Control device, program, and control method for rotary electric machine

Abstract

A control device (80) for a rotary electric machine (31) executes: a normal control process for executing powering control, which is switching control of an inverter (34) for causing a q-axis current flowing through a stator winding (31a) to be greater than 0, or regenerative control, which is switching control of the inverter for causing the q-axis current flowing through the stator winding to be less than 0; a process for determining whether or not the voltage of a capacitor (39) has exceeded a threshold value during the execution of the regenerative control when a rotor (37) is rotating; and a process for switching from the regenerative control to reduction control, which is switching control of the inverter for reducing the magnitude of an induction voltage generated in the stator winding, when it is determined that the voltage of the capacitor has exceeded the threshold value.

Description

Control device, program, and control method for rotating electrical machine Cross-reference to Related Applications

[0001] This application is based on Japanese Patent Application No. 2025-053877 filed on March 27, 2025, the content of which is incorporated herein by reference.

[0002] The present disclosure relates to a control device, a program, and a control method for a rotating electrical machine.

[0003] Conventionally, as described, for example, in Patent Document 1, there is known a system including a rotating electrical machine having a rotor and a stator winding, and an inverter that transfers power between a DC power source and the stator winding.

[0004] Japanese Unexamined Patent Publication No. 2011-93676

[0005] A control device applied to the above system selects and executes power running control or regenerative control. The power running control is switching control of the upper and lower arm switches of the inverter that makes the q-axis current flowing through the stator winding larger than 0. The regenerative control is switching control of the upper and lower arm switches that makes the q-axis current flowing through the stator winding smaller than 0.

[0006] During execution of regenerative control when the rotor is rotating, for example, when a large regenerative torque is generated in the rotating electrical machine, a large regenerative current is supplied to a capacitor connected in parallel to the series connection body of the upper and lower arm switches, and the voltage of the capacitor can increase significantly. In this case, there is a concern that the voltage of the capacitor or its peripheral circuit components may exceed the withstand voltage.

[0007] In order to suppress the voltage rise of the capacitor, it is also conceivable to perform short-circuit control that turns on all phases of the switch of either one of the upper and lower arms. In this case, although the voltage rise of the capacitor can be suppressed, the induced voltage generated in the stator winding causes a freewheeling current to flow in the closed circuit including the stator winding and the switch turned on by the short-circuit control, and there is a concern that the inverter and the rotating electrical machine may become overheated.

[0008] The primary purpose of this disclosure is to provide a control device, program, and control method for a rotating electric machine that can suppress the voltage rise of a capacitor while suppressing the occurrence of overheating of the inverter and the rotating electric machine.

[0009] This disclosure relates to a control device for a rotating electric machine applied to a system comprising: a rotating electric machine having a rotor and stator windings; an inverter for transmitting power between a DC power supply and the stator windings; and a capacitor connected in parallel to a series connection of the upper and lower arm switches of the inverter, wherein the control device performs: a normal control process that executes a power control, which is a switching control of the upper and lower arm switches that makes the q-axis current flowing through the stator windings greater than 0, or a regenerative control, which is a switching control of the upper and lower arm switches that makes the q-axis current flowing through the stator windings less than 0; a process that determines whether the voltage of the capacitor exceeds a threshold while the regenerative control is being executed when the rotor is rotating; and, if it is determined that the voltage of the capacitor exceeds the threshold, a process that switches from the regenerative control to a reduction control, which is a switching control of the upper and lower arm switches that reduces the magnitude of the induced voltage generated in the stator windings.

[0010] This reduces the magnitude of the induced voltage and the amount of regenerative current that flows from the stator winding through the inverter to the capacitor. As a result, it is possible to suppress the occurrence of overheating in the inverter and rotating electric machine while suppressing the voltage rise of the capacitor.

[0011] The above-mentioned objectives and other objectives, features and advantages of this disclosure will become clearer from the following detailed description with reference to the attached drawings. The drawings are as follows: Figure 1 is an overall configuration diagram of an autonomous vehicle according to the first embodiment; Figure 2 is a diagram showing the electric drive unit and its peripheral configuration; Figure 3 is a diagram showing the configuration of the inverter and rotating electric machine; Figure 4 is a block diagram of the control processing performed by the controller; Figure 5 is a flowchart of the induced voltage reduction control processing performed by the controller; Figure 6 is a time chart showing the reduction control processing mode; Figure 7 is a flowchart of the main switch control processing performed by the higher-level controller; Figure 8 is a flowchart of the induced voltage reduction control processing performed by the controller according to the second embodiment; and Figure 9 is a flowchart of the induced voltage reduction control processing performed by the controller according to the third embodiment.

