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

Abstract

The application relates to a method and system for weakening torque ripple of a permanent magnet synchronous motor, wherein the method comprises: respectively controlling a dynamometer and a motor to be tested to carry out speed closed-loop control and torque closed-loop control, so as to obtain a fundamental current instruction; after entering a speed stable state, torque ripple and position information of a rotor of the motor to be tested are comprehensively obtained to obtain a trigonometric function relationship between the torque ripple and the position information; for a torque ripple component expected to be weakened, a compensation current instruction is obtained based on the trigonometric function relationship; the compensation current instruction is superposed with the fundamental current instruction to obtain a superposed current instruction; the above steps are repeated to obtain a series of superposed current instructions under different speeds and torques and the series of superposed current instructions are saved; in an application occasion in which motor torque ripple needs to be reduced, a corresponding superposed current instruction under current speed and torque is determined, and current closed-loop control is carried out based on the superposed current instruction. Compared with the prior art, the application can simply and quickly obtain a current instruction value for weakening motor torque ripple.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of motor torque ripple control, in particular to a method and system for weakening torque ripple of a permanent magnet synchronous motor. BACKGROUND

[0002] Torque ripple of a permanent magnet synchronous motor is related to design of motor stator teeth and rotor permanent magnet, control of motor current, etc., and generally, the torque ripple is expected to be as small as possible. However, in actual application, it is difficult to achieve very small torque ripple only by optimizing the design of the motor body, and appropriate current control technology is often added. However, the current command for weakening the torque ripple of the motor is difficult to obtain. The industry has proposed to calculate a large number of parameters based on the internal magnetic field distribution of the motor to obtain the current command, and the relevant parameters under different torque and speed commands require a large amount of calculation, which is difficult to ensure the rapidity, accuracy and effectiveness of parameter calculation. The main shortcomings of the prior art are:

[0003] 1. The motor body design is optimized, but the current supplied by the inverter is not ideal, and there is still obvious torque ripple;

[0004] 2. The current command value for weakening the torque ripple is difficult to accurately obtain;

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

[0006] The purpose of the application is to provide a method and system for weakening the torque ripple of a permanent magnet synchronous motor, which accurately obtains the current command value for weakening the torque ripple and effectively weakens the torque ripple.

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

[0008] A method for weakening the torque ripple of a permanent magnet synchronous motor, comprising the following steps:

[0009] Step 1) A drag test platform of a to-be-tested motor and a dynamometer is built, the drag test platform comprises a host computer, a to-be-tested motor, a to-be-tested motor controller, a torque meter, a dynamometer and a dynamometer controller, and the entire platform is controlled by the host computer;

[0010] Step 2) The host computer controls the dynamometer to perform smooth speed closed-loop control, so that the speed of the drag test platform is stable;

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

[0012] Step 4) After the test platform enters a steady state, the torque fluctuation of the motor to be tested is measured by the torque meter and transmitted to the host computer in real time.

[0013] Step 5) The host computer comprehensively analyzes the torque fluctuation and the position information of the rotor of the motor to be tested to obtain a trigonometric function relationship therebetween.

[0014] Step 6) The motor controller to be tested processes the trigonometric function relationship obtained in step 5) to obtain a compensation current instruction for weakening the torque fluctuation component.

[0015] Step 7) The motor controller to be tested superimposes the compensation current instruction obtained in step 6) and the fundamental current instruction for torque control in step 3) to obtain a superimposed current instruction.

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

[0017] Step 9) In an actual application scenario where the motor torque fluctuation needs to be reduced, the motor controller to be tested obtains the corresponding superimposed current instruction at the current speed and torque from the non-volatile memory and performs closed-loop current control based on the superimposed current instruction.

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

[0019] The torque meter is connected to the host computer through a data acquisition cable and transmits data to the 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 step 5), for m times frequency torque fluctuation, the trigonometric function relationship between the torque fluctuation and the position information of the rotor of the motor to be tested is Te=Tm·sin(mωt+θ0), wherein Te represents the analyzed torque fluctuation variable, Tm represents the m times frequency torque fluctuation, θ0 represents the phase difference between the m times frequency torque fluctuation and the rotor position, ω is the rotor electric angular velocity, ω=p·2πn / 60, n is the rotational speed (revolutions per minute), and p is the number of magnetic pole pairs of the motor.

