Torque fluctuation suppression method and control device based on permanent magnet flux linkage harmonic identification

Abstract

The application discloses a torque fluctuation suppression method and control device based on permanent magnet flux linkage harmonic identification, the method comprises an online identification process and a torque fluctuation suppression process, and is used for suppressing torque fluctuation of an interior permanent magnet synchronous motor; the online identification process comprises a permanent magnet flux linkage harmonic identification step, a dead zone voltage harmonic compensation step and an extracted harmonic component step; the torque fluctuation suppression process comprises the following steps: obtaining 5th and 7th permanent magnet flux linkage harmonics by inputting a pre-identified flux linkage harmonic lookup table, predicting torque fluctuation according to a magnetic co-energy model, outputting optimal stator current reference values, obtaining 6th harmonic voltage for suppressing torque fluctuation, and superimposing a fundamental component and a harmonic component and then driving the motor by using an SVPWM strategy.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of permanent magnet synchronous motor control, and particularly relates to a permanent magnet synchronous motor torque fluctuation suppression method and control device based on permanent magnet flux linkage harmonic online identification. BACKGROUND

[0002] Permanent magnet synchronous motors have the advantages of compact structure, high power density, high air gap flux, and high torque inertia ratio, and are widely used in high-precision AC servo, electric vehicle driving, wind power generation, and other systems. In actual applications, due to design compromises and manufacturing tolerances, the permanent magnet flux linkage of the motor is not sinusoidal, and there are permanent magnet flux linkage harmonics. When the motor is working, the permanent magnet flux linkage harmonics and the current interact to produce torque harmonics. Torque fluctuations will cause vibration and noise in the motor system, and even damage the mechanical structure of the rotating shaft, which has an adverse effect on high-precision applications, and in the field of electric vehicles, it also affects the passenger's ride experience.

[0003] Gu Xin et al. proposed a harmonic current suppression method, a closed-loop harmonic current detection system extracts the harmonic current, and finally adopts a deadbeat current prediction control strategy to generate a compensation voltage for suppressing the harmonic current (Permanent Magnet Synchronous Motor Harmonic Current Suppression Strategy Based on Deadbeat Current Prediction Control, Transactions of Electrical Engineering Technology, 2022: Vol. 37, No. 24). Heonyoung Kim et al. proposed a sinusoidal current control strategy based on harmonic voltage injection, and also proposed an offline scheme and an online scheme for identifying permanent magnet flux linkage harmonics (A Sinusoidal Current Control Strategy Based on Harmonic Voltage Injection for Harmonic Loss Reduction of PMSMs With Non-Sinusoidal Back-EMF, IEEE TRANS-ACTIONS ON INDUSTRY APPLICATIONS, 2020: VOL. 56, NO. 6).

[0004] In order to suppress the motor torque fluctuation caused by the non-sinusoidal permanent magnet flux linkage harmonics, a torque harmonic is generated by injecting a current harmonic component into the stator to offset the torque fluctuation caused by the permanent magnet flux linkage harmonics. The injected current harmonic reference value is related to the parameters of the permanent magnet flux linkage harmonics. If the parameters of the permanent magnet flux linkage harmonics are inaccurate, the injected current harmonics will also be inaccurate, and the purpose of suppressing torque fluctuation cannot be achieved. As a nonlinear function, the permanent magnet flux linkage harmonics will change with the load change of the motor. At present, the method for obtaining the permanent magnet flux linkage harmonics is calculated by offline inverse calculation, without considering the influence of motor load change on the flux linkage harmonics. Summary of the Invention

[0005] The present invention aims to provide a method and control device for suppressing torque fluctuations in a permanent magnet synchronous motor based on online identification of permanent magnet flux harmonics, for suppressing torque fluctuations in a built-in permanent magnet synchronous motor. To address the problem of torque fluctuations caused by flux harmonics in the permanent magnets of a permanent magnet synchronous motor, and considering that the flux harmonics of the permanent magnets vary with motor load, the voltage equations in the 5th and 7th order synchronous rotating coordinate systems containing inverter dead-zone terms are used to identify the flux harmonics of the permanent magnets. The identified flux harmonics are used to predict torque fluctuations and calculate current harmonic reference values ​​used to suppress torque fluctuations, thereby improving the stability of the system's torque output and providing strong robustness.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for suppressing torque fluctuations of a permanent magnet synchronous motor based on online identification of permanent magnet flux harmonics, the method comprising an online identification process and a torque fluctuation suppression process;

