Hybrid control system of dual three-phase motor and control method thereof

Abstract

The hybrid control system comprises a speed controller, two sets of controllers and two sets of three-phase inverters based on wide bandgap devices (such as SiC / GaN) and IGBTs (Insulated Gate Bipolar Translator), which are respectively connected with two sets of windings of the motor; the speed controller is integrated with a q-axis current distribution module, dynamically distributes q-axis current and controls high-frequency operation of the wide bandgap inverter (more than two times of the frequency of the IGBT inverter) and low-frequency operation of the IGBT inverter, and efficiency is optimized cooperatively. The control method comprises the steps that threshold current of a single winding is set, q-axis reference current is dynamically distributed, only the high-frequency inverter operates in the low load state, the high-frequency inverter outputs the threshold current in the high load state, and the IGBT inverter compensates the difference value. The high-frequency advantage of the wide bandgap device and the low-cost large-current characteristic of the IGBT are fused, the dynamic current distribution strategy is combined, the working efficiency and the high load capacity of high-frequency operation are considered, and the heat loss and the manufacturing cost of the controller are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of motor drive, and particularly to a hybrid control system and a control method for a dual three-phase motor. Background Art

[0002] With the rapid development of new energy vehicle technology and the third-generation semiconductor technology represented by SiC devices, the technology of electric drive products has been continuously iterated in the direction of high efficiency / low loss and high power / torque density. Among them, because the permanent magnet synchronous motor (PMSM) has the characteristics of high power density, high efficiency and easy maintenance, such motors have been widely used in new energy vehicles.

[0003] In the field of main drives of large commercial vehicles with high power requirements for motors (≥200kW), a dual three-phase permanent magnet synchronous motor with two sets of armature windings on the stator side of the motor and related control devices are often used as the drive method at a higher power level. In addition to having more excellent characteristics compared with the traditional three-phase permanent magnet synchronous drive method in a certain space volume, such as lower harmonic components in the drive system (including low torque ripple and low DC-side current harmonics), higher fault tolerance performance, higher system efficiency, and flexible power / torque distribution ability.

[0004] Traditional dual three-phase drive includes two aspects: a dual three-phase permanent magnet synchronous motor and a dual three-phase inverter, as Figure 1 shown. In traditional dual three-phase drive, the dual three-phase inverter is composed of two sets of six-arm three-phase inverters connected in parallel, and each three-phase inverter is often composed of a single type of semiconductor device, such as using silicon-based IGBT as the switching device.

[0005] CN116436271A discloses a hybrid power device for a motor controller and its control method. The hybrid power device is realized by connecting a wide-bandgap semiconductor device, that is, a new generation of semiconductor device and a traditional IGBT single tube in parallel, and the new generation of semiconductor device is controlled by a first drive chip, and the IGBT single tube is controlled by a second drive chip. In this way, the motor controller can dynamically switch the working states of the new generation of semiconductor device and IGBT according to the actual working conditions to achieve more efficient energy utilization and response performance. Through this hybrid power device, the respective advantages of the two power devices can be fully utilized, and the system efficiency can be improved while realizing low cost. However, this hybrid power device directly changes the inverter structure, increasing the complexity of the system; and only one set of power devices in the two sets of controllers is connected to the motor, increasing the hardware cost of the system.

[0006] Therefore, it is urgent to improve the overall efficiency of the electric drive system without increasing system complexity and hardware costs, achieve more efficient energy utilization and response performance, and thereby increase the driving range and service life of the vehicle battery. Summary of the Invention

[0007] The present invention aims to provide a hybrid control system and a control method for a dual three-phase motor, which can simultaneously utilize the high-frequency advantages of the new generation of wide-bandgap semiconductor devices and the large-current advantages of traditional IGBT devices in the low-frequency band, thereby further improving the efficiency of the dual three-phase electric drive system. The technical solutions are as follows.

