Motor controller

Abstract

To allow more appropriate control of a motor.SOLUTION: A motor controller 10 comprises a control unit 22 that controls power to be supplied to a motor 2 through PWM control, and can switch a modulation system in the PWM control between three-phase modulation and two-phase modulation. The control unit 22 determines an area Sa in which the number of rotations of the motor 2 is a first number of rotations N1 or less and torque is first torque T1 or less as a three-phase modulation area in which the three-phase modulation is performed, and an area Sb other than the three-phase modulation area as a two-phase modulation area in which the two-phase modulation is performed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a motor control device. [Background technology]

[0002] In recent years, efforts to realize a low-carbon or carbon-free society have become more active, and research and development into motor control technology is being conducted in order to reduce CO2 emissions and improve energy efficiency in vehicles. One such technology is disclosed in Patent Document 1, which describes a motor control device that varies the power supplied to a motor through PWM control. When the motor is in a high rotation range or a low rotation range with high torque, the modulation method is three-phase modulation and the carrier frequency is set to a reference frequency, and when the motor is in a low rotation range with low torque, the modulation method is three-phase modulation and the carrier frequency is switched to a low frequency. Furthermore, in Patent Document 1, when the motor is in a specific range of low rotation speed and low torque, the modulation method is changed to two-phase modulation and the carrier frequency is switched to a low frequency. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2023 / 281285 Summary of the Invention [Problem to be solved by the invention]

[0004] In motor control technology, it is desirable to further reduce vibration, noise, heat generation, and the like. However, conventional technologies can generate unpleasant vibrations and noise when the motor is operating at low speeds and low torque, and can also increase switching losses when the motor is operating at high speeds, which can be disadvantageous in terms of heat generation and energy efficiency. The present invention has been made in view of the above circumstances, and has an object to enable more appropriate control of a motor, which in turn contributes to improving energy efficiency. [Means for solving the problem]

[0005] The present invention provides a motor control device that includes a control unit that controls the power supplied to a motor by PWM control, is capable of switching the modulation method in PWM control between three-phase modulation and two-phase modulation, and is capable of switching the carrier frequency in multiple stages, and the control unit defines a region where the rotation speed of the motor is equal to or less than a first rotation speed and where the torque is equal to or less than a first torque as a three-phase modulation region where the three-phase modulation is performed, and defines a region outside the three-phase modulation region as a two-phase modulation region where the two-phase modulation is performed. [Effects of the Invention]

[0006] The present invention allows for better control of the motor. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram showing a motor control device according to an embodiment of the present invention together with its peripheral configuration; [Figure 2] 1 is a diagram showing the relationship between the rotation speed and torque of a motor, and the modulation method and carrier frequency of PWM control. [Figure 3] 10 is a diagram showing the relationship between the rotation speed and torque of a motor, and the modulation method and carrier frequency of PWM control according to a modified example. FIG. [Figure 4] 10 is a diagram showing the relationship between the rotation speed and torque of a motor, and the modulation method and carrier frequency of PWM control according to a modified example. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a motor control device 10 according to an embodiment of the present invention together with the peripheral configuration. The motor control device 10 is mounted on an electric vehicle 1 and drives a motor 2 for driving the vehicle. The electric vehicle 1 is a two-wheeled vehicle. Note that the electric vehicle 1 is not limited to two-wheeled vehicles, and any vehicle driven by a motor, such as a three-wheeled vehicle, a four-wheeled vehicle, or even an electric-powered bicycle, can be used. The electric vehicle 1 may also be a hybrid electric vehicle 1 (e.g., HEV) equipped with an internal combustion engine that uses fuel, such as a diesel engine or a gasoline engine, as its energy source.

[0009] The motor 2 is an electric motor that provides driving force to the electric vehicle 1, and can also be called a traction motor or a rotating electric machine. The motor 2 is, for example, a three-phase AC brushless DC motor. The three phases are U-phase, V-phase, and W-phase. The motor control device 10 includes a PDU (Power Drive Unit) 20 that converts DC power from a battery 3 into AC power (three-phase AC power in this embodiment) for driving the motor. The battery 3 is a high-voltage battery that serves as a power source for the vehicle, and includes multiple battery cells connected in series or parallel. The motor control device 10 is also referred to as a PCU (Power Control Unit).

