the second storage battery 32.

[0032] The system includes a battery ECU 90 that controls the battery unit 30, a motor ECU 100 that controls the inverter 20, and an EVECU 110 that manages the system. The battery ECU 90 is an electronic control unit and includes a processor 91 and a storage unit 92 as hardware. The motor ECU 100 is an electronic control unit and includes a processor 101 and a storage unit 102 as hardware. The EVECU 110 is an electronic control unit and includes a processor 111 and a storage unit 112 as hardware. The EVECU 110 is a higher-level control unit than the battery ECU 90 and the motor ECU 100. The battery ECU 90 and the motor ECU 100 can exchange information via the EVECU 110.

[0033] The memory units 92, 102, 112 include hardware memory and storage. The memory is a storage device for storing data used in the processing of the battery ECU 90, the motor ECU 100, or the EVECU 110. The memory provides the processors 91, 101, 111 with a working area for temporary use when the processors 91, 101, 111 perform processing, for example. The memory includes, for example, a ROM or a RAM. The storage is a storage device for storing various programs and data to be read and executed by the processors 91, 101, 111, and is a non-transitory tangible storage medium. The storage includes, for example, an HDD or flash memory. The storage stores program information and the like for processing, such as that shown in FIG. 11, which will be described later.

[0034] For example, program information stored on a non-transient physical recording medium is installed in the storage units 92, 102, and 112. The recording medium is, for example, a USB memory, a CD-ROM, or a DVD. Also, for example, program information transmitted via a communication network, such as over the air (OTA), is installed in the storage units 92, 102, and 112.

[0035] The battery ECU 90 receives detection values ​​from the first current sensor 81A, the second current sensor 81B, the first voltage sensor 85A, the second voltage sensor 85B, and the first and second temperature sensors 88A and 88B. The motor ECU 100 receives detection values ​​from the phase current sensor 82, the motor current sensor 83, the capacitor voltage sensor 84, the power supply voltage sensor 86, and the rotation angle sensor 87.

[0036] The main switches SMRH, SMRL, SMRP, 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, the motor ECU 100, or the EVECU 110, or may be controlled by an ECU other than the ECUs 90, 100, 110. In this embodiment, hereinafter, the main switches SMRH, SMRL, SMRP, the inter-battery switch 50, the bypass switch 60, and the motor-side switches 71, 72 are assumed to be controlled by the motor ECU 100.

[0037] Next, the drive control will be described. The drive control rotates the rotor 13 of the motor 10.

[0038] 2 shows the control state of each switch when drive control is executed. When the motor ECU 100 determines that there is a drive request (corresponding to an "operation request"), it turns off the connection switches DCRH and DCRL, the bypass switch 60, the precharge main switch SMRP, the first motor side switch 71, and the second motor side switch 72, and turns on the high potential side main switch SMRH, the low potential side main switch SMRL, and the battery switch 50. In this embodiment, the drive request is a request to run the vehicle by rotating the rotor 13.

[0039] In drive control, the motor ECU 100 performs switching control of the upper and lower arm switches SUH to SWL of each phase of the inverter 20 to feedback control the control variable of the motor 10 to a command value based on the detection values ​​of each sensor. The control variable is, for example, torque. In each phase, the upper arm switch and the lower arm switch are alternately turned on. This feedback control transmits the rotational power of the rotor 13 to the drive wheels, causing the vehicle to run.

[0040] Next, the external charging control will be described.

[0041] In this embodiment, the external charger is a high-voltage charger 200 or a low-voltage charger 210, as shown in FIGS. 3 and 4 . 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.

[0042] 3 shows the control state of each switch during external charging control using the high-voltage charger 200. The motor ECU 100 determines that there is a high-voltage charging request (corresponding to an "operation request") in the following cases, for example, and executes external charging control using the high-voltage charger 200. The vehicle user electrically connects the charging plug of the high-voltage charger 200 to each connection switch DCRH, DCRL, thereby electrically connecting the high-voltage charger 200 and the power conversion device. When the motor ECU 100 determines that the external charger connected to the power conversion device is the high-voltage charger 200, it determines that there is a high-voltage charging request. When the motor ECU 100 determines that there is a high-voltage charging request, 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 SUH to 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.

[0043] As a result, the first storage battery 31 and the second storage battery 32 are connected in series to the high-voltage charger 200. Therefore, 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. In this case, because the upper-arm switches SUH, SVH, 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.

[0044] 4 shows the control state of each switch during external charging control using the low-voltage charger 210. The motor ECU 100 determines that there is a low-voltage charging request (corresponding to an "operation request") in the following cases, for example, and executes external charging control using the low-voltage charger 210. The vehicle user electrically connects the charging plug of the low-voltage charger 210 to each connection switch DCRH, DCRL, thereby electrically connecting the low-voltage charger 210 and the power conversion device. When the motor ECU 100 determines that the external charger connected to the power conversion device is the low-voltage charger 210, it determines that there is a low-voltage charging request. When the motor ECU determines that there is a low-voltage charging request, 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.

[0045] In the external charging control by the low-voltage charger 210, the motor ECU 100 performs switching control to alternately turn on the upper and lower arm switches of at least one phase, or performs switching control to switch on the upper arm switch of at least one phase while keeping the lower arm switches SUL, SVL, and 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 motor ECU 100 performs step-down control, which is the switching control described above, to control the voltage detected by the capacitor voltage sensor 84 (hereinafter referred to as the neutral point capacitor voltage VN) to the target charging voltage Vtgt. 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 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. Hereinafter, for convenience, in the external charging control by the low-voltage charger 210, the upper and lower arm switches of at least one phase that are alternately turned on by the motor ECU 100, and the upper arm switch of at least one phase that is switching controlled while the lower arm switches SUL, SVL, SWL of all phases of the inverter 20 are turned off, will be referred to as the "target switch".

