Electric power conversion system and drive system

Abstract

To provide an electric power conversion system and a drive system capable of detecting an abnormality in an electric conduction path and a current sensor.SOLUTION: An electric power conversion circuit 4 has invertors 8, 9. The invertor 8 is connected to one end of coils 3U, 3V, 3W via an output line 13. The invertor 9 is connected to the other end of the coils 3U, 3V, 3W via the output line 13. A first current sensor 121 detects a current flowing in the output line 13. A second current sensor 121 detects a current flowing in the output line 14. A controller 15 uses detection values I1, I2 of the current sensors 121, 122 to detect the occurrence of an abnormality in the current sensors 121, 122. The controller 15 controls a rotary electric machine 3 by using one of the first detection value I1 and the second detection value I2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] TECHNICAL FIELD The disclosure herein relates to power conversion devices and drive systems. [Background technology]

[0002] Patent Document 1 discloses a power conversion device including a first inverter connected to one end of a winding of a rotating electric machine and a second inverter connected to the other end of the winding. A current sensor is provided in the connection path connecting the first inverter and the winding. One current sensor is provided for each of the three-phase connection paths. The contents of the prior art documents are incorporated by reference as explanations of the technical elements in this specification. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-177342 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned Patent Document 1, there is a concern that even if an abnormality occurs in the current path such as the winding or the current sensor, the abnormality in the current path or the current sensor cannot be detected. From the above-mentioned viewpoints and other viewpoints not mentioned, further improvements in power conversion modules are required.

[0005] One disclosed object is to provide a power conversion device and a drive system that can detect abnormalities in current paths and current sensors. [Means for solving the problem]

[0006] One aspect of the disclosure is A power conversion device (4) that converts power supplied to a rotating electric machine (3), a first inverter (8) connected to one end of a winding of the rotating electric machine via a first path (13); a second inverter (9) connected to the other end of the winding via a second path (14); a first current sensor (121) for detecting a current flowing through a first path in a target phase that is at least one of the multiple phases; a second current sensor (122) for detecting a current flowing through a second path in a target phase; The power conversion device is provided with:

[0007] According to the above power conversion device, in the target phase, the first current sensor detects the current flowing in the first path, and the second current sensor detects the current flowing in the second path. With this configuration, it is possible to determine whether an abnormality has occurred in the current path of the windings, etc., or in the first or second current sensor using the detection results of the first and second current sensors. Therefore, it is possible to detect an abnormality in the current path or the current sensor.

[0008] One aspect of the disclosure is A rotating electric machine (3), a power converter (4) that converts power supplied to the rotating electric machine; A drive system (1) for driving a rotating electric machine by a power conversion device, comprising: a first inverter (8) connected to one end of a winding of the rotating electric machine via a first path (13); a second inverter (9) connected to the other end of the winding via a second path (14); a first current sensor (121) for detecting a current flowing through a first path in a target phase that is at least one of the multiple phases; a second current sensor (122) for detecting a current flowing through a second path in a target phase; The drive system is provided with:

[0009] According to the drive system, like the power conversion device, it is possible to detect abnormalities in the current paths and current sensors.

[0010] The various aspects disclosed in this specification employ different technical means to achieve their respective objectives. The reference numerals in parentheses in the claims and in this section are intended to exemplify correspondences with the following embodiments and are not intended to limit the technical scope. The objectives, features, and advantages disclosed in this specification will become more apparent by reference to the following detailed description and the accompanying drawings. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 illustrates a power conversion circuit and a drive system. [Figure 2] FIG. 4 is a diagram showing an example of an operating point map of the rotating electric machine. [Figure 3] FIG. 1 is a diagram showing a star-connected drive. [Figure 4] FIG. 10 is a diagram illustrating an open connection drive. [Figure 5] FIG. 2 is a circuit diagram showing a state in which an external device is connected. [Figure 6] 10 is a flowchart showing the procedure of a rotation control process. [Figure 7] FIG. 10 is a diagram illustrating a reference example. [Figure 8] FIG. 10 is a diagram illustrating a reference example. [Figure 9] FIG. 10 is a diagram illustrating a power conversion circuit and a drive system according to a modified example. [Figure 10] FIG. 10 is a diagram illustrating a power conversion circuit and a drive system according to a modified example. [Figure 11] FIG. 10 is a diagram illustrating a power conversion circuit and a drive system according to a modified example. [Figure 12] FIG. 10 is a diagram illustrating a power conversion circuit and a drive system according to a modified example. [Figure 13] FIG. 10 is a diagram illustrating a power conversion circuit and a drive system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, several embodiments will be described with reference to the drawings. Note that in each embodiment, corresponding components are designated by the same reference numerals, and redundant description may be omitted. When only a portion of the configuration is described in each embodiment, the configuration of another embodiment previously described may be applied to the remaining portion of the configuration. Furthermore, in addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations of several embodiments may be partially combined together even if not explicitly stated, provided that there is no particular problem with the combination.

[0013] The power conversion module of this embodiment is applied to, for example, a mobile body using a rotating electric machine as a drive source, such as an electric vehicle (BEV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), an aircraft such as an electric vertical take-off and landing aircraft or a drone, a ship, a construction machine, an agricultural machine, etc.

[0014] (First embodiment) First, the schematic configuration of a drive system for a moving body will be described with reference to FIG.

[0015] <Drive systems for moving objects> As shown in FIG. 1, a drive system 1 for a moving body includes a DC power supply 2, a rotating electric machine 3, and a power conversion circuit 4.

[0016] The DC power supply 2 may be, for example, a rechargeable secondary battery such as a lithium ion battery or a nickel-metal hydride battery. The DC power supply 2 may also be one that converts AC power to DC and outputs it. The DC power supply 2 supplies power to the rotating electrical machine 3. The DC power supply 2 corresponds to a power supply unit.

[0017] The rotating electric machine 3 is a three-phase open-winding type rotating electric machine with an open neutral point. The rotating electric machine 3 has a U-phase winding 3U, a V-phase winding 3V, and a W-phase winding 3W. Hereinafter, the U-phase winding 3U, the V-phase winding 3V, and the W-phase winding 3W may be simply referred to as windings 3U, 3V, and 3W.

[0018] The rotating electric machine 3 functions, for example, as a drive source for a moving body, that is, as an electric motor. If the moving body is a vehicle, the rotating electric machine 3 generates torque for driving drive wheels (not shown). The rotating electric machine 3 is not limited to an electric motor. The rotating electric machine 3 may be a motor generator that functions as both an electric motor and a generator, or may be a generator.

[0019] The power conversion circuit 4 converts power between the DC power source 2 and the rotating electric machine 3. The power conversion circuit 4 corresponds to a power conversion device. The power conversion circuit 4 is a three-phase power conversion device. The drive system 1 is a common power supply system in which a common DC power source 2 supplies power to two inverters 8 and 9 (described later) to drive the rotating electric machine 3. The drive system 1 may include only one common DC power source 2 as illustrated in FIG. 1, or multiple common DC power sources 2. The drive system 1 may include a power supply switch (not shown), such as an SMR, between the DC power source 2 and the power conversion circuit 4. SMR is an abbreviation for System Main Relay. Turning on the power supply switch enables power supply from the DC power source 2 to the rotating electric machine 3, and turning off the power supply switch cuts off the power supply from the DC power source 2 to the rotating electric machine 3.

[0020] <Power conversion circuit> Next, the power conversion circuit 4 will be described with reference to Fig. 1. Fig. 1 shows an example of the power conversion circuit 4. The power conversion circuit 4 shown in Fig. 1 includes power lines 5 and 6, a smoothing capacitor 7, inverters 8 and 9, a changeover switch 10, and snubber circuits 11 and 12.

[0021] The power supply line 5 is a high-potential power line. The power supply line 5 is connected to the positive electrode of the DC power supply 2. The power supply line 5 may be referred to as a positive-side power supply line, P line, etc. The power supply line 5 has a wiring 5A. The wiring 5A is a part of the wiring that constitutes the power supply line 5. The wiring 5A is a part of the power supply line 5 that connects the inverter 8 and the inverter 9. The power supply line 6 is a low-potential power line. The power supply line 6 is connected to the negative electrode of the DC power supply 2. The power supply line 6 may be referred to as a negative-side power supply line, N line, etc. The power supply line 6 has a wiring 6A. The wiring 6A is a part of the wiring that constitutes the power supply line 6. The wiring 6A is a part of the power supply line 6 that connects the inverter 8 and the inverter 9. The power supply lines 5, 6 are configured to include a bus bar that is, for example, a metal plate.