[0010] The PDU 20 includes a power converter 21 and a control unit 22. The power converter 21 includes an inverter that converts DC power into three-phase AC power, a converter that performs voltage conversion such as step-up and step-down, and the like. The inverter includes an internal circuit (not shown) in which three series circuits are connected in parallel: a high-side circuit, which is a parallel circuit of a semiconductor element (which can also be called a switching element) such as an IGBT or MOSFET, and a feedback diode; and a low-side circuit, which is a parallel circuit of a semiconductor element and a feedback diode. When a high signal (high voltage) gate signal is applied to the gate of each semiconductor element in the high-side circuit and the low-side circuit, the semiconductor element becomes conductive (short-circuited), and when a low signal (low voltage lower than the high voltage) gate signal is applied, the semiconductor element becomes non-conductive. The control unit 22 controls the gate signals of the semiconductor elements to switch between conductive and non-conductive states (switching), thereby converting DC power into AC power suitable for driving the motor 2. The switching timing is adjusted by PWM (Pulse Width Modulation) control by the control unit 22. The converter converts power from the battery 3 into a voltage suitable for driving the motor 2, etc., using the control unit 22.

[0011] The control unit 22 includes a processor and peripheral circuits, and acquires driving operation information such as accelerator opening and vehicle information such as the rotation speed and vehicle speed of the motor 2 via various sensors provided in the electric vehicle 1. The control unit 22 sets a rotation speed command value and a torque command value for the motor 2 based on the acquired driving operation information and vehicle information. The control unit 22 generates a reference sine wave based on a rotation speed command value (corresponding to the period of the reference sine wave) and a torque command value (corresponding to the amplitude of the reference sine wave), inputs the reference sine wave and a triangular wave of a predetermined carrier frequency to a comparator, generates a PWM signal as a signal representing the magnitude relationship between them, and outputs the PWM signal to the power converter 21.

[0012] The control unit 22 of this embodiment has a function of switching the modulation method in PWM control between three-phase modulation and two-phase modulation, and a function of switching the carrier frequency. FIG. 2 is a diagram showing the relationship between the rotation speed and torque of the motor 2, and the modulation method and carrier frequency of PWM control. As shown in FIG. 2, a specific region Sa where the rotation speed of the motor 2 is equal to or less than a first rotation speed N1 and the torque is equal to or less than a first torque T1 is set as a three-phase modulation region where three-phase modulation is performed. The specific region Sa is a region in which the motor 2 rotates relatively slowly and has low torque, and is a driving condition in which the user is likely to find the sounds and vibrations emitted from the motor 2 and motor drive system, etc., unpleasant due to factors such as the low level of ambient noise.

[0013] Switching the PWM control modulation method between three-phase modulation and two-phase modulation affects the conversion efficiency and the operating characteristics of Motor 2. With three-phase modulation, all phases are modulated within one cycle, so the output waveform of each phase becomes sinusoidal. Compared to two-phase modulation, three-phase modulation can drive Motor 2 more efficiently and achieve smoother operation. Therefore, by performing three-phase modulation in the specific region Sa, it is possible to suppress the occurrence of unpleasant vibrations and noise when the rotation speed and torque are relatively low.

[0014] It should be noted that the rotation speed and torque conditions that cause unpleasant vibrations and noise may vary depending on the specifications of the motor 2 and the motor drive system, and therefore the first rotation speed N1 and first torque T1 may be set to appropriate values ​​based on the results of experiments, simulations, etc.

[0015] As shown in FIG. 2, a specific region Sb where the rotation speed of the motor 2 exceeds the first rotation speed N1 and the torque of the motor 2 exceeds the first torque T1 is set as a two-phase modulation region where two-phase modulation is performed. Two-phase modulation is a method of generating a pseudo three-phase waveform in PWM control by fixing one phase for a specific section of one cycle and modulating the other two phases. With two-phase modulation, the switching control of one of the phases is always stopped, so the number of switching operations is 2 / 3 of that with three-phase modulation. In other words, switching losses can be reduced to 2 / 3 compared to three-phase modulation. Selecting two-phase modulation can suppress the temperature rise of the inverter due to switching losses. In this embodiment, two-phase modulation is performed in the specific region Sb of relatively high rotation speed or high torque, so the number of switching operations during running can be reduced, resulting in reduced switching loss and improved energy efficiency.