[0046] In this embodiment, the motor ECU 100 executes a temperature rise / drive mode in which temperature rise control and drive control are executed, or a temperature rise / charge mode in which temperature rise control and external charging control are executed. When executing the temperature rise / drive mode, the motor ECU 100 turns on the first motor side switch 71 and the second motor side switch 72 in Fig. 2. When executing the temperature rise / charge mode, the motor ECU 100 turns on the first motor side switch 71 and the second motor side switch 72 in Fig. 3, or turns on the inter-battery switch 50 in Fig. 4.

[0047] In the temperature rise control, an AC temperature rise current is passed between the first storage battery 31 and the second storage battery 32, thereby raising the temperatures of the first and second storage batteries 31, 32. The temperature rise control will be described below.

[0048] An equivalent circuit of a power conversion device used in temperature rise control is shown in Figure 5. In Figure 5, the armature windings 11U to 11W of each phase are shown as armature windings 11, the upper-arm switches SUH, SVH, and SWH are shown as upper-arm switches SH, and the upper-arm diodes DUH, DVH, and DWH are shown as upper-arm diodes DH. Furthermore, the lower-arm switches SUL, SVL, and SWL are shown as lower-arm switches SL, and the lower-arm diodes DUL, DVL, and DWL are shown as lower-arm diodes DL.

[0049] The equivalent circuit of Figure 5 can be shown as the equivalent circuit of Figure 6. The circuit of Figure 6 is a buck-boost chopper circuit capable of bidirectional power transmission between the first storage battery 31 and the second storage battery 32. In Figure 6, IBH represents the current flowing through the first storage battery 31, VBH represents the terminal voltage of the first storage battery 31, IBL represents the current flowing through the second storage battery 32, and VBL represents the terminal voltage of the second storage battery 32. IBH and IBL are negative when charging currents flow through the first and second storage batteries 31 and 32, and positive when discharging currents flow through the first and second storage batteries 31 and 32. VR represents the terminal voltage of the armature winding 11, and IMr represents the current flowing to the neutral point O. The neutral point current IMr is defined as positive when it flows from the armature winding 11 through the connection path 73 toward the low potential side intermediate terminal BL, and is defined as negative when it flows from the low potential side intermediate terminal BL toward the armature winding 11 through the connection path 73.

[0050] 6, when the upper switch SH is turned on, the voltage VR across the terminals of the armature winding 11 becomes "VBH." On the other hand, when the lower switch SL is turned on, the voltage VR across the terminals of the armature winding 11 becomes "-VBL." In other words, when the upper switch SH is turned on, an excitation current can be made to flow through the armature winding 11 in the positive direction of the neutral point current IMr, and when the lower switch SL is turned on, an excitation current can be made to flow through the armature winding 11 in the negative direction of the neutral point current IMr.

[0051] FIG. 7 shows a block diagram of the control executed in the temperature increase / drive mode.

[0052] In the motor ECU 100, a d-axis / q-axis command current setting unit 120 sets a d-axis command current Id* and a q-axis command current Iq* based on a torque command value Trq* of the motor 10, and inputs the currents to a d-axis deviation calculation unit 121d and a q-axis deviation calculation unit 121q. The d-axis deviation calculation unit 121d calculates a d-axis current deviation ΔId by subtracting the d-axis current Idr from the d-axis command current Id*, and inputs the current deviation ΔId to a d-axis control unit 122d. The q-axis deviation calculation unit 121q calculates a q-axis current deviation ΔIq by subtracting the q-axis current Iqr from the q-axis command current Iq*, and inputs the current deviation ΔIq to a q-axis control unit 122q. The d-axis current Idr and the q-axis current Iqr are calculated based on the detected values ​​of the phase current sensor 82 and the electrical angle of the motor 10. The electrical angle may be a detected value of the rotation angle sensor 87 or an estimated value estimated by position sensorless control.

[0053] The d-axis control unit 122d calculates a d-axis voltage Vd as an operation amount for feedback-controlling the d-axis current deviation ΔId calculated by the d-axis deviation calculation unit 121d to zero, and inputs the calculated voltage to the three-phase conversion unit 123. The q-axis control unit 122q calculates a q-axis voltage Vq as an operation amount for feedback-controlling the q-axis current deviation ΔIq calculated by the q-axis deviation calculation unit 121q to zero, and inputs the calculated voltage to the three-phase conversion unit 123. In this embodiment, proportional-integral control is used as the feedback control of each of the control units 122d, 122q. Note that the feedback control is not limited to proportional-integral control, and may be, for example, proportional-integral-derivative control.

[0054] The three-phase converter 123 calculates U- to W-phase command voltages Vu to Vw in a three-phase fixed coordinate system based on the d-axis voltage Vd, the q-axis voltage Vq, and the electrical angle. When it is determined that a drive request exists, the U- to W-phase command voltages Vu to Vw are sinusoidal signals with the same amplitude but shifted in phase by 120 electrical degrees.

[0055] The motor ECU 100 includes a temperature rise control unit 130. The temperature rise control unit 130 includes a command value setting unit 131, a neutral point deviation calculation unit 132, a neutral point control unit 133, and U-phase to W-phase superimposing units 134U to 134W.