[0022] The smoothing capacitor 7 mainly smoothes the DC voltage supplied from the DC power supply 2. The smoothing capacitor 7 is provided between the power supply lines 5 and 6. The positive electrode of the smoothing capacitor 7 is connected to the power supply line 5 between the DC power supply 2 and the inverters 8 and 9. The negative electrode of the smoothing capacitor 7 is connected to the power supply line 6 between the DC power supply 2 and the inverters 8 and 9. The smoothing capacitor 7 is connected in parallel to the inverters 8 and 9.

[0023] The inverters 8 and 9 are DC-AC conversion circuits. The inverters 8 and 9 are three-phase inverter circuits. The inverter 8 corresponds to a first inverter, and the inverter 9 corresponds to a second inverter. The inverter 8 is configured with upper and lower arm circuits 8HL for three phases. The upper and lower arm circuits 8HL are sometimes referred to as legs. The upper and lower arm circuit 8HL has an upper arm 8H and a lower arm 8L. The upper arm 8H and the lower arm 8L are connected in series between the power supply lines 5 and 6, with the upper arm 8H on the power supply line 5 side.

[0024] The connection point between the upper arm 8H and the lower arm 8L is connected to the winding of the corresponding phase in the rotating electric machine 3 via an output line 13. The inverter 8 has six arms. Each arm is configured with a switching element. The number of switching elements configuring each arm is not particularly limited. There may be one or more. When there are more than one switching elements, the multiple switching elements connected in parallel to each other are turned on and off at the same timing by a common gate drive signal (drive voltage).

[0025] In the example shown in FIG. 1, an n-channel MOSFET 8S is used as the switching element constituting each arm. MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor. In the upper arm 8H, the drain terminal of the MOSFET 8S is connected to the power supply line 5. In the lower arm 8L, the source terminal of the MOSFET 8S is connected to the power supply line 6. The source terminal of the MOSFET 8S in the upper arm 8H and the drain terminal of the MOSFET 8S in the lower arm 8L are connected to each other.

[0026] A freewheeling diode 8D is connected in antiparallel to each MOSFET 8S. The diode 8D may be a parasitic diode (body diode) of the MOSFET 8S, or may be provided separately from the parasitic diode. The anode terminal of the diode 8D is connected to the source terminal of the corresponding MOSFET 8S, and the cathode terminal is connected to the drain terminal.

[0027] The inverter 9 has the same configuration as the inverter 8. The inverter 9 is configured with upper and lower arm circuits 9HL for three phases. The upper and lower arm circuit 9HL has an upper arm 9H and a lower arm 9L. The upper arm 9H and the lower arm 9L are connected in series between the power supply lines 5 and 6, with the upper arm 9H on the power supply line 5 side.

[0028] The connection point between the upper arm 9H and the lower arm 9L is connected to the winding of the corresponding phase in the rotating electric machine 3 via an output line 14. The inverter 9 also has six arms. Each arm is configured with a switching element. The number of switching elements constituting each arm is not particularly limited. It may be one or more.

[0029] In the example shown in Fig. 1, an n-channel MOSFET 9S is used as the switching element constituting each arm. In the upper arm 9H, the drain terminal of the MOSFET 9S is connected to the power supply line 5. In the lower arm 9L, the source terminal of the MOSFET 9S is connected to the power supply line 6. The source terminal of the MOSFET 9S in the upper arm 9H and the drain terminal of the MOSFET 9S in the lower arm 9L are connected to each other. A freewheeling diode 9D is connected in anti-parallel to each MOSFET 9S.

[0030] As described above, the high-potential terminals (drain terminals) of the upper arms 8H, 9H of the inverters 8, 9 are connected to the power line 5. The low-potential terminals (source terminals) of the lower arms 8L, 9L are connected to the power line 6. A node connecting the upper arm 8H and the lower arm 8L is connected to one end of the corresponding phase winding via an output line 13, and a node connecting the upper arm 9H and the lower arm 9L is connected to the other end of the corresponding phase winding via an output line 14. Specifically, one end of the U-phase winding 3U is connected to a node U1 of the U-phase upper and lower arm circuit 8HL, and the other end of the U-phase winding 3U is connected to a node U2 of the U-phase upper and lower arm circuit 9HL. One end of the V-phase winding 3V is connected to a node V1 of the V-phase upper and lower arm circuit 8HL, and the other end of the V-phase winding 3V is connected to a node V2 of the V-phase upper and lower arm circuit 9HL. One end of the W-phase winding 3W is connected to a node W1 of a W-phase upper and lower arm circuit 8HL, and the other end of the W-phase winding 3W is connected to a node W2 of a W-phase upper and lower arm circuit 9HL.

[0031] The switching elements constituting the inverters 8 and 9 are not limited to the MOSFETs described above. For example, IGBTs may be used. IGBT stands for Insulated Gate Bipolar Transistor. In the case of an IGBT, a freewheeling diode is also connected in anti-parallel.

[0032] The changeover switch 10 is a semiconductor switch. A semiconductor switch has a switching element formed on a semiconductor chip. The switching element is not particularly limited and may have the same configuration as the switching element constituting at least one of the inverters 8, 9, or may have a different configuration. The changeover switch 10 is provided between the inverters 8 and 9 on at least one of the power supply lines 5, 6. When the changeover switch 10 is closed, it connects the high-potential side terminal of the upper arm 9H of the inverter 9 to the smoothing capacitor 7 (DC power supply 2). When the changeover switch 10 is open, it cuts off the connection between the high-potential side terminal of the upper arm 9H and the smoothing capacitor 7 (DC power supply 2). The changeover switch 10 may also be called a switch or an open / close switch.

[0033] The switching element of the changeover switch 10 illustrated in FIG. 1 is a MOSFET. A diode is connected in anti-parallel to the MOSFET. The diode is, for example, a parasitic diode. The changeover switch 10 includes changeover switches 10A and 10B. The changeover switch 10A is arranged on wiring 5A of the power supply line 5. The changeover switch 10A is arranged on wiring 5A so that the drain terminal of the MOSFET is on the inverter 8 side and the source terminal is on the inverter 9 side. In other words, the changeover switch 10A is arranged so that the forward direction of the diode is from the inverter 9 to the inverter 8.

[0034] The changeover switch 10B is arranged on the wiring 6A of the power supply line 6. The changeover switch 10B is arranged on the wiring 6A so that the drain terminal of the MOSFET is on the inverter 9 side and the source terminal is on the inverter 8 side. In other words, the changeover switch 10B is arranged so that the forward direction of the diode is from the inverter 8 to the inverter 9. When the MOSFET is turned on and the changeover switch 10 is closed, the inverter 9 is electrically connected to the smoothing capacitor 7 (DC power supply 2). When the MOSFET is turned off and the changeover switch 10 is opened, the electrical connection between the inverter 9 and the smoothing capacitor 7 is interrupted.

[0035] The snubber circuit 11 is connected in parallel to the inverter 9, i.e., the upper and lower arm circuits 9HL. The snubber circuit 11 reduces the inductance of the upper and lower arm circuits 9HL. In other words, the snubber circuit 11 absorbs a transient high voltage, or so-called switching surge, that occurs when the switching elements (MOSFETs 9S) that make up the upper and lower arm circuits 9HL are switched. This enables the inverter 9 to perform high-speed switching.

[0036] The snubber circuit 11 has at least a capacitor 11C. The snubber circuit 11 may be, for example, a C snubber circuit having a capacitor, or an RC snubber circuit having a capacitor and a resistor. It may also be an RCD snubber circuit having a capacitor, a resistor, and a diode. The snubber circuit 11 shown in FIG. 1 is an RC snubber circuit in which a capacitor 11C and a resistor 11R are connected in series. One end of the snubber circuit 11 is connected to the power supply line 5. Another end of the snubber circuit 11 is connected to a portion of the wiring 5A that connects the changeover switch 10 and the inverter 9. The other end of the snubber circuit 11 is connected to the power supply line 6.