[0016] As shown in FIG. 2, in this embodiment, a specific region Sa, which is a three-phase modulation region, is divided into multiple (three in this example) specific regions Sa1, Sa2, and Sa3, and each of the regions Sa1, Sa2, and Sa3 is set to a region with a different carrier frequency. The specific region Sa1 is a region where the rotation speed of the motor 2 is equal to or less than the second rotation speed N2 and the torque is equal to or less than the second torque T2, and the carrier frequency is set to the highest value of 16 kHz.

[0017] Specific region Sa2 is a region where the rotation speed of motor 2 ranges from second rotation speed N2 to third rotation speed N3, and the torque of motor 2 ranges from second torque T2 to third torque T3, and the carrier frequency is set to the next highest 13 kHz. Specific region Sa3 is a region where the rotation speed of motor 2 ranges from third rotation speed N3 to first rotation speed N1, and the torque of motor 2 ranges from third torque T3 to first torque T1, and the carrier frequency is set to 8 kHz. The second rotation speed N2<the third rotation speed N3<the first rotation speed N1, and the second torque T2<the third torque T3<the first torque T1.

[0018] In the specific region Sb, which is a two-phase modulation region, the carrier frequency is set to 8 kHz. It is to be noted that the rotation speed and torque conditions that cause unpleasant vibrations and noise may change depending on the specifications of the motor 2. Therefore, the rotation speeds N1 to N3 and torques T1 to T3 may be set to appropriate values ​​based on the results of experiments, simulations, etc.

[0019] When the carrier frequency of PWM control is switched, the operating characteristics of the motor 2, such as the smoothness of the drive of the motor 2 and the conversion efficiency of the energy required for drive, are affected. In this embodiment, the carrier frequency of specific regions Sa1 and Sa2, which are part of the three-phase modulation region, is set to a value higher than that of specific region Sb, which is the two-phase modulation region, thereby making it possible to control motor 2 more precisely and drive motor 2 more smoothly, which is advantageous in reducing vibration and noise of motor 2.

[0020] Furthermore, the carrier frequency of the remaining specific region Sa3 of the three-phase modulation region is set to the same value as the specific region Sb, which is the two-phase modulation region. In other words, in this embodiment, as the rotation speed and torque of the motor 2 increase, the motor 2 changes through the specific regions Sa1, Sa2, Sa3, and Sb in this order, so that the carrier frequency can be reduced in stages when transitioning from the three-phase modulation region to the two-phase modulation region.

[0021] This allows the carrier frequency to gradually decrease when transitioning from the three-phase modulation region (specific regions Sa1, Sa2, Sa3) to the two-phase modulation region (specific region Sb), preventing large changes in vibration and noise. Furthermore, when the carrier frequency is low, switching loss is reduced, improving energy efficiency. Furthermore, when transitioning from the two-phase modulation region (specific region Sb) to the specific regions Sa3, Sa3, and Sa1 of the three-phase modulation region in order, the carrier frequency can be increased in stages, thereby suppressing large changes in the vibration and sound of the motor 2 when transitioning from the two-phase modulation region to the three-phase modulation region.

[0022] In this embodiment, the carrier frequency is lowest when the rotation speed of motor 2 is equal to or higher than the third rotation speed N3 or when the torque of motor 2 is equal to or higher than the third torque T3, so that when the rotation speed of motor 2 is high, the switching loss of the inverter can be reduced, and when the torque of motor 2 is high, the heat loss associated with the large current flowing through the inverter can be reduced.

[0023] The relationship between the rotation speed and torque of the motor 2 and the modulation method and carrier frequency of the PWM control may be changed as appropriate. For example, in FIG. 2, when transitioning between the three-phase modulation region (specific region Sa) and the two-phase modulation region (specific region Sb), the carrier frequency is gradually reduced as the rotation speed or torque of motor 2 increases within the three-phase modulation region, and the carrier frequency is kept constant within the two-phase modulation region, but this is not limiting. For example, as shown in Fig. 3, the carrier frequency is set to 13 Hz in the three-phase modulation region (specific region Sa). Furthermore, the two-phase modulation region (specific region Sb) is divided into multiple (three in this example) specific regions Sb1, Sb2, and Sb3, and each region Sb1, Sb2, and Sb3 is set to a region with a different carrier frequency so that the carrier frequency decreases as the rotation speed or torque of the motor 2 increases.