[0012] Multiple embodiments will be described with reference to the drawings. In multiple embodiments, functionally and / or structurally corresponding and / or related parts may be given the same reference numeral, or reference numerals that differ by hundreds or more digits. For corresponding and / or related parts, refer to the descriptions of other embodiments.

[0013] <First Embodiment> Hereinafter, a first embodiment of the control device according to the present disclosure will be described with reference to the drawings. The control device of this embodiment is applied to an automated guided vehicle (AGV) guided by a magnetic tape which is a guide line in a factory or warehouse, etc. The automated guided vehicle is, for example, an unmanned transport vehicle or an unmanned transport robot. The automated guided vehicle may be a manned transport vehicle or a manned transport robot.

[0014] First, the overall configuration of the autonomous vehicle 10 will be explained using Figures 1 and 2.

[0015] The autonomous vehicle 10 comprises a vehicle body 11, drive wheels 12, and a drive unit 20. The upper part of the vehicle body 11 is a mounting section on which transported items can be placed. The right drive wheel 12 and the left drive wheel 12 are positioned opposite each other in the vehicle width direction of the autonomous vehicle 10. In this embodiment, two sets of drive wheels 12 are provided, one as the front wheel and one as the rear wheel.

[0016] The drive unit 20 is a device for rotating each drive wheel 12 and is housed within the vehicle body 11. The drive unit 20 includes an electric drive device 30 corresponding to each drive wheel 12, a brake 60 corresponding to each drive wheel 12, a higher-level controller 70, a battery 71, a main switch 73, a brake switch 75, and sensors 77, etc. The main switch 73 and the brake switch 75 are, for example, relays (specifically, for example, mechanical relays). The battery 71 corresponds to a "DC power supply" and is a rechargeable secondary battery. In Figure 1, the power lines PL1 and PL2 are shown as solid lines, and the signal line SL is shown as a dashed line.

[0017] Each electric drive unit 30 drives a drive shaft 13 connected to each drive wheel 12. Each electric drive unit 30 is equipped with an MCU (Motor Control Unit) 58 and a reduction gear 59.

[0018] Each MCU 58 is connected to the battery 71 via a power line PL1. A main switch 73 is provided between the battery 71 and the four MCUs 58 on the power line PL1. The main switch 73 can be switched between ON, which supplies power from the battery 71 to each MCU 58, and OFF, which cuts off the power supply to each MCU 58. When the main switch 73 is ON, each MCU 58 operates by being powered from the battery 71.

[0019] The reduction gear 59 reduces the rotational speed of the rotor 37 (see Figure 3) of the rotating electric machine 31 of the MCU 58 and transmits it to the drive shafts 13R and 13L. The reduction gear 59 is, for example, a planetary gear mechanism or a cycloidal gear mechanism.

[0020] The brakes 60 are devices that apply braking force to the drive shafts 13. The brakes 60 are connected to the battery 71 by a power line PL2. A brake switch 75 is provided between the battery 71 and each brake 60 in the power line PL2. The brake switch 75 can be switched between ON, which supplies power from the battery 71 to each brake 60, and OFF, which cuts off the power supply to each brake 60. Each brake 60 is powered and driven by the battery 71 when the brake switch 75 is ON. The braking force applied by each brake 60 to each drive shaft 13 can also be controlled by each MCU 58 or a higher-level controller 70.

[0021] The upper-level controller 70 and each MCU 58 are connected to each other by a signal line SL. The signal line SL is a signal line that conforms to the communication standard of, for example, CAN (Controller Area Network). The upper-level controller 70 includes a processor as hardware, a memory unit, and a communication bus connecting the processor and the memory unit.

[0022] The memory unit includes memory and storage as hardware. Memory is a storage device for storing data used in the controller's processing. Memory provides the processor with a temporary workspace for use when the processor is performing processing. Memory includes, for example, ROM or RAM. Storage is a storage device that stores various programs and data for the processor to read and execute, and is a non-transitory tangible storage medium. Storage includes, for example, HDD or flash memory. The storage stores program information and the like for processing described later.