[0056] The command value setting unit 131 sets the neutral point command current IM* and inputs it to the neutral point deviation calculation unit 132. In this embodiment, the waveform of the neutral point command current IM* is set as a sine wave, as shown in FIG. 8 . Specifically, the neutral point command current IM* has an amplitude Ia and a period Tc. The neutral point command current IM* is set so that the positive and negative neutral point command currents IM* are point-symmetric with respect to the timing at which the value of the neutral point command current IM* changes from a non-zero value to zero (hereinafter referred to as the zero-crossing timing). As a result, in FIG. 8 , the period from the first zero-crossing timing C1 to the second zero-crossing timing C2 of the neutral point command current IM* is equal to the period from the second zero-crossing timing C2 to the third zero-crossing timing C3.

[0057] In addition, in one cycle Tc of the neutral point command current IM*, the area S1 of the first region and the area S2 of the second region are equal. The area S1 of the first region is the region surrounded by the positive neutral point command current IM* and the time axis from the first zero-cross timing C1 to the second zero-cross timing C2 of the neutral point command current IM* in one cycle Tc of the neutral point command current IM*. The area S2 of the second region is the region surrounded by the negative neutral point command current IM* and the time axis from the second zero-cross timing C2 to the third zero-cross timing C3 of the neutral point command current IM* in one cycle Tc.

[0058] By setting the area S1 of the first region and the area S2 of the second region to be equal, it is possible to balance the charge / discharge currents of the first storage battery 31 and the second storage battery 32 in one cycle Tc. Therefore, it is possible to prevent the difference between the terminal voltage VBH of the first storage battery 31 and the terminal voltage VBL of the second storage battery 32 from increasing due to the temperature rise control.

[0059] Returning to the explanation of Figure 7, the neutral point deviation calculation unit 132 calculates the neutral point current deviation ΔIM by subtracting the neutral point current IMr, which is the current detected by the motor current sensor 83, from the neutral point command current IM*, and inputs it to the neutral point control unit 133.

[0060] The neutral point control unit 133 calculates an offset correction amount CF as a manipulated variable for feedback-controlling the calculated neutral point current deviation ΔIM to zero, and inputs the calculated offset correction amount CF to the U-phase to W-phase superimposing units 134U to 134W. In this embodiment, proportional-integral control is used as this feedback control. Note that the feedback control is not limited to proportional-integral control, and may be, for example, proportional-integral-derivative control.

[0061] The U-phase superimposing unit 134U calculates a U-phase final command voltage "Vu+CF" by adding an offset correction amount CF to the U-phase command voltage Vu input from the three-phase conversion unit 123. The V-phase superimposing unit 134V calculates a V-phase final command voltage "Vv+CF" by adding an offset correction amount CF to the V-phase command voltage Vv input from the three-phase conversion unit 123. The W-phase superimposing unit 134W calculates a W-phase final command voltage "Vw+CF" by adding an offset correction amount CF to the W-phase command voltage Vw input from the three-phase conversion unit 123.

[0062] The motor ECU 100 includes U- to W-phase modulation units 135U to 135W. The U-phase modulation unit 135U calculates a U-phase modulation factor Mu by dividing the U-phase final command voltage input from the U-phase superimposing unit 134U by the smoothing capacitor voltage Vdc. The V-phase modulation unit 135V calculates a V-phase modulation factor Mv by dividing the V-phase final command voltage input from the V-phase superimposing unit 134V by the smoothing capacitor voltage Vdc. The W-phase modulation unit 135W calculates a W-phase modulation factor Mw by dividing the W-phase final command voltage input from the W-phase superimposing unit 134W by the smoothing capacitor Vdc.

[0063] The motor ECU 100 performs switching control of the switches SUH to SWL based on the calculated modulation factors Mu, Mv, and Mw. Specifically, for example, the motor ECU 100 may perform switching control using PWM control based on a magnitude comparison between the modulation factors Mu, Mv, and Mw and a carrier signal (e.g., a triangular wave signal).

[0064] 9 shows the transition of the modulation factors Mu, Mv, and Mw when the neutral point command current IM* is set to a sine wave. In this embodiment, the frequency of the neutral point command current IM* is lower than the frequencies of the modulation factors Mu, Mv, and Mw.

[0065] When the motor ECU 100 determines that there is a temperature increase request and a high-voltage charge request, it executes the temperature increase / charge mode. In this case, the motor ECU 100 calculates the modulation factors Mu, Mv, and Mw by setting the U- to W-phase command voltages Vu, Vv, and Vw to 0, for example, in the process shown in FIG. 10 . The motor ECU 100 controls the switching of the switches SUH to SWL based on the calculated modulation factors Mu, Mv, and Mw. In this case, a current corresponding to the neutral point command current IM* flows through the U- to W-phase armature windings 11U, 11V, and 11W.

[0066] When the motor ECU 100 determines that there is a temperature increase request and a low-voltage charging request, it executes the temperature increase / charge mode. In this case, the temperature increase / charge mode controls the neutral point current IMr to the neutral point command current IM* shown in Fig. 8 and performs step-down control during external charging control using the low-voltage charger 210. When this mode is executed by the motor ECU 100, a current corresponding to the neutral point command current IM* and the step-down control flows through the U- to W-phase armature windings 11U, 11V, 11W.

[0067] FIG. 10 is a block diagram showing the control process of the power conversion device executed by the motor ECU 100. As shown in FIG.

[0068] The motor ECU 100 includes a temperature rise determination unit 140 , an operation determination unit 141 , a priority determination unit 142 , and a switch control unit 145 .

