Method and system for weakening torque ripple of permanent magnet synchronous motor

Abstract

The invention relates to a method and system for weakening torque ripple of a permanent magnet synchronous motor, and the method comprises the steps: respectively controlling a dynamometer and a motor to be tested to carry out the rotating speed closed-loop control and torque closed-loop control, and obtaining a fundamental current instruction; after entering a speed stable state, integrating the torque pulsation and the position information of the to-be-tested motor rotor to obtain a trigonometric function relationship between the torque pulsation and the to-be-tested motor rotor; for a torque ripple component expected to be weakened, a compensation current instruction is obtained based on a trigonometric function relation; superposing the compensation current instruction and the fundamental wave current instruction to obtain a superposed current instruction; repeating the steps to obtain a series of superimposed current instructions under different speeds and torques, and storing the superimposed current instructions; and in an application occasion where the torque ripple of the motor needs to be reduced, a superimposed current instruction corresponding to the current speed and torque is determined, and closed-loop control of the current is carried out based on the superimposed current instruction. Compared with the prior art, the current instruction value for weakening the torque ripple of the motor can be simply and quickly obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of motor torque pulsation control, and in particular to a method and system for weakening the torque pulsation of a permanent magnet synchronous motor. Background Art

[0002] The torque pulsation of a permanent magnet synchronous motor involves the design of the motor's stator teeth, the rotor's permanent magnets, the control of the motor's current, etc. The overall goal is to keep the torque pulsation as small as possible. However, in actual applications, it is difficult to achieve very small torque pulsation simply by optimizing the design of the motor body, and appropriate current control technology can often be added. However, it is difficult to obtain current instructions that weaken the motor's torque pulsation. The industry has proposed calculating a large number of parameters based on the internal magnetic field distribution of the motor to achieve the acquisition of current instructions, and the relevant parameters under different torque and speed instructions require a lot of calculations, making it difficult to ensure the speed, accuracy and effectiveness of parameter calculations. The main disadvantages of the prior art are:

[0003] 1. The motor design is optimized, but the inverter power supply current is not ideal and there is still obvious torque pulsation;

[0004] 2. It is difficult to accurately obtain the current command value that weakens the torque ripple;

[0005] 3. The general current closed-loop control effect is not ideal. Summary of the invention

[0006] The purpose of the present invention is to provide a method and system for weakening the torque pulsation of a permanent magnet synchronous motor, accurately obtain a current command value for weakening the torque pulsation, and effectively weaken the torque pulsation.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A method for reducing torque pulsation of a permanent magnet synchronous motor comprises the following steps:

[0009] Step 1) building a towing test platform for the motor to be tested and the dynamometer, wherein the towing test platform includes a host computer, the motor to be tested, a motor controller to be tested, a torque meter, a dynamometer and a dynamometer controller, and the entire platform is under the control of the host computer;

[0010] Step 2) The host computer controls the dynamometer to perform smooth speed closed-loop control to stabilize the speed of the towing platform;

[0011] Step 3) the host computer controls the motor to be tested to perform torque closed-loop control, the torque command of the motor to be tested is converted into a corresponding fundamental current command inside the motor controller to be tested, the motor to be tested is subjected to current closed-loop control based on the fundamental current command, and the position information of the rotor of the motor to be tested is transmitted to the host computer in real time;

[0012] Step 4) After the towing test platform enters a speed stable state, the torque pulsation of the motor to be tested is measured by a torque meter and transmitted to the host computer in real time;

[0013] Step 5) The host computer integrates the torque pulsation and the position information of the motor rotor to be measured, and performs mathematical analysis to obtain the trigonometric function relationship between the two;

[0014] Step 6) the motor controller to be tested processes the trigonometric function relationship obtained in step 5) with respect to the torque pulsation component to be weakened, and obtains a compensation current instruction for weakening the torque pulsation;