[0023] For example, program information stored on a non-transitional physical recording medium is installed in the storage unit. The recording medium may be, for example, a USB memory stick, CD-ROM, or DVD. Furthermore, program information transmitted via a communication network, such as OTA (Over The Air), is also installed in the storage unit.

[0024] The higher-level controller 70 and each MCU 58 transmit and receive information from each other via the signal line SL. The higher-level controller 70 controls each MCU 58 by inputting commands to each MCU 58 via the signal line SL. The higher-level controller 70 switches the main switch 73 and the brake switch 75 on and off. The higher-level controller 70 keeps the main switch 73 and the brake switch 75 on while the drive unit 20 is operating.

[0025] The sensors 77 include, for example, an abnormal stop button, a collision detection switch, a location information sensor that reads current location information, a guide sensor that detects guidance lines on the floor (specifically, magnetic tape), and a human presence sensor that detects people. The detection results from the sensors 77 are input to the higher-level controller 70.

[0026] Next, we will explain the electric drive unit 30 and its surrounding configuration using Figure 2. Since each electric drive unit 30 has a similar configuration, we will explain using one electric drive unit 30 as an example.

[0027] The electric drive unit 30 includes a power switch 32, an inverter 34, a current sensor 41, and an angle sensor 42. The electric drive unit 30 also includes a rotating electric machine 31, a reduction gear 59, and a controller 80. The power switch 32 is, for example, a relay (specifically, for example, a mechanical relay).

[0028] The inverter 34 is connected to the battery 71 via a power switch 32 and a main switch 73. The power switch 32 can be switched between ON, which supplies power from the battery 71 to the inverter 34, and OFF, which cuts off the power.

[0029] The inverter 34 is equipped with upper and lower arm switches corresponding to each phase. The inverter 34 converts the DC power supplied from the battery 71 into AC power and supplies the converted AC power to the stator winding 31a of the rotating electric machine 31. As a result, the rotor of the rotating electric machine 31 rotates, and consequently the drive wheels 12 rotate.

[0030] The current sensor 41 detects the current flowing through the stator winding 31a. The angle sensor 42 detects the rotation angle (electrical angle) of the rotor. The detected values ​​from the current sensor 41 and the angle sensor 42 are input to the controller 80.

[0031] The autonomous vehicle 10 is equipped with a voltage sensor 43 that detects the voltage across the terminals of a capacitor 39, which will be described later. The value detected by the voltage sensor 43 is input to the controller 80.

[0032] The controller 80 is an ECU that performs various controls on the electric drive unit 30, and comprises a processor 81 as hardware, a storage unit 82, and a communication bus 83 that connects the processor 81 and the storage unit 82.

[0033] The memory unit 82 includes memory and storage as hardware. The memory is a storage device for storing data used in the processing of the controller 80. The memory provides the processor 81 with a temporary workspace for use when the processor 81 performs processing. The memory includes, for example, ROM or RAM. The storage is a storage device that stores various programs and data for the processor 81 to read and execute, and is a non-transitory tangible storage medium. The storage includes, for example, an HDD or flash memory. The storage stores program information and the like for processing described later.

[0034] For example, program information stored on a non-transitional physical recording medium is installed in the storage unit 82. The recording medium is, for example, a USB memory stick, a CD-ROM, or a DVD. Also, for example, program information transmitted via a communication network, such as OTA (Over The Air), is installed in the storage unit 82.

[0035] Incidentally, the electric drive unit 30 may have multiple power switches 32, inverters 34, current sensors 41, and angle sensors 42, rather than just one.

[0036] The inverter 34 and the rotating electric machine 31 will be explained using Figure 3.

[0037] The rotating electric machine 31 is equipped with a rotor 37. The rotor 37 is equipped with permanent magnets 38 that serve as field poles. In other words, the rotating electric machine 31 in this embodiment is a permanent magnet field type synchronous machine. The rotational power of the rotor 37 is transmitted to the drive wheels 12 via the drive shaft 13.

[0038] The rotating electric machine 31 is equipped with U, V, and W phase windings 36U, 36V, and 36W as stator windings 31a, which are connected in a star configuration with an electrical angle offset from each other by 120°.

