Control method, device and system for suppressing zero-sequence current of permanent magnet synchronous motor

Abstract

The invention discloses a control method, device and system for suppressing zero-sequence current of a permanent magnet synchronous motor, and the method comprises the steps: determining the zero-sequence voltage generated by an inverter, and determining the inverter zero-sequence current generated by the motor under the independent action of the zero-sequence voltage based on a pre-established motor control model in a discrete domain; wherein according to a set discretization period, the zero sequence voltage is enabled to meet the following relational expression in a z domain: # imgabs0 #; performing Laplace transformation on the zero-sequence voltage, and performing z transformation after a transformation result is combined with the relational expression to obtain the motor control model; obtaining the counter electromotive force of the motor, and determining the counter electromotive force zero-sequence current generated by the motor under the excitation of the counter electromotive force; and offsetting the inverter zero-sequence current and the counter electromotive force zero-sequence current to obtain an output current for controlling a closed-loop control system of the motor. Based on the method, the switching frequency of the switching device in the system can be reduced, and the system operation cost is reduced.

Description

Technical Field

[0001] The present application relates to, in particular, a control method, device and system for suppressing zero-sequence current of a permanent magnet synchronous motor. Background Art

[0002] For conventional motors, the driver that controls the motor usually uses a voltage source type three-phase two-bridge arm topology inverter. When the motor back electromotive force is large, if a three-phase two-level inverter is used to connect the motor in a Y connection, the bus voltage connected to the motor is high, and the switching device has a high withstand voltage requirement. For the drive inverter using high-voltage resistant switching devices, its manufacturing cost is high. Therefore, in the prior art, a driver with an open winding topology can be used. The driver is connected by setting two identical three-phase two-level inverters, and the two inverters are connected by a common bus. Based on this setting, although the number of switching devices is doubled, the switching devices do not need to withstand high voltage, so the cost of the driver is lower than that of the driver using high-voltage resistant switching devices.

[0003] In the case of a motor controlled by a driver based on an open winding topology, since the neutral point of the motor is opened, when the motor is operating normally, the third harmonic back EMF will be generated under the third harmonic excitation of the permanent magnet in the motor, which will cause the third harmonic zero-sequence circulating current of the winding and introduce low-frequency torque pulsation and additional losses in the motor. For motors with lower fundamental frequencies, the prior art has disclosed methods of suppressing the torque pulsation of the motor by continuous domain modeling of the motor and by designing a resonant controller. However, for motors with higher fundamental frequencies, the above-mentioned prior art methods are still used to suppress the zero-sequence current, and the switching frequency of the switching devices needs to be increased, resulting in an increase in the total loss of the switching devices in the driver, which makes the operating cost of the electric drive system higher. The total loss of the switching devices can be expressed by the following formula: ; In the formula, represents the total loss of the switching device, represents the switching frequency, Represents the single switching loss of the device.

[0004] Therefore, it is urgent to provide a control method for suppressing the zero-sequence current of a permanent magnet synchronous motor to solve the problem of high operating cost of the electric drive system. Summary of the invention

[0005] In order to address the deficiencies of the prior art, the purpose of the present application is to provide a control method, device and system for suppressing the zero-sequence current of a permanent magnet synchronous motor, which method can reduce the switching frequency of switching devices in the system and reduce the operating cost of the system.

[0006] To achieve the above objectives, this application adopts the following technical solutions: In a first aspect, the present application provides a control method for suppressing zero-sequence current of a permanent magnet synchronous motor, the method comprising: The zero-sequence voltage generated by the inverter is determined, and based on the motor control model in the pre-established discrete domain, the inverter zero-sequence current generated by the motor under the action of the zero-sequence voltage alone is determined; wherein, according to the set discretization period, the zero-sequence voltage satisfies the following relationship in the z domain: (Formula 1); Laplace transform is performed on the zero-sequence voltage, and the transformed result is combined with Formula 1 to perform z-transformation, and the one-beat delay of the closed-loop control system used to control the motor is considered, and Formula 1 is corrected to obtain the motor control model. The motor control model satisfies the following relationship: (Formula 2); In Formula 1 and Formula 2, Indicates the inverter zero-sequence current, represents the zero sequence voltage, represents the phase resistance, represents the zero-sequence inductance, represents the discretization period, represents the z operator, represents the base of natural logarithms; Obtain the back-EMF of the motor and determine the back-EMF zero-sequence current generated by the motor under the action of the back-EMF alone; The inverter zero-sequence current and the back-EMF zero-sequence current are offset against each other to obtain the output current of the closed-loop control system for controlling the motor. The output current is generated by the combined action of the inverter and the back-EMF.

