Control Method, Device and System for Suppressing Zero-Sequence Current of Permanent Magnet Synchronous Motor

Abstract

The present application discloses a control method, device and system for suppressing zero-sequence current of a permanent magnet synchronous motor, the method comprising: determining the zero-sequence voltage generated by an inverter, and determining the inverter zero-sequence current generated by the motor under the action of the zero-sequence voltage alone based on a motor control model in a pre-established discrete domain; wherein, according to a set discretization period, the zero-sequence voltage satisfies the following relationship in the z domain:; Laplace transform is performed on the zero-sequence voltage, and the transformed result is combined with the relationship and then z-transformed to obtain the motor control model; the back-electromotive force of the motor is obtained, and the back-electromotive force zero-sequence current generated by the motor under the back-electromotive force excitation is determined; the inverter zero-sequence current and the back-electromotive force zero-sequence current are offset against each other to obtain the output current of the closed-loop control system for controlling the motor. Based on this method, the switching frequency of the switching devices in the system can be reduced, and the system operation cost can be 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 a conventional motor, the inverter for controlling the motor usually adopts a voltage-source three-phase two-leg topology. When the back electromotive force of the motor is large, if a three-phase two-level inverter is used for the motor connected in Y, the bus voltage connected to the motor is relatively high, which has a high withstand voltage requirement for the switching devices. For an inverter using high-voltage withstand switching devices, its manufacturing cost is relatively high. Therefore, in the prior art, a driver with an open-winding topology can be used. This driver is configured by setting two identical three-phase two-level inverters, and the two inverters are connected with a common bus. Based on such a configuration, although the number of switching devices doubles, the switching devices do not need to withstand high voltage. Therefore, the cost of this driver is lower than that of a driver using high-voltage withstand switching devices.

[0003] When controlling a motor with a driver based on an open-winding topology, since the neutral point of the motor is open, during normal operation of the motor, a third-harmonic back electromotive force will be generated under the excitation of the third harmonic of the permanent magnet in the motor, which will cause a third-harmonic zero-sequence circulating current in the winding, and introduce low-frequency torque pulsation and additional losses in the motor. For a motor with a relatively low fundamental frequency, in the prior art, it has been disclosed to suppress the torque pulsation of the motor by performing continuous-domain modeling on the motor and designing a resonant-type controller, etc. However, for a motor with a relatively high fundamental frequency, if the above prior art method is still used to suppress the zero-sequence current, it is necessary to increase the switching frequency of the switching devices, resulting in an increase in the total loss of the switching devices in the driver, and the operating cost of the electric drive system is relatively high. The total loss of the switching devices can be expressed by the following formula: ; where represents the total loss of the switching devices, represents the switching frequency, represents the single-switching loss of the device.

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

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

[0006] To achieve the above purpose, the present application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a control method for suppressing zero-sequence current of a permanent magnet synchronous motor, and the method includes:

[0008] Determine the zero-sequence voltage generated by the inverter, and based on the pre-established motor control model in the discrete domain, determine the zero-sequence current of the inverter generated by the motor under the sole action of the zero-sequence voltage; wherein, according to the set discretization period, the zero-sequence voltage satisfies the following relational expression in the z-domain: (Formula 1); perform Laplace transform on the zero-sequence voltage, and after combining the transformed result with Formula 1 and performing z-transform, and considering the one-beat delay of the closed-loop control system for controlling the motor, correct Formula 1 to obtain the motor control model, and the motor control model satisfies the following relational expression: (Formula 2);

[0009] In Formulas 1 and 2, represents the zero-sequence current of the inverter, 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 the natural logarithm;

[0010] Obtain the back electromotive force of the motor, and determine the zero-sequence current of the back electromotive force generated by the motor under the sole action of the back electromotive force;

[0011] Cancel out the zero-sequence current of the inverter and the zero-sequence current of the back electromotive force to obtain the output current of the closed-loop control system for controlling the motor, and the output current is generated by the combined action of the inverter and the back electromotive force.