[0039] The inverter 34 comprises a series connection of U, V, W phase upper arm switches SUH, SVH, SWH and U, V, W phase lower arm switches SUL, SVL, SWL. In this embodiment, each switch SUH, SVH, SWH, SUL, SVL, SWL is an N-channel MOSFET. Each switch SUH, SVH, SWH, SUL, SVL, SWL is equipped with body diodes DUH, DVH, DWH, DUL, DVL, DWL.

[0040] The positive terminal of the battery 71 is connected to the drain, which is the high-potential terminal of the U, V, W phase upper arm switches SUH, SVH, and SWH, via the power switch 32 and the main switch 73. The ground is connected to the source, which is the low-potential terminal of the U, V, W phase lower arm switches SUL, SVL, and SWL, and to the negative terminal of the battery 71. In each phase, the first ends of the windings 36U, 36V, and 36W are connected to the source of the upper arm switches SUH, SVH, and SWH and to the drain of the lower arm switches SUL, SVL, and SWL. The second ends of each phase winding 36U, 36V, and 36W are connected at the neutral point. Note that the stator windings are not limited to star-connected configurations, but may also be delta-connected configurations.

[0041] The MCU 58 includes a capacitor 39. A first end of the capacitor 39 is connected to drains of the upper-arm switches SUH, SVH, SWH for respective phases. A second end of the capacitor 39 is connected to ground. That is, the capacitor 39 is connected in parallel to a series connection body of the upper-arm switches SUH, SVH, SWH for respective phases and lower-arm switches SUL, SVL, SWL for respective phases. The capacitor 39 may be built in the inverter 34, or may be provided outside the inverter 34.

[0042] Returning to the description of FIG. 2 above, the controller 80 controls the power switch 32 to be turned on or off. Specifically, the controller 80 keeps the power switch 32 turned on during operation of the electric drive device 30. The controller 80 performs switching control of the upper and lower arm switches of the inverter 34 based on commands from the host controller 70 and detection values of the current sensor 41, the angle sensor 42, and the voltage sensor 43.

[0043] The controller 80 performs powering running control or regenerative control in a state where the power switch 32 and the main switch 73 are turned on. Powering running control is switching control of the inverter 34 that converts DC power output from the battery 71 into AC power and supplies the AC power to the stator winding 31a. Regenerative control is switching control of the inverter that converts AC power generated by the stator winding 31a into DC power and supplies the DC power to the battery 71.

[0044] Next, a control process for a rotating electric machine executed by the controller 80 will be described with reference to FIG. 4.

[0045] In the controller 80, a speed calculation unit 90 calculates the rotational speed Nr of the drive wheels 12 based on the detection value of the angle sensor 42. Specifically, the speed calculation unit 90 calculates the rotational speed Nr based on the detection value of the angle sensor 42 and the gear ratio (specifically, the reduction ratio) of the speed reducer 59.

[0046] A speed deviation calculation unit 91 calculates a rotational speed difference ΔN (=N*−Nr), which is the difference between a command rotational speed Ntgt input from a host controller 70 and a calculated rotational speed Nr. Note that the host controller 70 may acquire the command rotational speed Ntgt from, for example, a PLC (Programmable Logic Controller) provided outside the autonomous vehicle 10.

[0047] A command current calculation unit 92 calculates a d-axis command current Idtgt and a q-axis command current Iqtgt to be passed through a stator winding 31a as operation amounts for performing feedback control to bring the calculated rotational speed difference ΔN to 0. The feedback control is, for example, proportional-integral control. When powering running control is executed, the command current calculation unit 92 sets the q-axis command current Iqtgt to a positive value. On the other hand, when regenerative control is executed, the command current calculation unit 92 sets the q-axis command current Iqtgt to a negative value.

[0048] A current feedback control unit 93 calculates d-axis command voltage Vd* and q-axis command voltage Vq* to be applied to the stator winding 31a as operation amounts for performing feedback control that matches the calculated d- and q-axis command currents Idtgt and Iqtgt to d- and q-axis currents Idr and Iqr flowing in the stator winding 31a. The feedback control in the current feedback control unit 93 is, for example, proportional-integral control. The current feedback control unit 93 calculates the d- and q-axis currents Idr and Iqr based on detection values from a current sensor 41 and detection values from an angle sensor 42.