[0007] Furthermore, the process of obtaining the output current includes: The back-EMF zero-sequence current is input into the pre-established discrete domain current loop model; wherein the back-EMF zero-sequence current is used as the disturbance of the closed-loop control system, and the output current is determined according to the disturbance, so that the back-EMF zero-sequence current and the output current satisfy the following relationship: (Formula 3); In formula 3, represents the back-EMF zero-sequence current, Represents the output current, Indicates time, represents the electrical frequency of the back-EMF zero-sequence current, represents the amplitude of the back-EMF zero-sequence current, Indicates the amplitude of the output current, represents the time constant, Indicates the phase of the back-EMF zero-sequence current, Indicates the phase of the output current; Perform Laplace transform on formula 3 and consider the parameter and parameters , to obtain the first closed-loop transfer function, and the first closed-loop transfer function is discretized using pre-distortion bilinear transformation, let ,and , to obtain the discrete domain current loop model, the discrete domain current loop model satisfies the following relationship: (Formula 4); The second closed-loop transfer function of the discrete domain current loop model is determined, and the transfer function of the controller in the closed-loop control system is obtained by reverse deduction based on the second closed-loop transfer function. The transfer function of the controller satisfies the following relationship: (Formula 5); In Formula 4 and Formula 5, represents the first closed-loop transfer function, represents the discrete domain transfer function of the inverter side model, represents the coefficients used in the bilinear transformation operation, represents the Laplace operator.

[0008] Further, in the case of determining the transfer function of the controller, it includes: The transfer function of the controller is corrected so that the transfer function of the corrected controller satisfies the following relationship: (Formula 6); where is a positive integer greater than or equal to 2; In Formula 6, Indicates the number of beats of controller delay, Indicates the expected bandwidth.

[0009] Furthermore, in the process of correcting the transfer function of the controller, it includes: Set the controller Replace it with a delay compensator so that the transfer function of the delay compensator satisfies the following relationship: (Formula 7); In formula 7, represents a fixed coefficient, and >0; After the delay compensator is used to compensate, the transfer function of the controller is corrected to (Formula 8).

[0010] Furthermore, the method further comprises: When the filter used in the feedback channel of the closed-loop control system is a second-order Butterworth filter, the transfer function of the filter is determined. The transfer function of the filter satisfies the following relationship: (Formula 9); In formula 9, represents the damping ratio of the filter, represents the cutoff frequency of the filter, represents the Laplace operator.

[0011] Furthermore, in the case of determining the transfer function of the filter, it also includes: The filter is modeled using pre-distortion bilinear transformation, and the built model is compensated to avoid the instability of the closed-loop control system caused by the phase lag of the filter. The model of the compensated filter satisfies the following relationship: (Formula 10); where , is the inverse of the switching frequency of the inverter.

[0012] Furthermore, in the process of determining the back-electromotive force zero-sequence current, it includes: When only the third and multiple frequency current harmonics are considered, the back-EMF zero-sequence current is determined so that the back-EMF zero-sequence current satisfies the following relationship: (Formula 11); where ; In formula 11, The discrete domain transfer function representing the back-EMF side model, represents the continuous domain transfer function of the back EMF side model, The discrete domain transfer function representing the back EMF, The continuous domain transfer function representing the back EMF, The continuous domain transfer function representing the back-EMF zero-sequence current, Indicates the order of the back-EMF zero-sequence current harmonic, Indicates the electrical frequency of the motor.