[0037] In the power conversion circuit 4 illustrated in FIG. 1, a snubber circuit 11 is provided for each phase of the upper and lower arm circuits 9HL. The power conversion circuit 4 includes three snubber circuits 11. One end of each snubber circuit 11 is connected to the power supply line 5, and the other end is connected to the power supply line 6. Each snubber circuit 11 includes a capacitor 11C and a resistor 11R. One of the snubber circuits 11 is connected in parallel to the U-phase upper and lower arm circuit 9HL. The other snubber circuit 11 is connected in parallel to the V-phase upper and lower arm circuit 9HL. The other snubber circuit 11 is connected in parallel to the W-phase upper and lower arm circuit 9HL.

[0038] The snubber circuit 12 is connected in parallel to the inverter 8, i.e., the upper and lower arm circuits 8HL. The snubber circuit 12 reduces the inductance of the upper and lower arm circuits 8HL, thereby enabling high-speed switching of the inverter 8. The snubber circuit 12 includes at least a capacitor 12C. The snubber circuit 12 may be, for example, a C snubber circuit, an RC snubber circuit, or an RCD snubber circuit. The snubber circuit 12 shown in FIG. 1 is an RC snubber circuit in which a capacitor 12C and a resistor 12R are connected in series. One end of the snubber circuit 12 is connected to the power supply line 5. The other end of the snubber circuit 12 is connected to the power supply line 6.

[0039] In the power conversion circuit 4 illustrated in FIG. 1, a snubber circuit 12 is provided for each phase of the upper and lower arm circuits 8HL. The power conversion circuit 4 includes three snubber circuits 12. One end of each snubber circuit 12 is connected to the power supply line 5, and the other end is connected to the power supply line 6. Each snubber circuit 12 includes a capacitor 12C and a resistor 12R. One of the snubber circuits 12 is connected in parallel to the U-phase upper and lower arm circuit 8HL. The other snubber circuit 12 is connected in parallel to the V-phase upper and lower arm circuit 8HL. The other snubber circuit 12 is connected in parallel to the W-phase upper and lower arm circuit 8HL.

[0040] As illustrated in FIG. 1, the power conversion circuit 4 may include a control unit (CTR) 15. The control unit 15 may include, for example, a processor 15a, a memory 15b, and a storage 15c. The processor 15a accesses the memory 15b to execute various processes. The memory 15b is a rewritable volatile storage medium. The memory 15b is, for example, a RAM. RAM is an abbreviation for Random Access Memory. The storage 15c is a rewritable nonvolatile memory. The storage 15c may be realized by at least one type of non-transitory tangible storage medium, such as a semiconductor memory, a magnetic medium, or an optical medium. The storage 15c may include multiple types of storage media, such as a ROM and a flash memory. ROM is an abbreviation for Read Only Memory.

[0041] The storage 15c stores a program 15d executed by the processor 15a. The program 15d configures a plurality of functional units by causing the processor 15a to execute a plurality of instructions. The processing performed by the control unit 15 may be realized by software processing in which the processor 15a executes the program 15d described above, or may be realized by hardware processing using a dedicated electronic circuit. It may also be realized by a combination of software processing and hardware processing. The program 15d includes a program for executing a rotation control process, which will be described later.

[0042] The control unit 15 may include, for example, a drive command generation unit and a drive circuit unit (not shown). The drive command generation unit controls the inverters 8 and 9. The drive command generation unit generates drive commands (command signals) for controlling the on / off of the MOSFETs 8S and 9S and outputs them to the drive circuit unit. The drive command generation unit generates drive commands based on drive requests for the rotating electric machine 3, such as torque command values ​​input from a higher-level ECU (not shown), and signals detected by various sensors. The various sensors may include current sensors, rotation angle sensors, voltage sensors, and the like (not shown). The current sensors detect phase currents flowing through the windings 3U, 3V, and 3W of each phase. The rotation angle sensor detects the rotation angle of the rotor of the rotating electric machine 3. The voltage sensor detects the voltage across the smoothing capacitor 7. Current sensors include current sensors 121 and 122 (described later).

[0043] The drive command generation unit controls the changeover switch 10 (10A, 10B). The drive command generation unit generates drive commands for controlling the on / off of the changeover switch 10 and outputs the drive commands to the drive circuit unit. The drive circuit unit is sometimes referred to as a driver. The drive circuit unit can independently control the on / off of the MOSFET 8S, MOSFET 9S, and changeover switch 10 based on the drive commands. For convenience, signal lines for transmitting drive signals from the control unit 15 to each switching element are omitted in FIG. 1.

[0044] <Star connection drive and open connection drive> Next, star connection driving and open connection driving will be described with reference to Figures 2, 3, and 4. Figure 2 shows an example of an operating point map of a rotating electric machine, with the horizontal axis representing rotation speed and the vertical axis representing torque. Figure 3 is a diagram showing star connection driving. Figure 4 is a diagram showing open connection driving. For convenience, the control unit 15 is omitted from Figures 3 and 4.

[0045] As shown in FIG. 2, the driving range of the rotating electric machine 3 is divided into two ranges depending on the rotation speed and torque. One of the driving ranges is the star connection driving range. The star connection driving range is the normal use range. The other driving range is the open connection driving range. The open connection driving range is a range with higher rotation speeds or higher torque than the star connection driving range.

[0046] When the operating point is in the star connection drive region, the control unit 15 executes star connection drive control. Star connection drive is sometimes referred to as Y drive. The control unit 15 controls the MOSFETs 8S and 9S and the changeover switch 10 so that the windings 3U, 3V, and 3W are in a star connection state. Specifically, as shown in FIG. 3, the MOSFETs of the changeover switch 10 (10A, 10B) are turned off and the changeover switch 10 is opened. The inverter 9 is also neutralized. As shown in FIG. 3, for example, the MOSFETs 9S of the upper arms 9H of all phases may be turned on and the MOSFETs 9S of the lower arms 9L of all phases may be turned off. The MOSFETs 9S of the upper arms 9H of all phases may be turned off and the MOSFETs 9S of the lower arms 9L of all phases may be turned on. The MOSFETs 8S of the inverter 8 are then controlled according to drive requirements, etc.

[0047] FIG. 3 shows one current conduction pattern in star-connection drive. The dashed-dotted arrows in FIG. 3 indicate an example of a current path. FIG. 3 shows the current path when the MOSFET 8S in the U-phase upper arm 8H and the MOSFET 8S in the W-phase lower arm 8L are turned on. In the example shown in FIG. 3, the upper arm 9H of the inverter 9 is turned on and the lower arm 9L is turned off. The current flows in the following order: U-phase upper arm 8H → node U1 → U-phase winding 3U → node U2 → U-phase upper arm 9H → W-phase upper arm 9H → node W2 → W-phase winding 3W → node W1 → W-phase lower arm 8L. In this way, in star-connection drive, current flows without passing through the selector switch 10.

[0048] When the operating point is in the open connection drive region, the control unit 15 executes open connection drive control. Open connection drive is sometimes referred to as H drive. The control unit 15 turns on the MOSFET of the changeover switch 10 (10A, 10B) to close the changeover switch 10. The control unit 15 also opens the neutral point of the inverter 9. By opening the neutral point, an open connection circuit of the U-phase upper and lower arm circuits 8HL, 9HL is formed via the U-phase winding 3U. Similarly, an open connection circuit of the V-phase upper and lower arm circuits 8HL, 9HL is formed via the V-phase winding 3V. An open connection circuit of the W-phase upper and lower arm circuits 8HL, 9HL is formed via the W-phase winding 3W. The control unit 15 regards each phase as an independent open connection circuit and controls the applied voltage for each phase.

[0049] FIG. 4 shows one current conduction pattern in open-connection driving. The two-dot chain arrow in FIG. 4 indicates one example of a current path. FIG. 4 shows the current path when MOSFET 8S in W-phase lower arm 8L and MOSFET 9S in W-phase upper arm 9H are turned on. Current flows in the following order: changeover switch 10 → W-phase upper arm 9H → node W2 → W-phase winding 3W → node W1 → W-phase lower arm 8L. In this way, in open-connection driving, current flows via changeover switch 10.