[0015] Step 7) the motor controller to be tested superimposes the compensation current command obtained in step 6) with the fundamental current command for implementing torque control in step 3) to obtain a superimposed current command;

[0016] Step 8) The host computer changes the speed and torque instructions of the motor, and repeats the above steps 2) to 7), and the motor controller to be tested obtains a series of superimposed current instructions under different speeds and torques, and saves them in the non-volatile memory of the motor controller to be tested;

[0017] Step 9) In actual application scenarios where the motor torque pulsation needs to be reduced, the motor controller to be tested retrieves the superimposed current command corresponding to the current speed and torque from the non-volatile memory, and performs closed-loop current control based on the superimposed current command.

[0018] The motor controller to be tested and the dynamometer controller communicate with the host computer via the CAN bus.

[0019] The torque meter is connected to a host computer via a data acquisition cable, and transmits data to a data acquisition card of the host computer.

[0020] In step 2), if the speed fluctuation exceeds a preset range, a flywheel is added to stabilize the speed.

[0021] In the step 5), for the m-fold frequency torque pulsation, the trigonometric function relationship between the torque pulsation and the position information of the motor rotor to be measured is: Te = Tm·sin(mωt+θ 0 ), where Te represents the pulsating torque variable to be analyzed, Tm represents the m-fold frequency torque pulsation, θ 0 It represents the phase difference between the m-fold torque pulsation and the rotor position, ω is the rotor electrical angular velocity, ω=p·2πn / 60, n is the speed (rpm), and p is the number of magnetic pole pairs of the motor.

[0022] In step 6), for the m-fold frequency torque ripple, the compensation current command is idc=0 and iqc=iqm·sin(mωt+θ 0+π), where, iqm=Tm / (1.5pΨ f ), f is the permanent magnet flux value of the permanent magnet synchronous motor, p is the number of magnetic pole pairs of the motor, θ 0 It represents the phase difference between the m-fold frequency torque pulsation and the rotor position, ω is the rotor electrical angular velocity, idc is the d-axis compensation current command, and iqc is the q-axis compensation current command.

[0023] The closed-loop control of current based on the superimposed current instruction includes a closed-loop control process based on a fundamental current instruction and a closed-loop control process based on a compensation current instruction.

[0024] The closed-loop control process based on the fundamental current command is specifically as follows: real-time sampling of the motor current and rotor position, transformation into the dq rotor coordinate system and the corresponding harmonic coordinate system, obtaining the current feedback value, and performing closed-loop control of the current in the dq rotor coordinate system according to the fundamental current command.

[0025] The closed-loop control process based on the compensation current instruction is specifically as follows: for the torque pulsation of m times the frequency, the closed-loop control of the compensation current is performed in the m-1th and m+1th rotating coordinate systems, wherein:

[0026] The current command value in the m-1 times rotating coordinate system is:

[0027] idm1*=iqc / 2·sin(θ 0 +π / 2)

[0028] iqm1*=iqc / 2·cos(θ 0 +π / 2)

[0029] The current command value in the m+1-time rotating coordinate system is:

[0030] idm2*=-iqc / 2·sin(θ 0 +π / 2)

[0031] iqm2*=iqc / 2·cos(θ 0 +π / 2)

[0032] Among them, idm1* and iqm1* are the d-axis and q-axis current instructions in the m-1-fold rotating coordinate system, idm2* and iqm2* are the d-axis and q-axis current instructions in the m+1-fold rotating coordinate system, and iqc is the q-axis compensation current instruction;

[0033] Based on the feedback of the three-phase current values ​​ia, ib, ic and the rotor electrical angle position θ, the feedback values ​​of the current in the m-1 and m+1 rotating coordinate systems are calculated:

[0034]

[0035] Among them, idm1 and iqm1 are the d-axis and q-axis current feedback values in the (m - 1)-th rotating coordinate system respectively, and idm2 and iqm2 are the d-axis and q-axis current feedback values in the (m + 1)-th rotating coordinate system respectively;

[0036] After current closed-loop control, respective voltage command values are obtained. After passing through respective coordinate transformations, the voltage command values in the αβ two-phase stationary coordinate system are obtained, and then transformed into the three-phase coordinate system to obtain the control voltage command values ua, ub, and uc. Based on the SPWM or SVPWM algorithm, six switches in the inverter circuit of the motor controller are controlled to output appropriate voltages to the motor to complete the current closed-loop control.