[0013] In a second aspect, the present application also provides a control device for suppressing zero-sequence current of a permanent magnet synchronous motor, the device comprising: An acquisition unit, used for acquiring the zero-sequence voltage generated by the inverter and the back electromotive force generated by the motor; The first determination unit is used to determine the inverter zero-sequence current generated by the motor under the action of the zero-sequence voltage alone based on a pre-established motor control model in the discrete domain; wherein, according to a set discretization period, the zero-sequence voltage satisfies the following relationship in the z domain: (Formula 1); Laplace transform is performed on the zero-sequence voltage, and the transformed result is combined with Formula 1 to perform z-transformation, and the one-beat delay of the closed-loop control system used to control the motor is considered, and Formula 1 is corrected to obtain the motor control model. The motor control model satisfies the following relationship: (Formula 2); In Formula 1 and Formula 2, Indicates the inverter zero-sequence current, represents the zero sequence voltage, represents the phase resistance, represents the zero-sequence inductance, represents the discretization period, represents the z operator, represents the base of natural logarithms; A second determination unit is used to establish a motor control model to determine the back-EMF zero-sequence current generated by the motor under back-EMF excitation; The processing unit is used to offset the inverter zero-sequence current and the back-electromotive force zero-sequence current to obtain the output current of the closed-loop control system. The output current is generated by the inverter and the back-electromotive force.

[0014] In a third aspect, the present application also provides a control system for suppressing the zero-sequence current of a permanent magnet synchronous back-electromotive force, the system comprising a motor and the control device in the above-mentioned second aspect.

[0015] In a fourth aspect, the present application further provides a computer-readable storage medium, in which a computer program is stored, and when the computer program is executed by a processor, any method in the first aspect is implemented.

[0016] In the embodiment of the present application, the control method for suppressing the zero-sequence current of the permanent magnet synchronous back-EMF is to determine the inverter zero-sequence current generated by the inverter under the excitation of the zero-sequence voltage through a pre-established motor control model, wherein the motor control model is based on a discretized cycle, and the zero-sequence voltage is transformed in the z domain and obtained by Laplace transformation, and the inverter zero-sequence current and the back-EMF zero-sequence current are offset to obtain the output current of the closed-loop control system for controlling the motor. The above method can reduce the switching frequency of the switching device in the system and reduce the system operation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a first flow chart of a control method for suppressing zero-sequence current of a permanent magnet synchronous motor in an embodiment of the present application; Figure 2 A second flow chart of the control method for suppressing zero-sequence current of a permanent magnet synchronous motor in an embodiment of the present application; Figure 3 is a relationship curve between the closed-loop pole of the system and the coefficient k under different controller parameters a in the implementation manner of the present application; Figure 4 The closed-loop pole distribution of the system under different compensator parameters μ in the implementation mode of this application; Figure 5 This is a flow chart of implementing phase compensation based on a filter in an implementation manner of the present application; Figure 6 A schematic diagram of a partial structure of a closed-loop control system in an embodiment of the present application; Figure 7This is an overall schematic diagram of a closed-loop control system in an embodiment of the present application; Figure 8 This is a simulation diagram of the zero-sequence current time domain waveform when no delay compensation is applied in the implementation mode of the present application; Fig. 9 This is a simulation diagram of the time domain waveform of the zero-sequence current when delay compensation is applied in the implementation manner of the present application; Fig.10 Schematic diagram of a control device for suppressing zero-sequence current of a permanent magnet synchronous motor in an embodiment of the present application; Fig.11 Schematic diagram of a control system for suppressing zero-sequence current of a permanent magnet synchronous motor in an embodiment of the present application. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the specific implementation manner of the present application will be clearly and completely described below in conjunction with the drawings in the implementation manner of the present application.

[0019] like Figure 1 As shown, in a first aspect, the present application provides a control method for suppressing zero-sequence current of a permanent magnet synchronous motor, the method comprising the following steps: S101: Determine the zero-sequence voltage generated by the inverter, and determine the inverter zero-sequence current generated by the motor under the action of the zero-sequence voltage alone based on a motor control model established in a discrete domain in advance.

[0020] Among them, according to the set discretization period, the zero-sequence voltage satisfies the following relationship in the z domain: (Formula 1); Laplace transform is performed on the zero-sequence voltage, and the transformed result is combined with Formula 1 to perform z-transformation, and the one-beat delay of the closed-loop control system used to control the motor is considered, and Formula 1 is corrected to obtain the motor control model. The motor control model satisfies the following relationship: (Formula 2).

[0021] In Formula 1 and Formula 2, Indicates the inverter zero-sequence current, represents the zero sequence voltage, represents the phase resistance, represents the zero-sequence inductance, represents the discretization period, represents the z operator, Represents the base of natural logarithms.