[0008] The online identification process includes permanent magnet flux harmonic identification step, dead zone voltage harmonic compensation step and harmonic component extraction step;

[0009] Step 1: Identify the flux harmonics: Sample and obtain the d-axis and q-axis current feedback values ​​i of the permanent magnet synchronous motor d 、i q , electrical angle θ, electrical angular velocity ω e Extract the 5th and 7th current harmonics based on the sampled stator current to obtain the d-axis and q-axis stator voltages and stator currents; wherein the d-axis and q-axis current feedback values ​​contain the fundamental component;

[0010] Step 2: Dead zone voltage harmonic compensation: perform inverter nonlinear compensation based on the voltage error generated in the inverter dead zone to obtain the dead zone compensation voltage;

[0011] Step 3: Use a low-pass filter (LPF) to extract the 5th and 7th current harmonics and the DC component in the synchronous rotating coordinate system;

[0012] Step 4: Use a proportional-integral (PI) controller to suppress the 5th and 7th current harmonics to obtain the suppressed 5th and 7th voltage harmonics;

[0013] Step 5: Superimpose the fundamental component obtained in step 1, the dead zone compensation voltage obtained in step 2, and the suppressed 5th and 7th voltage harmonics obtained in step 4 to obtain the dq axis voltage, and use the SVPWM (space vector pulse width modulation) strategy to drive the motor;

[0014] The online identification process further includes calculating the permanent magnet flux harmonic amplitude based on the suppressed 5th and 7th voltage harmonics obtained in step 4, and calculating the fundamental current feedback value i d 、i q , and flux harmonic amplitudes Ψ5 and Ψ7 to establish a pre-identified flux harmonic lookup table.

[0015] The torque fluctuation suppression process includes:

[0016] Step 1: Sampling to obtain the d-axis and q-axis current feedback values ​​i of the permanent magnet synchronous motor d 、i q , electrical angle θ, electrical angular velocity ω e ; Among them, the d and q axis current feedback values ​​contain fundamental components;

[0017] Step (2): Input the sampled feedback value into the pre-identified flux harmonic lookup table generated by the online identification process to obtain the 5th and 7th permanent magnet flux harmonics; predict torque fluctuations based on the magnetic common energy model, output the optimal stator current reference value to suppress torque, and use a proportional resonant (PR) controller to control the actual current to follow the current reference value to obtain the 6th harmonic voltage used to suppress torque fluctuations;

[0018] Step (3): The fundamental component obtained in step (1) and the fundamental current i in step (2) are d0 、i q0 u generated by the PI controller d0 、u q0 The superimposed dq axis voltage is obtained by superimposing the 6th harmonic voltage for suppressing torque fluctuation obtained in step (2), and the motor is driven using the SVPWM (space vector pulse width modulation) strategy.

[0019] Furthermore, step 1 in the online identification process specifically includes:

[0020] S11: Use the current sensor and encoder to perform sampling measurement and calculate the stator voltage, stator current, electrical angle, and electrical angular velocity of the permanent magnet synchronous motor;

[0021] S12: Extract the 5th and 7th current harmonics i in the synchronous rotating coordinate system d5 、i q5 、i d7 、i q7 , establish the voltage equation in the 5, 7 synchronous rotating coordinate system including the inverter dead zone term, the equation is:

[0022]

[0023]

[0024] Where, are the d-axis and q-axis stator voltages after the 5th and 7th voltage harmonics are transformed into 5th and 7th synchronous rotating coordinates respectively; R is the stator resistance of the motor; i d5 、i q5 、i d7 、i q7 are the d-axis and q-axis stator currents after the 5th and 7th current harmonics undergo 5th and 7th synchronous rotating coordinate transformations, respectively; L d , L q is the d and q axis inductance, ψ d5 , ψ q5 , ψ d7 , ψ q5 The d and q axis magnetic fluxes are the 5th and 7th magnetic flux harmonics, ω e is the electrical angular velocity in the synchronous rotating coordinate system; V dead_d5 、V dead_q5 、 V dead_d7 、 V dead_q7 are the 5th and 7th d-axis and q-axis voltage components generated in the inverter dead zone, which are preset parameter values.