[0008] In a first aspect: A hybrid control system for a dual three-phase motor, including a speed controller, a first controller, a second controller, a high-frequency inverter, and a low-frequency inverter, where the high-frequency inverter and the low-frequency inverter are respectively connected to the first winding and the second winding of the dual three-phase motor; characterized in that: The high-frequency inverter is composed of wide-bandgap semiconductor devices, and the low-frequency inverter is composed of IGBT devices; The first controller is configured to control the high-frequency inverter to operate at a first switching frequency, and the second controller is configured to control the low-frequency inverter to operate at a second switching frequency, where the first switching frequency is more than twice the second switching frequency; The speed controller includes a q-axis reference current distribution module; the q-axis reference current distribution module is configured to perform dynamic asymmetric current distribution, where only the high-frequency inverter operates under low load, and the high-frequency inverter outputs a threshold current under high load, and the low-frequency inverter compensates for the difference.

[0009] Further, the wide-bandgap semiconductor device is SiC or GaN.

[0010] Further, the first switching frequency ≥ 20 kHz; the second switching frequency ≤ 30 kHz.

[0011] Further, the high-frequency inverter and the low-frequency inverter are six-arm three-phase inverters.

[0012] In a second aspect: A control method for a hybrid control system of a dual three-phase motor, applied to the hybrid control system as described above, includes: Setting a threshold current for a single winding of the dual three-phase motor; Obtaining the q-axis reference current required for motor control in real time; When the q-axis reference current is less than or equal to the threshold current, only drive the first winding through the high-frequency inverter; When the q-axis reference current is greater than the threshold current, control the high-frequency inverter to output a current equal to the threshold current to the first winding, and control the low-frequency inverter to output a compensation current to the second winding, where the compensation current is the difference between the q-axis reference current and the threshold current.

[0013] Further, the first switching frequency is N times the second switching frequency, where N is an integer greater than or equal to 2.

[0014] Further, the threshold current is 50% of the rated maximum current value of the dual three-phase motor.

[0015] Compared with the prior art, the significant features of the present invention are: By integrating the high-frequency advantages of wide-bandgap devices with the low-cost and high-current characteristics of IGBTs, and combining a dynamic current distribution strategy, the present invention takes into account high-frequency efficiency and high load capacity, and reduces thermal losses and costs. Description of the Drawings

[0016] Figure 1 is the dual-IGBT drive topology diagram of a traditional dual three-phase permanent magnet synchronous motor; Figure 2 is the SiC+IGBT hybrid drive topology diagram of the dual three-phase permanent magnet synchronous motor of the present invention; Figure 3 is the control block diagram of a traditional dual three-phase permanent magnet synchronous motor; Figure 4 is the control block diagram of the dual three-phase permanent magnet synchronous motor of the present invention; Figure 5 is the power splitting control algorithm block diagram of the present invention; Figure 6 is the q-axis reference current legend when the q-axis reference current is greater than 0.5Imax; Figure 7 is the comparison of the controller efficiency between the control method of the present hybrid control system and the traditional control method; Figure 8 is the calculation example of the speed-torque-torque spectrum when the motor speed = 1500 rpm in the SiC+IGBT mode; Figure 9 is the calculation example of the torque-torque spectrum when the motor speed = 1500 rpm in the IGBT+IGBT mode; Figure 10 is the calculation example of the torque-torque spectrum when the motor speed = 1500 rpm in the SiC+SiC mode; Figure 11 is the motor speed = 1500 rpm, an example of calculating the DC - side current in the SiC + IGBT mode. Detailed implementation manners

[0017] To further illustrate each embodiment, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention, mainly used to illustrate the embodiments, and can be combined with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are usually used to represent similar components.

[0018] Now, the present invention will be further described in combination with the accompanying drawings and specific implementation manners.

[0019] Figure 2 A topology diagram of a hybrid control system for a dual - three - phase motor is given. The hybrid control system includes a three - phase inverter composed of a group of traditional silicon - based IGBT (Insulated Gate Bipolar Transistor) devices and a three - phase inverter composed of a group of new - generation wide - bandgap semiconductor devices, such as SiC (Silicon Carbide), GaN (Gallium Arsenide), etc. The two three - phase inverters are respectively connected to two armature windings of the dual - three - phase motor to form a parallel relationship.

[0020] As Figure 3 shown, the existing control system of a dual - three - phase motor includes a PI speed controller, a current controller, two sets of SVPWM (Space Vector Pulse Width Modulators), and two sets of three - phase inverters. Since the two sets of three - phase inverters use the same switching semiconductor devices, the same switching frequency is adopted in the two sets of three - phase inverters. For a dual - three - phase permanent - magnet synchronous motor, the traditional control method is based on the dual - dq model. Under the traditional control strategy, all the q - axis reference currents are generated by the PI speed controller and are equally divided (50% / 50%) and then flow into the two armature windings.