[0022] In some embodiments, the zero-sequence voltage on the inverter side and the inverter zero-sequence current under its excitation are as follows:

[0023] In the formula, represents the zero sequence voltage, represents the phase resistance, is the Hey operator, represents the zero-sequence inductance, Indicates the inverter zero-sequence current.

[0024] in, Satisfy the expression , , and They represent the three-phase voltages applied by the inverter to the motor. In a closed-loop control system, if a discrete cycle , then the output voltage on the inverter side has a zero-order holding property.

[0025] S102: Acquire the back-EMF of the motor, and determine the back-EMF zero-sequence current generated by the motor under the action of the back-EMF alone.

[0026] Among them, the back EMF Back-EMF zero-sequence current under its excitation satisfy: ; When only the third and multiple frequency current harmonics are considered, the back-EMF zero-sequence current is determined so that the back-EMF zero-sequence current satisfies the following relationship: ; in, ; In the above formula for back-EMF zero-sequence current, The discrete domain transfer function representing the back-EMF side model, represents the continuous domain transfer function of the back EMF side model, The discrete domain transfer function representing the back EMF, The continuous domain transfer function representing the back EMF, The continuous domain transfer function representing the back-EMF zero-sequence current, Indicates the order of the back-EMF zero-sequence current harmonic, Indicates the electrical frequency of the motor.

[0027] S103: offsetting the inverter zero-sequence current and the back-EMF zero-sequence current to obtain an output current of a closed-loop control system for controlling the motor, wherein the output current is generated by the inverter and the back-EMF.

[0028] The above method can reduce the switching frequency of the switching device in the system and reduce the system operation cost.

[0029] like Figure 2 As shown, further, in the process of obtaining the output current, it includes: S1021: Input the back-electromotive force zero-sequence current into the pre-established discrete domain current loop model.

[0030] Among them, the back-EMF zero-sequence current is used as the disturbance quantity of the closed-loop control system, and the output current is determined according to the disturbance quantity, so that the back-EMF zero-sequence current and the output current satisfy the following relationship: (Formula 3); In formula 3, represents the back-EMF zero-sequence current, Represents the output current, Indicates time, represents the electrical frequency of the back-EMF zero-sequence current, represents the amplitude of the back-EMF zero-sequence current, Indicates the amplitude of the output current, represents the time constant, Indicates the phase of the back-EMF zero-sequence current, Indicates the phase of the output current; S1022: Performing Laplace transformation on the back-electromotive force zero-sequence current and the output current to obtain a first closed-loop transfer function, and discretizing the first closed-loop transfer function using a pre-distortion bilinear transformation to obtain a discrete domain current loop model.

[0031] It should be noted that when performing Laplace transformation on the back EMF zero-sequence current and output current, the parameters and parameters When the first closed-loop transfer function is discretized using predistortion bilinear transformation, let ,and The discrete domain current loop model obtained based on the above processing satisfies the following relationship: (Formula 4).

[0032] S1023: Determine a second closed-loop transfer function of the discrete domain current loop model, and obtain a transfer function of a controller in the closed-loop control system by reverse deduction based on the second closed-loop transfer function.

[0033] Among them, the transfer function of the controller satisfies the following relationship: (Formula 5); In Formula 4 and Formula 5, represents the first closed-loop transfer function, represents the discrete domain transfer function of the inverter side model, represents the coefficients used in the bilinear transformation operation, represents the Laplace operator.

[0034] As an implementation method, when determining the transfer function of the controller, it includes: The transfer function of the controller is corrected so that the transfer function of the corrected controller satisfies the following relationship: (Formula 6); where is a positive integer greater than or equal to 2; In Formula 6, Indicates the number of beats of controller delay, Indicates the expected bandwidth.

[0035] It should be noted that since the numerator order of the z-domain transfer function in the closed-loop control system cannot be higher than the denominator order, the transfer function of the controller in Formula 5 cannot be realized. Therefore, the transfer function of the controller needs to be corrected so that Corrected to Based on the above correction, the transfer function of the modified controller is obtained.

[0036] Furthermore, in the process of correcting the transfer function of the controller, it includes: Set the controller Replace it with a delay compensator so that the transfer function of the delay compensator satisfies the following relationship: (Formula 7). In formula 7, represents a fixed coefficient, and >0.