[0025] Furthermore, during the online identification process, the 5th and 7th voltage harmonics generated by the inverter dead zone are compensated in step 2:

[0026] The voltage equation V in step 1 after dead zone compensation dead_d5 、V dead_q5 、V dead_d7 、V dead_q7 is eliminated and becomes the following form,

[0027]

[0028] Furthermore, the permanent magnet flux harmonic amplitude is calculated based on the suppressed 5th and 7th voltage harmonics obtained in step 4, specifically including:

[0029] After step 4, i d5 =0, i q5 =0, i d7 =0, i q7 = 0, the voltage equation in step 2 can be rewritten as

[0030]

[0031]

[0032] In the formula, the time derivative of the magnetic flux harmonic is very small and can be ignored, so the voltage equation can be transformed into

[0033]

[0034]

[0035] Calculation of flux harmonics

[0036]

[0037]

[0038]

[0039] Where Ψ5 and Ψ7 are the 5th and 7th harmonic amplitudes of permanent magnet flux linkage, respectively.

[0040] The present invention also discloses a control device for a permanent magnet synchronous motor, wherein the permanent magnet synchronous motor has a rotor and a three-phase winding. The control device includes a sensing module and a control circuit. The sensing module is used to obtain d-axis and q-axis current feedback values, stator voltage, stator current, electrical angle, and electrical angular velocity of the permanent magnet synchronous motor. The control circuit includes an online identification module and a fluctuation suppression module.

[0041] The online identification module is used to extract the 5th and 7th current harmonics based on the stator current sampled by the sensor module, and calculate the d and q axis stator voltages; perform inverter nonlinear compensation on the voltage error generated in the inverter dead zone to obtain the compensated d and q axis harmonic voltages; then use a low-pass filter to extract the 5th and 7th current harmonics, and use a proportional-integral controller to suppress the 5th and 7th current harmonics to obtain the suppressed 5th and 7th voltage harmonics; superimpose the fundamental component of the d and q axis current feedback values ​​collected by the sensor module, the dead zone compensation voltage and the obtained suppressed 5th and 7th voltage harmonics to obtain the d and q axis voltages, and use the SVPWM (space vector pulse width modulation) strategy to drive the motor;

[0042] The torque fluctuation suppression module uses the d-axis and q-axis current feedback values, electrical angles and electrical angular velocity inputs obtained by the sensor module to pre-identify the flux harmonic lookup table and obtain the 5th and 7th permanent magnet flux harmonics; predicts the torque fluctuation based on the magnetic common energy model, designs the optimal stator current reference value to suppress the torque, and uses the proportional resonance (PR) controller to control the actual current to follow the current reference value to obtain the 6th harmonic voltage after the torque is suppressed; the fundamental component of the d-axis and q-axis current feedback values ​​obtained by the sensor module and the fundamental current i d0 、i q0 u generated by the PI controller d0 、u q0 The dq axis voltage is obtained by superimposing the 6th harmonic voltage that suppresses torque fluctuation, and the SVPWM strategy is used to drive the motor.

[0043] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0044] The present invention addresses the issue of permanent magnet flux harmonics varying with motor load during the process of suppressing torque fluctuations in a built-in permanent magnet synchronous motor with a non-sinusoidal permanent magnet flux. The method uses voltage equations in 5th and 7th order synchronous rotating coordinate systems containing inverter dead-zone terms to identify permanent magnet flux harmonics. The identified permanent magnet flux harmonics are then used to predict torque fluctuations and calculate current harmonics used to suppress torque fluctuations. Compared to other methods for offline measurement of permanent magnet flux harmonics, online identification of permanent magnet flux harmonics can adapt to load changes, and the calculated reference value of current harmonics used to suppress torque fluctuations is more accurate. This method, based on an analysis of torque fluctuations caused by permanent magnet flux harmonics, can improve the stability of torque output and exhibit strong robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A block diagram of the online identification process of the permanent magnet flux harmonics online identification method for suppressing torque fluctuations of a permanent magnet synchronous motor according to the present invention;