[0021] As Figure 4 shown, the hybrid control system proposed by the present invention includes a PI speed controller, a current controller, two sets of SVPWM (Space Vector Pulse Width Modulators), and two sets of three - phase inverters. Among them, the q - axis reference current distribution module is integrated in the PI speed controller. The q - axis reference current distribution module is configured to perform dynamic asymmetric current distribution and adjust the q - axis reference current distribution ratio of the first controller and the second controller according to the motor load demand. The two sets of three - phase inverters use different semiconductor switching devices. To give full play to the performance of the new - generation wide - bandgap semiconductor devices and traditional IGBTs, different switching frequencies are adopted in the two sets of three - phase inverters. At the same time, compared with the system using two sets of SiC MOSFET devices, the cost of this hybrid control system will be relatively lower.

[0022] The hybrid control system of the dual-three-phase motor of the present invention, the core of its control strategy lies in: (1) adopting dynamic asymmetric power splitting to dynamically distribute the q-axis current ratio; (2) adopting different switching frequencies in two sets of three-phase inverters to adapt to the switching characteristics of two types of devices. The specific description is as follows.

[0023] (1) Dynamic asymmetric power splitting: Since the efficiency of SiC power semiconductors is higher than that of IGBT devices, therefore, in the new energy motor drive system, preferably, the SiC inverter is used only as long as possible. Therefore, the power splitting control method (i.e., the q-axis reference current distribution algorithm) of this SiC+IGBT hybrid controller is as Figure 5 shown.

[0024] The specific control logic is: Define the rated maximum current of the dual-three-phase motor , and by default, the rated maximum currents of the two three-phase motors are equal, then the rated maximum current (hereinafter referred to as the threshold current) of a single set of armature windings is 0.5 .

[0025] Obtain the q-axis reference current required for motor control from the speed controller in real time .

[0026] If the total q-axis reference current is lower than the threshold current (0.5 ) of a single set of armature windings, then the output current value of the SiC inverter is the total q-axis reference current ; the IGBT controller does not provide current; that is = ， = 0 。

[0027] If the total q-axis reference current is higher than the threshold current (0.5 ) of a single set of armature windings, then the output current value of the SiC inverter only supports the threshold current; while the output current value of the IGBT inverter is the difference between =0.5 ; = - = - 0.5 . As Figure 6 shown.

[0028] Based on dynamic asymmetric power splitting ， In the driving process, the hybrid control system preferentially uses the SiC inverter, so as to give full play to the high-frequency advantages of SiC power semiconductors and improve the overall driving efficiency. When the load of the inverter is low, the output power of the SiC inverter is much higher than that of the Si inverter. Compared with the symmetric power splitting, the hybrid control system can obtain a higher overall driving efficiency, as Figure 7 shown.

[0029] (2)Adopt different switching frequencies in two sets of three-phase inverters.

[0030] Relatively speaking, the IGBT inverter has the advantages of low cost and large current in the low-frequency band. Therefore, a lower switching frequency is adopted in the IGBT controller, such as ; The SiC inverter has high-frequency advantages and high driving efficiency at high frequencies. Therefore, a higher switching frequency is adopted in the SiC controller, such as .

[0031] In specific applications, f s1 and f s2 are set respectively based on the maximum switching frequency characteristics of wide-bandgap semiconductor devices and IGBT devices.

[0032] For example: Set: the switching frequency of the IGBT controller ; The switching frequency of the SiC controller .

[0033] For a dual three-phase motor at a speed , modulation coefficient under the condition of the base frequency

[0034] For the harmonic order of the 2 kHz switching frequency is

[0035] For the harmonic order of the 4 kHz switching frequency is

[0036] In this case, the speed, torque and harmonic order of the torque of the dual three-phase motor are as Figure 8 shown.

[0037] It can be seen that adopting different switching frequencies for the SiC controller and the IGBT controller can not only give full play to their respective performance advantages, but also avoid the superposition of torque fluctuations, thereby effectively controlling the magnitude of torque harmonics and improving the performance of torque fluctuations. Comparing Figure 9 andFigure 10 The torque and torque harmonics of the dual-IGBT controller and the dual-SiC controller with the same switching frequency are adopted, and the torque-torque ripple performance of this hybrid control system is better.