[0050] As described above, the power conversion circuit 4 is configured to be switchable between star connection drive and open connection drive. The power conversion circuit 4 is configured to be able to execute star connection drive. The power conversion circuit 4 is configured to be able to execute open connection drive. By executing open connection drive instead of star connection drive, it is possible to output a higher rotation speed range or a higher torque range.

[0051] <Charging using a power conversion circuit> Next, charging using the power conversion circuit 4 will be described with reference to Fig. 5. Fig. 5 shows a circuit configuration showing a state in which an external device is connected. In Fig. 5, the external device is shown in a simplified form.

[0052] As shown in FIG. 5, the external device 16 is connected to the power supply lines 5 and 6. The external device 16 is connected in parallel to the DC power supply 2. The external device 16 is an element separate from the elements constituting the drive system 1. The external device 16 may be, for example, an element external to a moving body (vehicle). An example of the external device 16 is a charger. The charger charges the DC power supply 2. The voltage supplied by the external device 16 is lower than the power supply voltage of the DC power supply 2. For example, the DC power supply 2 is 800 V, and the external device 16 (charger) is 400 V. In the rotating electric machine 3 and the power conversion circuit 4, the windings 3U, 3V, and 3W of the rotating electric machine 3 and the upper and lower arm circuit 8HL constituting the inverter 8 function as a boost circuit.

[0053] The external device 16 is connected to the drive system 1 (power conversion circuit 4) while the vehicle is stopped, for example. When the external device 16 is connected, the control unit 15 controls the inverters 8 and 9 and the selector switch 10 to boost the supply voltage of the external device 16 and charge the DC power supply 2. The boost operation may use one phase or multiple phases (multi-phase). The control unit 15 turns off the MOSFET of the selector switch 10. In this state, the control unit 15 turns on the upper arm 9H of the inverter 9 and controls the on / off of the upper and lower MOSFETs 8S of the upper and lower arm circuit 8HL in the corresponding phase.

[0054] External device 16 may be a DC power supply (external power supply) separate from DC power supply 2. The external power supply may be, for example, a secondary battery or may include a DC-AC conversion circuit. DC power supply 2 charges external device 16. The power supply voltage of external device 16 is lower than the power supply voltage of DC power supply 2. In rotating electric machine 3 and power conversion circuit 4, windings 3U, 3V, 3W of rotating electric machine 3 and upper arm 8H of inverter 8 function as a step-down circuit.

[0055] When an external device 16 is connected to the drive system 1, the control unit 15 controls the inverters 8 and 9 and the selector switch 10 to step down the power supply voltage of the DC power supply 2 and charge the external device 16. In the step-down operation, one phase or multiple phases (multi-phase) may be used. The control unit 15 turns off the MOSFET of the selector switch 10. In this state, the control unit 15 turns on the upper arm 9H of the inverter 9 and controls the on / off of the MOSFET 8S of the upper arm 8H of the corresponding phase. The MOSFET 8S of the lower arm 8L of the corresponding phase is turned off. When the MOSFET 8S of the upper arm 8H is turned off, a current flows through the diode of the lower arm 8L of the corresponding phase.

[0056] <Current sensor> As shown in Fig. 1, the drive system 1 has a first current sensor 121 and a second current sensor 122. The current sensors 121 and 122 detect phase currents flowing through the windings 3U, 3V, and 3W of each phase. The current sensors 121 and 122 are magnetic sensors such as Hall sensors. The magnetic sensors are formed to include a sensor element such as a Hall element. The current sensors 121 and 122 may also be formed to include a resistive element such as a shunt resistor.

[0057] Current sensors 121 and 122 are provided for each of the three phases. The first current sensor 121 includes first current sensors 121U, 121V, and 121W. The second current sensor 122 includes second current sensors 122U, 122V, and 122W. In the U phase, current sensors 121U and 122U detect the current flowing through the U-phase winding 3U. In the V phase, current sensors 121V and 122V detect the current flowing through the V-phase winding 3V. In the W phase, current sensors 121W and 122W detect the current flowing through the W-phase winding 3W. In this embodiment, the U phase, V phase, and W phase each correspond to a target phase. The U phase may be referred to as the first phase, the V phase as the second phase, and the W phase as the third phase.

[0058] The first current sensor 121 detects the current flowing in the output line 13. The first current sensor 121 is provided on the output line 13 but not on the output line 14. The first current sensor 121 is provided on the output line 13 between the windings 3U, 3V, 3W and the inverter 8. The U-phase first current sensor 121U detects the current flowing in the U-phase output line 13 as the current flowing in the U-phase winding 3U. The V-phase first current sensor 121V detects the current flowing in the V-phase output line 13 as the current flowing in the V-phase winding 3V. The W-phase first current sensor 121W detects the current flowing in the W-phase output line 13 as the current flowing in the W-phase winding 3W. The output line 13 corresponds to the first path, and the output line 14 corresponds to the second path.

[0059] The second current sensor 122 detects the current flowing in the output line 14. The second current sensor 122 is provided on the output line 14 but not on the output line 13. The second current sensor 122 is provided on the output line 14 between the windings 3U, 3V, 3W and the inverter 9. The U-phase second current sensor 122U detects the current flowing in the U-phase output line 14 as the current flowing in the U-phase winding 3U. The V-phase second current sensor 122V detects the current flowing in the V-phase output line 14 as the current flowing in the V-phase winding 3V. The W-phase second current sensor 122W detects the current flowing in the W-phase output line 14 as the current flowing in the W-phase winding 3W.

[0060] The power conversion circuit 4 has a current path through which a current flows. The current path includes power lines 5 and 6, a selector switch 10, output lines 13 and 14, and windings 3U, 3V, and 3W. Between the first current sensor 121 and the second current sensor 122, a portion of output line 13, a portion of output line 14, and windings 3U, 3V, and 3W form the current path. Losses such as resistance losses and heat losses are likely to occur in the current path between the first current sensor 121 and the second current sensor 122. Losses occurring in the windings 3U, 3V, and 3W are particularly likely to be larger than losses occurring in a portion of output line 13 or a portion of output line 14. Because the losses occurring in the windings 3U, 3V, and 3W are relatively large, differences are likely to occur between the detection results of the first current sensor 121 and the second current sensor 122.

[0061] The power supply lines 5 and 6 connect the inverter 8 and the inverter 9 without passing through the windings 3U, 3V, and 3W. The power supply lines 5 and 6 correspond to direct paths. In the power supply line 5, the wiring 5A connects the inverter 8 and the inverter 9. The wiring 5A connects the upper arm 8H and the upper arm 9H. The wiring 5A corresponds to the upper direct path. In the power supply line 6, the wiring 6A connects the inverter 8 and the inverter 9. The wiring 6A connects the lower arm 8L and the lower arm 9L. The wiring 6A corresponds to the lower direct path. The power supply lines 5 and 6 electrically connect the DC power supply 2 and the inverters 8 and 9.

[0062] Current sensors 121 and 122 are communicatively connected to control unit 15. Current sensors 121 and 122 output to control unit 15 detection signals corresponding to the currents flowing through windings 3U, 3V, and 3W.

[0063] The control unit 15 performs rotation control, which is control of the rotating electric machine 3. The rotation control includes control of star connection drive and control of open connection drive. The rotation control also includes control of the power conversion circuit 4. The control of the power conversion circuit 4 includes control of the inverters 8 and 9 and control of the changeover switch 10. The control unit 15 performs rotation control by executing a rotation control process. The control unit 15 repeatedly executes the rotation control process at a predetermined control period. The control unit 15 has a function of executing the processing of each step of the rotation control process. The rotation control process will be described with reference to the flowchart of FIG. 6.