[0012] Further, in the process of obtaining the output current, it includes:

[0013] Input the zero-sequence current of the back electromotive force into the pre-established discrete-domain current loop model; wherein, use the zero-sequence current of the back electromotive force as the disturbance quantity of the closed-loop control system, and determine the output current according to the disturbance quantity, so that the zero-sequence current of the back electromotive force and the output current satisfy the following relational expression: (Formula 3);

[0014] In Formula 3, represents the zero-sequence current of the back electromotive force, represents the output current, represents time, represents the electrical frequency of the zero-sequence current of the back electromotive force, represents the amplitude of the zero-sequence current of the back electromotive force, represents the amplitude of the output current, represents the time constant, represents the phase of the zero-sequence current of the back electromotive force, Represents the phase of the output current;

[0015] Take the Laplace transform of Equation 3 and consider the parameters and parameter , to obtain the first closed-loop transfer function, and discretize the first closed-loop transfer function using the pre-distorted bilinear transform. Let , and , to obtain the discrete-domain current loop model. The discrete-domain current loop model satisfies the following relationship: (Equation 4);

[0016] Determine the second closed-loop transfer function of the discrete-domain current loop model, and inversely deduce the transfer function of the controller in the closed-loop control system based on the second closed-loop transfer function. The transfer function of the controller satisfies the following relationship: (Equation 5);

[0017] In Equations 4 and 5, represents the first closed-loop transfer function, represents the discrete-domain transfer function of the inverter-side model, represents the coefficient used in the bilinear transform operation, represents the Laplace operator.

[0018] Furthermore, in the case of determining the transfer function of the controller, it includes:

[0019] Modify the transfer function of the controller so that the modified transfer function of the controller satisfies the following relationship: (Equation 6); where is a positive integer greater than or equal to 2;

[0020] In Equation 6, represents the number of beats of the controller delay, represents the desired bandwidth.

[0021] Furthermore, in the process of modifying the transfer function of the controller, it includes:

[0022] Replace in the controller with a delay compensator so that the transfer function of the delay compensator satisfies the following relationship: (Equation 7);

[0023] In Equation 7, represents a fixed coefficient, and > 0;

[0024] After compensation by the delay compensator, modify the transfer function of the controller to (Equation 8).

[0025] Further, the method further includes:

[0026] When the filter used in the feedback channel of the closed-loop control system is a second-order Butterworth filter, determining the transfer function of the filter, and the transfer function of the filter satisfies the following relationship: (Equation 9);

[0027] In Equation 9, represents the damping ratio of the filter, represents the cut-off frequency of the filter, represents the Laplace operator.

[0028] Further, when the transfer function of the filter is determined, it further includes:

[0029] Modeling the filter using pre-distorted bilinear transformation and compensating the established model to avoid instability of the closed-loop control system caused by the phase lag of the filter. The model of the filter after compensation satisfies the following relationship: (Equation 10); where , is the reciprocal of the switching frequency of the inverter.

[0030] Further, in the process of determining the back electromotive force zero-sequence current, it includes:

[0031] When only considering the third and its multiple frequency current harmonics, determining the back electromotive force zero-sequence current so that the back electromotive force zero-sequence current satisfies the following relationship:

[0032] (Equation 11); where ;

[0033] In Equation 11, represents the discrete-domain transfer function of the back electromotive force side model, represents the continuous-domain transfer function of the back electromotive force side model, represents the discrete-domain transfer function of the back electromotive force, represents the continuous-domain transfer function of the back electromotive force, represents the continuous-domain transfer function of the back electromotive force zero-sequence current, represents the order of the back electromotive force zero-sequence current harmonic, represents the electrical frequency of the motor.

[0034] In a second aspect, the present application further provides a control device for suppressing the zero-sequence current of a permanent magnet synchronous motor. The device includes:

[0035] An acquisition unit for acquiring the zero-sequence voltage generated by the inverter and the back electromotive force generated by the motor;

[0036] 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);

[0037] 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;

[0038] A second determination unit 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;

[0039] 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, and the output current is generated by the inverter and the back-electromotive force.

[0040] 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.

[0041] 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.

