Motor drive unit

Abstract

It provides good protection for the components of the motor drive unit connected to an open-winding motor. [Solution] The motor drive device of the present disclosure includes an upper arm and a lower arm, each connected to each of a plurality of coils of an open-winding motor, and includes first and second inverters connected in parallel to a positive-side power line and a negative-side power line connected to a battery; a switch provided on the positive-side power line for connecting the positive terminal of the battery to one of the first and second inverters and for disconnecting the two; and a control device that, in response to a shutdown request, shuts down the first and second inverters and then opens the switch on the positive-side power line after a predetermined delay time has elapsed that is shorter than the time allowed for current discharged from the plurality of coils of the open-winding motor to flow to the battery.

Description

Technical Field

[0001] The present disclosure relates to a motor drive device for driving an open-winding motor.

Background Art

[0002] Conventionally, a motor drive device applied to an open-winding motor having a plurality of phase coils has been known (see, for example, Patent Document 1). This motor drive device includes a first inverter including upper and lower arm switches connected to one end of each coil of the open-winding motor, and a second inverter including upper and lower arm switches connected to the other end of each coil of the open-winding motor. The first and second inverters are connected in parallel to a DC power supply via a high-potential connection line and a low-potential connection line, and a connection line switch for conducting or interrupting the high-potential connection line between the first and second inverters is provided in the high-potential connection line. According to such a motor drive device, in a state where the connection line switch is opened (off), all the upper arm switches of the second inverter are fixed on and all the lower arm switches are fixed off, and by performing switching control on the first inverter, a plurality of coils of the open-winding motor are connected by a Y connection, and the open-winding motor can be efficiently driven (Y drive) by a single first inverter. Further, by performing switching control on the first and second inverters in reverse phases in a state where the connection line switch is closed (on), it becomes possible to drive the open-winding motor so as to output higher torque (H drive).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the event of any malfunction in the conventional motor drive system or open-wound motor, it is necessary to shut down the first and second inverters and open the connection line switch to protect the DC power supply, etc. However, if the connection line switch is opened at the same time as the shutdown of the first and second inverters, the discharge paths of multiple coils in the open-wound motor will be opened, which may cause a surge voltage exceeding the withstand voltage of the components of the motor drive system to occur between the terminals of the second inverter, potentially failing to protect those components.

[0005] Therefore, the primary purpose of this disclosure is to provide adequate protection for the components of a motor drive when a motor drive connected to an open-winding motor is required to be shut down. [Means for solving the problem]

[0006] The motor drive device of the present disclosure is a motor drive device for driving an open-winding motor including a plurality of coils, and includes an upper arm and a lower arm, respectively, connected to each of the plurality of coils of the open-winding motor, and includes first and second inverters connected in parallel to a positive-side power line and a negative-side power line connected to a battery; a switch provided on the positive-side power line for connecting the positive terminal of the battery to one of the first and second inverters and for disconnecting the two; and a control device that, in response to a shutdown request, shuts down the first and second inverters and then opens the switch after a predetermined delay time has elapsed that is shorter than the time permitted for current discharged from the plurality of coils of the open-winding motor to flow to the battery.

[0007] In the motor drive device of this disclosure, in response to a shutdown request, the first and second inverters are shut down, and after a predetermined delay time shorter than the allowable time for the current discharged from the multiple coils of the open-winding motor to flow to the battery has elapsed since the shutdown of the first and second inverters, the switch on the positive-side power line is opened. As a result, the upper and lower arms of the first and second inverters are connected to the battery from the time the first and second inverters are shut down until the switch on the positive-side power line is opened, and the voltage discharged from the multiple coils of the open-winding motor is clamped by the battery. Therefore, when the switch on the positive-side power line is opened, the occurrence of a surge voltage between one terminal of the first and second inverters can be effectively suppressed. As a result, when a shutdown of the motor drive device connected to an open-winding motor is requested, the components of the motor drive device can be effectively protected. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing a vehicle including a motor drive system in this disclosure. [Figure 2] This is a flowchart of the routines executed in the motor drive device of this disclosure. [Figure 3] This is a time chart showing the procedure for shutting down the motor control device of this disclosure. [Modes for carrying out the invention]

[0009] Next, with reference to the drawings, embodiments for carrying out the invention of this disclosure will be described.