[0064] The control unit 15 performs a current detection process in step S101 shown in FIG. 6. In the current detection process, a process for detecting the current flowing through the windings 3U, 3V, and 3W is performed. In the current detection process, a first detection value I1 and a second detection value I2 are detected. The first detection value I1 is a detection value of the current flowing through the output line 13 for each of the three phases. The second detection value I2 is a detection value of the current flowing through the output line 14 for each of the three phases. The control unit 15 calculates the detection values ​​I1 and I2 for each of the U, V, and W phases using the detection signals of the current sensors 121 and 122. The first detection value I1 is the detection result of the first current sensor 121. The second detection value I2 is the detection result of the second current sensor 122.

[0065] For example, control unit 15 calculates first detected values ​​I1U, I1V, and I1W using detection signals from first current sensors 121U, 121V, and 121W. Control unit 15 also calculates second detected values ​​I2U, I2V, and I2W using detection signals from second current sensors 122U, 122V, and 122W. Detected values ​​I1U and I2U are detected values ​​of the current flowing through U-phase winding 3U. Detected values ​​I1V and I2V are detected values ​​of the current flowing through V-phase winding 3V. Detected values ​​I1W and I2W are detected values ​​of the current flowing through W-phase winding 3W.

[0066] In step S102, the control unit 15 calculates the detection difference Idif using the detection values ​​I1 and I2. The detection difference Idif is the difference between the first detection value I1 and the second detection value I2. The control unit 15 calculates the detection difference Idif for each of the three phases. For example, the control unit 15 calculates the difference between the first detection value I1U and the second detection value I2U as the detection difference Idif for the U phase. The control unit 15 calculates the difference between the first detection value I1V and the second detection value I2V as the detection difference Idif for the V phase. The control unit 15 calculates the difference between the first detection value I1W and the second detection value I2W as the detection difference Idif for the W phase.

[0067] In step S103, the control unit 15 determines whether the detected difference Idif is greater than the difference threshold JI. When the absolute value of the detected difference Idif is greater than the difference threshold JI, the control unit 15 determines that the detected difference Idif is greater than the difference threshold JI. The difference threshold JI is a value determined in advance by testing or the like, and is stored in the memory 15b or the like. The difference threshold JI is a value that indicates that the detected difference Idif is abnormally large. The function of the control unit 15 that executes the process of step S103 corresponds to the abnormality determination unit.

[0068] As described above, a difference is likely to occur between the first detection value I1 and the second detection value I2 due to losses occurring in the windings 3U, 3V, and 3W. In other words, the detection difference Idif is likely to be greater than zero. The difference threshold JI is set to a value that corresponds to the losses occurring in the windings 3U, 3V, and 3W. The difference threshold JI is set to a value that indicates that the detection difference Idif is within the normal range.

[0069] The detection difference Idif may be greater than the difference threshold JI when at least one of the first detection value I1 and the second detection value I2 is abnormal. The first detection value I1 may be abnormal when an abnormality such as a failure occurs in the first current sensor 121. The second detection value I2 may be abnormal when an abnormality occurs in the second current sensor 122. The detection difference Idif being greater than the difference threshold JI is sometimes referred to as an abnormal detection value. For example, an abnormal detection value may occur in at least one of the three phases.

[0070] Furthermore, when the detected difference Idif becomes a value larger than the difference threshold JI, the control unit 15 may determine that an abnormality has occurred in the current path. For example, when an abnormality such as a ground fault occurs in the current path of one phase between the first current sensor 121 and the second current sensor 122, the detected difference Idif may become a value larger than the difference threshold JI. For example, when an abnormality such as a ground fault occurs in one of the U-phase winding 3U, the V-phase winding 3V, and the W-phase winding 3W, the control unit 15 may determine that an abnormality has occurred in the current path of one phase, in addition to determining that an abnormality has occurred in the current sensors 121 and 122.

[0071] If the detected difference Idif is not greater than the difference threshold JI, the control unit 15 determines that no abnormality has occurred in the current sensors 121, 122. If the detected difference Idif is not greater than the difference threshold JI in any of the three phases, the control unit 15 determines that no abnormality has occurred in the current sensors 121, 122, and proceeds to step S104. In step S104, the control unit 15 uses the detected values ​​I1 and I2 to determine whether or not an abnormality has occurred in the current flow path. Examples of abnormalities in the current flow path include abnormalities that have occurred in the power lines 5, 6, the selector switch 10, the output lines 13, 14, and the windings 3U, 3V, and 3W. Examples of abnormalities in the current flow path include a short circuit, leakage current, and ground fault in the output line 14.

[0072] The control unit 15 can determine whether a phase-to-phase short circuit has occurred between the output lines 13 and 14. The control unit 15 can determine whether a phase-to-phase short circuit has occurred in the output line 13 using the first detection value I1. For example, if the first detection value I1W is a normal value while both the first detection values ​​I1U and I1V are abnormal values, the control unit 15 determines that a phase-to-phase short circuit has occurred, in which the U-phase output line 13 and the V-phase output line 13 are shorted. The control unit 15 can also determine whether a phase-to-phase short circuit has occurred in the output line 14 using the second detection value I2. For example, if the second detection value I2 is a normal value while both the second detection values ​​I2U and I2V are abnormal values, the control unit 15 determines that a phase-to-phase short circuit has occurred, in which the U-phase output line 14 and the V-phase output line 14 are shorted.

[0073] If a current supply abnormality occurs, the control unit 15 proceeds to step S115 and performs a current supply stop process. In the current supply stop process, a process for stopping current supply to the windings 3U, 3V, and 3W is performed. The control unit 15 can stop the driving of the rotating electric machine 3 by the current supply stop process. However, the current supply stop process does not necessarily stop the driving of the rotating electric machine 3. For example, if it is not possible to stop the moving body, the control unit 15 may continue the supply of current to the windings 3U, 3V, and 3W so that the rotating electric machine 3 operates at the minimum necessary output. In the current supply stop process, a notification process may be performed to notify an occupant or the like of abnormality information regarding the current supply abnormality. In the notification process, the abnormality information is notified to the occupant or the like by sound, image, or the like. The abnormality information includes the location where the current supply abnormality occurred, the type of the current supply abnormality, and the like.

[0074] If no abnormality in power supply has occurred, the control unit 15 performs normal control to drive the rotating electric machine 3 in steps S105 and S106. In step S105 of the normal control, the control unit 15 sets normal parameters. The normal parameters are control parameters used in the normal control. The control unit 15 sets one of the first detection value I1 and the second detection value I2 as the control parameter.

[0075] The control unit 15 performs normal drive processing in step S106. In the normal drive processing, processing for driving the rotating electric machine 3 is performed using control parameters. The control unit 15 drives the rotating electric machine 3 using the first detection value I1. The control unit 15 can drive the rotating electric machine 3 by star connection drive or open connection drive. The function of the control unit 15 for executing steps S105 and S106 includes a function for star connection drive of the rotating electric machine 3 and a function for open connection drive of the rotating electric machine 3.

[0076] If the detection difference Idif is greater than the difference threshold JI in at least one of the three phases, the control unit 15 determines that an abnormality in the detection value has occurred, and proceeds to step S107. In step S107, the control unit 15 performs an alert process. The alert process includes a process for notifying the occurrence of an abnormality in the current sensors 121, 122. The alert process notifies the occupants or the like of the abnormality in the current sensors 121, 122 by sound, image, or the like.

[0077] In steps S108 to S110, control unit 15 performs identification processing to identify the sensor in which the abnormality has occurred. The identification processing is processing to identify whether the abnormality has occurred in first current sensor 121 or second current sensor 122. The function of control unit 15 that executes the processing of steps S108 to S110 corresponds to the abnormality identification unit.

[0078] In step S108 of the identification process, the control unit 15 calculates a first estimated value Ia1 and a second estimated value Ia2 using the detected values ​​I1 and I2. The control unit 15 calculates the estimated values ​​Ia1 and Ia2 for the phase in which the abnormal detected value occurred among the three phases. The first estimated value Ia1 is a value obtained by estimating the first detected value I1 of one of the three phases from the first detected values ​​I1 of the remaining two phases. The second estimated value Ia2 is a value obtained by estimating the second detected value I2 of one of the three phases from the second detected values ​​I2 of the remaining two phases.