[0037] It should be noted that the transfer function of the modified controller adopts Although the closed-loop control system can realize the function of suppressing the zero-sequence current of the reverse electromotive force, it will cause the closed-loop pole of the closed-loop control system to be close to the imaginary axis (see Figure 3 ). It can be seen that the controller This will lead to a decrease in the stability of the closed-loop control system. Based on this, Replaced by a delay compensator. In addition, the larger k is, the larger the real part of the closed-loop pole of the closed-loop control system is, and the more likely the closed-loop control system is to become unstable. Therefore, in the embodiment of the present application, k is 2.

[0038] like Figure 4 As shown in the figure, after the delay compensator is applied, the dominant pole of the closed-loop control system moves away from the imaginary axis, making the closed-loop control system stable.

[0039] For example, when =0.7, the real part of the dominant pole of the system is approximately = 3 times of that when it is 0, which reflects the effect of the delay compensator.

[0040] After the delay compensator is used to compensate, the transfer function of the controller is corrected to (Formula 8).

[0041] Through the above method, a discrete domain delay compensator is designed, so that zero-sequence current suppression can be achieved even when the switching frequency of the switching device in the system is only 10 times the electrical frequency of the zero-sequence current.

[0042] like Figure 5 As shown, as an implementation mode, the method further includes: S201: When the filter used in the feedback channel of the closed-loop control system is a second-order Butterworth filter, determine a transfer function of the filter.

[0043] Among them, the transfer function of the filter satisfies the following relationship: (Formula 9); In formula 9, represents the damping ratio of the filter, represents the cutoff frequency of the filter, represents the Laplace operator.

[0044] It should be noted that for a closed-loop control system, there must be a hardware filter in its feedback channel, which will affect the phase margin of the closed-loop control system (an indicator of the relative stability of the control system). Therefore, it is necessary to accurately model the hardware filter so that the filter can be compensated by the microcontroller.

[0045] S202: Modeling the filter using pre-distortion bilinear transformation, and compensating the built model to avoid instability of the closed-loop control system caused by phase lag of the filter.

[0046] like Figure 6 A schematic diagram of a closed-loop control system is provided. For example, if the filter is modeled using a predistorted bilinear transformation and a transfer function Compensation can effectively avoid the instability of the closed-loop system caused by the phase lag of the filter. Figure 6 In the schematic diagram It represents the feedback amount of the back-EMF zero-sequence current after phase compensation. is the given quantity of the controller, that is, the control target of the controller is 0A.

[0047] The model of the compensated filter satisfies the following relationship: (Formula 10); where , is the inverse of the switching frequency of the inverter.

[0048] like Figure 7 As shown, a closed-loop control system of zero-sequence current loop phase compensation and delay compensation is implemented based on the above compensator and filter.

[0049] For example, first, the delay compensator is not considered, and the effect of the phase compensator is investigated. The closed-loop control system is simulated, with a motor speed of 15,000 rpm (steady state), a phase current base frequency of 500 Hz, a zero-sequence current frequency of 1500 Hz, a switching frequency of 18 kHz, a switching frequency to a carrier ratio of 12 for the third harmonic, and a second-order Butterworth filter with a cutoff frequency of 10 kHz; controller parameters Take 20. Start the zero-sequence current suppression algorithm at 0.05s. The simulation results are as follows Figure 8 The simulation results show the effectiveness of the zero-sequence current suppression algorithm. If the phase compensation algorithm is not used, the closed-loop system will diverge, which shows the effectiveness of phase compensation.

[0050] Secondly, considering the phase compensation, the effect of the delay compensator is investigated. The motor speed is 15000rpm and the switching frequency is 15kHz. At this time, the switching frequency is only 10 times the zero-sequence current frequency. The other parameters of the motor and controller remain unchanged and the simulation is performed. The simulation results are as follows Fig. 9 The simulation results show the effectiveness of the delay compensation algorithm.

[0051] Through the above method, based on the established discrete domain current loop model, the discrete domain controller is used to suppress the zero-sequence current, so that the zero-sequence current suppression can be achieved even when the switching frequency of the switching device in the system is only 12 times the zero-sequence current electrical frequency. In addition, the controller only has one parameter a that needs to be adjusted, and the controller parameter adjustment is simple.