[0049] The current feedback control unit 93 converts the d and q axis command voltages Vd* and Vq* in the two-phase rotating coordinate system (dq-axis coordinate system) into U, V, and W phase command voltages Vu*, Vv*, and Vw* in the three-phase fixed coordinate system (UVW coordinate system) based on the values ​​detected by the angle sensor 42. Based on the converted U, V, and W phase command voltages Vu*, Vv*, and Vw* and the values ​​detected by the voltage sensor 43, the current feedback control unit 93 generates drive signals to turn on or off the upper and lower arm switches of each phase of the inverter 34. The current feedback control unit 93 supplies the generated drive signals to the gates of the upper and lower arm switches of each phase. This controls the switching of the upper and lower arm switches of the inverter 34 so that the rotational speed Nr becomes the commanded rotational speed Ntgt.

[0050] Next, the reduction control of the controller 80, which is a characteristic configuration of this embodiment, will be described. The reduction control is a control to suppress the voltage rise of the capacitor 39 during the execution of regenerative control.

[0051] Figure 5 is a flowchart showing the steps of the reduction control process performed by the controller 80.

[0052] In step S10, it is determined whether or not regenerative control is being performed. In regenerative control, the d-axis command current Idtgt should be set to 0 or a value close to 0.

[0053] If it is determined that regenerative control is being performed, the process proceeds to step S11, where the bus voltage Vdc, which is the terminal voltage of the capacitor 39 detected by the voltage sensor 43, is obtained. Then, it is determined whether the obtained bus voltage Vdc exceeds the threshold Vth. In this embodiment, the threshold Vth is set to a value lower than the withstand voltage of the capacitor 39 or the withstand voltage of the peripheral circuit components of the capacitor 39 (for example, the switches SUH, SVH, SWH, SUL, SVL, SWL of the inverter 34). Specifically, for example, the threshold Vth is set to a value lower than the lower of the withstand voltage of the capacitor 39 or the withstand voltage of the peripheral circuit components of the capacitor 39.

[0054] If it is determined that the bus voltage Vdc exceeds the threshold Vth, the process proceeds to step S12, and the system switches from regenerative control to reduction control. Reduction control is a control that shifts the q-axis command current Iqtgt, which is input from the command current calculation unit 92 to the current feedback control unit 93, to the positive side to 0A or more in order to reduce the magnitude of the induced voltage generated in the stator winding 31a by the rotation of the rotor 37. This prevents the rotating electric machine 31 from generating regenerative torque and suppresses the occurrence of regenerative current flowing into the capacitor 39.

[0055] In this embodiment in particular, the q-axis command current Iqtgt is set from a negative value to 0A. This makes it possible to suppress the voltage rise of the capacitor 39 while preventing the generation of torque (specifically, power torque) that would propel the autonomous vehicle 10 forward when deceleration of the autonomous vehicle 10 is required. In the reduction control, the d-axis command current Idtgt should be set to 0 or a value close to 0.

[0056] In step S13, it is determined whether the bus voltage Vdc has fallen below the threshold Vth. In other words, the reduction control continues until it is determined that the bus voltage Vdc has fallen below the threshold Vth that ensures the safe state of each switch SUH, SVH, SWH, SUL, SVL, SWL.

[0057] If it is determined in step S13 that the bus voltage Vdc has fallen below the threshold Vth, the process proceeds to step S13 and a recovery process is executed to switch from reduction control to regenerative control or power control.

[0058] Next, the effects of this embodiment will be explained using the time chart in Figure 6. In Figure 6, (a) shows the changes in command rotational speed Ntgt and rotational speed Nr, (b) shows the changes in q-axis current Idr, (c) shows the changes in bus voltage Vdc, and (d) shows the changes with and without reduction control execution.

[0059] From time t1 onward, the vehicle is powered so that the commanded rotational speed Ntgt remains constant. Then, at time t2, the upper controller 70 issues a deceleration command to each controller 80 for the automated vehicle 10, switching from powered control to regenerative control, and the commanded rotational speed Ntgt for each controller 80 decreases to 0. As a result, the rotational speed Nr gradually decreases towards 0, and regenerative current flows from the stator winding 31a to the capacitor 39 via the inverter 34, causing the bus voltage Vdc to rise. At time t3, when it is determined that the bus voltage Vdc has exceeded the threshold Vth, the system switches from regenerative control to reduction control. This causes the q-axis command current Iqtgt to become 0, bringing the regenerative current closer to 0. As a result, the rise in bus voltage Vdc can be suppressed.