[0079] Control unit 15 calculates estimated values ​​Ia1 and Ia2 from detected values ​​I1 and I2 using current correlation information indicating the correlation between the currents flowing through windings 3U, 3V, and 3W. The current correlation information includes the correlation between the currents flowing through U-phase winding 3U, V-phase winding 3V, and W-phase winding 3W. The current correlation information also includes the correlation between the currents flowing through windings 3U, 3V, and 3W and the currents flowing through output line 13 and output line 14. The current correlation information may be a map, an arithmetic expression, a function, or the like. The current correlation information is stored in memory 15b or the like.

[0080] For example, if an abnormality in the detection value occurs in the U-phase, the control unit 15 calculates a first estimated value Ia1 of the U-phase using the first detected value I1V of the V-phase and the first detected value I1W of the W-phase. The control unit 15 also calculates a second estimated value Ia2 of the U-phase using the second detected value I2V of the V-phase and the second detected value I2W of the W-phase. The control unit 15 calculates the estimated values ​​Ia1 and Ia2 depending on the driving state of the rotating electric machine 3.

[0081] In step S109, the control unit 15 calculates a first deviation value Ib1 and a second deviation value Ib2 using the estimated values ​​Ia1 and Ia2. The deviation values ​​Ib1 and Ib2 are values ​​that indicate the magnitude of deviation between the detected values ​​I1 and I2 and the estimated values ​​Ia1 and Ia2 for a phase in which an abnormal detected value has occurred among the three phases. The control unit 15 calculates the difference between the first detected value I1 and the first estimated value Ia1 for the phase in which an abnormal detected value has occurred as the first deviation value Ib1. The control unit 15 also calculates the difference between the second detected value I2 and the second estimated value Ia2 as the second deviation value Ib2. For example, if an abnormal detected value has occurred in the U phase, the control unit 15 calculates the deviation values ​​Ib1 and Ib2 for the U phase.

[0082] In step S110, the control unit 15 uses the deviation values ​​Ib1 and Ib2 to identify the abnormal sensor. The abnormal sensor is the current sensor in which the abnormality occurred, either the first current sensor 121 or the second current sensor 122, for the phase in which the abnormal detection value occurred. The control unit 15 determines that the larger of the first deviation value Ib1 and the second deviation value Ib2 is the abnormal deviation value. For example, if the absolute value of the first deviation value Ib1 is larger than the absolute value of the second deviation value Ib2, the control unit 15 determines that the first deviation value Ib1 is the abnormal deviation value.

[0083] The control unit 15 may determine whether each of the first deviation value Ib1 and the second deviation value Ib2 is greater than a deviation threshold value. The deviation threshold value is a value determined in advance through testing or the like and stored in the memory 15b or the like. The deviation threshold value indicates that the deviation values ​​Ib1 and Ib2 are abnormally large. If the first deviation value Ib1 is greater than the deviation threshold value, the control unit 15 determines that the first deviation value Ib1 is an abnormal deviation value. If the second deviation value Ib2 is greater than the deviation threshold value, the control unit 15 determines that the second deviation value Ib2 is an abnormal deviation value. For this reason, the control unit 15 may determine that both the first deviation value Ib1 and the second deviation value Ib2 are abnormal deviation values.

[0084] Furthermore, in steps S108 to S110, only one of the first detection value I1 and the second detection value I2 may be used to identify which of the first current sensor 121 and the second current sensor 122 is the abnormal sensor. For example, in steps S108 and S109, the control unit 15 calculates the first estimated value Ia1 and the first deviation value Ib1. Then, in step S110, the control unit 15 determines whether the first current sensor 121 is the abnormal sensor by determining whether the first deviation value Ib1 is greater than a deviation threshold value. If the control unit 15 determines that the first current sensor 121 is the abnormal sensor, it may determine that the second current sensor 122 is not the abnormal sensor. If the control unit 15 determines that the first current sensor 121 is not the abnormal sensor, it may determine that the second current sensor 122 is the abnormal sensor.

[0085] The control unit 15 determines that one of the first current sensor 121 and the second current sensor 122, which was used to calculate the abnormal deviation value, is the abnormal sensor. For example, when an abnormality in the detection value occurs for the U phase and the first deviation value Ib1 is greater than the second deviation value Ib2, the control unit 15 determines that an abnormality has occurred in the first current sensor 121 of the U phase. The control unit 15 also determines that one of the first detection value I1 and the second detection value I2, which was used to calculate the abnormal deviation value, is the abnormal value.

[0086] In steps S111 to S114, the control unit 15 performs fail-safe control for driving the rotating electric machine 3 in a situation where an abnormal sensor is present. The control unit 15 sets a fail-safe parameter in step S111 of the fail-safe control. The fail-safe parameter is a control parameter used for the fail-safe control. The control unit 15 sets the non-abnormal value of the first detection value I1 or the second detection value I2 as the fail-safe parameter. For example, when the control unit 15 determines that an abnormality has occurred in the first current sensor 121 for the U phase, it sets the second detection value I2U for the U phase as the fail-safe parameter. In this case, for the V phase and the W phase, any of the first detection values ​​I1V, I1W and the second detection values ​​I2V, I2W may be set as the fail-safe parameter.

[0087] In step S112, the control unit 15 determines whether open connection driving is necessary. For example, it determines whether the rotating electric machine 3 needs to be driven at high rotation speed or high torque in order to move the moving body. If it is necessary to drive the rotating electric machine 3 at high rotation speed or high torque, the control unit 15 determines that open connection driving is necessary.

[0088] If open connection drive is necessary, the control unit 15 proceeds to step S113 and performs star connection drive processing. In the star connection drive processing, processing is performed to drive the rotating electric machine 3 in a star connection manner using fail-safe parameters. If open connection drive is not necessary, the control unit 15 proceeds to step S114 and performs open connection drive processing. In the open connection drive processing, processing is performed to drive the rotating electric machine 3 in an open connection manner using fail-safe parameters.

[0089] <Summary of the First Embodiment> According to this embodiment, in the target phase, the first current sensor 121 detects the current flowing in the output line 13, and the second current sensor 122 detects the current flowing in the output line 14. With this configuration, it is possible to determine, using the first detection value I1 and the second detection value I2, whether or not an abnormality has occurred in the current paths of the windings 3U, 3V, 3W, etc., or in the first current sensor 121 or the second current sensor 122. Therefore, it is possible to detect an abnormality in the current paths or the current sensors 121 and 122.

[0090] According to this embodiment, the first current sensor 121 detects the current flowing through the output line 13, with each of the three phases being the target phase. The second current sensor 122 detects the current flowing through the output line 14, with each of the three phases being the target phase. With this configuration, the detected values ​​I1 and I2 for each of the three phases can be used as control parameters in controlling the rotating electric machine 3. For example, it is not necessary to use the detected values ​​I1 and I2 for two of the three phases and an estimated value estimated from the detected values ​​I1 and I2 for the remaining phase. Therefore, by using the detected values ​​I1 and I2 detected for each of the three phases in rotation control, it is possible to improve the reliability of driving the rotating electric machine 3.

[0091] According to this embodiment, the control unit 15 uses the detection values ​​I1 and I2 in at least one phase to determine whether an abnormality has occurred in at least one of the first current sensor 121 and the second current sensor 122. In this configuration, it is possible to detect in which phase the current sensor abnormality has occurred by calculating the detection difference Idif from the detection values ​​I1 and I2, for example.

[0092] According to this embodiment, when an abnormality occurs in the current sensors 121, 122 in one of the three phases, the control unit 15 uses the detection values ​​I1, I2 in the remaining two phases to identify in which of the first current sensor 121 and the second current sensor 122 in the one phase the abnormality has occurred. In this configuration, the control unit 15 can notify an operator or the like of information such as which of the first current sensor 121 and the second current sensor 122 the abnormality should be resolved. This reduces the workload of the operator when performing work to resolve the abnormality in the power conversion circuit 4.

[0093] According to this embodiment, power supply lines 5 and 6 connect inverters 8 and 9 without passing through windings 3U, 3V, and 3W. In this configuration, current sensors 121 and 122 are provided on output lines 13 and 14, making it possible to detect an abnormality in power supply lines 5 and 6 using detected values ​​I1 and I2. Also, changeover switch 10 is provided on power supply lines 5 and 6. In this configuration, it is possible to detect an abnormality in changeover switch 10 using detected values ​​I1 and I2.