[0042] 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

[0043] Figure 1This is the first flowchart of the control method for suppressing zero - sequence current of a permanent - magnet synchronous motor in the embodiment of the present application;

[0044] Figure 2 This is the second flowchart of the control method for suppressing zero - sequence current of a permanent - magnet synchronous motor in the embodiment of the present application;

[0045] Figure 3 This is the relationship curve of the system closed - loop poles with the coefficient k under different controller parameters a in the embodiment of the present application;

[0046] Figure 4 This is the distribution of the system closed - loop poles under different compensator parameters μ in the embodiment of the present application;

[0047] Figure 5 This is the flowchart of realizing phase compensation based on a filter in the embodiment of the present application;

[0048] Figure 6 This is the schematic diagram of a part of the structure of the closed - loop control system in the embodiment of the present application;

[0049] Figure 7 This is the overall schematic diagram of the closed - loop control system in the embodiment of the present application;

[0050] Figure 8 This is the simulation diagram of the zero - sequence current time - domain waveform without applying delay compensation in the embodiment of the present application;

[0051] Figure 9 This is the simulation diagram of the zero - sequence current time - domain waveform with applying delay compensation in the embodiment of the present application;

[0052] Figure 10 This is the schematic diagram of the control device for suppressing zero - sequence current of a permanent - magnet synchronous motor in the embodiment of the present application;

[0053] Figure 11 This is the schematic diagram of the control system for suppressing zero - sequence current of a permanent - magnet synchronous motor in the embodiment of the present application. Detailed implementation mode

[0054] In order to enable those skilled in the art to better understand the solution of the present application, the technical solutions in the specific implementation mode of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present application.

[0055] As Figure 1 shown, in the first aspect, the present application provides a control method for suppressing zero - sequence current of a permanent - magnet synchronous motor, and the method includes the following steps:

[0056] S101: Determine the zero - sequence voltage generated by the inverter, and based on the pre - established motor control model in the discrete domain, determine the inverter zero - sequence current generated by the motor under the sole action of the zero - sequence voltage.

[0057] 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).

[0058] 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.

[0059] In some embodiments, the zero-sequence voltage on the inverter side and the inverter zero-sequence current under its excitation are as follows:

[0060]

[0061] 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.

[0062] 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.

[0063] 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.

[0064] Among them, the back EMF Back-EMF zero-sequence current under its excitation satisfy:

[0065] ;

[0066] Considering only the third - order and its harmonic - frequency current harmonics, determine the zero - sequence back - electromotive - force (EMF) current such that the zero - sequence back - EMF current satisfies the following relationship:

[0067] ;

[0068] where, ; in the above formula of the zero - sequence back - EMF current, represents the discrete - domain transfer function of the back - EMF side model, represents the continuous - domain transfer function of the back - EMF side model, represents 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 zero - sequence back - EMF current, represents the order of the zero - sequence back - EMF current harmonics, represents the electrical frequency of the motor.

[0069] S103: Cancel out the zero - sequence inverter current and the zero - sequence back - EMF current 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.

[0070] By the above method, the switching frequency of the switching devices in the system can be reduced, and the operation cost of the system can be lowered.

[0071] As Figure 2 shown, further, in the process of obtaining the output current, it includes:

[0072] S1021: Input the zero - sequence back - EMF current into the pre - established discrete - domain current - loop model.

[0073] where, take the zero - sequence back - EMF current as the disturbance quantity of the closed - loop control system, and determine the output current according to the disturbance quantity, such that the zero - sequence back - EMF current and the output current satisfy the following relationship: (Formula 3);

[0074] In Formula 3, represents the zero - sequence back - EMF current, represents the output current, represents time, represents the electrical frequency of the zero - sequence back - EMF current, represents the amplitude of the zero - sequence back - EMF current, represents the amplitude of the output current, represents the time constant, represents the phase of the zero - sequence back - EMF current, represents the phase of the output current;

[0075] S1022: Perform Laplace transforms on the back electromotive force zero-sequence current and the output current to obtain a first closed-loop transfer function, and discretize the first closed-loop transfer function using pre-distorted bilinear transformation to obtain a discrete-domain current loop model.

[0076] It should be noted that when performing Laplace transforms on the back electromotive force zero-sequence current and the output current, parameters and parameter need to be considered. When discretizing the first closed-loop transfer function using pre-distorted bilinear transformation, let , and . The discrete-domain current loop model obtained based on the above processing satisfies the following relationship: (Equation 4).

[0077] S1023: Determine the second closed-loop transfer function of the discrete-domain current loop model, and inversely deduce the transfer function of the controller in the closed-loop control system based on the second closed-loop transfer function.