[0069] The temperature rise determination unit 140 determines whether there is a temperature rise request for the first storage battery 31 and the second storage battery 32. In this embodiment, the temperature rise determination unit 140 determines that there is a temperature rise request when it determines that the temperature rise target temperature Tr is equal to or lower than the target temperature T*. Here, the temperature rise target temperature Tr is, for example, the lower of the temperatures of the first storage battery 31 and the second storage battery 32, or the average temperature of the first storage battery 31 and the second storage battery 32. The temperature of the first storage battery 31 used in the temperature rise determination unit 140 is, for example, the value detected by the first temperature sensor 88A. The temperature of the second storage battery 32 used in the temperature rise determination unit 140 is, for example, the value detected by the second temperature sensor 88B. The temperature rise determination unit 140 inputs the determination result to the priority determination unit 142 and the switch control unit 145.

[0070] The operation determination unit 141 receives a request to rotate the rotor 13 or a request to externally charge the first and second storage batteries 31, 32. The operation determination unit 141 determines whether the request is a drive request or an external charge request, and inputs the determination result to the priority determination unit 142 and the switch control unit 145.

[0071] When the determination result by temperature rise determination unit 140 that a temperature rise request has been made and the determination result by operation determination unit 141 that a drive request has been made are input, priority determination unit 142 determines which of the temperature rise request and the drive request to prioritize. Furthermore, when the determination result by temperature rise determination unit 140 that a temperature rise request has been made and the determination result by operation determination unit 141 that an external charging request has been made are input, priority determination unit 142 determines which of the temperature rise request and the external charging request to prioritize. Priority determination unit 142 inputs the determination result to switch control unit 145.

[0072] When the priority determination unit 142 receives a determination result that a temperature increase request and a drive request have been made, for example, when it determines that the temperature to be increased Tr is equal to or lower than the temperature increase priority temperature Th*, which is a temperature lower than the target temperature T*, it determines that the temperature increase request should be prioritized.

[0073] When a determination result indicating that a temperature increase request and an external charging request have been made is input, the priority determination unit 142 determines, for example, based on the determination result of the EVECU 110, which of the temperature increase request and the external charging request should be prioritized. The EVECU 110, for example, acquires the temperature increase target temperature Tr from the battery ECU 90 and calculates the output power W of the high-voltage charger 200 or the low-voltage charger 210. The EVECU 110 calculates, based on the temperature increase target temperature Tr and the output power W, a first charging efficiency ηh of the first and second storage batteries 31, 32 when the temperature increase request is prioritized, and a second charging efficiency ηc of the first and second storage batteries 31, 32 when the external charging request is prioritized. The EVECU 110 compares the first charging efficiency ηh with the second charging efficiency ηc to determine whether the temperature increase request or the external charging request should be prioritized. Specifically, when the EVECU 110 determines that the first charging efficiency ηh is greater than the second charging efficiency ηc, it determines that the temperature increase request is prioritized. On the other hand, when the EVECU 110 determines that the first charging efficiency ηh is equal to or less than the second charging efficiency ηc, it determines that the external charging request is prioritized. The EVECU 110 inputs the determination result to the motor ECU 100. The priority determination unit 142 determines which of the temperature increase request and the external charging request is to be prioritized based on the determination result input from the EVECU 110.

[0074] Furthermore, for example, when the priority determination unit 142 determines that the target temperature Tr is equal to or lower than a threshold temperature below freezing, the priority determination unit 142 determines that the temperature increase request is prioritized. The threshold temperature is, for example, a temperature equal to or higher than −20° C. and equal to or lower than −10° C.

[0075] The motor ECU 100 includes a parameter calculation unit 143 and a threshold determination unit 144. The parameter calculation unit 143 calculates a current conduction rate α (corresponding to a "determination parameter"). The current conduction rate α is expressed by the following equation (eq1).

[0076] In the above equation (eq1), VO is the voltage at the neutral point O, which is referred to as the neutral point voltage, and Vbat is the power supply voltage.

[0077] [Heating-Up / Drive Mode] The neutral point voltage VO in the heating-up / drive mode is expressed by the following equation (eq2).

[0078] In the above equation (eq2), Rmg is the impedance of each phase armature winding 11U to 11W and is referred to as the winding impedance. IMc is the current flowing through each phase armature winding 11U to 11W and is referred to as the winding current. VL is the voltage across the terminals of the second storage battery 32.

[0079] The following equation (eq3) can be derived from the above equations (eq1) and (eq2).

[0080] The parameter calculation unit 143 calculates the duty ratio α based on the above equation (eq3). The parameter calculation unit 143 may use the amplitude Ia of the neutral point command current IM* or the phase current detected by the phase current sensor 82 (specifically, for example, the maximum value of the phase current) as the winding current IMc. The parameter calculation unit 143 may also use the sum of the detected values ​​of the first voltage sensor 85A and the second voltage sensor 85B as Vbat, and the detected value of the second voltage sensor 85B as VL. Note that the smoothing capacitor voltage Vdc may also be used as Vbat.

[0081] [Heating-Up / Charging Mode] The neutral point voltage VO in the heating-up / charging mode is expressed by the following equation (eq4).

[0082] In the above equation (eq4), Rbat is the impedance of the second storage battery 32.

[0083] The following equation (eq5) can be derived from the above equations (eq1) and (eq4).

[0084] The parameter calculation unit 143 calculates the duty ratio α in the temperature rise / charging mode during low-voltage charging based on the above equation (eq5). The parameter calculation unit 143 may use the amplitude Ia of the neutral point command current IM* or the phase current (specifically, for example, the maximum value of the phase current) detected by the phase current sensor 82 as the winding current IMc. The parameter calculation unit 143 may also use the sum of the detected values ​​of the first voltage sensor 85A and the second voltage sensor 85B as Vbat, and the detected value of the second voltage sensor 85B as VL. Alternatively, the smoothing capacitor voltage Vdc may be used as Vbat.