[0094] 7 and 8 show reference examples of power conversion circuits. Fig. 7 shows an example of a current conduction pattern when star-connected driving is performed in the reference example. Fig. 8 shows a current conduction pattern with timing different from that in Fig. 4 when star-connected driving is performed. In the reference example, the symbols of related elements shown in this embodiment are indicated by adding r to the end.

[0095] The control unit performs star connection drive while switching between multiple current conduction patterns. The control unit performs star connection drive using, for example, a PWM control method. PWM is an abbreviation for Pulse Width Modulation. The multiple current conduction patterns include the zero vector current conduction patterns shown in Figures 7 and 8. The current conduction pattern shown in Figure 7 is a zero vector pattern in which all upper arms 8Hr of the inverter 8r are turned on and all lower arms 8Lr are turned off. The current conduction pattern shown in Figure 8 is a zero vector pattern in which all lower arms 8Lr of the inverter 8r are turned on and all upper arms 8Hr are turned off. The power line 5r has a wiring 5A11r connecting the inverter 8 and the selector switch 10r and a wiring 5A12r connecting the selector switch 10r and the inverter 9r.

[0096] As shown in Figures 7 and 8, in the power conversion circuit 4r of the reference example, the snubber circuit 11r connected in parallel to the inverter 9r is connected to a wiring 5A12r of the power line 5r that connects the selector switch 10r and the inverter 9r. One end of the snubber circuit 11r is connected to the wiring 5A12r of the power line 5r, and the other end is connected to the power line 6r. For convenience, Figures 7 and 8 omit the smoothing capacitor and the snubber circuit connected in parallel to the inverter 8r. Furthermore, the snubber circuit 11r is common to each phase of the inverter 9r.

[0097] In the examples shown in Figures 7 and 8, inverter 9r is neutralized by turning on all three upper arms 9Hr of inverter 9r. In this state, as shown in Figure 7, when all three upper arms 8Hr of inverter 8r are turned on, the voltage across capacitor 11Cr becomes approximately equal to the supply voltage of DC power supply 2r, i.e., power supply voltage Vdc. Furthermore, as shown in Figure 8, when all three lower arms 8Lr of inverter 8r are turned on, the voltage across capacitor 11Cr becomes approximately 0 V (zero volts).

[0098] As described above, star connection driving is performed while switching between multiple current patterns, so the voltage across capacitor 11Cr of snubber circuit 11r fluctuates during star connection driving. The voltage across capacitor 11Cr fluctuates between 0 V and Vdc. As a result, capacitor 11Cr is charged and discharged during star connection driving, resulting in low power conversion efficiency. Resistor 11Rr of snubber circuit 11r consumes the energy stored in capacitor 11Cr and generates heat. This heat affects capacitor 11Cr.

[0099] In contrast to this reference example, in this embodiment, in which the changeover switch 10B is provided on the wiring 6A, the MOSFET of the changeover switch 10B is off, i.e., the changeover switch 10B is in an open state, during star connection driving. Therefore, the potential on the negative side of the capacitor 11C provided in the snubber circuit 11 becomes a floating potential. Therefore, fluctuations in the voltage across the capacitor 11C can be suppressed during star connection driving. In other words, charging and discharging of the capacitor 11C can be suppressed. This improves power conversion efficiency. Furthermore, the effect of heat generated by the resistor 11R due to charging and discharging can be suppressed on the capacitor 11C. This is suitable not only for open connection driving but also for star connection driving.

[0100] <Modification> In the present embodiment, an example has been shown in which the changeover switch 10 is provided on each of the wiring 5A and the wiring 6A, but this is not limiting. The changeover switch 10 may be provided on only one of the wiring 5A and the wiring 6A. For example, as shown in FIG. 9, the changeover switch 10 may be provided on the wiring 5A but not on the wiring 6A.

[0101] In the present embodiment, an example has been shown in which a changeover switch 10 and a snubber circuit 11 are provided for each phase of the upper and lower arm circuits 9HL, but the present invention is not limited to this. For example, as shown in Fig. 10 and Fig. 11, one changeover switch 10 and one snubber circuit 11 may be provided for each of the three-phase upper and lower arm circuits 9HL that constitute the inverter 9.

[0102] In the present embodiment, an example has been shown in which one end of the snubber circuit 11 is connected to the inverter 9 on the power line 5 without passing through the changeover switch 10, but the present invention is not limited to this. For example, as shown in FIGS. 10 and 12 , one end of the snubber circuit 11 may be connected to the inverter 9 on the power line 5 via the changeover switch 10. That is, one end of the snubber circuit 11 may be connected between the changeover switch 10 and the inverter 8 on the wiring 5A. For example, the power line 5 has a wiring 5A1 that connects the inverter 8 and the changeover switch 10, and a wiring 5A2 that connects the changeover switch 10 and the inverter 9. In this configuration, one end of the snubber circuit 11 is connected to the wiring 5A1 of the wiring 5A1 and the wiring 5A2.

[0103] (Second embodiment) This embodiment is a modification based on the previous embodiment, and the description of the previous embodiment can be used. In the previous embodiment, the current sensors 121 and 122 are provided for each of the three phases, but this is not limited to this. In this embodiment, the current sensors 121 and 122 may be provided for at least one of the three phases.

[0104] <Power conversion circuit> Fig. 13 shows a power conversion circuit 4 according to this embodiment. In the power conversion circuit 4 shown in Fig. 13, current sensors 121 and 122 are provided on the output lines 14 of two of the three phases, but are not provided on the output line 14 of the remaining phase. For example, a first current sensor 121 is provided on each of the U-phase output line 13 and the V-phase output line 13, but is not provided on the W-phase output line 13. A second current sensor 122 is provided on each of the U-phase output line 14 and the V-phase output line 14, but is not provided on the W-phase output line 14.

[0105] The control unit 15 controls the driving of the rotating electric machine 3 using the detected values ​​I1 and I2 of two of the three phases. For example, the control unit 15 performs normal driving processing similar to the first embodiment using the detected values ​​I1 and I2 of the two phases. In the normal driving processing, the control unit 15 calculates the current of the remaining phase as a current estimation value using the detected values ​​I1 and I2 of the two phases. For example, the control unit 15 detects the first detected value I1U of the U phase and the first detected value I1V of the V phase, and calculates the current estimation value of the W phase. Then, similar to steps S105 and S106 of the first embodiment, the control unit 15 sets the first detected value I1U of the U phase, the first detected value I1V of the V phase, and the current estimation value of the W phase as normal parameters, and performs normal driving processing.

[0106] In a configuration in which current sensors 121, 122 are provided on output line 14 for only two of the three phases, control unit 15 can calculate detection values ​​I1, I2 for the two phases but cannot calculate detection value I1, I2 for the remaining phase. Even in this configuration, control unit 15 can determine whether an abnormality has occurred in the current paths, such as power lines 5, 6, selector switch 10, output lines 13, 14, and windings 3U, 3V, and 3W, by using current correlation information. For example, as described above, control unit 15 can determine whether an abnormality has occurred in selector switch 10.

[0107] (Other embodiments) The disclosure in this specification and drawings, etc. is not limited to the exemplified embodiments. The disclosure encompasses the exemplified embodiments and modifications thereto by those skilled in the art. For example, the disclosure is not limited to the combinations of parts and / or elements shown in the embodiments. The disclosure can be implemented in various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure encompasses the omission of parts and / or elements from the embodiments. The disclosure encompasses the substitution or combination of parts and / or elements between one embodiment and another embodiment. The disclosed technical scope is not limited to the description of the embodiments. Some disclosed technical scopes are defined by the claims, and should be interpreted as including all modifications within the meaning and scope equivalent to the claims.

[0108] The disclosure in the specification, drawings, etc. is not limited by the claims. The disclosure in the specification, drawings, etc. encompasses the technical ideas described in the claims, and extends to more diverse and broader technical ideas than the technical ideas described in the claims. Therefore, various technical ideas can be extracted from the disclosure in the specification, drawings, etc. without being bound by the claims.