[0046] Figure 2 A block diagram of the fluctuation suppression process in the method for suppressing torque fluctuations of a permanent magnet synchronous motor by online identification of permanent magnet flux harmonics according to the present invention;

[0047] Figure 3 A flow chart of an online identification process in the method for suppressing torque fluctuations of a permanent magnet synchronous motor by online identification of permanent magnet flux harmonics;

[0048] Figure 4 The present invention is a flow chart of the fluctuation suppression process in the method for suppressing torque fluctuation of a permanent magnet synchronous motor by online identification of permanent magnet flux harmonics. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions, beneficial effects and significant improvements of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the drawings provided in the examples of the present invention. Obviously, all the described embodiments are only partial embodiments of the present invention, rather than all embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0050] A method for suppressing torque fluctuations of a permanent magnet synchronous motor by online identification of permanent magnet flux harmonics is disclosed. The method includes an online identification process and a fluctuation suppression process.

[0051] Among them, such as Figure 1 , Figure 3As shown, the online identification process includes a permanent magnet flux linkage harmonic identification step, a dead zone voltage harmonic compensation step, and a step of extracting harmonic components using a PI controller.

[0052] Step one, using the 5, 7th synchronous rotating coordinate system voltage equation containing inverter dead zone items to identify the permanent magnet flux linkage harmonic

[0053] S11: Use current sensors and encoders for sampling measurement to obtain permanent magnet synchronous motor stator current, electrical angle, and electrical angular velocity, etc.

[0054] The motor stator three-phase winding is usually connected in star, and under ideal conditions, the winding is symmetrically distributed, so the motor back electromotive force waveform is half-wave symmetric, that is, the winding back electromotive force waveform does not contain even harmonics, and the three-phase n-th harmonic currents differ by 2nπ / 3. Therefore, the stator harmonic current can be expressed as:

[0055] Where i a i b i c is the three-phase current of the permanent magnet synchronous motor stator, I1, I5, I7 are the amplitudes of the fundamental component, 5th harmonic component, and 7th harmonic component of the stator three-phase stator current, and θ1, θ5, θ7 are the initial phase angles of the fundamental component, 5th harmonic component, and 7th harmonic component of the stator three-phase stator current.

[0056] The obtained stator harmonic current data is converted according to the principle of abc / dq coordinate transformation to obtain the d, q axis stator currents; the obtained motor electrical angle θ is differentiated to obtain the electrical angular velocity ω e .

[0057] S12: Extract 5, 7th current harmonics i d5 , i q5 , i d7 , i q7 in the synchronous rotating coordinate system, establish the 5, 7th synchronous rotating coordinate system voltage equation containing the inverter dead zone item, and the equation is:

[0058]

[0059]

[0060] In the formula, are the d, q axis stator voltages of the 5, 7th voltage harmonics after 5, 7th synchronous rotating coordinate transformation; R is the stator resistance of the motor; i d5 , i q5 , i d7 , i q7are the d-axis and q-axis stator currents after the 5th and 7th current harmonics undergo 5th and 7th synchronous rotating coordinate transformations, respectively; L d , L q is the d and q axis inductance, ψ d5 , ψ q5 , ψ d7 , ψ q5 The d and q axis magnetic fluxes are the 5th and 7th magnetic flux harmonics, ω e is the electrical angular velocity in the synchronous rotating coordinate system; V dead_d5 、V dead_q5 、V dead_d7 、V dead_q7 are the 5th and 7th d-axis and q-axis voltage components generated in the inverter dead zone, which are preset parameter values.

[0061] Step 2: Dead zone voltage harmonic compensation

[0062] Calculate the three-phase voltage error △U caused by dead time a , △U b , △U c , the formula is:

[0063]

[0064] Among them, i a 、i b 、i c For the three-phase current extracted by the current sensor, the sign function is defined as:

[0065]

[0066] The voltage error △U caused by the inverter dead zone a △U b △U c In the 5th and 7th synchronous rotation coordinate systems, it is expressed as V dead_d5 、V dead_q5 、V dead_d7 、V dead_q7 ;

[0067] Inject △U into the fundamental voltage d_err △U q_err To eliminate the 5th and 7th voltage harmonics V generated by the inverter dead zone dead_d5 、V dead_q5 、V dead_d7 、V dead_q7 ;

[0068]

[0069] The voltage equation V in step 1 after dead zone compensation dead_d5 、V dead_q5 、V dead_d7、V dead_q7 is eliminated and becomes the following form:

[0070]

[0071]

[0072] Step 3: Use a low-pass filter (LPF) to extract the 5th and 7th current harmonics i in a synchronous rotating coordinate system. d5 、i q5 、i d7 、i q7 ;

[0073] The multiple synchronous rotation d, q coordinate transformation method is used to extract the harmonic components.