[0085] The parameter calculation unit 143 inputs the calculated duty ratio α to the threshold determination unit 144. If the threshold determination unit 144 determines that the duty ratio α is equal to or less than the threshold, it inputs a determination result that limit control will not be executed to the switch control unit 145. If the threshold determination unit 144 determines that the duty ratio α is greater than the threshold, it inputs a determination result that limit control will be executed to the switch control unit 145. In this embodiment, the threshold is set to 1.

[0086] The switch control unit 145 receives the determination results output from the temperature rise determination unit 140, operation determination unit 141, priority determination unit 142, and threshold determination unit 144. Based on the determination results, the switch control unit 145 inputs switching signals for the upper and lower arm switches SUH to SWL to the upper and lower arm switches SUH to SWL. Specifically, the determination result by the temperature rise determination unit 140 that a temperature rise request has been made and the determination result by the operation determination unit 141 that a drive request has been made are input to the switch control unit 145. In this case, the switch control unit 145 controls the switching of the upper and lower arm switches SUH to SWL to execute the temperature rise / drive mode.

[0087] Furthermore, the determination result by temperature rise determination unit 140 that a temperature rise request has been made and the determination result by operation determination unit 141 that an external charging request has been made are input to switch control unit 145. In this case, switch control unit 145 controls the switching of each of the upper and lower arm switches SUH to SWL to execute the temperature rise / charging mode.

[0088] When the switch control unit 145 receives the determination result from the threshold determination unit 144 that the limit control is to be executed and the temperature increase / drive mode is executed, the switch control unit 145 controls the switching of each of the upper and lower arm switches SUH to SWL so that the duty ratio α is equal to or less than 1. Specifically, the switch control unit 145 sets the amplitude Ia of the neutral point command current IM* or the magnitude of the current vector flowing through the armature winding 11 to be smaller than when the limit control is not executed, and controls the switching of each of the upper and lower arm switches SUH to SWL.

[0089] When the switch control unit 145 receives the determination result from the threshold determination unit 144 that limit control is to be executed and executes the temperature increase / charging mode, the switch control unit 145 controls the switching of the upper and lower arm switches SUH to SWL so that the duty ratio α is equal to or less than 1. Specifically, the switch control unit 145 sets the amplitude Ia or the charging power of the second storage battery 32 during low-voltage charging to be smaller than when limit control is not executed, and controls the switching of the upper and lower arm switches SUH to SWL. Reducing the charging power can be achieved, for example, by lowering the target charging voltage Vtgt of the second storage battery 32.

[0090] 11 is a flowchart showing the procedure of the temperature increase control process, which is repeatedly executed by the motor ECU 100 at predetermined control intervals, for example.

[0091] In step S10, the temperature rise determination unit 140 determines whether there is a temperature rise request for the first storage battery 31 and the second storage battery 32. If it is determined in step S10 that there is a temperature rise request, the process proceeds to step S11. In step S11, the switch control unit 145 calculates a neutral point command current IM*, which is a command value for the neutral point current IMr (corresponding to the "heat rise current") required to set the temperature rise target temperature Tr to the target temperature T*.

[0092] In step S12, the operation determination unit 141 determines whether or not there is a request to rotate the rotor 13. If it is determined in step S12 that there is a request to rotate the rotor 13, the process proceeds to step S13, where the d, q-axis command current setting unit 120 calculates the d-axis command current Id* and the q-axis command current Iq*.

[0093] In step S14, the conduction rate α is calculated based on the amplitude Ia of the neutral point command current IM* calculated in step S11, the detected values ​​of the first and second voltage sensors 85A and 85B, and the above equation (eq3).

[0094] In step S15, the threshold value determination unit 144 determines whether the conduction rate α calculated in step S15 is equal to or less than 1. If it is determined in step S15 that the conduction rate α is equal to or less than 1, the process proceeds to step S16.

[0095] In step S16, the switch control section 145 executes the temperature increase / drive mode.

[0096] If it is determined in step S15 that the energization rate α is greater than 1, the process proceeds to step S17. In step S17, the priority determination unit 142 determines which of the temperature increase request and the drive request should be given priority.

[0097] If it is determined in step S17 that the temperature increase request has priority, the process proceeds to step S18, where the duty ratio α is set to 1 or less, and at least one of the d-axis command current Id* and the q-axis command current Iq* is reduced. This reduces the U- to W-phase final command voltages Vu+CF, Vv+CF, and Vw+CF. This reduces the maximum value of the current flowing through the U- to W-phase armature windings 11U, 11V, and 11W, allowing the duty ratio α to be reduced.

[0098] On the other hand, if it is determined that the drive request has priority, the process proceeds to step S19, where the neutral point command current IM* is calculated to reduce the amplitude Ia under the condition that the duty ratio α is set to 1 or less. By reducing the amplitude Ia, the offset correction amount CF is reduced, and the U- to W-phase final command voltages Vu+CF, Vv+CF, and Vw+CF are reduced. As a result, the maximum value of the current flowing through the U- to W-phase armature windings 11U, 11V, and 11W is reduced, allowing the duty ratio α to be reduced.

[0099] If it is determined in step S12 that there is no drive request, the process proceeds to step S20, where it is determined whether there is an external charging request. In the following, it is assumed that the external charging request is a low-voltage charging request.

[0100] If it is determined in step S20 that there is a request for external charging, the process proceeds to step S21. In step S21, the switch control unit 145 calculates the conduction rate α based on the amplitude Ia calculated in step S11, the detection values ​​of the first and second voltage sensors 85A and 85B, and the above equation (eq5).

