ENGINE CONTROL UNIT, VEHICLE, COMPUTER PROGRAM AND RECORDING MEDIUM THAT STORES THE COMPUTER PROGRAM

Abstract

The aim is to specify a motor control device capable of operating a drive motor to which several inverters are coupled, with high power efficiency. A motor control device that controls the operation of a first inverter and a second inverter, each configured to control a feed current to a three-phase AC motor.The motor control device is configured to: switch between a single-inverter control mode, in which one of the first and second inverters is operated to control the supply current to the motor, and a dual-inverter control mode, in which both the first and second inverters are operated to control the supply current to the motor; calculate each of the first power losses resulting from the single-inverter control mode and the second power losses resulting from the dual-inverter control mode; and specify the control mode based on the first power losses or the second power losses, whichever is smaller.

Description

Technical area

[0001] The present invention relates to an engine control device, a vehicle, a computer program and a recording medium storing the computer program. State of the art

[0002] Hybrid electric vehicles and battery electric vehicles (hereinafter collectively referred to as electric vehicles) have a drive motor that provides driving power for the vehicle. Recently, driving a drive motor using multiple inverters has been investigated to increase the torque or current of the drive motor to ensure powertrain redundancy.

[0003] For example, PTL 1 discloses a control device for a vehicle in which two inverters are coupled to a motor, and the operation of the first inverter and the operation of the second inverter are selectively controlled based on the current to be used for the motor, so that the first and second inverters operate with high efficiency. PTL 2 also discloses a motor drive system with two inverters controlling two stators of a dual-stator axial gap motor. BibliographyPatent literature PTL 1: Japanese Unexamined Patent Application Publication JP 2009- 29 397 A PTL 2: Japanese Unexamined Patent Application Publication JP 2016- 131 444 A Summary of the inventionTechnical problem

[0004] In the motor drive systems described in PTL 1 and PTL 2, the power supply to the drive motor can be distributed by driving the drive motor using two inverters. Consequently, a large current can be supplied to the drive motor while suppressing an increase in wiring resistance due to a rise in the inverter temperature. Also, when the three-phase windings, each comprising a u-phase, a v-phase, and a w-phase, are coupled to the inverter, the currents supplied to the three-phase windings are distributed, so the copper loss of the three-phase windings can be reduced.

[0005] However, when the drive motor is driven by two inverters, it is difficult to fully synchronize the control of the two inverters, for example, due to steady-state errors or the residual setpoint deviation of the sensors used to control the inverter, variations in component manufacturing, and deviation in control timing. Therefore, there is room for improvement, considering that the power efficiency of the drive motor may be reduced when driven by two inverters compared to the power efficiency when driven by a single inverter.

[0006] In contrast, when the drive motor is powered by an inverter, the current flowing through the electrical wiring of a power system increases compared to the current when the drive motor is powered by two inverters. Consequently, the wiring resistance losses increase, and the temperature of the electrical wiring rises. Since the wiring resistance depends on the temperature of the electrical wiring, the increase in wiring resistance and the increase in losses can escalate.

[0007] The present invention has been conceived in view of the above-described problem, and an object of the present invention is to provide a motor control device, a vehicle, a computer program, and a recording medium storing the computer program, which are capable of driving a drive motor to which a plurality of inverters are coupled with a high power efficiency. Solution to the problem

[0008] One aspect of the present invention provides a motor controller configured to control the operation of a first inverter and a second inverter, each configured to control a supply current to a three-phase AC motor. The motor controller includes one or more processors and one or more memories communicatively coupled to the one or more processors. The one or more processors are configured to switch a control mode between a single-inverter control mode, in which one of the first inverter and the second inverter is operated to control the supply current to the motor, and a dual-inverter control mode, in which both the first inverter and the second inverter are operated to control the supply current to the motor;each of first power losses due to the single-inverter control mode and second power losses due to the dual-inverter control mode is calculated based on the power losses of the motor, the power losses of the first inverter, the power losses of the second inverter, the power losses of a power supply path from the first inverter to the motor, and the power losses of a power supply path from the second inverter to the motor; and sets the control mode to the first power losses or the second power losses, whichever is smaller.

[0009] One aspect of the present invention provides a vehicle having a motor drive system. The motor drive system includes a three-phase AC motor, and a first inverter and a second inverter, each configured to control the supply current to the motor. A motor controller configured to control the motor drive system is configured to switch a control mode between a single-inverter control mode, in which one of the first inverter and the second inverter is operated to control the supply current to the motor, and a dual-inverter control mode, in which both the first inverter and the second inverter are operated to control the supply current to the motor;each of first power losses due to the single-inverter control mode and second power losses due to the dual-inverter control mode is calculated based on the power losses of the motor, the power losses of the first inverter, the power losses of the second inverter, the power losses of a power supply path from the first inverter to the motor, and the power losses of a power supply path from the second inverter to the motor; and sets the control mode to the first power losses or the second power losses, whichever is smaller.

[0010] One aspect of the present invention provides a computer program applied to a motor drive system configured to control the operation of a first inverter and a second inverter, each configured to control a supply current to a three-phase AC motor. The motor drive system is configured to switch a control mode between a single-inverter control mode, in which one of the first inverter and the second inverter is operated to control the supply current to the motor, and a dual-inverter control mode, in which both the first inverter and the second inverter are operated to control the supply current to the motor.The computer program causes the one or more processors to perform the following: calculating each of first power losses due to the single-inverter control mode and second power losses due to the dual-inverter control mode based on the power losses of the motor, the power losses of the first inverter, the power losses of the second inverter, the power losses of a power supply path from the first inverter to the motor, and the power losses of a power supply path from the second inverter to the motor; and setting the control mode to the first power losses or the second power losses, whichever is smaller. A recording medium that stores the computer program is also specified. Advantageous effects of the invention