[0074] The transformation matrix for transforming the abc coordinate system into the synchronous rotating coordinate system corresponding to the 5th and 7th harmonics is:

[0075]

[0076]

[0077] After transformation, the expression of the motor stator current in the 5th and 7th synchronous rotating coordinate systems can be obtained as follows:

[0078]

[0079]

[0080] Among them, I d5h I q5h I d7h I q7h It is the representation of the three-phase current in the 5th and 7th times synchronous rotating coordinate system.

[0081] From the above formula, we can see that in the synchronously rotating coordinate system corresponding to the 5th harmonic, the 5th harmonic component is a DC quantity, and the fundamental and other harmonic components are AC components. In the synchronously rotating coordinate system corresponding to the 7th harmonic, the 7th harmonic component is a DC quantity, and the fundamental and other harmonic components are AC components.

[0082] The DC component in the 5th and 7th synchronous rotating coordinate systems is obtained by filtering with a low-pass filter.

[0083]

[0084]

[0085] Step 4: Use the proportional integral (PI) controller to control the 5th and 7th current harmonics and suppress them to 0, so that i d5=0, i q5 =0, i d7 =0, i q7 =0, the 5th and 7th voltage harmonics output by the controller are u d5 、u q5 、u d7 、u q7 ;

[0086] After step 4, i d5 =0, i q5 =0, i d7 =0, i q7 = 0, the voltage equations (6) and (7) in step 2 can be rewritten as

[0087]

[0088]

[0089] The fundamental component of the sampled d-axis and q-axis current feedback values, the voltage harmonics used to compensate for the inverter dead zone in step 2, and the voltage harmonics obtained in step 4 to control the current harmonics are superimposed to obtain the d-axis and q-axis voltages, and the SVPWM (space vector pulse width modulation) strategy is used to drive the motor.

[0090] Step 5: Use the deformed voltage equation (14) and equation (15) to calculate the permanent magnet flux harmonic amplitudes Ψ5 and Ψ7, specifically including:

[0091] In the formula, the time derivative of the magnetic flux harmonic is very small and can be ignored, so the voltage equation can be transformed into

[0092]

[0093]

[0094] Substitute Equation 16 and Equation 17 into the following formula to calculate the 5th and 7th permanent magnet flux harmonic amplitudes Ψ5 and Ψ7:

[0095]

[0096]

[0097]

[0098] Step 6: Generate a pre-identified flux harmonic lookup table, where the input of the lookup table is the fundamental current feedback value i d0 、i q0 The output is the 5th and 7th permanent magnet flux harmonic amplitudes Ψ5 and Ψ7.

[0099] like Figure 2 、 Figure 4 The torque fluctuation suppression process specifically includes:

[0100] Step (I): Using the method of step S11 in the online identification process, re-collect the d, q-axis current feedback values i d0 , i q0 , the electrical angle θ, and the electrical angular velocity ω e ;

[0101] Step (II): Input the feedback values obtained by sampling into the pre-identified flux harmonic lookup table generated in step six, extract the 6th current harmonics i d6 and i q6 ; predict the torque fluctuation according to the magnetic co-energy model, and design the optimal stator current reference value to suppress torque, and use a proportional resonant (PR) controller to control the actual current to follow the current reference value

[0102] Magnetic co-energy model:

[0103] where t e is the total torque generated by the permanent magnet synchronous motor, including the DC component and the harmonic component, L dq = diag{L d , L q} is the dq-axis inductance matrix, ψ dq = [ψ d ψ q ] T and i dq = [i d i q ] T are the dq-axis permanent magnet flux linkage and current vectors, t cog is the cogging torque, K P = 3P / 2 and P is the number of pole pairs, and "×" is the cross product defined as [ab] × [cd] T = ad-bc. Here, the harmonics in inductance and cogging torque are ignored. According to the magnetic co-energy model, torque harmonics depend on the harmonics of the permanent magnet flux linkage and the stator current.