[0052] In summary, through the above method, when the switching frequency of the switching device in the closed-loop control system is low, the zero-sequence current of the motor can be suppressed, thereby solving the problem of high operating cost of the closed-loop control system.

[0053] like Fig.10 As shown, in a second aspect, the present application further provides a control device 100 for suppressing zero-sequence current of a permanent magnet synchronous motor, the device comprising: An acquisition unit 11 is used to acquire the zero-sequence voltage generated by the inverter and the back electromotive force generated by the motor; The first determination unit 12 is used to determine the inverter zero-sequence current generated by the motor under the action of the zero-sequence voltage alone based on the motor control model in the pre-established discrete domain; wherein, according to the set discretization period, the zero-sequence voltage satisfies the following relationship in the z domain: (Formula 1); Laplace transform is performed on the zero-sequence voltage, and the transformed result is combined with Formula 1 to perform z-transformation, and the one-beat delay of the closed-loop control system used to control the motor is considered, and Formula 1 is corrected to obtain the motor control model. The motor control model satisfies the following relationship: (Formula 2); In Formula 1 and Formula 2, Indicates the inverter zero-sequence current, represents the zero sequence voltage, represents the phase resistance, represents the zero-sequence inductance, represents the discretization period, represents the z operator, represents the base of natural logarithms; The second determination unit 13 is used to establish a motor control model and determine the back-EMF zero-sequence current generated by the motor under the back-EMF excitation; The processing unit 14 is used to offset the inverter zero-sequence current and the back-electromotive force zero-sequence current to obtain the output current of the closed-loop control system for controlling the motor, and the output current is generated by the inverter and the back-electromotive force.

[0054] like Fig.11 As shown, in a third aspect, the present application further provides a control system for suppressing zero-sequence current of a permanent magnet synchronous motor, the system comprising a motor 200 and the control device 100 in the above-mentioned second aspect.

[0055] In a fourth aspect, the present application further provides a computer-readable storage medium, in which a computer program is stored, and when the computer program is executed by a processor, any of the methods in the first aspect is implemented. A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing related hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it may include the processes of the embodiments of the above-mentioned methods. Among them, any reference to a memory, a database or other medium used in the embodiments provided in the present application may include at least one of a non-volatile and volatile memory. The database involved in the embodiments provided in the present application may include at least one of a relational database and a non-relational database.

[0056] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A control method for suppressing zero-sequence current of a permanent magnet synchronous motor, characterized in that: The method comprises: Determine the zero-sequence voltage generated by the inverter, and determine the inverter zero-sequence current generated by the motor under the action of the zero-sequence voltage alone based on a pre-established motor control model in the discrete domain; wherein, according to the set discretization period, the zero-sequence voltage satisfies the following relationship in the z domain: (Formula 1); Laplace transform is performed on the zero-sequence voltage, and the transformed result is combined with Formula 1 to perform z-transformation, and considering the one-beat delay of the closed-loop control system used to control the motor, Formula 1 is corrected to obtain the motor control model, and the motor control model satisfies the following relationship: (Formula 2); In Formula 1 and Formula 2, represents the inverter zero-sequence current, represents the zero-sequence voltage, represents the phase resistance, represents the zero-sequence inductance, represents the discretization period, represents the z operator, represents the base of natural logarithms; Acquire the back electromotive force of the motor, and determine the back electromotive force zero-sequence current generated by the motor under the action of the back electromotive force alone; The inverter zero-sequence current and the back-electromotive force zero-sequence current are offset against each other to obtain an output current of a closed-loop control system for controlling the motor, wherein the output current is generated by the combined action of the inverter and the back-electromotive force.

2. The control method according to claim 1, characterized in that: The process of obtaining the output current includes: The back-EMF zero-sequence current is input into a pre-established discrete domain current loop model; wherein the back-EMF zero-sequence current is used as a disturbance of the closed-loop control system, and the output current is determined according to the disturbance, so that the back-EMF zero-sequence current and the output current satisfy the following relationship: (Formula 3); In formula 3, represents the back-EMF zero-sequence current, represents the output current, Indicates time, represents the electrical frequency of the back-EMF zero-sequence current, represents the amplitude of the back-EMF zero-sequence current, represents the amplitude of the output current, represents the time constant, represents the phase of the back-EMF zero-sequence current, represents the phase of the output current; Perform Laplace transform on formula 3 and consider the parameter and parameters , to obtain the first closed-loop transfer function, and the first closed-loop transfer function is discretized by using pre-distortion bilinear transformation, so that ,and , to obtain the discrete domain current loop model, the discrete domain current loop model satisfies the following relationship: (Formula 4); A second closed-loop transfer function of the discrete domain current loop model is determined, and a transfer function of a controller in the closed-loop control system is obtained by reverse deduction based on the second closed-loop transfer function. The transfer function of the controller satisfies the following relationship: (Formula 5); In Formula 4 and Formula 5, represents the first closed-loop transfer function, represents the discrete domain transfer function of the inverter side model, represents the coefficients used in the bilinear transformation operation, represents the Laplace operator.