[0037] A system for weakening the torque ripple of a permanent magnet synchronous motor, used to implement the method as described above. The system includes:

[0038] A counter-rotating test platform, which includes a host computer, a motor under test, a motor controller under test, a torque meter, a dynamometer, and a dynamometer controller. The entire platform is under the control of the host computer;

[0039] A superimposed current command acquisition module, used to execute steps 2)-7) of the method for weakening the torque ripple of the permanent magnet synchronous motor to obtain a superimposed current command;

[0040] A superimposed current command storage module. The host computer changes the speed and torque commands of the motor, repeatedly calls the superimposed current command acquisition module to obtain the superimposed current command. The motor controller under test obtains a series of superimposed current commands at different speeds and torques and saves them in the non-volatile memory of the motor controller under test;

[0041] A control module. In actual application scenarios where it is necessary to reduce the torque ripple of the motor, the motor controller under test takes out the superimposed current command corresponding to the current speed and torque from the non-volatile memory and performs current closed-loop control based on the superimposed current command.

[0042] Compared with the prior art, the present invention can simply and quickly obtain the current command value for weakening the torque ripple of the motor, and effectively weaken the torque ripple of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a flowchart of the method of the present invention;

[0044] Figure 2 is a schematic structural diagram of the counter-rotating test platform in an embodiment;

[0045] Figure 3 is a block diagram of the motor current control system in an embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0047] Example 1

[0048] This embodiment provides a method for reducing the torque pulsation of a permanent magnet synchronous motor. Figure 1 As shown, the following steps are included:

[0049] Step 1) Build a test platform for the motor to be tested and the dynamometer, such as Figure 2 As shown, the towing test platform includes a host computer, a motor to be tested, a motor controller to be tested, a torque meter, a dynamometer and a dynamometer controller, and the entire platform is under the control of the host computer.

[0050] Step 2) The host computer controls the dynamometer through CAN communication to perform smooth speed closed-loop control, so that the speed of the towing platform is stabilized at n (rpm, revolutions per minute). If the speed fluctuates greatly, a flywheel can be added to stabilize the speed.

[0051] Step 3) The host computer controls the motor to be tested to perform torque closed-loop control through CAN communication. The torque command of the motor to be tested is converted into corresponding fundamental current commands id1 and iq1 inside the motor controller to be tested, where id1 and iq1 represent the fundamental current commands of the d-axis and q-axis respectively. Based on the fundamental current command, the current of the motor to be tested is closed-loop controlled, and the position information of the rotor of the motor to be tested is transmitted to the host computer in real time through CAN communication.

[0052] Step 4) After the towing test platform enters a speed stable state, the torque pulsation of the motor to be tested is measured by a torque meter and transmitted to the host computer in real time through a data acquisition cable.

[0053] Step 5) The host computer integrates the torque pulsation and the position information of the motor rotor to be measured, and performs mathematical analysis to obtain the trigonometric function relationship between the two.

[0054] For m-fold frequency torque pulsation, the trigonometric function relationship between the torque pulsation and the position information of the motor rotor to be measured is:

[0055] Te=Tm·sin(mωt+θ 0 ) (1)

[0056] Among them, Te represents the torque variable to be analyzed, Tm represents the m-fold torque pulsation, θ 0It represents the phase difference between the m-fold torque pulsation and the rotor position, ω is the rotor electrical angular velocity, ω=p·2πn / 60, n is the speed, and p is the number of magnetic pole pairs of the motor. Usually, m is a positive integer multiple of 6.