[0101] In step S22, the threshold value determining unit 144 determines whether the conduction rate α is equal to or less than 1. If it is determined in step S22 that the conduction rate α is equal to or less than 1, the process proceeds to step S23.

[0102] In step S23, the switch control unit 145 executes the temperature increase / charge mode.

[0103] If it is determined in step S22 that the energization rate α is greater than 1, the process proceeds to step S24. In step S24, the priority determination unit 142 determines which of the temperature increase request and the external charging request should be given priority.

[0104] If it is determined in step S24 that the temperature increase request is to be prioritized, the process proceeds to step S25, where a condition is imposed that the energization rate α be equal to or less than 1, and the charging power of the second storage battery 32 is reduced, specifically, for example, the target charging voltage Vtgt of the second storage battery 32 is reduced. This allows the energization rate α to be reduced.

[0105] On the other hand, if it is determined that the external charging request is to be prioritized, the process proceeds to step S26, where the condition that the conduction rate α is 1 or less is imposed, and the neutral point command current IM* is calculated so as to reduce the amplitude Ia.

[0106] According to the present embodiment described above in detail, the following effects can be obtained.

[0107] If the temperature rise control and the drive control of the motor 10 are executed simultaneously, the neutral point current IMr that is passed to raise the temperatures of the first storage battery 31 and the second storage battery 32 may not flow in a sinusoidal waveform, which may reduce the efficiency of the temperature rise control. Also, there is a concern that the controllability of the motor 10 may be reduced.

[0108] If the temperature rise control and the external charging control in which the first and second storage batteries 31, 32 are charged by the low-voltage charger 230 are simultaneously executed, the neutral point current IMr will not flow in a sinusoidal waveform, which may reduce the efficiency of the temperature rise control. Also, if an AC current is added to the DC current flowing through the first and second storage batteries 31, 32, there is a concern that the charging efficiency of the first storage battery 31 and the second storage battery 32 will decrease.

[0109] Therefore, in this embodiment, limit control is executed when it is determined that the duty ratio α expressed by the above equation (eq1) is greater than 1. Here, the duty ratio α is the ratio of the voltage at the neutral point O to the power supply voltage Vbat. In the limit control, in the temperature rise / drive mode, the duty ratio α is set to 1 or less, and the neutral point command current IM* is calculated to reduce the magnitude of the current vector or reduce the amplitude Ia. In the temperature rise / charge mode, the duty ratio α is set to 1 or less, and the neutral point command current IM* is calculated to reduce the charging power of the second storage battery 32 or reduce the amplitude Ia. This makes it possible to prevent a decrease in the efficiency of temperature rise control and a decrease in the controllability of the motor 10 in the temperature rise / drive mode. In the temperature rise / charge mode, it is possible to prevent a decrease in the efficiency of temperature rise control and a decrease in the charging efficiency of the first and second storage batteries 31, 32.

[0110] When it is determined that there is a temperature increase request and a drive request, the priority determination unit 142 determines which of the temperature increase request and the drive request should be prioritized. This makes it possible to suppress a decrease in the amplitude Ia of the neutral point command current IM* when temperature increase is prioritized, and to suppress a decrease in the magnitude of the current vector flowing through the armature winding 11 when drive is prioritized. Furthermore, when it is determined that there is a temperature increase request and an external charging request, the priority determination unit 142 determines which of the temperature increase request and the external charging request should be prioritized. This makes it possible to suppress a decrease in the amplitude Ia when temperature increase is prioritized, and to suppress a decrease in the charging power of the second storage battery 32 when charging is prioritized.

[0111] Second Embodiment The second embodiment will be described below with reference to the drawings, focusing on differences from the first embodiment. In this embodiment, as shown in FIG. 12 , a connection path 73 electrically connects the neutral point O of the armature winding 11 to the high-potential-side intermediate terminal BH. The high-potential-side intermediate terminal BH is on a path connecting the inter-battery switch 50 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.

[0112] 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 .

[0113] Next, the external charging control of this embodiment will be described. Figure 13 shows the control state of each switch during external charging control using the low-voltage charger 210. When the motor ECU 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 charges the second storage battery 32.

[0114] In the external charging control by the low-voltage charger 210, the motor ECU 100 performs switching control to alternately turn on upper and lower arm switches (corresponding to the "target switches") of at least one phase, or performs switching control to turn on at least one lower arm switch (corresponding to the "target switches") of at least one phase while keeping the upper arm switches SUH, SVH, and 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 motor ECU 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.

[0115] In this embodiment, the motor ECU 100 executes the voltage boost / drive mode or the voltage boost / charge mode, as in the first embodiment. In this embodiment, when the temperature increase / drive mode is executed, the neutral point voltage VO is expressed by the following equation (eq6).

[0116] In the above equation (eq6), VH is the terminal voltage of the first storage battery 31.

[0117] The following equation (eq7) can be derived from the above equations (eq1) and (eq6).

[0118] The parameter calculation unit 143 calculates the conduction rate α based on the above equation (eq7). The parameter calculation unit 143 may use the detection value of the first voltage sensor 85A as VH.

[0119] In this embodiment, when the boost / charge mode during low-voltage charging is executed, the neutral point voltage VO is expressed by the following equation (eq8).

[0120] In the above equation (eq8), Rbat is the impedance of the first storage battery 31.

[0121] The following equation (eq9) can be derived from the above equations (eq1) and (eq8).

[0122] The parameter calculation unit 143 calculates the conduction rate α in the temperature rise / charging mode during low voltage charging based on the above equation (eq9). The parameter calculation unit 143 may use the detection value of the first voltage sensor 85A as VH.