[0010] Figure 1 is a schematic diagram showing a vehicle 1 including the motor drive unit 2 of this disclosure. The vehicle 1 shown in the figure is a battery electric vehicle (BEV) including a motor generator MG and a battery (energy storage device) B. The motor drive unit 2 exchanges power with the battery B to drive the motor generator MG and is controlled by an electronic control unit (hereinafter referred to as "ECU") 10 as a control device.

[0011] The motor-generator MG is a three-phase AC motor (synchronous generator motor) including a U-phase coil Lu, a V-phase coil Lv, and a W-phase coil Lw, each wound around a stator (stator core) (not shown), and is an open-winding motor in which the ends of the U-phase coil Lu, V-phase coil Lv, and W-phase coil Lw are not connected to each other. The motor-generator MG is connected to an output shaft, which is connected to the left and right wheels (drive wheels) W via a differential gear DG and a drive shaft DS, via a reduction mechanism (not shown), and is driven by power from the battery B to output drive torque to the output shaft. In addition, the motor-generator MG outputs regenerative braking torque to the output shaft when the vehicle 1 is braked. Note that the U-phase coil Lu, V-phase coil Lv, and W-phase coil Lw may include multiple coils connected in parallel.

[0012] Battery B is, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery having a rated output voltage of 200 to 800V. The positive terminal of battery B is connected to the positive side power line PL, and the negative terminal of battery B is connected to the negative side power line NL. The first and second inverters 3 and 4 are electrically connected in parallel to the positive side power line PL and the negative side power line NL.

[0013] The motor drive unit 2 includes a first inverter 3 and a second inverter 4. The first inverter 3 includes six transistors (e.g., insulated-gate bipolar transistors (IGBTs)) Tr1, Tr2, Tr3, Tr4, Tr5, and Tr6 as switching elements, and six diodes D1, D2, D3, D4, D5, and D6 connected in parallel in opposite directions to each of the transistors Tr1-Tr6. The transistors Tr1-Tr6 are paired up so that they act as the source and sink sides with respect to the positive power line PL and the negative power line NL. As shown in Figure 1, one end of the U-phase coil Lu of the motor generator MG is electrically connected to the connection point between the pair of transistors Tr1 and Tr2. Also, one end of the V-phase coil Lv of the motor generator MG is electrically connected to the connection point between the pair of transistors Tr3 and Tr4. Furthermore, one end of the W-phase coil Lw of the motor generator MG is electrically connected to the connection point between the pair of transistors Tr5 and Tr6. Transistors Tr1, Tr3, and Tr5 constitute the upper arm of the first inverter 3, and transistors Tr2, Tr4, and Tr6 constitute the lower arm of the first inverter 3.

[0014] The second inverter 4 includes six transistors (e.g., IGBTs) Tra, Trb, Trc, Trd, Tre, and Trb as switching elements, and six diodes Da, Db, Dc, Dd, De, and Df connected in parallel in the opposite direction to each transistor Tra-Trf. The transistors Tra-Trf are paired up so that they act as the source and sink sides with respect to the positive power line PL and the negative power line NL. As shown in Figure 1, the other end of the U-phase coil Lu of the motor generator MG is electrically connected to the connection point between the pair of transistors Tra and Trb. Also, the other end of the V-phase coil Lv of the motor generator MG is electrically connected to the connection point between the pair of transistors Trc and Trd. Furthermore, the other end of the W-phase coil Lw of the motor generator MG is electrically connected to the connection point between the pair of transistors Tre and Trb. Transistors Tra, Trc, and Tre constitute the upper arm of the second inverter 4, and transistors Trb, Trd, and Tref constitute the lower arm of the second inverter 4.