[0060] Subsequently, at time t4, when it is determined that the bus voltage Vdc has fallen below the threshold Vth, the control is switched from reduction control to regenerative control or power control. Then, at time t5, the rotational speed Nr becomes 0, and the autonomous vehicle 10 stops.

[0061] Furthermore, if the controller 80 determines that the braking force to be applied to the autonomous vehicle 10 is insufficient during the execution of the reduction control, it may apply braking force to the autonomous vehicle 10 by controlling the brake 60. In the example shown in Figure 6, braking force is applied by the brake 60 at least during the period from time t3 to t5.

[0062] According to the embodiment described above, when it is determined that the bus voltage Vdc exceeds the threshold Vth, the magnitude of the induced voltage in the stator winding 31a can be reduced, and the magnitude of the regenerative current that attempts to flow from the stator winding 31a to the capacitor 39 via the inverter 34 can be reduced. As a result, it is possible to suppress the occurrence of overheating of the inverter 34 and the rotating electric machine 31 while suppressing the voltage rise of the capacitor 39.

[0063] On the other hand, Figure 6 shows the changes in the q-axis current Idr and bus voltage Vdc in the comparative example. In the comparative example, since regenerative control continues even after time t3, the bus voltage Vdc significantly exceeds the threshold Vth.

[0064] However, if the main switch 73 is switched off, the battery 71 and the inverter 34, which are the recipients of the regenerative current, will be electrically disconnected, raising concerns that the rate of increase in the bus voltage Vdc will become significant. Even in such cases, the increase in the bus voltage Vdc can be effectively suppressed by the reduction control.

[0065] Figure 7 shows the procedure for controlling the main switch 73, which is performed by the higher-level controller 70.

[0066] In step S20, it is determined whether or not specific conditions have been met for turning off the main switch 73 (corresponding to the "shut-off switch"). These specific conditions include, for example, the condition that the abnormal stop button has been operated, the condition that the automated driving vehicle 10 has derailed from the guide line based on the values ​​detected by the guide sensor, the condition that the automated driving vehicle 10 is unable to perform sufficient deceleration despite a request for deceleration, or the condition that an off command for the main switch 73 has been input from an external PLC.

[0067] If it is determined in step S20 that the specific condition is not met, the process proceeds to step S21, and the main switch 73 remains ON. On the other hand, if it is determined in step S20 that the specific condition is met, the process proceeds to step S22, and the main switch 73 is switched OFF.

[0068] Furthermore, the above-mentioned problem can occur not only with the main switch 73, but also when the power switch 32 of the MCU 58 (corresponding to the "shut-off switch") is switched to the off position.

[0069] <Second Embodiment> The second embodiment will be described below, focusing on the differences from the first embodiment, with reference to the drawings. In this embodiment, the processing content of the reduction control has been changed.

[0070] Figure 8 is a flowchart showing the reduction control processing procedure performed by the controller 80. Note that, for convenience, the same reference numerals are used in Figure 8 for processes that are identical to those shown in Figure 5.

[0071] If it is determined in step S11 that the bus voltage Vdc exceeds the threshold Vth, the process proceeds to step S15, and the system switches from regenerative control to reduction control. In this embodiment, the reduction control keeps the q-axis command current Iqtgt below 0A, and the larger the magnitude of the regenerative current Ignt flowing from the stator winding 31a to the inverter 34, the larger the correction amount ΔI (>0) added to the q-axis command current Iqtgt. In other words, the value obtained by adding the correction amount Δ to the q-axis command current Iqtgt calculated by the command current calculation unit 92 (= Iqtgt + ΔI) is used in the current feedback control unit 93. The magnitude of the regenerative current Ignt can be calculated, for example, based on the induced voltage constant and the electrical angular velocity based on the detection value of the angle sensor 42.

[0072] According to the process in step S15, the larger the magnitude of the regenerative current Ignt, the closer the q-axis command current Iqtgt approaches 0A, and as a result, switching control of the inverter 34 is performed such that the magnitude of the regenerative current decreases. This suppresses the occurrence of overheating of the inverter 34 and the rotating electric machine 31, while also suppressing the voltage rise of the capacitor 39.