[0011] As described above, according to the present invention, it is possible to operate a drive motor to which a plurality of inverters are coupled with a high power efficiency. Short description of the drawings Fig. 1 is a schematic diagram illustrating a configuration example of a vehicle to which an engine control device according to an embodiment may be applied. Fig. 2 is a block diagram schematically illustrating a configuration example of a motor drive system. Fig. 3 is a circuit diagram illustrating the configuration example of the motor drive system. Fig. 4 is a block diagram illustrating a functional configuration of a motor control device according to the embodiment. Fig. 5 is a flowchart illustrating an example of calculation processing performed by an engine control device according to a first embodiment of the present invention. Fig. Figure 6 is an explanatory diagram illustrating how the output power torque is transmitted at the time of inverter switching. Fig. 7 is a flowchart showing the processing of switching an inverter to be used, taking into account the temperature of a power supply path, according to the same embodiment. Fig. 8 is a flowchart illustrating an example of calculation processing performed by an engine control device according to a second embodiment of the present invention. Fig. 9 is a flowchart illustrating the processing for specifying an inverter to be used according to the same embodiment. Fig. Figure 10 is an explanatory diagram illustrating the energy consumption of the inverters. Fig. Figure 11 is an explanatory diagram showing the energy consumption when one inverter is used continuously and when the inverters are switched. Description of embodiments

[0012] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the description and drawings, components with substantially similar functions and configurations are denoted by the same reference numerals, and redundant descriptions thereof will be omitted. 1. Basic configuration

[0013] First, the basic configuration common to the embodiments of the present invention will be described. 1-1. Vehicle configuration example

[0014] Fig. 1 is a schematic diagram illustrating a configuration example of a vehicle 1 in which an engine control device according to an embodiment can be used. The vehicle 1 shown in Fig. 1 is a four-wheeled electric vehicle having a left front wheel 3LF, a right front wheel 3RF, a left rear wheel 3LR, and a right rear wheel 3RR (hereinafter generally referred to as “wheels 3” unless otherwise specified), and is configured as a two-wheel drive electric vehicle that transmits the drive torque output from a drive motor 10 as a drive force source that generates the drive torque of the vehicle 1 to the left front wheel 3LF and the right front wheel 3RF (hereinafter collectively referred to as “front wheels 3F” unless otherwise specified).

[0015] Alternatively, the vehicle 1 may be configured as a four-wheel drive electric vehicle. In this case, the vehicle 1 may be equipped with a front-wheel drive motor and a rear-wheel drive motor, or it may be equipped with in-wheel motors mounted on the wheels.

[0016] The vehicle 1 includes an engine drive system 2 and a hydraulic braking system 16. The hydraulic braking system 16 includes brake devices 17LF, 17RF, 17LR, and 17RR (hereinafter collectively referred to as brake devices 17) arranged in the wheels 3, and a brake hydraulic control device 19 that controls the hydraulic pressure supplied to each of the brake devices 17. Each of the brake devices 17 is configured, for example, as a device that applies a braking force to the wheel 3 by sandwiching a brake disc, which rotates together with the wheel, with brake pads using a supplied hydraulic pressure.

[0017] The brake hydraulic control device 19 includes an electric motor pump that discharges brake fluid, a plurality of solenoid valves that adjust the hydraulic pressures supplied to the brake devices 17, and a brake control device that controls the operation of the electric motor pump and the solenoid valve. The hydraulic brake system 16 generates a predetermined braking force at each of the front / rear, left / right wheels 3LF, 3RF, 3LR, and 3RR by controlling the hydraulic pressure supplied to the corresponding brake device 17. The hydraulic brake system 16 is used in combination with regenerative braking using the drive motor 10.

[0018] The motor drive system 2 includes the drive motor 10, an inverter unit 20, a power converter unit 30, a battery 40, and a controller 50. The controller 50 functions as a motor control device that controls the drive motor 10. An exemplary configuration of the motor drive system 2 will be described in detail later.

[0019] The vehicle 1 also includes a vehicle condition sensor 45. The vehicle condition sensor 45 is connected to the control device 50 via a dedicated line or via a communication method such as a CAN (Controller Area Network) or a LIN (Local Interconnect Network).

[0020] The vehicle condition sensor 45 has one or more sensors that detect the operating state and behavior of the vehicle 1 (hereinafter also collectively referred to as "vehicle condition"). The vehicle condition sensor 45 has, for example, one or more of a steering angle sensor, an accelerator pedal position sensor, a brake stroke sensor, a brake pressure sensor, and an engine speed sensor. The vehicle condition sensor 45 detects the operating state of the vehicle 1, such as the steering angle of the steering wheel or the steered wheel, the accelerator pedal opening degree, the brake application value, or the engine speed. The vehicle condition sensor 45 also has, for example, one or more of a vehicle speed sensor, an acceleration sensor, and an angular velocity sensor. The vehicle condition sensor 45 detects the behavior of the vehicle 1, such as:the vehicle speed, the longitudinal acceleration, the lateral acceleration, or the yaw rate. The vehicle condition sensor 45 transmits a sensor signal containing the detected information to the control device 50.

[0021] In the present embodiment, the vehicle state sensor 45 includes at least the accelerator pedal position sensor, the brake stroke sensor, and the vehicle speed sensor. The accelerator pedal position sensor detects the amount of operation of the accelerator pedal by a driver driving the vehicle. For example, the accelerator pedal position sensor may be a sensor that detects a rotational value of a rotating shaft of an accelerator pedal, but it is not limited thereto. The brake stroke sensor detects the amount of operation of a brake pedal by the driver.

[0022] The brake stroke sensor may be a sensor that detects the movement value of an output rod coupled to the brake pedal, a sensor that detects the rotation value of a rotating shaft of the brake pedal, or a sensor that detects the depression force of the brake pedal, but is not limited to these. The vehicle speed sensor may be, for example, a sensor that detects the rotational speed of any of a rotating shaft of the drive motor 10, a front-wheel drive axle 5F, and a rear-wheel drive axle 5R, but is not limited to these. 1-2. Motor drive system

[0023] Next, an exemplary configuration of the motor drive system 2 is described.

[0024] Fig. 2 and Fig. 3 are explanatory diagrams illustrating a configuration example of the motor drive system 2. Fig. 2 is a block diagram schematically illustrating a configuration example of the motor drive system 2. Fig. 3 is a circuit diagram illustrating the configuration example of the motor drive system 2.

[0025] As in Fig. As illustrated in Figure 2, the motor drive system 2 includes the drive motor 10, the inverter unit 20, the power converter unit 30, the battery 40, and the controller 50. The battery 40 is a chargeable and dischargeable secondary battery. For example, the battery 40 may be a lithium-ion battery with a nominal voltage of 200V, but the nominal voltage and type of the battery 40 are not limited thereto. The battery 40 is coupled to the drive motor 10 via the power converter unit 30 and the inverter unit 20 and stores electrical energy to be supplied to the drive motor 10. The battery 40 is provided with a battery management device 41 that detects, for example, the open-circuit voltage, the output voltage, and the battery temperature of the battery 40 and transmits the detected values ​​to the controller 50.