[0015] Furthermore, as shown in Figure 1, the motor drive unit 2 includes a drive mode selector switch 5 provided on the positive-side power line PL and the negative-side power line NL, and a switch 6 provided on the positive-side power line PL. The drive mode selector switch 5 includes a switching element 5p that connects the positive-side power line PL, i.e., the positive terminal of battery B, to the second inverter 4 and also disconnects the connection between them, and a switching element 5n that connects the negative-side power line NL, i.e., the negative terminal of battery B, to the second inverter 4 and also disconnects the connection between them, thereby enabling the electrical connection between battery B and the second inverter 4 to be disconnected. The switch 6 also connects the positive-side power line PL, i.e., the positive terminal of battery B, to the second inverter 4 and also disconnects the connection between them.

[0016] The ECU10 includes a microcomputer with a CPU, ROM, RAM, input / output interface, etc. (not shown). The ECU10 acquires the accelerator opening from an accelerator pedal position sensor (not shown), the vehicle speed from a vehicle speed sensor (not shown), the detection value of a resolver (not shown) that detects the rotational position of the rotor of the motor generator MG, the detection values ​​of various voltage sensors, the detection values ​​of various current sensors, the temperature TTa of transistor Tra of the second inverter 4 detected by the temperature sensor 7, and the temperature TTb of transistor Trb of the second inverter 4 detected by the temperature sensor 8. The ECU10 also calculates the rotational speed Nm of the motor generator MG based on the detection value of the resolver. Furthermore, the ECU10 sets the required torque required for the vehicle 1 to run based on the accelerator opening and vehicle speed, and sets the torque command value Tm* to the motor generator MG based on the set required torque. In addition, the ECU10 controls the opening and closing of the drive mode selector switch 5 and switch 6.

[0017] The ECU 10 controls the first and second inverters 3 and 4 of the motor drive unit 2 based on the rotational speed Nm and torque command value Tm* when the vehicle 1 is running. More specifically, while the vehicle 1 is running, the ECU 10 functions as a mode setting unit that sets one of the following operating modes for the first and second inverters 3 and 4: upper-phase single-sided drive mode (hereinafter referred to as "upper-phase Y drive mode"), lower-phase single-sided drive mode (hereinafter referred to as "lower-phase Y drive mode"), or both-sided drive mode (hereinafter referred to as "H (full-bridge) drive mode"), in response to the rotational speed Nm and torque command value Tm*, i.e., the requests to the motor generator MG, and controls the first and second inverters 3 and 4 in a manner corresponding to the set operating mode.

[0018] When the operating mode is the upper-phase Y drive mode, the ECU 10 opens the drive mode selector switch 5 (switching elements 5p and 5n) and closes switch 6, thereby turning on the upper arm of the second inverter 4 (one of the first and second inverters 3 and 4), namely transistors Tra, Trc and Tre, and turning off the lower arm, namely transistors Trb, Trd and Tref. As a result, a neutral point (neutral potential) is formed by the turned-on transistors Tra, Trc and Tre, and the other ends of the U-phase coil Lu, V-phase coil Lv and W-phase coil Lw of the motor generator MG are connected in a Y connection. Furthermore, the ECU 10 switches transistors Tr1-Tr6 of the first inverter 3 (the other of the first and second inverters 3 and 4) based on the torque command value Tm*. This allows the motor generator MG to be driven efficiently by a single first inverter 3.

[0019] Furthermore, when the operating mode is the lower-phase Y drive mode, the ECU 10 opens the drive mode selector switch 5 (switching elements 5p and 5n) and closes switch 6, thereby turning on the lower arm of the second inverter 4, i.e., transistors Trb, Trd and Tref, and turning off the upper arm, i.e., transistors Tra, Trc and Tre. As a result, a neutral point (neutral potential) is formed by the turned-on transistors Trb, Trd and Tref, and the other ends of the U-phase coil Lu, V-phase coil Lv, and W-phase coil Lw of the motor generator MG are connected in a Y connection. In this case as well, the ECU 10 switches and controls the transistors Tr1-Tr6 of the first inverter 3 based on the torque command value Tm*. This makes it possible to efficiently drive the motor generator MG with a single first inverter 3.