[0022] In step 6), for m times frequency torque fluctuation, the compensation current instruction is idc=0 and iqc=iqm·sin(mωt+θ0+π), wherein iqm=Tm / (1.5pΨ f ), Ψf is the permanent magnet flux linkage value of the permanent magnet synchronous motor, p is the number of magnetic poles of the motor, θ0 represents the phase difference between the m times frequency torque ripple and the rotor position, ω is the rotor electric 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 the current based on the superimposed current command comprises a closed-loop control process based on a fundamental wave current command and a closed-loop control process based on a compensation current command.

[0024] The closed-loop control process based on the fundamental wave current command specifically comprises the following steps: sampling the motor current and the rotor position in real time, transforming into a dq rotor coordinate system and a corresponding harmonic coordinate system to obtain current feedback values, and performing closed-loop control of the current in the dq rotor coordinate system according to the fundamental wave current command.

[0025] The closed-loop control process based on the compensation current command specifically comprises the following steps: for the m times frequency torque ripple, performing closed-loop control of the compensation current in m-1 and m+1 rotating coordinate systems, wherein,

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

[0027] idm1*=iqc / 2·sin(θ0+π / 2)

[0028] iqm1*=iqc / 2·cos(θ0+π / 2)

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

[0030] idm2*=-iqc / 2·sin(θ0+π / 2)

[0031] iqm2*=iqc / 2·cos(θ0+π / 2)

[0032] wherein idm1* and iqm1* are respectively the d-axis and q-axis current commands in the m-1 rotating coordinate system, idm2* and iqm2* are respectively the d-axis and q-axis current commands in the m+1 rotating coordinate system, and iqc is the q-axis compensation current command.

[0033] 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, and ic and the rotor electric angular position θ:

[0034]

[0035] wherein idm1 and iqm1 are respectively the d-axis and q-axis current feedback values in the m-1 rotating coordinate system, and idm2 and iqm2 are respectively the d-axis and q-axis current feedback values in the m+1 rotating coordinate system.

[0036] After the current closed-loop control, the respective voltage command values are obtained, the voltage command values are converted into the voltage command values in the alpha-beta two-phase stationary coordinate system through the respective coordinate conversion, and then are converted into the control voltage command values ua, ub and uc in the three-phase coordinate system to control the six switches in the inverter circuit of the motor controller based on the SPWM or SVPWM algorithm, so that appropriate voltage is output to the motor to complete the closed-loop control of the current.

[0037] A system for weakening torque ripple of a permanent magnet synchronous motor for implementing the method described above, the system comprising:

[0038] A drag test platform, the drag test platform comprising a host computer, a motor to be tested, a motor controller to be tested, a torque meter, a dynamometer and a dynamometer controller, the whole platform being under the control of the host computer;

[0039] A superimposed current command acquisition module for executing steps 2) to 7) of the method for weakening torque ripple of a 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 command of the motor, repeatedly calls the superimposed current command acquisition module to obtain the superimposed current command, and the motor controller to be tested obtains a series of superimposed current commands at different speeds and torques and saves them into the non-volatile memory of the motor controller to be tested;

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

[0042] Compared with the prior art, the current command value for weakening the torque ripple of the motor can be obtained simply and quickly, and the torque ripple of the motor can be effectively weakened. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 A flowchart of the method of the present application;

[0044] Figure 2 A structure schematic diagram of a drag test platform in an embodiment;

[0045] Figure 3 A block diagram of a motor current control system in an embodiment. DETAILED DESCRIPTION

[0046] The application will be described in detail below in conjunction with the drawings and specific embodiments. The embodiments are implemented on the premise of the technical solutions of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following embodiments.

[0047] Embodiment 1

[0048] The embodiment provides a method for weakening torque ripple of a permanent magnet synchronous motor, as shown in the formula (1), comprising the following steps: Figure 1

[0049] Step 1) A test platform for drag test of the motor to be tested and a dynamometer is built, as shown in the formula (1), and the test platform for drag test comprises a host computer, the motor to be tested, a motor controller of the motor to be tested, a torque meter, the dynamometer and a dynamometer controller, and the whole platform is controlled by the host computer. Figure 2

[0050] Step 2) The host computer controls the dynamometer to perform smooth speed closed-loop control through CAN communication, so that the speed of the test platform for drag test is stabilized at n (rpm, revolutions per minute), and if the speed fluctuation is large, 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, and the torque instruction of the motor to be tested is converted into corresponding fundamental current instructions id1 and iq1 in the motor controller of the motor to be tested, wherein id1 and iq1 respectively represent the fundamental current instructions of the d-axis and the q-axis. The position information of the rotor of the motor to be tested is transmitted to the host computer in real time through CAN communication based on the fundamental current instructions for closed-loop control of the current of the motor to be tested.