[0026] The drive motor 10 outputs drive torque to be transmitted to the front wheels 3F via a differential mechanism 7 and the front-wheel drive axle 5F. The drive of the drive motor 10 is controlled by the controller 50. The drive motor 10 includes a rotor 13 and a stator 11 arranged with a gap around the outer periphery of the rotor 13. The drive motor 10 is configured as a three-phase AC motor, but the number of phases is not limited thereto. In the drive motor 10, the rotor 13 rotates by means of a rotating magnetic field formed by a three-phase AC current supplied to the stator 11, and drive torque is output.Also, the drive motor 10 has a function of performing regenerative energy recovery when the rotor 13 rotates by receiving a rotational torque of the front wheels 3F transmitted through the front wheel drive axle 5F in a state where the three-phase alternating current is not supplied to the stator 11.

[0027] The inverter unit 20 includes a first inverter 21a and a second inverter 21b. In the present embodiment, the drive motor 10 is configured as a dual three-phase motor having two three-phase windings for one stator 11 and controlled by two inverters consisting of the first inverter 21a and the second inverter 21b. Each of the first inverter 21a and the second inverter 21b converts DC power supplied from the battery 40 into three-phase AC power and supplies the three-phase AC power to the stator 11 of the drive motor 10. Also, the first inverter 21a and the second inverter 21b convert three-phase AC power regenerated by the stator 11 into DC power and supply the DC power to the power converter unit 30. The driving of the inverter unit 20 is controlled by the control device 50.

[0028] The power converter unit 30 includes a booster circuit 31. The booster circuit 31 converts the voltage of the electrical energy regenerated by the drive motor 10 into a required charging voltage of the battery 40 and supplies the converted voltage to the battery 40. The booster circuit 31 can function to step up or step down the output voltage of the battery 40 and supply the step-up or step-down voltage to the inverter unit 20. The driving of the power converter unit 30 is controlled by the control device 50. Alternatively, the booster circuit 31 can be omitted from the motor drive system 2.

[0029] As in Fig. As illustrated in Figure 3, each of the first inverter 21a and the second inverter 21b includes a plurality of switching elements. The operations of the switching elements of the first inverter 21a and the second inverter 21b are controlled by the controller 50. The first inverter 21a and the second inverter 21b have the same configuration. The configuration of the first inverter 21a will be described below, and the description of the configuration of the second inverter 21b will be omitted.

[0030] The first inverter 21a has three branch circuits 23ua, 23va, and 23wa (hereinafter referred to simply as branch circuits 23a unless otherwise specified). The branch circuit 23ua is electrically coupled to a u-phase coil of the stator 11 of the drive motor 10. The branch circuit 23va is electrically coupled to a v-phase coil of the stator 11 of the drive motor 10. The branch circuit 23wa is electrically coupled to a w-phase coil of the stator 11 of the drive motor 10. Each branch circuit 23a has an upper arm electrically coupled to the positive electrode side of the battery 40 and a lower arm electrically coupled to the negative electrode side of the battery 40.

[0031] The upper branches of the branch circuits 23a are provided with switching elements 25ua, 25va, and 25wa, to which diodes are electrically coupled inverse parallel. The lower branches of the branch circuits 23a are provided with switching elements 27ua, 27va, and 27wa, to which diodes are electrically coupled inverse parallel. The switching elements 25ua, 27ua, 25va, 27va, 25wa, and 27wa can be, for example, MOSFETs (metal-oxide-semiconductor field-effect transistors) or IGBTs (insulated-gate bipolar transistors), but they can also be other switching elements.

[0032] The u-phase, v-phase, and w-phase coils of the stator 11 of the drive motor 10 are electrically coupled to coupling regions between the upper and lower branches of the branch circuits 23ua, 23va, and 23wa. The operations of the switching elements 25ua, 27ua, 25va, 27va, 25wa, and 27wa of the branch circuits 23ua, 23va, and 23wa are controlled by the control device 50.

[0033] The second inverter 21b is configured similarly to the first inverter 21a.

[0034] A booster circuit 31 includes a coil 39, two switching elements 35 and 37, and a smoothing capacitor 29. The booster circuit 31 includes an upper arm electrically coupled to the upper arm sides of the first inverter 21a and the second inverter 21b, and a lower arm electrically coupled to the lower arm sides of the first inverter 21a and the second inverter 21b. The upper arm and the lower arm are each provided with switching elements 35 and 37, to which diodes are electrically coupled in inverse parallel. The switching elements 35 and 37 can be, for example, MOSFETs or IGBTs, but they can also be other switching elements.

[0035] When the electric power of the battery 40 is supplied to the first inverter 21a and the second inverter 21b, switching control is performed on each of the two switching elements 35 and 37 of the booster circuit 31, so that the electric power of the battery 40 is boosted and supplied to the first inverter 21a and the second inverter 21b. Also, when the battery 40 is charged with the power regenerated by the drive motor 10, switching control is performed on each of the two switching elements 35 and 37 of the booster circuit 31, so that the regenerated power output from the first inverter 21a and the regenerated power output from the second inverter 21b are boosted and supplied to the battery 40. The boost ratio is adjusted according to the on / off ratio of the switching elements 35 and 37.The operations of the switching elements 35 and 37 are controlled by the control device 50.

[0036] One end of the coil 39 is electrically coupled to the positive electrode side of the battery 40, and the other end of the coil 39 is electrically coupled between the two switching elements 35 and 37. The smoothing capacitor 29 is coupled in parallel to the battery 40 with respect to each of the first inverter 21a and the second inverter 21b.

[0037] The controller 50 controls the operation of the first inverter 21a, the second inverter 21b, and the booster circuit 31, thus driving the drive motor 10. For example, the controller 50 calculates a requested torque of the drive motor 10 based on a requested acceleration of the vehicle 1. When the requested acceleration is a positive value, the controller 50 controls the operation of the switching elements included in the first inverter 21a, the second inverter 21b, and the booster circuit 31 based on the calculated requested torque to drive the drive motor 10. Consequently, the drive motor 10 outputs a driving torque of the vehicle 1.