[0024] Specific region Sb1 is a region where the rotation speed of motor 2 ranges from first rotation speed N1 to fourth rotation speed N4, and the torque of motor 2 is a region where first torque T1 to fourth torque T4 or less, and the carrier frequency is set to 13 kHz, the same as the three-phase modulation region. Specific region Sb2 is a region where the rotation speed of motor 2 ranges from fourth rotation speed N4 to fifth rotation speed N5, and the torque of motor 2 ranges from fourth torque T4 to fifth torque T5, and the carrier frequency is set to the next highest, 10 kHz. Specific region Sb3 is a region where the rotation speed of motor 2 is equal to or greater than fifth rotation speed N5, and the torque of motor 2 is equal to or greater than fifth torque T5, and the carrier frequency is set to the lowest, 8 kHz.

[0025] It should be noted that the first rotation speed N1<the fourth rotation speed N4<the fifth rotation speed N5, and the first torque T1<the fourth torque T4<the fifth torque T5. As a result, the carrier frequency remains unchanged in the three-phase modulation region (specific region Sa), and after transitioning to the two-phase modulation region (specific region Sb), the carrier frequency can be gradually lowered within the two-phase modulation region (specific regions Sb1, Sb2, Sb3) as the rotation speed or torque of motor 2 increases. In this case, too, large changes in the vibration and sound of motor 2 can be suppressed.

[0026] 4, when transitioning between the three-phase modulation region (specific regions Sa1, Sa2, Sa3) and the two-phase modulation region (specific regions Sb1, Sb2, Sb3), the regions Sa1 to Sa3 and Sb1 to Sb3 may be set to regions with different carrier frequencies so that the carrier frequency decreases as the rotation speed or torque of the motor 2 increases in each of the three-phase modulation region (specific regions Sa1, Sa2, Sa3) and the two-phase modulation region (specific regions Sb1, Sb2, Sb3). This also makes it possible to suppress large changes in vibration and sound when transitioning between the three-phase modulation region (specific region Sa) and the two-phase modulation region (specific region Sb).

[0027] As described above, in the motor control device 10 of this embodiment, as shown in Figures 2 to 4, the region Sa where the rotation speed of the motor 2 is equal to or less than the first rotation speed N1 and the torque is equal to or less than the first torque T1 is set as a three-phase modulation region where three-phase modulation is performed, and the region Sb outside the three-phase modulation region is set as a two-phase modulation region where two-phase modulation is performed. This configuration performs three-phase modulation at relatively low rotation speeds and low torque, thereby suppressing the occurrence of unpleasant vibrations and noise, while performs two-phase modulation at relatively high rotation speeds or high torque, thereby reducing the number of switching operations while driving and improving energy efficiency.

[0028] Furthermore, motor control device 10 can switch the carrier frequency in PWM control between multiple stages, and the carrier frequency in at least a portion of the three-phase modulation region is set to a value higher than the carrier frequency in the two-phase modulation region. This configuration enables smoother driving of motor 2 in the three-phase modulation region, which is a low rotation speed, low torque region where the sound and vibration of motor 2 are easily noticeable to the user, thereby suppressing vibration and sound.

[0029] Furthermore, in the three-phase modulation region, the higher the rotation speed or torque of the motor 2, the lower the carrier frequency the controller 22 reduces. This configuration makes it possible to suppress large changes in the vibration and noise of the motor 2 in the three-phase modulation region. Furthermore, by setting the carrier frequency low in the high rotation region where the number of switching operations is high, switching loss can be reduced. Furthermore, by setting the carrier frequency low in the high torque region where a large current flows through the motor control device 10, heat loss of the motor control device 10 can be reduced.

[0030] Furthermore, the carrier frequency in the three-phase modulation region is set to be equal to or higher than the carrier frequency in the two-phase modulation region, and the controller 22 lowers the carrier frequency in each of the three-phase modulation region and the two-phase modulation region as the rotation speed or torque of the motor 2 increases. This configuration further reduces significant changes in the vibration and noise of the motor 2 when transitioning between the three-phase modulation region and the two-phase modulation region. Furthermore, by setting the carrier frequency low in the high rotation region where the number of switching operations is high, switching loss can be reduced. Furthermore, by setting the carrier frequency low in the high torque region where a large current flows through the motor control device 10, heat loss in the motor control device 10 can be reduced.

[0031] [Other embodiments] The above-described embodiment merely shows one aspect of the present invention, and any modifications and applications are possible without departing from the spirit of the present invention.