[0104] In order to model the torque harmonics of the permanent magnet synchronous motor PMSM, the permanent magnet flux linkage ψ dq and the stator current i dq are represented in the form of Fourier series:

[0105]

[0106]

[0107]

[0108] The above parameters are defined as follows:

[0109] 1)Ψ0 is the average permanent magnet flux on the d-axis, ψ d6 , ψ q6 is the 6th harmonic of permanent magnet flux linkage of d and q axes; d6 and Ψ q6 is the amplitude of the 6th harmonic component of the dq axis magnetic flux;

[0110] 2)I d0 and I q0 is the average value of dq axis current; i d6 and i q6 is the 6th harmonic current of dq axis; I d6 and I q6 is the amplitude of the sixth harmonic component of the dq axis stator current, φ d6 and φ q6 is the phase angle of the corresponding stator current harmonic;

[0111] Design the optimal stator current reference value To suppress the torque. And use the proportional resonance (PR) controller to control the actual current to follow the current reference value

[0112] The stator harmonic currents used to minimize torque ripple will result in additional motor losses, which are approximately proportional to the square of the harmonic current amplitude. Therefore, the second goal of stator current optimization design is to minimize the motor losses caused by stator harmonic currents, that is, to minimize the square of the harmonic current amplitude, as follows:

[0113]

[0114] The stator harmonic current amplitude can be obtained by solving the two objectives of minimizing torque harmonics and minimizing motor harmonic current losses. and phase angle

[0115]

[0116]

[0117]

[0118]

[0119] Among them L Δ =L d -L q

[0120] The implementation diagram of harmonic current injection is as follows: Figure 2 The dq-axis reference currents contain the direct current component for motor control and the harmonic component for torque ripple minimization in the torque command.

[0121] The dq-axis reference currents contain the direct current component for motor control and the harmonic component for torque ripple minimization in the torque command.

[0122] Two independent controllers are employed to control the actual current to follow the reference current: 1) a PI controller for direct current control; 2) a proportional resonant (PR) controller for harmonic current control.

[0123] The outputs of the PI and PR controllers are then added to form the dq-axis reference voltages, which are fed back to the voltage source inverter to achieve torque ripple minimization for motor drive.

[0124] The above embodiments are only used to illustrate the technical solutions of the present application, rather than limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced equivalently, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application. The non-essential improvements and adjustments or replacements made by those skilled in the art based on the content of the present application are within the scope of the present application.

Claims

1. A method for suppressing torque fluctuations based on permanent magnet flux harmonic identification, characterized in that: The method includes an online identification process and a torque fluctuation suppression process; The online identification process includes a permanent magnet flux harmonic identification step, a dead zone voltage harmonic compensation step, and a harmonic component extraction step; Step 1: Identify the flux harmonics: Sample and obtain the d-axis and q-axis current feedback values ​​i of the permanent magnet synchronous motor d 、i q , electrical angle θ, electrical angular velocity ω e Extract the 5th and 7th current harmonics based on the sampled stator current to obtain the d-axis and q-axis stator voltages and stator currents; wherein the d-axis and q-axis current feedback values ​​contain the fundamental component; Step 2: Dead zone voltage harmonic compensation: Perform inverter nonlinear compensation based on the voltage error generated in the inverter dead zone to obtain the dead zone compensation voltage; Step 3: Use a low-pass filter (LPF) to extract the 5th and 7th current harmonics and the DC component in the synchronous rotating coordinate system; Step 4: Use a proportional-integral (PI) controller to suppress the 5th and 7th current harmonics to obtain the suppressed 5th and 7th voltage harmonics; Step 5: Superimpose the fundamental component obtained in step 1, the dead zone compensation voltage obtained in step 2, and the suppressed 5th and 7th voltage harmonics obtained in step 4 to obtain the dq axis voltage, and use the SVPWM (space vector pulse width modulation) strategy to drive the motor; The online identification process further includes calculating the permanent magnet flux harmonic amplitude based on the suppressed 5th and 7th voltage harmonics obtained in step 4, and calculating the fundamental current feedback value i d0 、i q0 , flux harmonic amplitudes Ψ5 and Ψ7 to establish a pre-identified flux harmonic lookup table; The torque fluctuation suppression process includes: Step 1: Sampling to obtain the d-axis and q-axis current feedback values ​​i of the permanent magnet synchronous motor d 、i q , electrical angle θ, electrical angular velocity ω e ; Among them, the d and q axis current feedback values ​​contain fundamental components; Step (2): Input the sampled feedback value into the pre-identified flux harmonic lookup table generated by the online identification process to obtain the 5th and 7th permanent magnet flux harmonics; predict torque fluctuations based on the magnetic common energy model, output the optimal stator current reference value to suppress torque, and use a proportional resonant (PR) controller to control the actual current to follow the current reference value to obtain the 6th harmonic voltage used to suppress torque fluctuations; Step (3): The fundamental component obtained in step (1) and the fundamental current i obtained in step (2) are d0 、i q0 u generated by the PI controller d0 、u q0 The dq axis voltage is obtained by superimposing the 6th harmonic voltage obtained in step (2) to suppress torque fluctuations, and the SVPWM strategy is used to drive the motor.