[0038] Conversely, if the requested acceleration is a negative value, the controller 50 controls the operation of the switching elements included in the first inverter 21a, the second inverter 21b, and the booster circuit 31 based on the calculated requested torque, causing the drive motor 10 to perform regenerative power generation. Consequently, the drive motor 10 performs regenerative power generation and thus generates a regenerative braking torque.

[0039] In the present embodiment, the controller 50 is configured to be capable of switching the control mode between the single-inverter control mode, in which one of the first inverter 21a and the second inverter 21b is operated to control a supply current to the drive motor 10, and the dual-inverter control mode, in which both the first inverter 21a and the second inverter 21b are operated to control the supply current to the drive motor 10. The controller 50 selects the single-inverter control mode or the dual-inverter control mode so as to increase power efficiency. 1-3. Functional configuration of the control device

[0040] The functional configuration of the control device 50 will be briefly described below. An exemplary embodiment of the control processing by a processing unit 51 will be described in detail later.

[0041] The control device 50 functions as a device that controls the drive motor 10 by means of a processor, such as one or more CPUs, executing a computer program. The computer program is a computer program for causing the processor to execute an operation (described later) to be performed by the control device 50. The computer program to be executed by the processor may be recorded on a recording medium functioning as a storage device (memory) included in the control device 50, or may be recorded on a recording medium built into the control device 50, or any recording medium that can be externally connected to the control device 50.

[0042] The recording medium on which the computer program is recorded may be any of media including: a magnetic medium such as a hard disk, a floppy disk, or a magnetic tape; an optical recording medium such as a CD-ROM (Compact Disk Read Only Memory), a DVD (Digital Versatile Disk), or a Blu-ray (registered trademark); a magneto-optical medium such as a optical disk; a storage device such as a RAM (Random Access Memory) or a ROM (Read Only Memory); a flash memory such as a USB (Universal Serial Bus) memory or an SSD (Solid State Drive); and any other medium capable of storing a program.

[0043] Fig. 4 is a block diagram illustrating the functional configuration of the controller 50.

[0044] The control device 50 includes a processing unit 51 and a memory device 53. The processing unit 51 includes a processor, such as one or more CPUs (central processing units). Alternatively, the processing unit 51 may be formed partially or entirely from an updatable object, such as firmware, or it may be a program module or the like to be executed by means of an instruction from the processor. However, the processing unit 51 may also be formed partially or entirely using hardware.

[0045] The storage device 53 is formed of one or more storage device elements (memory), such as RAM (Random Access Memory) or ROM (Read Only Memory), communicatively coupled to the processing unit 51. However, the number of types of storage devices 53 is not limited thereto. The storage device 53 stores a computer program to be executed by the processing unit 51 and data such as various parameters used for calculation processing, detection data, and a calculation result. Furthermore, the control device 50 has an interface for communicating with, for example, the battery management device 41 and the vehicle condition sensor 45.

[0046] The processing unit 51 includes a detection device 61, a requested torque calculator 63, a power loss calculator 65, a control mode setting unit 67, and an inverter controller 69. Each of these units may be a function implemented by executing a computer program by the processor, but it may also be partially or entirely formed of hardware, such as an analog circuit. Recording device

[0047] The detection device 61 detects sensor signals output from various sensors provided in the motor drive system 2 and the vehicle 1. The sensors include temperature sensors arranged in the drive motor 10, the first inverter 21a, the second inverter 21b, a power supply path from the first inverter 21a to the drive motor 10, and a power supply path from the second inverter 21b to the drive motor 10. The sensors also include a speed sensor that detects the speed of the drive motor 10. Requested torque calculator

[0048] The requested torque calculator 63 calculates the requested torque of the drive motor 10. For example, the requested torque calculator 63 calculates the requested torque (the requested drive torque) based on a requested acceleration of the vehicle 1. The requested acceleration is obtained, for example, based on an operation value of the accelerator pedal and an operation value of the brake pedal. When the vehicle 1 is under autonomous driving control, the requested torque calculator 63 calculates the requested torque (the requested drive torque) based on a requested acceleration requested in the autonomous driving control. Power loss calculator

[0049] The power loss calculator 65 calculates the power losses of the motor drive system 2. For example, the power loss calculator 65 calculates the power losses associated with the operation or drive of the drive motor 10 based on the power losses of the drive motor 10, the power losses of the first inverter 21a, the power losses of the second inverter 21b, the power losses of the power supply path from the first inverter 21a to the drive motor 10, and the power losses of the power supply path from the second inverter 21b to the drive motor 10.The power loss calculator 65 calculates the power losses (first power losses A) in the single-inverter control mode using the first inverter 21a, the power losses (first power losses B) in the single-inverter control mode using the second inverter 21b, and the power losses (second power losses) in the dual-inverter control mode using both the first inverter 21a and the second inverter 21b. Control mode setting unit

[0050] The control mode setting unit 67 sets the control mode of the drive motor 10 as a single-inverter control mode or a dual-inverter control mode based on the requested torque calculated by the requested torque calculator 63 and the power loss calculated by the power loss calculator 65. Even when the single-inverter control mode is set, the control mode setting unit 67 sets the inverter to be used as the first inverter 21a or the second inverter 21b. Inverter control

[0051] The inverter controller 69 controls the operation of one or both of the first inverter 21a and the second inverter 21b according to the control mode specified by the control mode specifying unit 67. When the single-inverter control mode using the first inverter 21a or the second inverter 21b is specified, the inverter controller 69 controls the operation of the first inverter 21a or the second inverter 21b to supply a three-phase alternating current to the drive motor 10. In this case, the inverter controller 69 obtains a target current value capable of outputting a drive torque corresponding to the requested torque and supplies the current to the drive motor 10 via either the first inverter 21a or the second inverter 21b.

[0052] Even when the dual inverter control mode is specified, the inverter controller 69 obtains a target current value including half of the requested torque as the requested torque of the first inverter 21a and half of the requested torque as the requested torque of the second inverter 21b, and supplies the current to the drive motor 10 via the first inverter 21a and the second inverter 21b.

[0053] The basic configuration common to the embodiments of the present invention is described above. The exemplary control processing by the controller 50 will be described in detail below for each embodiment. 2. Embodiments2.1 First embodiment

[0054] First, the calculation processing by a controller 50 according to a first embodiment of the present invention will be described.