[0057] Step 6) The motor controller to be tested processes the trigonometric function relationship (1) obtained in step 5) for the torque pulsation component that is expected to be weakened, and obtains a compensation current instruction for weakening the torque pulsation:

[0058] idc=0 (2)

[0059] iqc=iqm·sin(mωt+θ 0 +π) (3)

[0060] Where iqm = Tm / (1.5pΨ f ), f is the permanent magnet flux value of the permanent magnet synchronous motor, idc is the d-axis compensation current command, and iqc is the q-axis compensation current command.

[0061] Step 7) The motor controller to be tested superimposes the compensation current command obtained in step 6) with the fundamental current command for implementing torque control in step 3) to obtain a superimposed current command:

[0062] id=id1+idc (4)

[0063] iq=iq1+iqc (5)

[0064] This instruction can ensure that the motor under test outputs the expected torque while having a smaller torque pulsation, that is, the torque pulsation is weakened.

[0065] Step 8) The host computer changes the speed and torque instructions of the motor, and repeats the above steps 2) to 7), and the motor controller to be tested obtains a series of superimposed current instructions under different speeds and torques, and saves them in the non-volatile memory of the motor controller to be tested.

[0066] Step 9) In actual application scenarios where the motor torque pulsation needs to be reduced, the motor controller to be tested retrieves the superimposed current command corresponding to the current speed and torque from the non-volatile memory, and performs closed-loop current control based on the superimposed current command.

[0067] The closed-loop control of the current based on the superimposed current instruction includes a closed-loop control process based on the fundamental current instruction and a closed-loop control process based on the compensation current instruction.

[0068] Among them, the closed-loop control process based on the fundamental current command is specifically as follows: real-time sampling of the motor current and rotor position, transformation to the dq rotor coordinate system and the corresponding harmonic coordinate system (the harmonic coordinate system for the m-fold torque pulsation refers to the m-1 and m+1 rotating coordinate systems), obtaining the current feedback value, and performing closed-loop control of the current (id1 and iq1) according to the value of the fundamental current command in the dq rotor coordinate system.

[0069]

[0070] The closed-loop control process based on the compensation current command is as follows: for the m-fold torque pulsation, the closed-loop control of the compensation current (idc and iqc) is performed in the m-1 and m+1 rotating coordinate systems, using the following method: Figure 3 The control strategy shown in the block diagram can achieve high-performance current closed-loop control, thereby ultimately achieving the goal of effectively reducing the motor torque pulsation.

[0071] The current command value in the m-1 times rotating coordinate system is:

[0072] idm1*=iqc / 2·sin(θ 0 +π / 2) (7)

[0073] iqm1*=iqc / 2·cos(θ 0 +π / 2) (8)

[0074] The current command value in the m+1-time rotating coordinate system is:

[0075] idm2*=-iqc / 2·sin(θ 0 +π / 2) (9)

[0076] iqm2*=iqc / 2·cos(θ 0 +π / 2) (10)

[0077] Among them, idm1* and iqm1* are the d-axis and q-axis current instructions in the m-1-fold rotating coordinate system, idm2* and iqm2* are the d-axis and q-axis current instructions in the m+1-fold rotating coordinate system, and iqc is the q-axis compensation current instruction.

[0078] Current feedback value such as Figure 3 As shown, the feedback values ​​of the m-1 and m+1 rotating coordinate system currents are calculated based on the feedback three-phase current values ​​ia, ib, ic and the rotor electrical angle position θ:

[0079]

[0080]

[0081] Among them, idm1 and iqm1 are the d-axis and q-axis current feedback values ​​in the m-1-fold rotating coordinate system, respectively, and idm2 and iqm2 are the d-axis and q-axis current feedback values ​​in the m+1-fold rotating coordinate system, respectively.