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

[0053] Step 5) The host computer comprehensively analyzes the torque ripple and the position information of the rotor of the motor to be tested to obtain a trigonometric function relationship between them.

[0054] For m times frequency torque ripple, the trigonometric function relationship between the torque ripple and the position information of the rotor of the motor to be tested is as follows:

[0055] Te=Tm·sin(mωt+θ0) (1)

[0056] Wherein, Te represents the torque variable to be analyzed, Tm represents the m times frequency torque ripple, θ0 represents the phase difference between the m times frequency torque ripple and the rotor position, ω is the electrical angular velocity of the rotor, 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 under test processes the trigonometric function relationship (1) obtained in step 5) with respect to the torque pulsation component to be expected to be weakened, to obtain a compensation current command for weakening the torque pulsation:

[0058] idc = 0 (2)

[0059] iqc = iqm sin (mωt + θ0 + π) (3)

[0060] wherein iqm = Tm / (1.5pΨ f ), Ψ f is the permanent magnet flux linkage 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 under test superimposes the compensation current command obtained in step 6) and the fundamental current command for torque control in step 3) to obtain a superimposed current command:

[0062] id = id1 + idc (4)

[0063] iq = iq1 + iqc (5)

[0064] The command can ensure that the motor under test outputs the expected torque while having a small torque pulsation, i.e., the torque pulsation is weakened.

[0065] Step 8) The host computer changes the speed and torque command of the motor, and repeatedly executes steps 2) to 7) above, so that the motor controller under test obtains a series of superimposed current commands at different speeds and torques, and saves them to the non-volatile memory of the motor controller under test.

[0066] Step 9) In actual application scenarios where it is necessary to reduce the torque pulsation of the motor, the motor controller under test takes out the corresponding superimposed current command at the current speed and torque from the non-volatile memory, and performs closed-loop control of the current based on the superimposed current command.

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

[0068] The closed-loop control process based on the fundamental current command is specifically: real-time sampling of the motor current and rotor position, transformation into the dq rotor coordinate system and the corresponding harmonic coordinate system (the harmonic coordinate system for m times frequency torque pulsation refers to the m-1 and m+1 rotating coordinate systems), to obtain current feedback values, and closed-loop control of the current (id1 and iq1) according to the values 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 times frequency torque ripple, the closed-loop control of the compensation currents (idc and iqc) is performed in the m-1 order and m+1 order rotating coordinate systems, and the current closed-loop control with high performance is achieved by using the control strategy shown in the block diagram, so as to ultimately achieve the purpose of effectively weakening the motor torque ripple. Figure 3 The control strategy shown in the block diagram can achieve high-performance current closed-loop control, thereby ultimately achieving the purpose of effectively weakening the motor torque ripple. Among them,

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

[0072] idm1*=iqc / 2·sin(θ0+π / 2) (7)

[0073] iqm1*=iqc / 2·cos(θ0+π / 2) (8)

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

[0075] idm2*=-iqc / 2·sin(θ0+π / 2) (9)

[0076] iqm2*=iqc / 2·cos(θ0+π / 2) (10)

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

[0078] The current feedback value is as shown in Figure 3 The feedback values of the m-1 order and m+1 order rotating coordinate system currents are calculated based on the feedback three-phase current values ia, ib, ic and the rotor electric angle position θ:

[0079]

[0080]

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

[0082] After current closed-loop control, each phase obtains its own voltage command value. After undergoing its own coordinate transformation, the voltage command values ​​in the αβ two-phase stationary coordinate system are obtained. Then, the values ​​are 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, thus completing the current closed-loop control.

[0083] This embodiment is... Figure 3 The functions of each module are further explained below:

[0084] The host computer provides torque commands via CAN communication. Based on the torque command value and the current speed value of the motor, it looks up a table (the values ​​in the table are obtained through extensive testing on the test bench and calculations using formulas (1)-(3)) to determine the current command values ​​id1*, iq1* and the iqc and θ0 values ​​corresponding to the pulsating torque components. The PI current controller 1 performs current closed-loop regulation based on the difference between the command values ​​id1 and iq1 and the feedback value in the conventional control strategy (i.e., current closed-loop control without considering torque pulsation), and outputs voltage control quantities ud1 and uq1. The 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 the values ​​of iqc and θ0 and formulas (7)-(10) 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 quantity. The coordinate transformation 2 module converts the harmonic voltage control quantity 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 quantity. The coordinate transformation 3 module converts the harmonic voltage control quantity 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 adder in the above-mentioned three sets of voltage command values ​​in the αβ two-phase stationary coordinate system to obtain the total voltage command value in the αβ coordinate system. These values ​​are then processed... Figure 3 After the 2 / 3 transformation module, the voltage command values ​​ua, ub, and uc in the three-phase coordinate system are obtained. Then, through the commonly used SPWM or SVPWM algorithm, the six switches in the inverter circuit of the motor controller can be controlled to output the appropriate voltage to the motor and complete the closed-loop control of all currents.

[0087] Figure 3The current transformation unit in the figure transforms three sets of current values in the dq rotating coordinate system, m-1 order rotating coordinate system and m+1 order rotating coordinate system respectively by using three-phase current values obtained by the current sensor and rotor position values provided by the position sensor, and then passes through low-pass filters to obtain three sets of current values (id1 and iq1, idm1 and iqm1, idm2 and iqm2) for feedback. The motor speed calculation module in the figure can obtain speed information of the rotor by differentiating the rotor position, and is used for look-up table of current command and closed-loop control of speed.

[0088] Embodiment 2

[0089] The embodiment provides a system for weakening torque ripple of a permanent magnet synchronous motor, which is used for implementing the method in Embodiment 1, and the system comprises the following.

[0090] A drag test platform is provided, the drag test platform comprises a host computer, a to-be-tested motor, a to-be-tested motor controller, a torque meter, a dynamometer and a dynamometer controller, and the whole platform is controlled by the host computer.

[0091] A superimposed current command acquisition module is configured to execute steps 2) to 7) of the method for weakening torque ripple of a permanent magnet synchronous motor to acquire a superimposed current command.

[0092] A superimposed current command storage module is configured to change the speed and torque command of the motor, repeatedly call the superimposed current command acquisition module to acquire the superimposed current command, and save a series of superimposed current commands at different speeds and torques to a non-volatile memory of the to-be-tested motor controller.

[0093] A control module is configured to, in an actual application occasion in which it is required to reduce torque ripple of the motor, take out the corresponding superimposed current command at the current speed and torque from the non-volatile memory by the to-be-tested motor controller, and perform closed-loop control of 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 modules can refer to the corresponding process in the foregoing method embodiments, which will not be described herein.

[0095] The foregoing describes in detail the preferred embodiments of the application. It should be understood that those skilled in the art can make many modifications and changes to the application without creative labor based on the concept of the application. Therefore, any technical solution obtained by logical analysis, reasoning or limited experiments by those skilled in the art based on the prior art and the concept of the application should be within the protection scope defined by the claims.

Claims

1. A method of weakening torque ripple of a permanent magnet synchronous motor, characterized by, The method comprises the following steps: Step 1) build a test platform for the motor to be tested and the dynamometer, the test platform comprising a host computer, the motor to be tested, a motor controller of the motor to be tested, a torque meter, a dynamometer and a dynamometer controller, the whole platform being controlled by the host computer; Step 2) the host computer controls the dynamometer to perform smooth speed closed-loop control, so that the speed of the test platform is stable; Step 3) the host computer controls the motor to be tested to perform torque closed-loop control, the torque instruction of the motor to be tested being converted into corresponding fundamental current instruction in the motor controller of the motor to be tested, current closed-loop control being performed on the motor to be tested based on the fundamental current instruction, and the position information of the rotor of the motor to be tested being transmitted to the host computer in real time; Step 4) after the test platform enters the speed stable state, the torque pulsation of the motor to be tested is measured by the torque meter and transmitted to the host computer in real time; Step 5) the host computer comprehensively analyzes the torque pulsation and the position information of the rotor of the motor to be tested to obtain a trigonometric function relationship therebetween; Step 6) the motor controller of the motor to be tested processes the trigonometric function relationship obtained in step 5) to obtain a compensation current instruction for weakening the torque pulsation; Step 7) the motor controller of the motor to be tested superimposes the compensation current instruction obtained in step 6) and the fundamental current instruction for torque control in step 3) to obtain a superimposed current instruction; Step 8) the host computer changes the speed and torque instruction of the motor, and repeats steps 2) to 7) to obtain a series of superimposed current instructions at different speeds and torques, and save the superimposed current instructions to the non-volatile memory of the motor controller of the motor to be tested; Step 9) in an actual application scenario where the torque pulsation of the motor needs to be reduced, the motor controller of the motor to be tested takes out the corresponding superimposed current instruction at the current speed and torque from the non-volatile memory, and performs current closed-loop control based on the superimposed current instruction; the current closed-loop control based on the superimposed current instruction comprises a closed-loop control process based on the fundamental current instruction and a closed-loop control process based on the compensation current instruction, and the closed-loop control process based on the compensation current instruction specifically comprises: for the torque pulsation of m times frequency, compensation current closed-loop control is performed in m-1 and m+1 rotating coordinate systems.