[0055] Fig. 5 is a flowchart illustrating an example of calculation processing by the controller 50 according to the present embodiment.

[0056] First, the requested torque calculator 63 of the processing unit 51 calculates the requested torque of the drive motor 10 (step S11). For example, the requested torque calculator 63 calculates the requested torque of the drive motor 10 based on information about the vehicle speed and the requested acceleration. The vehicle speed information can be acquired based on a sensor signal from the vehicle speed sensor. Also, the requested acceleration information can be acquired based on a sensor signal transmitted from the accelerator pedal position sensor. The requested torque has a larger value when the vehicle speed is higher and when the requested acceleration is larger.

[0057] Next, the control mode setting unit 67 of the processing unit 51 determines whether the calculated requested torque exceeds the rated torque that can be output from the drive motor 10 by the power supply from each of the first inverter 21a and the second inverter 21b (step S13). The value of the rated torque per inverter is set in advance depending on the configuration of the inverter. Since the first inverter 21a and the second inverter 21b have the same configuration, the rated torque that can be output from the drive motor 10 by the power supply from the first inverter 21a is the same value as the rated torque that can be output from the drive motor 10 by the power supply from the second inverter 21b.

[0058] If the requested torque exceeds the rated torque value per inverter (step S13 / YES), the control mode setting unit 67 sets the control mode of the drive motor 10 as the dual-inverter control mode (step S19). If the requested torque exceeds the rated torque per inverter, the power supply from only one inverter may provide insufficient output power for the drive torque corresponding to the requested torque from the drive motor 10. Consequently, the power supply is shared between the first inverter 21a and the second inverter 21b.

[0059] When the dual inverter control mode is specified, the inverter controller 69 controls the operation of each of the first inverter 21a and the second inverter 21b to drive the drive motor 10 (step S21). For example, the inverter controller 69 sets a target current value for each of the first inverter 21a and the second inverter 21b using a value obtained by multiplying the requested torque by one and a half as the requested torque of each of the first inverter 21a and the second inverter 21b. Based on the target current value and the rotational speed of the drive motor 10, the inverter controller 69 controls the operation of each of the first inverter 21a and the second inverter 21b to control the power supply to the drive motor 10.

[0060] In contrast, in a case where the requested torque is equal to or less than the value of the rated torque per inverter (step S13 / NO), the power loss calculator 65 of the processing unit 51 calculates the power losses when the first inverter 21a is operated, the power losses when the second inverter 21b is operated, and the power losses when both the first inverter 21a and the second inverter 21b are operated (step S15). For each case, the power loss calculator 65 obtains the power losses of the drive motor 10, the power losses of the first inverter 21a, the power losses of the second inverter 21b, the power losses of the power supply path from the first inverter 21a to the drive motor 10, and the power losses of the power supply path from the second inverter 21b to the drive motor 10, and calculates the total power losses.

[0061] For example, the power loss calculator 65 can obtain the power efficiencies (power losses) of the first inverter 21a and the second inverter 21b by referring to a power-efficiency characteristic curve corresponding to the rotational speed of the drive motor 10, the required torque, and the temperatures of the inverters. The power-efficiency characteristic curve is obtained in advance through experiments, simulations, or the like and stored in the storage device 53. The power losses of the first inverter 21a and the second inverter 21b correspond to the power losses due to the operation of the switching elements.

[0062] The rotational speed of the drive motor 10 can be detected based on a sensor signal output from the rotational speed sensor or a current waveform supplied from each inverter. The temperatures of the first inverter 21a and the second inverter 21b can be detected based on sensor signals output from temperature sensors arranged in their circuits.

[0063] The power loss calculator 65 can also obtain the power losses of the drive motor 10 by referring to a power-efficiency characteristic curve corresponding to the speed and the required torque of the drive motor 10. The power-efficiency characteristic curve is obtained in advance through experiments, simulations, or the like and stored in the storage device 53. The power losses of the drive motor 10 correspond to the copper losses of the three-phase windings coupled to the first inverter 21a and the second inverter 21b. The power losses of the drive motor 10 can be corrected according to the temperature of the drive motor 10. In this case, the power losses are corrected to be larger when the temperature of the drive motor 10 is higher.The temperature of the drive motor 10 can be detected based on, for example, a sensor signal output from a temperature sensor arranged at a suitable position near the stator 11 of the drive motor 10.

[0064] Also, the power loss calculator 65 can obtain the power losses of the power supply path from the first inverter 21a to the drive motor 10 and the power losses of the power supply path from the second inverter 21b to the drive motor 10, for example, as follows. That is, if the reference temperature in the power supply path is t, the temperature coefficient of resistance is αt, and the resistance at the reference temperature t is denoted by Rt, then the resistance value R at a wiring temperature T can be expressed by the following equation (1). R=Rt×(1+αt(T−t))

[0065] Consequently, the power losses of the power supply path from each inverter to the drive motor 10 can be easily obtained from the above equation (1) by using the temperature of any part of the power supply path as a representative value. Alternatively, the power supply path can be divided into predetermined regions, taking into account a temperature distribution provided by a thermal model of the electrical wiring, and the sum of the power losses of the regions can be specified as the power losses of the entire power supply path.

[0066] The power losses calculated by the Power Loss Calculator 65 are listed below. • EL1-A = Lm1 + Li1 + Lw1 (requested torque output by operation of the first inverter 21a) • EL1-B = Lm2 + Li2 + Lw2 (requested torque output by operating the second inverter 21b) • EL2 = Lm1 + Li1 + Lw1 (requested torque, output by operating the two inverters) EL1-A: Power losses (first power losses A) in single-inverter control mode using the first inverter 21a EL1-B: Power losses (first power losses B) in single-inverter control mode using the second inverter 21b EL2: Power losses (second power losses) in dual inverter control mode Lm1: Power losses of the drive motor 10 (the three-phase winding coupled to the first inverter 21a) Lm2: Power losses of the drive motor 10 (the three-phase winding, coupled to the second inverter 21b) Li1: Power losses of the first inverter 21a Li2: Power losses of the second inverter 21b Lw1: Power losses of the current supply path from the first inverter 21a to the drive motor 10 Lw2: Power losses of the current supply path from the second inverter 21b to the drive motor 10

[0067] Next, the control mode setting unit 67 determines whether the calculated first power losses A EL1-A or second power losses B EL1-B in the single-inverter control mode are greater than the second power losses EL2 in the dual-inverter control mode (step S17). If the first power losses A EL1-A or the second power losses B EL1-B are greater than the second power losses EL2 (step S17 / YES), the control mode setting unit 67 sets the control mode of the drive motor 10 to the dual-inverter control mode (step S19). If the dual-inverter control mode is set, the inverter controller 69 controls the operation of each of the first inverter 21a and the second inverter 21b to drive the drive motor 10 (step S21).