[0020] Furthermore, when the operation mode is the H drive mode, the ECU 10 closes the drive mode changeover switch 5 (switching elements 5p and 5n) and the switch 6, and performs switching control on the transistors Tr1-Tr6 of the first inverter 3 and the transistors Tra-Trf of the second inverter 4 in opposite phases. Thereby, when setting the H drive mode, the phase voltage can be made approximately twice that in the case of setting the upper-phase Y drive mode and the lower-phase Y drive mode, and higher torque can be output to the motor generator MG.

[0021] Also, in the vehicle 1, with the switching elements 5p of the drive mode changeover switch 5 and the switch 6 open, the external power source 9 is connected to the second inverter 4 via a charger (not shown) as necessary (see the two-dot chain line in FIG. 1), and the battery B can be charged by forming a neutral point by the second inverter 4 and performing switching control on the first inverter 3. That is, in the vehicle 1, the power supplied from the external power source 9 to the second inverter 4 is boosted by the motor generator MG and the first inverter 3 as a multiphase boost converter, and the battery B can be charged with the boosted power. Furthermore, when charging the battery B with the power from the external power source 9, by performing complementary switching control on the transistors Tr1 and Tr2 of the first inverter 3 with the switch 6 open, a triangular-wave current with an average current of zero amperes can be made to flow through the battery B to warm up the battery B.

[0022] Subsequently, while referring to FIGS. 2 and 3, a procedure for shutting down the motor drive device 2 when any abnormality occurs in the motor generator MG, the battery B, the motor drive device 2, etc. during startup of the system of the vehicle 1 (excluding the charging of the battery B with the power from the external power source 9) will be described.

[0023] FIG. 2 is a flowchart showing a routine executed by the ECU 10 when a shutdown request for the motor drive device 2 is issued in response to the occurrence of some abnormality. When a shutdown request for the motor drive device 2 is issued, the ECU 10 turns off the inverter enable (ENA) signal that permits the operation of the first and second inverters 3 and 4 so that all the transistors Tr1 - Tr6 of the first inverter 3 and all the transistors Tra - Trf of the second inverter 4 are turned off (step S100). Next, the ECU 10 increments the counter C (step S110) and determines whether the counter C is equal to or greater than a predetermined threshold value Cref (step S120).

[0024] If the counter C is less than the threshold value Cref (step S120: NO), the ECU 10 increments the counter C at a predetermined increment period (step S110) and determines whether the counter C is equal to or greater than the threshold value Cref (step S120). When the counter C becomes equal to or greater than the threshold value Cref (step S120: YES), the ECU 10 turns off the switch closing signal (step S130) to open the drive mode changeover switch 5 (switching elements 5p and 5n) and the switch 6 of the positive power line PL, and ends the routine of FIG. 2.

[0025] As a result of the execution of the routine in Figure 2, the inverter enable signal is turned off in step S100, causing transistors Tr1-Tr6 and Tra-Trf to be turned off approximately simultaneously (time t1 in Figure 3), and the first and second inverters 3 and 4 to be shut down. At this time, switch 6 remains closed, and as shown by the dashed line in Figure 1, a discharge path is formed for the U-phase coil Lu: U-phase coil Lu - diode Da - diode of switching element 5p - switch 6 - positive side power line PL - battery B - negative side power line NL - diode D2 - U-phase coil Lu. Similarly, when the inverter enable signal is turned off, a discharge path is formed for the V-phase coil Lv - diode Dc - diode of switching element 5p - switch 6 - positive side power line PL - battery B - negative side power line NL - diode D4 - V-phase coil Lv, and a discharge path is formed for the U-phase coil Lu - W-phase coil Lw - diode Df - diode of switching element 5p - switch 6 - positive side power line PL - battery B - negative side power line NL - diode D6 - W-phase coil Lw.