[0073] <Third Embodiment> The third embodiment will be described below, focusing on the differences from the first embodiment, with reference to the drawings. In this embodiment, the processing content of the reduction control has been changed.

[0074] Figure 9 is a flowchart showing the reduction control processing procedure performed by the controller 80. Note that, for convenience, the same reference numerals are used in Figure 9 for processes that are identical to those shown in Figure 5.

[0075] If it is determined in step S11 that the bus voltage Vdc exceeds the threshold Vth, the process proceeds to step S16, and the system switches from regenerative control to reduction control. In this embodiment, the reduction control increases the q-axis command current Iqtgt to a value greater than 0, and increases the q-axis command current Iqtgt as the increase in the bus voltage Vdc relative to the threshold Vth, ΔV (= Vdc - Vth), increases.

[0076] According to the process in step S16, the larger the rise ΔV, the greater the q-axis command current Iqtgt (>0), which increases the charge released from capacitor 39. As a result, the voltage rise of capacitor 39 can be effectively and appropriately suppressed. This prevents the inverter 34 and the rotating electric machine 31 from overheating while suppressing the voltage rise of capacitor 39.

[0077] <Other Embodiments> The above embodiments may be modified and implemented as follows.

[0078] - The reduction control is not limited to those exemplified in the above embodiments. For example, the switching control of the inverter 34 may be such that the induced voltage of the stator winding 31a is estimated each time based on the electrical angular velocity and the induced voltage constant, and the inverter 34 generates the same voltage as the estimated induced voltage.

[0079] In an autonomous vehicle, either the pair of front wheels or the pair of rear wheels may be driven wheels. Furthermore, an autonomous vehicle is not limited to four wheels; for example, it may be a two-wheeled electric vehicle or an electric vehicle with five or more wheels.

[0080] Furthermore, the mounting target for the control device of this disclosure is not limited to vehicles, but may also be a moving object such as an aircraft or a ship. Also, the mounting target is not limited to a moving object, but may be a stationary system.

[0081] In this disclosure or claims, the term "processor" means one or more hardware processors configured to execute processing defined by computer program code (i.e., one or more instructions of a computer program) contained in a computer program by reading the computer program code each time. In other words, a "processor" is a hardware device that executes one or more programmed processes. Therefore, computer program code can also be said to be software that can define the processing of the processor according to its content. A "processor" can be a general-purpose or specific-purpose processor, and may be, but is not limited to, a CPU, microprocessor, GPU, and DFP (Data Flow Processor).

[0082] In this disclosure or claims, the term “memory” means one or more hardware memories that are non-transitional tangible recording media configured to record computer program code and / or data in a manner accessible from a processor. “Memory” can be implemented by memory technology such as SRAM, SDRAM, non-volatile / flash type memory, or other types of memory. The computer program code that constitutes the program is recorded in memory and executed by a processor, thereby enabling the processor to perform the various functions described above.

[0083] In this disclosure or claims, the term “circuit” refers to one or more logic circuits as hardware, configured to perform specific processing defined by a pre-designed circuit configuration. In other words (and, in contrast to “processor”), “circuit” in this disclosure or claims refers to a hardware device that performs specific processing based on a circuit configuration, rather than processing defined by software such as the computer program code described above. For example, “circuit” may include custom ICs such as ASICs (Application Specific Integrated Circuits) and FPGAs (Field Programmable Gate Arrays) designed with Hardware Description Language (HDL). That is, “circuit” in this disclosure or claims includes all hardware circuits except for the processors described above that perform processing by reading computer program code.

[0084] In this disclosure or claims, the expression "at least one of the circuit and processor" should be interpreted as disjunctive (logical OR) and not as "at least one circuit and at least one processor." Therefore, in this disclosure or claims, "at least one of the circuit and processor causes the device to perform functions" includes cases where the circuit alone causes the device to perform all functions. Also, "at least one of the circuit and processor causes the device to perform functions" includes cases where the processor alone causes the device to perform all functions. Furthermore, "at least one of the circuit and processor causes the device to perform functions" includes cases where the circuit causes the device to perform some functions and the processor causes the device to perform the remaining functions. In the last example, for example, if the device performs functions A to C, functions A and B may be implemented by the circuit, and the remaining function C may be implemented by the processor.