[0068] If the first power losses A EL1-A or the second power losses B EL1-B are not greater than the second power losses EL2 (step S17 / NO), the control mode setting unit 67 sets the control mode of the drive motor 10 to the single-inverter control mode (step S23). Next, the control mode setting unit 67 determines whether the first power losses A EL1-A in the single-inverter control mode using the first inverter 21a are greater than the second power losses B EL1-B in the single-inverter control mode using the second inverter 21b (step S25).

[0069] If the first power losses A EL1-A are greater than the second power losses B EL1-B (step S25 / YES), the inverter controller 69 controls the operation of the second inverter 21b to drive the drive motor 10 (step S27). Conversely, if the first power losses A EL1-A are not greater than the second power losses B EL1-B (step S25 / NO), the inverter controller 69 controls the operation of the first inverter 21a to drive the drive motor 10 (step S29).

[0070] In this way, the processing unit 51 specifies the control mode and inverter to be used so that the power loss of the motor drive system 2 decreases, drives the drive motor 10, and causes the drive motor 10 to output the requested torque. The processing unit 51 determines whether the motor drive system 2 has stopped (step S31), returns to step S11 as long as the system has not stopped, and repeatedly executes the processing of each step described above. Conversely, if the system has stopped (step S31 / YES), the processing unit 51 ends the sequence of control processing.

[0071] When switching the inverter to be used, the inverter controller 69 can gradually change the ratio of the output torques over a predetermined time so that the sum of the output torque by the operation of the first inverter 21a and the output torque by the operation of the second inverter 21b satisfies the requested torque. For example, as shown in Fig. As shown in Figure 6, when the inverter to be used is alternately switched between the first inverter 21a and the second inverter 21b in the single-inverter control mode, the output torque from the inverter being used is gradually decreased relative to the requested torque, while the output torque from the inverter being started is gradually increased. That is, when the inverters are switched, the control mode is switched once to the dual-inverter control mode and then switched again to the single-inverter control mode, so that the output torque from the drive motor 10 is maintained. Therefore, it is possible to suppress a rapid change in torque at the time of switching the inverter to be used.

[0072] Also, while the drive motor 10 is operated in the single inverter control mode, the control mode setting unit 67 may switch the inverter to be used so that the temperature of the power supply path from the first inverter 21a to the drive motor 10 and the temperature of the power supply path from the second inverter 21b to the drive motor 10 are maintained to be lower than respective thermal resistance threshold values.

[0073] Fig. Figure 7 is a flowchart illustrating the processing for switching the inverter to be used, taking into account the temperature of the power supply path. The flowchart shown in Fig. 7 is replaced by step S23 to step S29 in the flowchart shown in Fig. 5. As described above, if it is determined in step S25 that the first power losses A EL1-A in the single-inverter control mode using the first inverter 21a are greater than the second power losses B EL1-B in the single-inverter control mode using the second inverter 21b (step S25 / YES), the control mode setting unit 67 determines whether the temperature of the power supply path from the second inverter 21b to the drive motor 10 is lower than a thermal resistance threshold (step S26).

[0074] If the temperature of the power supply path from the second inverter 21b to the drive motor 10 is lower than the thermal resistance threshold (step S26 / YES), the inverter controller 69 controls the operation of the second inverter 21b to drive the drive motor 10 (step S27). Conversely, if the temperature of the power supply path from the second inverter 21b to the drive motor 10 is equal to or higher than the thermal resistance threshold (step S26 / NO), the inverter controller 69 controls the operation of the first inverter 21a to drive the drive motor 10 (step S29).

[0075] Similarly, if it is determined in step S25 that the first power losses A EL1-A are not greater than the second power losses B EL1-B (step S25 / NO), the control mode setting unit 67 determines whether the temperature of the power supply path from the first inverter 21a to the drive motor 10 is lower than the thermal resistance threshold (step S28). If the temperature of the power supply path from the first inverter 21a to the drive motor 10 is lower than the thermal resistance threshold (step S28 / YES), the inverter controller 69 controls the operation of the first inverter 21a to drive the drive motor 10 (step S29).In contrast, when the temperature of the power supply path from the first inverter 21a to the drive motor 10 is equal to or higher than the thermal resistance threshold (step S28 / NO), the inverter controller 69 controls the operation of the second inverter 21b to drive the drive motor 10 (step S27).

[0076] By switching the inverter to be used so that the temperature of each power supply path is maintained lower than the corresponding thermal resistance threshold, it is possible to suppress overheating of the power supply path while controlling the operation of the drive motor 10 in the single-inverter control mode. It is also possible to prevent the wiring resistance of the power supply path from increasing excessively and power losses from increasing excessively.

[0077] As described above, even though the requested torque is equal to or less than the rated torque of an inverter, the controller 50 according to the first embodiment of the present invention compares the power losses EL1-A, EL1-B, and EL2 when the single-inverter control mode using the first inverter 21a, the single-inverter control mode using the second inverter 21b, and the dual-inverter control mode are specified, and selects the control mode and the inverter(s) with the smallest power losses. Consequently, it is possible to control the operation of the drive motor 10 in the control mode in which the power efficiency of the motor drive system 2 further increases.Also, if the inverter to be used is switched so that the temperature of each power supply path is maintained lower than the corresponding thermal resistance threshold, it is possible to suppress overheating of the power supply path while controlling the operation of the drive motor 10 in the single inverter control mode. 2-2. Second embodiment

[0078] Next, the calculation processing by a controller 50 according to a second embodiment of the present invention will be described.

[0079] Fig. 8 and Fig. 9 are flowcharts illustrating an example of calculation processing by the controller 50 according to the present embodiment.