3. The control method according to claim 2, characterized in that: In the case of determining the transfer function of the controller, it includes: The transfer function of the controller is corrected so that the corrected transfer function of the controller satisfies the following relationship: (Formula 6); where is a positive integer greater than or equal to 2; In Formula 6, represents the number of beats of the controller delay, Indicates the expected bandwidth.

4. The control method according to claim 3, characterized in that: The process of correcting the transfer function of the controller includes: The controller is replaced by a delay compensator, so that the transfer function of the delay compensator satisfies the following relationship: (Formula 7); In formula 7, represents a fixed coefficient, and >0; After the delay compensator is used to compensate, the transfer function of the controller is modified to (Formula 8).

5. The control method according to claim 1, characterized in that: The method further comprises: When the filter used in the feedback channel of the closed-loop control system is a second-order Butterworth filter, the transfer function of the filter is determined, and the transfer function of the filter satisfies the following relationship: (Formula 9); In formula 9, represents the damping ratio of the filter, represents the cutoff frequency of the filter, represents the Laplace operator.

6. The control method according to claim 5, characterized in that: In the case of determining the transfer function of the filter, it also includes: The filter is modeled by using pre-distortion bilinear transformation, and the built model is compensated to avoid the phase lag of the filter causing the closed-loop control system to become unstable. The model of the compensated filter satisfies the following relationship: (Formula 10); where , is the reciprocal of the switching frequency of the inverter.

7. The control method according to claim 1, characterized in that: The process of determining the back-electromotive force zero-sequence current includes: When only the third and multiple frequency current harmonics are considered, the back-EMF zero-sequence current is determined so that the back-EMF zero-sequence current satisfies the following relationship: (Formula 11); where ; In formula 11, The discrete domain transfer function representing the back-EMF side model, represents the continuous domain transfer function of the back EMF side model, Representing the discrete domain transfer function of the back EMF, represents the continuous domain transfer function of the back EMF, represents the continuous domain transfer function of the back-EMF zero-sequence current, represents the order of the back-EMF zero-sequence current harmonic, represents the electrical frequency of the motor.

8. A control device for suppressing zero-sequence current of a permanent magnet synchronous motor, characterized in that: include: An acquisition unit, used for acquiring the zero-sequence voltage generated by the inverter and the back electromotive force generated by the motor; The first determination unit is used to determine the inverter zero-sequence current generated by the motor under the action of the zero-sequence voltage alone based on a pre-established motor control model in a discrete domain; wherein, according to a set discretization period, the zero-sequence voltage satisfies the following relationship in the z domain: (Formula 1); Laplace transform is performed on the zero-sequence voltage, and the transformed result is combined with Formula 1 to perform z-transformation, and considering the one-beat delay of the closed-loop control system used to control the motor, Formula 1 is corrected to obtain the motor control model, and the motor control model satisfies the following relationship: (Formula 2); In Formula 1 and Formula 2, represents the inverter zero-sequence current, represents the zero-sequence voltage, represents the phase resistance, represents the zero-sequence inductance, represents the discretization period, represents the z operator, represents the base of natural logarithms; A second determination unit is used to establish a motor control model to determine the back-EMF zero-sequence current generated by the motor under the back-EMF excitation; A processing unit is used to offset the inverter zero-sequence current and the back-electromotive force zero-sequence current to obtain the output current of the closed-loop control system, wherein the output current is generated by the combined action of the inverter and the back-electromotive force.

9. A control system for suppressing zero-sequence current of a permanent magnet synchronous motor, characterized in that: It comprises a motor and the control device as claimed in claim 8.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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