[0078] Among them, the transfer function of the controller satisfies the following relationship: (Equation 5);

[0079] In Equation 4 and Equation 5, represents the first closed-loop transfer function, represents the discrete-domain transfer function of the inverter-side model, represents the coefficient used in the bilinear transformation operation, represents the Laplace operator.

[0080] As an implementation, when determining the transfer function of the controller, it includes:

[0081] Modify the transfer function of the controller so that the modified transfer function of the controller satisfies the following relationship: (Equation 6); where is a positive integer greater than or equal to 2;

[0082] In Equation 6, represents the number of beats of the controller delay, represents the desired bandwidth.

[0083] It should be noted that since the order of the numerator of the z-domain transfer function in the closed-loop control system cannot be higher than the order of the denominator, the transfer function of the controller in Equation 5 cannot be realized. Therefore, it is necessary to modify the transfer function of the controller so that in Equation 5 is modified to . Based on the above modification, the modified transfer function of the controller is obtained.

[0084] Furthermore, in the process of modifying the transfer function of the controller, it includes:

[0085] Replace the in the controller with a delay compensator, so that the transfer function of the delay compensator satisfies the following relationship: (Equation 7). In Equation 7, represents a fixed coefficient, and > 0.

[0086] It should be noted that although the transfer function of the corrected controller can enable the closed-loop control system to achieve the function of suppressing the zero-sequence current of the back electromotive force, it will cause the closed-loop poles of the closed-loop control system to approach the imaginary axis (see ). It can be seen that the Figure 3 in the controller will lead to a decrease in the stability of the closed-loop control system. Based on this, the in the controller is replaced with a delay compensator. In addition, the larger the k, the larger the real part of the closed-loop poles of the closed-loop control system, and the more likely the closed-loop control system is to become unstable. Therefore, in the embodiment of the present application, k is taken as 2.

[0087] As shown in Figure 4 , after the action of the delay compensator, the dominant poles of the closed-loop control system move away from the imaginary axis, making the closed-loop control system stable.

[0088] Exemplarily, when = 0.7, the real part of the system dominant pole is about three times that when

[0089] = 0, which reflects the role of the delay compensator. After compensation by the delay compensator, the transfer function of the controller is corrected to (Equation 8).

[0090] Through the above method, a discrete-domain delay compensator is designed, so that the switching frequency of the switching device in the system can achieve zero-sequence current suppression even when it is only 10 times the zero-sequence current frequency.

[0091] As shown in Figure 5 , as an implementation manner, the method further includes:

[0092] S201: When the filter used in the feedback channel of the closed-loop control system is a second-order Butterworth filter, determine the transfer function of the filter.

[0093] Among them, the transfer function of the filter satisfies the following relationship: (Equation 9);

[0094] In Equation 9, represents the damping ratio of the filter, represents the cut-off frequency of the filter, Denotes the Laplace operator.

[0095] 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 index to measure the relative stability of the control system). Therefore, it is necessary to accurately model this hardware filter so that the filter can be compensated by the microcontroller.

[0096] S202: Model the filter using pre-distorted bilinear transformation and compensate the established model to avoid instability of the closed-loop control system caused by the phase lag of the filter.

[0097] Such as Figure 6 provides a schematic diagram of a closed-loop control system. Exemplarily, if the filter is modeled using pre-distorted bilinear transformation and the transfer function is used for compensation, the instability of the closed-loop system caused by the phase lag of the filter can be effectively avoided. Among them, Figure 6 in the schematic diagram of represents the feedback quantity of the zero-sequence current of the back electromotive force after phase compensation, is the given quantity of the controller, that is, the control target of the controller is 0A.

[0098] The model of the filter after compensation satisfies the following relationship: (Equation 10); where , is the reciprocal of the switching frequency of the inverter.

[0099] Such as Figure 7 shown, is a closed-loop control system for zero-sequence current loop phase compensation and delay compensation implemented based on the above compensator and filter.