[0080] First, the requested torque calculator 63 of the processing unit 51 calculates the requested torque of the drive motor 10 (step S11). Next, the control mode setting unit 67 of the processing unit 51 determines whether the calculated requested torque exceeds the rated torque that can be output from the drive motor 10 by powering each of the first inverter 21a and the second inverter 21b (step S13). If the requested torque exceeds the rated torque value per inverter (step S13 / YES), the control mode setting unit 67 sets the control mode of the drive motor 10 as the dual-inverter control mode (step S19).When the dual inverter control mode is specified, the inverter controller 69 controls the operation of each of the first inverter 21a and the second inverter 21b to drive the drive motor 10 (step S21).

[0081] When the requested torque exceeds the value of the rated torque per inverter, the dual inverter control mode is specified, and the operation of the first inverter 21a and the second inverter 21b is controlled to operate the drive motor 10 in a manner similar to the first embodiment.

[0082] Conversely, if the requested torque is equal to or less than the rated torque value per inverter (step S13 / NO), the control mode setting unit 67 sets the control mode of the drive motor 10 to the single-inverter control mode (step S41). Next, the control mode setting unit 67 executes the processing for setting the inverter to be used (step S43).

[0083] Fig. Figure 9 is a flowchart illustrating the processing for specifying the inverter to be used.

[0084] The control mode setting unit 67 detects the wiring temperature of each of the power supply path from the first inverter 21a to the drive motor 10 and the power supply path from the second inverter 21b to the drive motor 10 (step S51). As the wiring temperature of each power supply path, the temperature of any region of the power supply path can be used as a representative value. The power supply path can be divided into predetermined regions, taking into account the temperature distribution determined by a thermal model of the electrical wiring, and the average value of the temperatures of the regions can be used as the wiring temperature.

[0085] Next, the control mode setting unit 67 determines whether the drive motor 10 was in a stopped state or the dual-inverter control mode was specified until the last processing cycle (step S53). If the determination in step S53 is affirmative (step S53 / YES), the control mode setting unit 67 determines whether the wiring temperature of the power supply path from the first inverter 21a to the drive motor 10 is lower than the wiring temperature of the power supply path from the second inverter 21b to the drive motor 10 (step S55).

[0086] If the determination in step S55 is affirmative (step S55 / YES), the inverter controller 69 controls the operation of the first inverter 21a to drive the drive motor 10 (step S57). Conversely, if the determination in step S55 is negative (step S55 / NO), the inverter controller 69 controls the operation of the second inverter 21b to drive the drive motor 10 (step S59). That is, immediately after switching to the single-inverter control mode, an inverter with a low wiring temperature of the power supply path is selected to drive the drive motor 10. Consequently, it is possible to suppress an increase in power loss due to an increase in the wiring temperature of the power supply path.

[0087] In contrast, in a case where the determination in step S53 is negative (step S53 / NO), that is, in a case where the single-inverter control mode continues, the power loss calculator 65 calculates the power losses when the inverter in use continues to be used and the power losses when the inverter to be used is switched (step S61). An example of a method for calculating the power losses when the inverter continues to be used and a method for calculating the power losses when the inverter to be used is switched will be described below.

[0088] The power loss calculator 65 calculates third power losses up to a predetermined time when the inverter in use continues to be used, and fourth power losses up to a predetermined time when the inverter to be used is switched and used. The predetermined time can be set to any value taking into account an operating time Ti for switching the inverter and a reference time Ta after the inverter is switched. For example, the predetermined time is set to a time after a time within a range of 10 milliseconds to several hundred milliseconds has elapsed, taking into account, for example, the response time of the inverter, the stability of the output torque, and the switching frequency of the inverter.

[0089] For example, assume that the drive motor 10 is currently operating in the single-inverter control mode using the first inverter 21a. In this case, the power loss calculator 65 calculates the power losses (third power losses) EL3 up to a predetermined time when the first inverter 21a continues to be used, as follows. That is, the power loss calculator 65 obtains the power losses of the drive motor 10, the power losses of the first inverter 21a, and the power losses of the power supply path from the first inverter 21a to the drive motor 10 when the first inverter 21a is used up to a predetermined time, with reference to the current demand torque and rotational speed of the drive motor 10, and sets the sum of the power losses as the third power losses EL3.The third power losses EL3 correspond to the total value of the power losses when the first inverter 21a is used for a predetermined time (Ti + Ta).

[0090] The power loss calculator 65 also calculates the power losses (fourth power losses EL4) up to a predetermined time when switching from the first inverter 21a to the second inverter 21b as follows. That is, the power loss calculator 65 anticipates the case where the usage ratio of the first inverter 21a and the usage ratio of the second inverter 21b change from 1:0 to 0:1 before the inverter switching operation time Ti elapses, and calculates the sum ELi of the power losses during this time. Also, the power loss calculator 65 assumes that the current demand torque and speed of the drive motor 10 do not change, and calculates the power losses ELa in the reference time Ta after switching to the second inverter 21b.Then, the sum of the sum ELi of the power losses in the inverter switching operation time Ti and the power losses ELa in the reference time Ta after switching to the second inverter 21b is specified as the fourth power losses EL4.

[0091] Next, the control mode setting unit 67 determines whether the third power loss EL3 is smaller than the fourth power loss EL4 until the predetermined time when the inverter is continuously used (step S63). If the third power loss EL3 is smaller than the fourth power loss EL4 (step S63 / YES), the inverter controller 69 controls the operation of the inverter while maintaining the inverter in use to drive the drive motor 10 (step S65). Conversely, if the third power loss EL3 is equal to or greater than the fourth power loss EL4 (step S63 / NO), the inverter controller 69 switches the inverter to be used and controls the operation of the inverter to drive the drive motor 10 (step S67).

[0092] Also in this embodiment, when switching the inverter to be used, the inverter controller 69 gradually changes the ratio of the output torques over a predetermined time so that the sum of the output torque by the operation of the first inverter 21a and the output torque by the operation of the second inverter 21b satisfies the required torque. That is, when switching the inverters, the control mode is switched once to the dual-inverter control mode and then switched again to the single-inverter control mode, so that the output torque from the drive motor 10 is maintained. Therefore, it is possible to suppress a rapid change in torque at the time of switching the inverter to be used.

[0093] Fig. 10 and Fig. 11 are diagrams to explain the power losses when the inverter in use is continued to be used and when the inverter to be used is switched and used.