[0123] According to the present embodiment described above, it is possible to achieve the same effects as the first embodiment.

[0124] Other Embodiments The above-described embodiments may be modified as follows.

[0125] If it is determined in step S15 of FIG. 11 that the energization rate α is greater than 1, step S19 may be executed without executing step S17.

[0126] If it is determined in step S22 of FIG. 11 that the energization rate α is greater than 1, step S24 may not be executed, and step S26 may be executed instead.

[0127] The method for setting the neutral point command current IM* is not limited to the method shown in Fig. 8. For example, the positive neutral point command current IM* and the negative neutral point command current IM* may be set to a trapezoidal wave or a rectangular wave, while satisfying a point-symmetric relationship between the positive neutral point command current IM* and the negative neutral point command current IM* with respect to the zero-cross timing of the neutral point command current IM* in one cycle Tc.

[0128] Furthermore, the method for setting the neutral point command current IM* is not limited to the point-symmetric relationship described above. For example, the neutral point command current IM* may be set so that, in one cycle Tc, the period from the first zero-cross timing C1 to the second zero-cross timing C2 of the neutral point command current IM* is different from the period from the second zero-cross timing C2 to the third zero-cross timing C3 of the neutral point command current IM*, and so that the area S1 of the first region and the area S2 of the second region are equal. Even in this case, the balance of the charge and discharge currents of the first storage battery 31 and the second storage battery 32 in one cycle Tc can be balanced.

[0129] In the power conversion device of the first embodiment, the inter-battery switch 50 and the bypass switch 60 do not have to be provided in the power conversion device as shown in Fig. 14. Furthermore, at least one of the inter-battery switch 50 and the bypass switch 60 does not have to be provided in the power conversion device. When the inter-battery switch 50 is not provided in the power conversion device, the negative terminal of the first storage battery 31 and the positive terminal of the second storage battery 32 are electrically connected.

[0130] The threshold value of the energization rate α may be set to a value smaller than 1. The threshold value of the energization rate α is, for example, a value greater than or equal to 0.9 and less than 1, or a value greater than or equal to 0.95 and less than 1.

[0131] In the flowchart shown in FIG. 11 , a correlation value of the ratio of the neutral point voltage VO to the power supply voltage Vbat may be used instead of the duty ratio α. For example, the correlation value is a voltage utilization ratio m. The voltage utilization ratio m is expressed, for example, by the following equation (eq10):

[0132] The parameter calculation unit 143 calculates the voltage utilization rate m based on the above equation (eq10). The parameter calculation unit 143 may use, for example, the d-axis voltage Vd calculated by the d-axis control unit 122d as Vd. The parameter calculation unit 143 may use, for example, the q-axis voltage Vq calculated by the q-axis control unit 122q as Vq.

[0133] The correlation value may be, for example, a modulation factor. The motor ECU 100 may use, as the modulation factor, the maximum value of the U- to W-phase modulation factors Mu, Mv, and Mw calculated by the U- to W-phase modulation units 135U to 135W.

[0134] 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.

[0135] 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.

[0136] The high-potential side main switch SMRH does not have to be provided.

[0137] 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.

[0138] The fuses 41 and 42 do not have to be provided.

[0139] 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.

[0140] The control device that performs the boost / drive mode or the boost / charge mode is not limited to the motor ECU 100. For example, each control may be performed by cooperation of a plurality of control devices such as the battery ECU 90, the EVECU 110, and the motor ECU 100.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] 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 including: an inverter (20) having upper and lower arm switches (SUH to SWL) of a plurality of phases; and a motor (10) having an armature winding (11U to 11W) electrically connected to a low potential side terminal of the upper arm switch of each phase and a high potential side terminal of the lower arm switch of each phase, the power conversion device including: a high potential side path (22H) electrically connecting a positive terminal of a 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 a 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 or the positive terminal of the second power storage unit and the armature winding; and a control device (100), wherein the control device a temperature rise determination unit (140) that determines whether or not there is a temperature rise request to flow an AC temperature rise current between the first power storage unit and the second power storage unit via the armature winding and the connection path; an operation determination unit (141) that determines whether or not there is an operation request to flow a DC operating current to at least one of the first power storage unit and the second power storage unit; a switch control unit (145) that, when it is determined that there is the temperature rise request and that there is the operation request, performs switching control of the upper and lower arm switches to flow the temperature rise current between the first power storage unit and the second power storage unit and to flow the operating current to at least one of the first power storage unit and the second power storage unit; and a threshold determination unit (144) that determines whether or not a determination parameter (α) that is either a ratio of a neutral point voltage of the armature winding to a voltage difference between the high potential side path and the low potential side path or a correlation value of the ratio is equal to or less than a threshold, When it is determined that the determination parameter is greater than the threshold value, the switch control unit performs limit control, which is the switching control that imposes a condition that the determination parameter be equal to or less than the threshold value.

2. The power conversion device according to claim 1, wherein the switch control unit, in the limit control, reduces the amplitude of the heating current compared to when it is determined that the determination parameter is equal to or less than the threshold value.

3. The power conversion device according to claim 1, wherein the switch control unit reduces the magnitude of the current vector flowing through the armature winding in the limit control compared to when it is determined that the judgment parameter is equal to or less than the threshold value.