2. The method of claim 1, wherein, The motor controller of the motor to be tested and the dynamometer controller communicate with the host computer through a CAN bus.

3. The method of claim 1, wherein, The torque meter is connected to the host computer through a data acquisition cable and transmits data to a data acquisition card of the host computer.

4. The method of claim 1, wherein, In step 2), if the speed fluctuation exceeds a preset range, a flywheel is added to stabilize the speed.

5. The method of claim 1, wherein, In the step 5), for the m times frequency torque pulsation, the trigonometric function relationship between the torque pulsation and the position information of the rotor of the motor to be tested is: Wherein, Te represents the pulsating torque variable to be analyzed, Tm represents the m times frequency torque pulsation, represents the phase difference between the m times frequency torque pulsation and the rotor position, is the rotor electric angular velocity, n is the rotating speed, and p is the pole pair number of the motor.

6. The method of claim 1, wherein, In the step 6), the compensation current command for m times frequency torque pulsation is With wherein, , is a permanent magnet flux linkage value of the permanent magnet synchronous motor, p is a number of magnetic pole pairs of the motor, Tm represents an m times frequency torque pulsation amount, represents a phase difference between the m times frequency torque pulsation and the rotor position, is a rotor electric angular velocity, is a d-axis compensation current command, is a q-axis compensation current command.

7. The method of claim 1, wherein, The closed-loop control process based on the fundamental current instruction specifically comprises: real-time sampling of the motor current and the rotor position, transformation into dq rotor coordinate system and corresponding harmonic coordinate system to obtain current feedback value, and closed-loop control of current in the dq rotor coordinate system according to the fundamental current instruction.

8. The method of claim 1, wherein, In the closed-loop control process based on the compensation current instruction, The current instruction value in the m-1 rotating coordinate system is: ， The current instruction value in the m+1 rotating coordinate system is: ， wherein, , are d-axis and q-axis current commands in an m-1th rotational coordinate system, respectively, , are d-axis and q-axis current commands in an m+1th rotational coordinate system, respectively, is a q-axis compensation current command; Feedback-based three-phase current values , , and the rotor electrical angular position θ calculating feedback values of m-1 and m+1 rotational coordinate system currents: ， wherein, , are d-axis and q-axis current feedback values in the m-1th rotational coordinate system, respectively, , are d-axis and q-axis current feedback values in the m+1th rotational coordinate system, respectively; After current closed-loop control, the respective voltage command values are obtained, which are respectively converted through respective coordinate conversion to obtain αβ The voltage command values in the two-phase stationary coordinate system are converted to the three-phase coordinate system to obtain the control voltage command values ua 、 ub 、 uc Based on the SPWM or SVPWM algorithm, the six switches in the motor controller inverter circuit are controlled to output appropriate voltage to the motor to complete the current closed-loop control.

9. A system for weakening torque ripple of a permanent magnet synchronous motor for implementing the method of any one of claims 1-8, characterized by, The system comprises: The test platform comprises a host computer, a motor to be tested, a motor controller to be tested, a torque instrument, a dynamometer and a dynamometer controller, and the whole platform is controlled by the host computer; The superimposed current instruction acquisition module is configured to execute steps 2) to 7) of the method for weakening torque ripple of the permanent magnet synchronous motor to obtain a superimposed current instruction; The superimposed current instruction storage module is configured to change the speed and torque instruction of the motor by the host computer, repeatedly call the superimposed current instruction acquisition module to obtain the superimposed current instruction, and obtain a series of superimposed current instructions at different speeds and torques by the motor controller to be tested and save the superimposed current instructions in a non-volatile memory of the motor controller to be tested; The control module is configured to take out the corresponding superimposed current instruction at the current speed and torque from the non-volatile memory by the motor controller to be tested in an actual application occasion in which the motor torque ripple needs to be reduced, and perform closed-loop control of the current based on the superimposed current instruction.

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