[0094] Fig. 10 illustrates the power consumption (instantaneous losses) of the first inverter 21a when the first inverter 21a is used to drive the drive motor 10, the power consumption (instantaneous losses) of the second inverter 21b when the second inverter 21b is used to drive the drive motor 10, and the power consumption (instantaneous losses) at the time of inverter switching. For example, the power consumption at the time of switching can be obtained by dividing an estimated value of losses during torque fluctuation of each inverter and cooperative control of each inverter by the inverter switching time, to the average value of the power consumption of the first inverter 21a and the power consumption of the second inverter 21b at the time of switching.

[0095] Fig. Figure 11 illustrates the energy consumption during a time corresponding to the inverter switching time when the first inverter 21a is continuously used without switching the inverter, and the energy consumption when the inverter to be used is switched to the second inverter 21b. The energy consumption when the inverter to be used is switched to the second inverter 21b corresponds to the average value of the energy consumption during the inverter switching time of the energy consumptions shown in Fig. 10 are illustrated.

[0096] In this example, the inverter to be used is switched from the first inverter 21a to the second inverter 21b at a time point at which the power consumption (D) when the first inverter 21a continues to be used without switching the inverter exceeds the power consumption (E) when the inverter to be used is switched to the second inverter 21b.

[0097] As described above, in the case where the requested torque is equal to or less than the rated torque of an inverter, the control device 50 according to the second embodiment of the present invention compares the power loss when the inverter in use continues to be used with the power loss when the inverter to be used is switched, and maintains the inverter to be used or switches it to be used, thus reducing the power loss. Consequently, it is possible to control the operation of the drive motor 10 in the control mode in which the power efficiency of the motor drive system 2 further increases.

[0098] Although the embodiments of the present invention are described in detail with reference to the accompanying drawings, the present invention is not limited to these examples. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the technical spirit of the invention as defined by the appended claims. These changes and modifications obviously fall within the technical scope of the present invention.

[0099] For example, although a double-three-phase motor is described as an example in the above embodiments, the drive motor may also be a double-stator axial gap motor with two stators. Although the drive motor is an axial gap motor, it is possible to specify the single-inverter control mode using the inverter that supplies electrical power to any one of the stators when the required torque is low, and the technique of the present invention can be applied. List of reference symbols 1 vehicle 2 Motor drive system 10 Drive motor 13 Rotor 16 hydraulic braking system 19 Brake hydraulic control device 20 inverter unit 21a first inverter 21b second inverter 30 power converter unit 31 Booster circuit 40 Battery 50 Control device QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2009-29 397 A

[0003] JP 2016-131 444 A

[0003]

Claims

[1] A motor control device configured to control the operation of a first inverter and a second inverter, each configured to control a supply current to a three-phase AC motor, the motor control device comprising: one or more processors; and one or more memories communicatively coupled to the one or more processors, wherein the one or more processors are configured to a control mode switches between a single inverter control mode in which one of the first inverter and the second inverter is operated to control the supply current to the motor, and a dual inverter control mode in which both the first inverter and the second inverter are operated to control the supply current to the motor, each of first power losses due to the single-inverter control mode and second power losses due to the dual-inverter control mode is calculated based on the power losses of the motor, the power losses of the first inverter, the power losses of the second inverter, the power losses of a power supply path from the first inverter to the motor, and the power losses of a power supply path from the second inverter to the motor; and sets the control mode to the first power losses or the second power losses, whichever is smaller. [2] Engine control device according to claim 1, wherein the one or more processors are configured to, during the single inverter control mode, a temperature of the power supply path from the first inverter to the motor and a temperature of the power supply path from the second inverter to the motor are detected, and switches the inverter to be used between the first inverter and the second inverter such that each of the temperature of the power supply path from the first inverter to the motor and the temperature of the power supply path from the second inverter to the motor is maintained to be lower than a thermal resistance threshold. [3] The motor control device of claim 1, wherein the one or more processors are configured to compare, during the single inverter control mode, third power losses when the inverter in use continues to be used with fourth power losses when the inverter to be used is switched and used, and if the third power losses are less than the fourth power losses, switch the inverter to be used between the first inverter and the second inverter. [4] Engine control device according to claim 3, wherein the one or more processors are configured to when the inverter to be used is switched during the single-inverter control mode, executes processing to maintain an output torque from the motor by switching the control mode once to the dual-inverter control mode and then switching the control mode back to the single-inverter control mode, each of the third power losses up to a predetermined time when the inverter in use continues to be used and the fourth power losses up to a predetermined time when the inverter to be used is switched and used, based on the power losses of the motor, the power losses of the first inverter, the power losses of the second inverter, the power losses of the power supply path from the first inverter to the motor, and the power losses of the power supply path from the second inverter to the motor, and if the third power losses are smaller than the fourth power losses, switches the inverter to be used between the first inverter and the second inverter. [5] Vehicle having: a motor drive system comprising a three-phase AC motor and a first inverter and a second inverter each configured to control a supply current to the motor; a motor control device configured to: Controlling the engine drive system, Switching the control mode between a single inverter control mode in which one of the first inverter and the second inverter is operated to control the supply current to the motor, and a dual inverter control mode in which both the first inverter and the second inverter are controlled to control the supply current to the motor, Calculating each of first power losses due to the single-inverter control mode and second power losses due to the dual-inverter control mode based on the power losses of the motor, the power losses of the first inverter, the power losses of the second inverter, the power losses of a power supply path from the first inverter to the motor, and the power losses of a power supply path from the second inverter to the motor; and Specify the control mode to the first power losses or the second power losses, whichever is smaller. [6] A computer program applied to a motor drive system configured to control the operation of a first inverter and a second inverter, each configured to control a supply current to a three-phase AC motor, wherein the motor drive system is configured to switch a control mode between a single inverter control mode in which one of the first inverter and the second inverter is operated to control the supply current to the motor, and a dual inverter control mode in which both the first inverter and the second inverter are operated to control the supply current to the motor, and wherein the computer program causes the one or more processors to perform the following: Calculating each of first power losses due to the single-inverter control mode and second power losses due to the dual-inverter control mode based on the power losses of the motor, the power losses of the first inverter, the power losses of the second inverter, the power losses of a power supply path from the first inverter to the motor, and the power losses of a power supply path from the second inverter to the motor; and Specify the control mode to the first power losses or the second power losses, whichever is smaller. [7] A recording medium storing the computer program according to claim 6.

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