[0109] When an element or layer is referred to as being "on," "coupled," "connected," or "bonded," it may be directly on, coupled, connected, or bonded to the other element or layer, and intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly coupled," "directly connected," or "directly bonded" to another element or layer, no intervening elements or layers are present. Other language used to describe relationships between elements should be construed in a similar manner (e.g., "between" vs. "directly between," "adjacent" vs. "directly adjacent," etc.).

[0110] As used in this specification, the term "and / or" includes any and all combinations of one or more of the associated listed items, i.e., reference to A and / or B means at least one of A and B, and may include A only, B only, or both A and B.

[0111] Spatially relative terms such as "inside," "outside," "back," "below," "low," "top," "top," and the like are used herein to facilitate the description of one element or feature's relationship to other elements or features, as illustrated. Spatially relative terms may be intended to encompass different orientations of the device during use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures were turned over, elements described as "below" or "directly below" other elements or features would then be oriented "above" the other elements or features. Thus, the term "bottom" can encompass both an orientation of top and bottom. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used in this specification would be interpreted accordingly.

[0112] In each of the above embodiments, the control unit 15 may use at least one of the first detection value I1 and the second detection value I2 to control the rotating electric machine 3. The control unit 15 may calculate a control parameter using the first detection value I1 and the second detection value I2. For example, the control unit 15 may calculate an average value of the first detection value I1 and the second detection value I2 and set this average value as the control parameter. In this configuration, when an abnormality occurs in one of the first current sensor 121 and the second current sensor 122, the control unit 15 may set the detection value detected by the one that is not abnormal as the control parameter.

[0113] In each of the above embodiments, the current sensors 121, 122 may be provided on either the output line 13 or the output line 14 for multiple phases. The current sensors 121, 122 may be provided on the output line 13 for two of the three phases, and on the output line 14 for the remaining phase. For example, the current sensors 121, 122 may be provided on the output line 13 for the U phase and the V phase, and on the output line 14 for the W phase.

[0114] In each of the above embodiments, the current sensors 121, 122 may be provided in at least one of the three phases. In this configuration, the at least one phase in which the current sensors 121, 122 are provided corresponds to the target phase. For example, the current sensors 121, 122 may be provided in the output lines 13, 14 in the U phase, but may not be provided in the output lines 13, 14 in the V phase and the W phase. In this configuration, the U phase in which the current sensors 121, 122 are provided corresponds to the target phase.

[0115] In each of the above embodiments, the drive system 1 may have a 3×n rotating electric machine 3. This drive system 1 has a 3×n power conversion circuit 4 to drive the 3×n rotating electric machine 3, where n is a natural number. For example, in the drive system 1, the 3×n power conversion circuit 4 is realized by connecting n three-phase inverters 8, 9 in parallel to the n×3-phase rotating electric machine 3.

[0116] In each of the above embodiments, the wiring 5A, 6A may directly or indirectly connect the inverter 8 and the inverter 9. For example, the wiring 5A, 6A may electrically connect the inverter 9 and the DC power supply 2 without passing through the inverter 8. In this configuration, the wiring 5A, 6A also indirectly connects the inverter 8 and the inverter 9 via the DC power supply 2.

[0117] (Disclosure of technical ideas) This specification discloses multiple technical ideas described in the following multiple clauses. Some clauses may be written in a multiple dependent form, with the subsequent clause referring to the preceding clause as an alternative. Furthermore, some clauses may be written in a multiple dependent form, referring to another multiple dependent clause. These multiple dependent clauses define multiple technical ideas.

[0118] (Technical thought 1) A power conversion device (4) that converts power supplied to a rotating electric machine (3), a first inverter (8) connected to one end of a winding of the rotating electric machine via a first path (13); a second inverter (9) connected to the other end of the winding via a second path (14); a first current sensor (121) for detecting a current flowing through the first path in a target phase that is at least one of the multiple phases; a second current sensor (122) for detecting a current flowing through the second path in the target phase; A power conversion device comprising:

[0119] (Technical thought 2) the first current sensor detects a current flowing through the first path in each of the three target phases; The power conversion device according to Technical Idea 1, wherein the second current sensor detects the current flowing through the second path in each of the three target phases.

[0120] (Technical Thought 3) A power conversion device according to technical idea 1 or 2, comprising an abnormality determination unit (S103) that determines whether an abnormality has occurred in at least one of the first current sensor and the second current sensor using the detection results of the first current sensor and the second current sensor.

[0121] (Technical Thought 4) The power conversion device according to Technical Idea 3 is provided with an abnormality identification unit (S108 to S110) that, when the abnormality determination unit determines that an abnormality has occurred in at least one of the first current sensor and the second current sensor in one of the three phases, identifies in which of the first current sensor and the second current sensor in the one phase the abnormality has occurred, using at least one of the detection results of the first current sensor and the detection results of the second current sensor in each of the remaining two phases.

[0122] (Technical Thought 5) The power conversion device according to any one of Technical Ideas 1 to 4, further comprising a direct path (5, 6) that connects the first inverter and the second inverter without passing through the winding.

[0123] (Technical Thought 6) The power conversion device according to Technical Idea 5 is provided with a changeover switch (10) that is provided in the direct path and connects the power supply unit (2) and the second inverter in a closed state and cuts off the connection between the power supply unit and the second inverter in an open state.

[0124] (Technical Thought 7) A rotating electric machine (3), a power converter (4) that converts the power supplied to the rotating electric machine; A drive system (1) that drives the rotating electric machine using the power conversion device, a first inverter (8) connected to one end of a winding of the rotating electric machine via a first path (13); a second inverter (9) connected to the other end of the winding via a second path (14); a first current sensor (121) for detecting a current flowing through the first path in a target phase that is at least one of the multiple phases; a second current sensor (122) for detecting a current flowing through the second path in the target phase; A drive system comprising: [Explanation of symbols]

[0125] 1... drive system, 2... DC power supply, 3... rotating electric machine, 3U, 3V, 3W... winding, 4... power conversion circuit, 8, 9... inverter, 13, 14... output line, 61H, 61L, 62H, 62L... semiconductor elements, 80, 81, 82... changeover switch, 121... first current sensor, 122... second current sensor, S103... abnormality determination unit, S108 to S110... abnormality identification unit.

Claims

1. A power conversion device (4) that converts power supplied to a rotating electric machine (3), a first inverter (8) connected to one end of a winding of the rotating electric machine via a first path (13); a second inverter (9) connected to the other end of the winding via a second path (14); a first current sensor (121) for detecting a current flowing through the first path in a target phase that is at least one of the multiple phases; a second current sensor (122) for detecting a current flowing through the second path in the target phase; A power conversion device comprising:

2. the first current sensor detects a current flowing through the first path in each of the three target phases; The power conversion device according to claim 1 , wherein the second current sensor detects a current flowing through the second path in each of the three target phases.

3. The power conversion device according to claim 1 or 2, further comprising an abnormality determination unit (S103) that determines whether an abnormality has occurred in at least one of the first current sensor and the second current sensor using the detection results of the first current sensor and the second current sensor.

4. The power conversion device according to claim 3, further comprising an abnormality identification unit (S108 to S110) that, when the abnormality determination unit determines that an abnormality has occurred in at least one of the first current sensor and the second current sensor in one of the three phases, identifies whether the abnormality has occurred in the first current sensor or the second current sensor in the one phase using at least one of the detection results of the first current sensor and the detection results of the second current sensor in each of the remaining two phases.

5. 3. The power conversion device according to claim 1, further comprising a direct path (5, 6) that connects the first inverter and the second inverter without passing through the winding.

6. 6. The power conversion device according to claim 5, further comprising a changeover switch (10) provided in the direct path, which connects the power supply unit (2) and the second inverter in a closed state and cuts off the connection between the power supply unit and the second inverter in an open state.

7. A rotating electric machine (3), a power conversion device (4) that converts the power supplied to the rotating electric machine; A drive system (1) comprising: a first inverter (8) connected to one end of a winding of the rotating electric machine via a first path (13); a second inverter (9) connected to the other end of the winding via a second path (14); a first current sensor (121) for detecting a current flowing through the first path in a target phase that is at least one of the multiple phases; a second current sensor (122) for detecting a current flowing through the second path in the target phase; A drive system comprising:

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