[0082] After the current closed-loop control, the respective voltage command values ​​are obtained respectively, and the voltage command values ​​in the αβ two-phase stationary coordinate system are obtained after the respective coordinate transformation, and then transformed to the three-phase coordinate system to obtain the control voltage command values ​​ua, ub, and uc. Based on the SPWM or SVPWM algorithm, the six switches in the inverter circuit in the motor controller are controlled to output the appropriate voltage to the motor to complete the current closed-loop control.

[0083] This embodiment Figure 3 The functions of each module are further explained as follows:

[0084] The host computer provides torque instructions through CAN communication, and determines the current instruction values ​​id1*, iq1* and iqc and θ corresponding to the pulsating torque components according to the torque instruction value and the current speed value of the motor (the values ​​in the table are obtained through a large number of tests on the towing test bench and the calculation of formulas (1)-(3)). 0 PI current controller 1 performs current closed-loop regulation based on the difference between the id1 and iq1 command values ​​and the feedback values ​​in the conventional control strategy (i.e., current closed-loop control without considering torque pulsation), and outputs ud1 and uq1 voltage control quantities. Coordinate transformation module 1 converts the voltage control quantities ud1 and uq1 in the dq coordinate system to the voltage command values ​​in the αβ two-phase stationary coordinate system.

[0085] The harmonic current command calculation module uses iqc and θ 0 The values ​​and formulas (7)-(10) are used to obtain the command values ​​of the m-1 and m+1 harmonic currents. The PI current controller 2 performs current closed-loop regulation based on the difference between the command value and the feedback value of the m-1 harmonic current, and outputs the corresponding voltage control value. The coordinate transformation 2 module converts the harmonic voltage control value in the m-1 rotating coordinate system to the voltage command value in the αβ two-phase stationary coordinate system. The PI current controller 3 performs current closed-loop regulation based on the difference between the command value and the feedback value of the m+1 harmonic current, and outputs the corresponding voltage control value. The coordinate transformation 3 module converts the harmonic voltage control value in the m+1 rotating coordinate system to the voltage command value in the αβ two-phase stationary coordinate system.

[0086] Figure 3 The voltage synthesizer in the αβ coordinate system adds the voltage command values ​​of the three groups of αβ two-phase stationary coordinate systems to obtain the voltage command value of the total αβ coordinate system. Figure 3After the 2 / 3 transformation module in the three-phase coordinate system, the voltage command values ​​ua, ub, and uc of the three-phase coordinate system are obtained. Then, the six switches in the inverter circuit in the motor controller can be controlled through the commonly used SPWM or SVPWM algorithm to output the appropriate voltage to the motor to complete the closed-loop control of all currents.

[0087] Figure 3 The current conversion unit in the figure uses the three-phase current value obtained by the current sensor and the rotor position value provided by the position sensor to transform into three sets of current values ​​in the dq rotating coordinate system, the m-1 rotating coordinate system, and the m+1 rotating coordinate system, and then passes through a low-pass filter to obtain three sets of current values ​​for feedback (id1 and iq1, idm1 and iqm1, idm2 and iqm2). The motor speed calculation module in the figure can obtain the rotor speed information by differential calculation of the rotor position, which is used for table lookup of current instructions and closed-loop control of speed.

[0088] Example 2

[0089] This embodiment provides a system for reducing torque ripple of a permanent magnet synchronous motor, which is used to implement the method described in the above embodiment 1. The system includes:

[0090] A towing test platform, the towing test platform includes a host computer, a motor to be tested, a motor controller to be tested, a torque meter, a dynamometer and a dynamometer controller, and the entire platform is under the control of the host computer;

[0091] A superimposed current instruction acquisition module, used to execute steps 2) to 7) of the method for weakening the torque pulsation of the permanent magnet synchronous motor to obtain a superimposed current instruction;

[0092] The superimposed current instruction storage module, the host computer changes the speed and torque instructions of the motor, repeatedly calls the superimposed current instruction acquisition module to obtain the superimposed current instruction, and the motor controller to be tested obtains a series of superimposed current instructions under different speeds and torques, and saves them in the non-volatile memory of the motor controller to be tested;

[0093] The control module, in actual application scenarios where the motor torque pulsation needs to be reduced, takes out the superimposed current command corresponding to the current speed and torque from the non-volatile memory by the motor controller to be tested, and performs closed-loop control of the current based on the superimposed current command.