[0085] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure.

Claims

1. A control device (80) for a rotating electric machine applied to a system comprising: a rotating electric machine (31) having a rotor (37) and a stator winding (31a); an inverter (34) that transmits power between a DC power supply (71) and the stator winding; and a capacitor (39) connected in parallel to a series connection of the upper and lower arm switches (SUH to SWL) of the inverter, wherein the control device (80) performs the following: a normal control process that performs a switching control of the upper and lower arm switches which makes the q-axis current flowing through the stator winding greater than 0, or a regenerative control which makes the switching control of the upper and lower arm switches which makes the q-axis current flowing through the stator winding less than 0; a process that determines whether the voltage of the capacitor exceeds a threshold while the regenerative control is being performed when the rotor is rotating; and a process that, if it is determined that the voltage of the capacitor has exceeded the threshold, switches from the regenerative control to a reduction control which makes the switching control of the upper and lower arm switches which reduces the magnitude of the induced voltage generated in the stator winding.

2. The control device for a rotating electric machine according to claim 1, wherein the reduction control is a switching control that reduces the magnitude of the induced voltage generated in the stator winding by making the q-axis current flowing through the stator winding 0 A or more.

3. The control device for a rotating electric machine according to claim 2, wherein the reduction control is the switching control that reduces the q-axis current flowing through the stator winding to 0 A.

4. The control device for a rotating electric machine according to claim 1, wherein the reduction control is a switching control that brings the q-axis current flowing through the stator winding closer to 0A as the magnitude of the regenerative current flowing from the stator winding to the inverter increases.

5. The control device for a rotating electric machine according to claim 1, wherein the threshold value is lower than the breakdown voltage of the peripheral circuit components of the capacitor, and the reduction control is a switching control that increases the q-axis current flowing through the stator winding as the amount of increase in the capacitor voltage relative to the threshold value increases, while making the q-axis current flowing through the stator winding greater than zero.

6. A control device for a rotating electric machine according to any one of claims 1 to 5, wherein if it is determined that the voltage of the capacitor falls below the threshold during the execution of the reduction control, a recovery process is executed to switch from the reduction control to the normal control process.

7. The control device for a rotating electric machine according to any one of claims 1 to 5, wherein the system includes a circuit breaker switch (32, 73) provided in the electrical path connecting the DC power supply and the inverter, and when it is determined that a specific condition has been met during the execution of the regenerative control, it performs a process to switch the circuit breaker switch to the OFF position.

8. A program applied to a system comprising: a rotating electric machine (31) having a rotor (37) and a stator winding (31a); an inverter (34) that transmits power between a DC power supply (71) and the stator winding; and a capacitor (39) connected in parallel to a series connection of the upper and lower arm switches (SUH to SWL) of the inverter, wherein the program includes: a processor (81) and at least one of the circuits, a normal control process that performs a switching control of the upper and lower arm switches to make the q-axis current flowing through the stator winding greater than 0, or a regenerative control that performs a switching control of the upper and lower arm switches to make the q-axis current flowing through the stator winding less than 0; a process that determines whether the voltage of the capacitor exceeds a threshold while the regenerative control is being performed when the rotor is rotating; and, if it is determined that the voltage of the capacitor exceeds the threshold, a process that switches from the regenerative control to a reduction control that performs a switching control of the upper and lower arm switches to reduce the magnitude of the induced voltage generated in the stator winding. A program that executes something.

9. A control method applicable to a system comprising: a rotating electric machine (31) having a rotor (37) and a stator winding (31a); an inverter (34) that transmits power between a DC power supply (71) and the stator winding; and a capacitor (39) connected in parallel to a series connection of the upper and lower arm switches (SUH to SWL) of the inverter, wherein at least one of the processor (81) and the circuit performs a normal control process which is a switching control of the upper and lower arm switches that makes the q-axis current flowing through the stator winding greater than 0, or a regenerative control that makes the q-axis current flowing through the stator winding less than 0; a process which determines whether the voltage of the capacitor exceeds a threshold while the regenerative control is being performed when the rotor is rotating; and, if it is determined that the voltage of the capacitor has exceeded the threshold, a process which switches from the regenerative control to a reduction control that is a switching control of the upper and lower arm switches that reduces the magnitude of the induced voltage generated in the stator winding. A control method to execute something.

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