[0026] As a result, as shown in Figure 3, from the time the enable signal is turned off in response to a shutdown request and the first and second inverters 3 and 4 are shut down, until a predetermined delay time tdly, which matches the product of the increment period and the threshold Cref, has elapsed (time t2 in Figure 3), the voltage discharged from the U-phase coil Lu, V-phase coil Lv, and W-phase coil Lw of the motor generator MG is opened, the voltage discharged from these coils is clamped by the battery B. In this embodiment, the delay time tdly, i.e., the increment period and the threshold Cref, are set to be longer than the discharge time tres of the current from the U-phase coil Lu, V-phase coil Lv, and W-phase coil Lw, and shorter than the time toc that is allowed to flow the overcurrent discharged from the U-phase coil Lu, V-phase coil Lv, and W-phase coil Lw to the battery B, as shown in Figure 3 (tres <Tdly<toc)。

[0027] As described above, in the motor drive unit 2, the first and second inverters 3 and 4 are shut down simultaneously in response to a shutdown request (step S100). After the shutdown of the first and second inverters 3 and 4, a predetermined delay time tdly, which is shorter than the allowable time toc for the overcurrent discharged from the U-phase coil Lu, V-phase coil Lv, and W-phase coil Lw of the motor generator MG to flow to the battery B, is elapsed (step S120: YES), at which point the switch 6 of the positive-side power line PL is opened (step S130). As a result, from the time the first and second inverters 3 and 4 are shut down until the switch 6 of the positive-side power line PL is opened, the upper and lower arms of the first and second inverters 3 and 4 are connected to the battery B, and the voltage discharged from the U-phase coil Lu, V-phase coil Lv, and W-phase coil Lw is clamped by the battery B. Therefore, in the motor drive unit 2, when the switch 6 of the positive-side power line PL is opened in response to the processing in step S130, it is possible to effectively suppress the generation of surge voltage (see dashed line in Figure 3) that may occur between the terminals of the second inverter 4 (between switching element 5p and switching element 5n) when the switch 6 is opened simultaneously with the shutdown of the first and second inverters 3 and 4. As a result, when a shutdown of the motor drive unit 2 connected to the motor generator MG, which is an open-winding motor, is required, it becomes possible to effectively protect the components of the motor drive unit 2, such as transistors Tr1-Tr6 and Tr-Trf.

[0028] Furthermore, when the operating mode is the upper-phase Y drive mode or the lower-phase Y drive mode, instead of fixing the inverter that forms the neutral point to the second inverter 4 as described above, the first inverter 3 may form the neutral point and the second inverter 4 may be switched control. Also, in the motor drive device 2, a mode in which the second inverter 4 forms the neutral point and the first inverter 3 is switched control, and a mode in which the first inverter 3 forms the neutral point and the second inverter 4 is switched control may be periodically switched. Moreover, the vehicle 1, which includes the ECU 10 as a motor control device, is not limited to a battery electric vehicle (BEV). That is, the vehicle 1 may be a two-motor hybrid vehicle (series-parallel type) with planetary gears for power distribution, a one-motor hybrid vehicle, a series hybrid vehicle, or a parallel hybrid vehicle. [Industrial applicability]

[0029] The invention disclosed herein can be used in industries such as the manufacturing of motor control devices. [Explanation of Symbols]

[0030] 1 Vehicle, 2 Motor drive unit, 3 First inverter, 4 Second inverter, 5 Drive mode selector switch, 6 Switch, 7,8 Temperature sensor, 9 External power supply, 10 Electronic control unit (ECU), B Battery, D1, D2, D3, D4, D5, D6, Da, Db, Dc, Dd, De, Df Diodes, Lu U-phase coil, Lv V-phase coil, Lw W-phase coil, MG Motor generator MG, NL Negative power line, PL Positive power line, Tr1, Tr2, Tr3, Tr4, Tr5, Tr6, Tra, Trb, Trc, Trd, Tre, Tref Transistors.

Claims

[Claim 1] A motor drive device for driving an open-winding motor including multiple coils, Each includes an upper arm and a lower arm connected to each of the plurality of coils of the open-winding motor, and first and second inverters connected in parallel to the positive and negative power lines connected to the battery, A switch is provided on the positive terminal power line, which connects the positive terminal of the battery to one of the first and second inverters, and also disconnects the connection between them. A control device that, in response to a shutdown request, shuts down the first and second inverters, and then opens the switch after a predetermined delay time has elapsed that is shorter than the time permitted for the current discharged from the plurality of coils of the open-winding motor to flow to the battery, A motor drive device equipped with the following features.

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