[0100] Exemplarily, first, without considering the delay compensator, examine the role of the phase compensator. Simulate the closed-loop control system. The motor speed is 15,000 rpm (steady state), the phase current fundamental frequency is 500 Hz, the zero-sequence current frequency is 1500 Hz, the switching frequency is 18 kHz, the carrier ratio of the switching frequency to the third harmonic is 12, the filter uses a second-order Butterworth filter, and the cut-off frequency is 10 kHz; the controller parameter is taken as 20. Turn on the zero-sequence current suppression algorithm at 0.05 s. The simulation results are as Figure 8 shown. 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 the phase compensation.

[0101] Secondly, on the basis of considering phase compensation, the role of the delay compensator is investigated. When the motor speed is 15000 rpm and the switching frequency is 15 kHz, the switching frequency is only 10 times the zero-sequence current frequency at this time. With the other parameters of the motor and the controller remaining unchanged, simulations are carried out. The simulation results are as Figure 9 shown. The simulation results demonstrate the effectiveness of the delay compensation algorithm.

[0102] Through the above method, based on the established discrete-domain current loop model, a discrete-domain controller is used to suppress the zero-sequence current, enabling the zero-sequence current to be suppressed even when the switching frequency of the switching devices in the system is only 12 times the zero-sequence current frequency. In addition, the controller only has one parameter a to be tuned, and the tuning of the controller parameters is simple.

[0103] In summary, through the above method, it is possible to suppress the zero-sequence current of the motor under the condition of a relatively low switching frequency of the switching devices in the closed-loop control system, and solve the problem of the high operating cost of the closed-loop control system.

[0104] As Figure 10 shown, in the second aspect, the present application also provides a control device 100 for suppressing the zero-sequence current of a permanent magnet synchronous motor. The device includes:

[0105] An acquisition unit 11, configured to acquire the zero-sequence voltage generated by the inverter and the back electromotive force generated by the motor;

[0106] A first determination unit 12, configured to determine the inverter zero-sequence current generated by the motor under the sole action of the zero-sequence voltage 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 relational expression in the z domain: (Formula 1); perform a Laplace transform on the zero-sequence voltage, and after combining the transformed result with Formula 1 and performing a z transform, and considering the one-beat delay of the closed-loop control system for controlling the motor, correct Formula 1 to obtain a motor control model, and the motor control model satisfies the following relational expression: (Formula 2);

[0107] In Formulas 1 and 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 the natural logarithm;

[0108] A second determination unit 13, configured to establish a motor control model and determine the back electromotive force zero-sequence current generated by the motor under the excitation of the back electromotive force;

[0109] A processing unit 14 is configured to cancel out the zero-sequence current of the inverter and the zero-sequence back electromotive force current to obtain an output current for controlling the closed-loop control system of the motor. The output current is generated by the combined action of the inverter and the back electromotive force.

[0110] As Figure 11 shown, in a third aspect, the present application further provides a control system for suppressing the zero-sequence current of a permanent magnet synchronous motor. The system includes a motor 200 and the control device 100 in the second aspect described above.

[0111] In a fourth aspect, the present application further provides a computer-readable storage medium. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, it implements the method in any one of the first aspects. Those of ordinary skill in the art can understand that all or part of the processes of implementing the methods in the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, a database, or other media used in the embodiments provided by the present application can include at least one of non-volatile and volatile memories. The databases involved in the embodiments provided by the present application can include at least one of relational databases and non-relational databases.

[0112] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, 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, it should be considered as the scope described in this specification.

[0113] The above embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended 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 a set discretization period, the zero-sequence voltage satisfies Formula 1 in the z domain: ; 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 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, represents the Laplace operator; 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 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 formula 4: ; In formula 4, represents the first closed-loop transfer function, Denote the discrete domain expression of the first closed-loop transfer function, represents the coefficients used in the bilinear transformation operation, represents the Laplace operator; in the parameter In, a represents the expected bandwidth; 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 Formula 5: ; In formula 5, A discrete domain expression of the first closed-loop transfer function is represented.

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 Formula 6: ;in, 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 Formula 7: ; In formula 7, represents a fixed coefficient, and >0; After being compensated by the delay compensator, the transfer function of the controller is corrected 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 Formula 9: ; In formula 9, represents the damping ratio of the filter, and , 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 Formula 10: ; In formula 10, , represents the discretization period.

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 Formula 11: ； 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 Formula 1 in the z domain: ; 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 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, represents the Laplace operator; 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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