[0094] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the described module can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0095] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning, or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for reducing torque pulsation of a permanent magnet synchronous motor, characterized in that: The following steps are involved: Step 1) building a towing test platform for the motor to be tested and the dynamometer, wherein the towing test platform includes a host computer, the motor to be tested, a motor controller to be tested, a torque meter, a dynamometer and a dynamometer controller, and the entire platform is under the control of the host computer; Step 2) The host computer controls the dynamometer to perform smooth speed closed-loop control to stabilize the speed of the towing platform; Step 3) the host computer controls the motor to be tested to perform torque closed-loop control, the torque command of the motor to be tested is converted into a corresponding fundamental current command inside the motor controller to be tested, the motor to be tested is subjected to current closed-loop control based on the fundamental current command, and the position information of the rotor of the motor to be tested is transmitted to the host computer in real time; Step 4) After the towing test platform enters a speed stable state, the torque pulsation of the motor to be tested is measured by a torque meter and transmitted to the host computer in real time; Step 5) The host computer integrates the torque pulsation and the position information of the motor rotor to be measured, and performs mathematical analysis to obtain the trigonometric function relationship between the two; Step 6) the motor controller to be tested processes the trigonometric function relationship obtained in step 5) with respect to the torque pulsation component to be weakened, and obtains a compensation current instruction for weakening the torque pulsation; Step 7) the motor controller to be tested superimposes the compensation current command obtained in step 6) with the fundamental current command for implementing torque control in step 3) to obtain a superimposed current command; Step 8) The host computer changes the speed and torque instructions of the motor, and repeats the above steps 2) to 7), and the motor controller to be tested obtains a series of superimposed current instructions under different speeds and torques, and saves them in the non-volatile memory of the motor controller to be tested; Step 9) In actual application scenarios where the motor torque pulsation needs to be reduced, the motor controller to be tested retrieves the superimposed current command corresponding to the current speed and torque from the non-volatile memory, and performs closed-loop current control based on the superimposed current command.

2. A method for reducing torque ripple of a permanent magnet synchronous motor according to claim 1, characterized in that: The motor controller to be tested and the dynamometer controller communicate with the host computer via the CAN bus.

3. The method for reducing torque pulsation of a permanent magnet synchronous motor according to claim 1, characterized in that: The torque meter is connected to a host computer via a data acquisition cable, and transmits data to a data acquisition card of the host computer.

4. The method for reducing torque ripple of a permanent magnet synchronous motor according to claim 1, characterized in that: In step 2), if the speed fluctuation exceeds a preset range, a flywheel is added to stabilize the speed.

5. The method for reducing torque pulsation of a permanent magnet synchronous motor according to claim 1, characterized in that: In the step 5), for the m-fold frequency torque pulsation, the trigonometric function relationship between the torque pulsation and the position information of the motor rotor to be measured is: Te=Tm·sin(mωt+θ0), wherein Te represents the pulsating torque variable to be analyzed, Tm represents the m-fold frequency torque pulsation amount, θ0 represents the phase difference between the m-fold frequency torque pulsation and the rotor position, ω is the rotor electrical angular velocity, ω=p·2πn / 60, n is the rotational speed, and p is the number of magnetic pole pairs of the motor.