[0038] In the parallel structure of two sets of controllers, the total DC-side current can be expressed as:

[0039] Where and represent the DC-side currents of the two inverters respectively.

[0040] Due to the different switching frequencies, when both the SiC controller and the IGBT controller are working, the fluctuation of the DC-side current can be effectively reduced, as shown in Figure 11 The reduction of the DC-side current ripple can increase the service life of the DC-side capacitor, and further increase the driving range and service life of the vehicle battery.

[0041] When the switching frequency of the SiC inverter is twice that of the IGBT inverter, if the switching frequency of the IGBT is set to , and the switching frequency of the SiC is , the q-axis reference current can be expressed as:

[0042] So,

[0043] It can be seen that and in have opposite phases of the harmonic components. Therefore, there will be a mutual reduction or complete cancellation of the harmonics in the harmonic components, and thus a more sinusoidal current waveform with higher smoothness will be obtained. It can be seen that this modulation algorithm can effectively reduce the harmonic components in the torque, thereby reducing the torque ripple in the output torque.

[0044] In specific applications, to give full play to the high-frequency advantages of wide-bandgap semiconductor devices such as SiC, the switching frequency of the SiC inverter can be set above 20 kHz. The higher the switching frequency, the lower the torque harmonics itself; at the same time, to give full play to the low-frequency and high-current advantages of IGBTs, the switching frequency of the IGBT inverter can be set below 10 kHz.

[0045] For the convenience of control, the switching frequency of the SiC inverter is N times that of the IGBT, where N is an integer greater than or equal to 2.

[0046] In summary, the present invention combines the high-frequency advantages of wide-bandgap devices with the low-cost and high-current characteristics of IGBTs, and combines a dynamic current distribution strategy to balance high-frequency efficiency and high load capacity, reducing thermal losses and costs. Thereby increasing the driving range and service life of vehicle batteries.

[0047] Although the present invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes can be made to the present invention in form and detail without departing from the spirit and scope of the present invention defined by the appended claims, and all such changes are within the scope of protection of the present invention.

Claims

1. A hybrid control system for a dual three-phase motor, comprising a speed controller, a first controller, a second controller, a high-frequency inverter and a low-frequency inverter, wherein the high-frequency inverter and the low-frequency inverter are respectively connected to a first winding and a second winding of the dual three-phase motor; characterized in that: The high-frequency inverter is composed of wide-bandgap semiconductor devices, and the low-frequency inverter is composed of IGBT devices; The first controller is configured to control the high-frequency inverter to operate at a first switching frequency, and the second controller is configured to control the low-frequency inverter to operate at a second switching frequency, wherein the first switching frequency is more than twice the second switching frequency; The speed controller includes a q-axis reference current distribution module; the q-axis reference current distribution module is configured to perform dynamic asymmetric current distribution, where only the high-frequency inverter operates at low load, and the high-frequency inverter outputs a threshold current at high load, and the low-frequency inverter compensates for the difference.

2. The hybrid control system according to claim 1, characterized in that: The wide bandgap semiconductor device is SiC or GaN.

3. The hybrid control system according to claim 1, characterized in that: The first switching frequency is ≥20kHz; the second switching frequency is ≤10kHz.

4. The hybrid control system according to claim 1, characterized in that: The high-frequency inverter and the low-frequency inverter are six-bridge-arm three-phase inverters.

5. A control method for a hybrid control system of dual three-phase motors, applied to the hybrid control system according to any one of claims 1 to 4, characterized in that: include: Setting the threshold current of a single winding in a dual three-phase motor; Obtain the q-axis reference current required for motor control in real time; When the q-axis reference current is less than or equal to a threshold current, driving the first winding only through the high-frequency inverter; When the q-axis reference current is greater than a threshold current, the high-frequency inverter is controlled to output a current equal to the threshold current to the first winding, and the low-frequency inverter is controlled to output a compensation current to the second winding, wherein the compensation current is the difference between the q-axis reference current and the threshold current.

6. The control method according to claim 5, characterized in that: The first switching frequency is N times the second switching frequency, where N is an integer greater than or equal to 2.

7. The control method according to claim 5, characterized in that: The threshold current is 50% of the rated maximum current value of the dual three-phase motor.

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