[0032] For example, although the present invention has been described as being applied to the motor control device 10 mounted on the electric vehicle 1, the present invention is not limited to this and may be applied to a motor control device that controls a motor used in any moving body including other than a vehicle, or a motor control device that controls a motor used for purposes other than a vehicle. In other words, the present invention is widely applicable to motor control devices that use PWM control to control the power supplied to motors used for various purposes.

[0033] [Configuration supported by the above embodiment] The above embodiment supports the following configurations.

[0034] (Configuration 1) A motor control device that includes a control unit that controls the power supplied to a motor by PWM control and is capable of switching the modulation method in PWM control between three-phase modulation and two-phase modulation, wherein the control unit defines a region where the rotation speed of the motor 2 is equal to or less than a first rotation speed and where the torque is equal to or less than a first torque as a three-phase modulation region where the three-phase modulation is performed, and defines a region other than the three-phase modulation region as a two-phase modulation region where the two-phase modulation is performed. This configuration performs three-phase modulation at relatively low rotation speeds and low torque, thereby suppressing unpleasant vibrations and noise. Also, two-phase modulation is performed at relatively high rotation speeds or high torque, thereby reducing the number of switching operations under high current conditions, improving energy efficiency and suppressing temperature increases. This allows for more appropriate motor control.

[0035] (Configuration 2) The motor control device according to Configuration 1, wherein the carrier frequency in PWM control can be switched between multiple stages, and the carrier frequency in at least a portion of the three-phase modulation region is set to a value higher than the carrier frequency in the two-phase modulation region. This configuration enables smoother motor driving in the three-phase modulation region, which is a low rotation speed and low torque region where motor noise and vibration are easily noticeable to the user, thereby suppressing vibration and noise.

[0036] (Configuration 3) The motor control device according to configuration 1 or 2, wherein the control unit reduces the carrier frequency as the rotation speed or the torque of the motor increases in the three-phase modulation region. This configuration can suppress large changes in motor vibration and noise in the three-phase modulation region. Furthermore, by setting the carrier frequency low in the high-speed rotation region where the number of switching operations is high, switching loss can be reduced. Furthermore, by setting the carrier frequency low in the high-torque region where a large current flows through the motor control device, heat loss in the motor control device can be reduced.

[0037] (Configuration 4) The motor control device according to any one of configurations 1 to 3, wherein a carrier frequency in the three-phase modulation region is set to be equal to or higher than a carrier frequency in the two-phase modulation region, and the control unit reduces the carrier frequency as the rotation speed or the torque of the motor increases in each of the three-phase modulation region and the two-phase modulation region. This configuration can further suppress significant changes in motor vibration and noise when transitioning between the three-phase modulation region and the two-phase modulation region. Furthermore, by setting the carrier frequency low in the high-speed rotation region where the number of switching operations is high, switching loss can be reduced. Furthermore, by setting the carrier frequency low in the high-torque region where a large current flows through the motor control device, heat loss in the motor control device can be reduced. [Explanation of symbols]

[0038] 1 Electric vehicles (mobile vehicles) 2 motors 3 Battery 10 Motor control device 20 PDU 21 Power Converter 22 Control Unit Sa, Sa1, Sa2, Sa3 Specific region (three-phase modulation region) Sb, Sb1, Sb2, Sb3 specific region (two-phase modulation region)

Claims

1. A motor control device including a control unit (22) that controls power supplied to a motor (2) by PWM control, and that can switch a modulation method in the PWM control between three-phase modulation and two-phase modulation, The control unit (22) defines a region where the rotation speed of the motor (2) is equal to or less than a first rotation speed and where the torque is equal to or less than a first torque as a three-phase modulation region where the three-phase modulation is performed, and defines a region other than the three-phase modulation region as a two-phase modulation region where the two-phase modulation is performed. Motor control device.

2. the motor control device is capable of switching a carrier frequency in PWM control among a plurality of stages; The carrier frequency of at least a part of the three-phase modulation region is set to a value higher than the carrier frequency of the two-phase modulation region. The motor control device according to claim 1 .

3. The control unit (22) reduces the carrier frequency as the rotation speed or the torque of the motor increases in the three-phase modulation region. The motor control device according to claim 1 or 2.

4. The carrier frequency of the three-phase modulation region is set to be equal to or higher than the carrier frequency of the two-phase modulation region, The control unit (22) reduces the carrier frequency as the rotation speed or the torque of the motor increases in each of the three-phase modulation region and the two-phase modulation region. The motor control device according to any one of claims 1 to 3.

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