4. A power conversion device according to any one of claims 1 to 3, further comprising a priority determination unit (142) that determines which of the temperature increase request and the operation request is to be given priority, wherein the operation request is a request to drive a rotor (13) of the motor, and wherein the switch control unit, when it is determined that the temperature increase request has priority, reduces the magnitude of the current vector to be passed through the armature winding in the limit control compared to when it is determined that the determination parameter is equal to or less than the threshold value, and when it is determined that the operation request has priority, reduces the amplitude of the temperature increase current in the limit control compared to when it is determined that the determination parameter is equal to or less than the threshold value.

5. The power conversion device according to any one of claims 1 to 3, further comprising a priority determination unit (142) that determines which of the temperature increase request and the operation request is to be given priority, wherein the operation request is an external charging request when an external charger (200, 210) is electrically connected to the high potential side path and the low potential side path, and wherein the switch control unit, when it is determined that the temperature increase request has priority, reduces the charging power of one of the second storage unit and the first storage unit that is charged from the external charger via the connection path from the external charger in the limit control compared to when it is determined that the determination parameter is equal to or less than the threshold, and when it is determined that the operation request has priority, reduces the amplitude of the temperature increase current in the limit control compared to when it is determined that the determination parameter is equal to or less than the threshold.

6. The power conversion device according to any one of claims 1 to 3, wherein the operation determination unit determines whether or not there is a request to rotate a rotor (13) of the motor as the operation request, and when it is determined that there is the temperature increase request and the rotation drive request, the switch control unit performs the switching control to flow the temperature increase current between the first power storage unit and the second power storage unit and to flow the operating current from the series connection of the first power storage unit and the second power storage unit to the inverter.

7. The power conversion device according to claim 4, wherein the operation determination unit determines whether or not there is a request to rotate a rotor (13) of the motor as the operation request, and when it is determined that there is the temperature increase request and the rotation drive request, the switch control unit performs the switching control to flow the temperature increase current between the first storage unit and the second storage unit and to flow the operating current from the series connection of the first storage unit and the second storage unit to the inverter.

8. The power conversion device according to any one of claims 1 to 3, wherein the operation determination unit determines whether or not an external charger (200, 210) is electrically connected to the high potential side path and the low potential side path and an external charging request is present as the operation request, and when it is determined that the temperature increase request and the external charging request are present, the switch control unit causes the temperature increase current to flow between the first power storage unit and the second power storage unit and performs the switching control to charge at least one of the first power storage unit and the second power storage unit with the external charger.

9. The power conversion device according to claim 5, wherein the operation determination unit determines whether or not an external charger (200, 210) is electrically connected to the high potential side path and the low potential side path and an external charging request is present as the operation request, and when it is determined that the temperature increase request and the external charging request are present, the switch control unit causes the temperature increase current to flow between the first storage unit and the second storage unit and performs the switching control to charge at least one of the first storage unit and the second storage unit with the external charger.

10. A program applicable to a power conversion device including: an inverter (20) having upper and lower arm switches (SUH to SWL) of a plurality of phases; and a motor (10) having an armature winding (11U to 11W) electrically connected to a low potential side terminal of the upper arm switch of each phase and a high potential side terminal of the lower arm switch of each phase, the power conversion device comprising: a high potential side path (22H) electrically connecting a positive terminal of a 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 a 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 or the positive terminal of the second power storage unit and the armature winding; and a computer (101), wherein the computer a temperature rise determination process for determining whether or not there is a temperature rise request to flow an AC temperature rise current between the first power storage unit and the second power storage unit via the armature winding and the connection path; an operation determination process for determining whether or not there is an operation request to flow a DC operating current to at least one of the first power storage unit and the second power storage unit; a control process for performing switching control of the upper and lower arm switches to flow the temperature rise current between the first power storage unit and the second power storage unit and to flow the operating current to at least one of the first power storage unit and the second power storage unit when it is determined that there is the temperature rise request and the operation request; and a threshold determination process for determining whether or not a determination parameter (α) is a ratio of a neutral point voltage of the armature winding to a voltage difference between the high potential side path and the low potential side path or a correlation value of the ratio is equal to or less than a threshold, and when it is determined that the determination parameter is greater than the threshold in the control process, the program performs limit control, which is the switching control with a condition that the determination parameter be set to be equal to or less than the threshold.

11. A control method for a power conversion device applicable to a power conversion device including: an inverter (20) having upper and lower arm switches (SUH to SWL) of a plurality of phases; and a motor (10) having an armature winding (11U to 11W) electrically connected to a low potential side terminal of the upper arm switches of each phase and a high potential side terminal of the lower arm switches of each phase, wherein the power conversion device includes: a high potential side path (22H) electrically connecting a positive terminal of a 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 a second power storage unit (32) and a low potential side terminal of the lower arm switch; and a connection path (73) electrically connecting the negative terminal of the first power storage unit or the positive terminal of the second power storage unit and the armature winding, the control system comprises: a temperature raising step of determining whether or not there is a temperature raising request to flow an AC temperature raising current between the first power storage unit and the second power storage unit via the armature winding and the connection path; an operation determining step of determining whether or not there is an operation request to flow a DC operating current to at least one of the first power storage unit and the second power storage unit; a control step of performing switching control of the upper and lower arm switches to flow the temperature raising current between the first power storage unit and the second power storage unit and to flow the operating current to at least one of the first power storage unit and the second power storage unit when it is determined that there is the temperature raising request and the operation request; and a threshold determining step of determining whether or not a determination parameter (α) which is either a ratio of a neutral point voltage of the armature winding to a voltage difference between the high potential side path and the low potential side path or a correlation value of the ratio is equal to or less than a threshold, A control method for a power conversion device, wherein, if it is determined in the control step that the judgment parameter is greater than the threshold, limit control is performed, which is the switching control that imposes a condition that the judgment parameter is equal to or less than the threshold.

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