6. The method for reducing torque ripple of a permanent magnet synchronous motor according to claim 1, characterized in that: In step 6), for the m-fold frequency torque pulsation, the compensation current command is idc=0 and iqc=iqm·sin(mωt+θ0+π), where iqm=Tm / (1.5pΨ f ), f is the permanent magnet flux linkage value of the permanent magnet synchronous motor, p is the number of magnetic pole pairs of the motor, θ0 represents the phase difference between the m-fold frequency torque pulsation and the rotor position, ω is the rotor electrical angular velocity, idc is the d-axis compensation current command, and iqc is the q-axis compensation current command.

7. The method for reducing torque ripple of a permanent magnet synchronous motor according to claim 1, characterized in that: The closed-loop control of current based on the superimposed current instruction includes a closed-loop control process based on a fundamental current instruction and a closed-loop control process based on a compensation current instruction.

8. The method for reducing torque ripple of a permanent magnet synchronous motor according to claim 7, characterized in that: The closed-loop control process based on the fundamental current command is specifically as follows: real-time sampling of the motor current and rotor position, transformation into the dq rotor coordinate system and the corresponding harmonic coordinate system, obtaining the current feedback value, and performing closed-loop control of the current in the dq rotor coordinate system according to the fundamental current command.

9. The method for reducing torque ripple of a permanent magnet synchronous motor according to claim 7, characterized in that: The closed-loop control process based on the compensation current instruction is specifically as follows: for the torque pulsation of m times the frequency, the closed-loop control of the compensation current is performed in the m-1 and m+1 rotating coordinate systems, wherein: The current command value in the m-1 times rotating coordinate system is: idm1*=iqc / 2·sin(θ0+π / 2) iqm1*=iqc / 2·cos(θ0+π / 2) The current command value in the m+1-time rotating coordinate system is: idm2*=-iqc / 2·sin(θ0+π / 2) iqm2*=iqc / 2·cos(θ0+π / 2) Among them, idm1* and iqm1* are the d-axis and q-axis current instructions in the m-1-fold rotating coordinate system, idm2* and iqm2* are the d-axis and q-axis current instructions in the m+1-fold rotating coordinate system, and iqc is the q-axis compensation current instruction; Based on the feedback of the three-phase current values ​​ia, ib, ic and the rotor electrical angle position θ, the feedback values ​​of the current in the m-1 and m+1 rotating coordinate systems are calculated: Among them, idm1 and iqm1 are the d-axis and q-axis current feedback values ​​in the m-1-times rotating coordinate system, and idm2 and iqm2 are the d-axis and q-axis current feedback values ​​in the m+1-times rotating coordinate system, respectively; After the current closed-loop control, the respective voltage command values ​​are obtained respectively. After the respective coordinate transformation, the voltage command values ​​in the αβ two-phase stationary coordinate system are obtained, and then transformed to the three-phase coordinate system to obtain the control voltage command values ​​ua, ub, and uc. Based on the SPWM or SVPWM algorithm, the six switches in the inverter circuit of the motor controller are controlled to output a suitable voltage to the motor to complete the closed-loop control of the current.

10. A system for reducing torque pulsation of a permanent magnet synchronous motor, used to implement the method according to any one of claims 1 to 9, characterized in that: The system includes: A towing test platform, the towing test platform includes a host computer, a motor to be tested, a motor controller to be tested, a torque meter, a dynamometer and a dynamometer controller, and the entire platform is under the control of the host computer; A superimposed current instruction acquisition module, used to execute steps 2) to 7) of the method for weakening the torque pulsation of the permanent magnet synchronous motor to obtain a superimposed current instruction; The superimposed current instruction storage module, the host computer changes the speed and torque instructions of the motor, repeatedly calls the superimposed current instruction acquisition module to obtain the superimposed current instruction, and the motor controller to be tested obtains a series of superimposed current instructions under different speeds and torques, and saves them in the non-volatile memory of the motor controller to be tested; The control module, in actual application scenarios where the motor torque pulsation needs to be reduced, takes out the superimposed current command corresponding to the current speed and torque from the non-volatile memory by the motor controller to be tested, and performs closed-loop control of the current based on the superimposed current command.

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