2. The method for suppressing torque fluctuations based on permanent magnet flux harmonic identification according to claim 1, characterized in that: Step 1 in the online identification process specifically includes: S11: Use the current sensor and encoder to perform sampling measurement and calculate the stator voltage, stator current, electrical angle, and electrical angular velocity of the permanent magnet synchronous motor; S12: Extract the 5th and 7th current harmonics i in the synchronous rotating coordinate system d5 、i q5 、i d7 、i q7 , establish the voltage equation in the 5, 7 synchronous rotating coordinate system including the inverter dead zone term, the equation is: Where, are the d-axis and q-axis stator voltages after the 5th and 7th voltage harmonics undergo 5th and 7th synchronous rotating coordinate transformations, respectively; R is the stator resistance of the motor; i d5 、i q5 、i d7 、i q7 are the d-axis and q-axis stator currents after the 5th and 7th current harmonics are transformed by the 5th and 7th synchronous rotating coordinates respectively; L d , L q is the d and q axis inductance, ψ d5 , ψ q5 , ψ d7 , ψ q5 are the d-axis and q-axis flux of the 5th and 7th flux harmonics, ω e is the electrical angular velocity in the synchronously rotating coordinate system; V dead_d5 、 V dead_q5 、 V dead_d7 、 V dead_q7 are the 5th and 7th d-axis and q-axis voltage components generated in the inverter dead zone, which are preset parameter values.

3. The method for suppressing torque fluctuations based on permanent magnet flux harmonic identification according to claim 1, characterized in that: During the online identification process, in step 2, the 5th and 7th voltage harmonics generated by the inverter dead zone are compensated: The voltage equation V in step 1 after dead zone compensation dead_d5 、V dead_q5 、V dead_d7 、V dead_q7 is eliminated and becomes the following form, 4. The method for suppressing torque fluctuations based on permanent magnet flux harmonic identification according to claim 1, characterized in that: The permanent magnet flux harmonic amplitude is calculated based on the suppressed 5th and 7th voltage harmonics obtained in step 4, specifically including: After step 4, i d5 =0, i q5 =0, i d7 =0, i q7 = 0, the voltage equation in step 2 can be rewritten as In the formula, the time derivative of the magnetic flux harmonic is very small and can be ignored, so the voltage equation can be transformed into Calculate the flux harmonics: Where Ψ5 and Ψ7 are the 5th and 7th harmonic amplitudes of permanent magnet flux linkage, respectively.

5. A control device for a permanent magnet synchronous motor, the permanent magnet synchronous motor comprising a rotor and a three-phase winding, the control device comprising a sensor module and a control circuit; The sensing module is used to obtain the d-axis and q-axis current feedback values, stator voltage, stator current, electrical angle, and electrical angular velocity of the permanent magnet synchronous motor; the control circuit includes an online identification module and a fluctuation suppression module; The online identification module is used to extract the 5th and 7th current harmonics based on the stator current sampled by the sensor module, and calculate the d and q axis stator voltages; perform inverter nonlinear compensation on the voltage error generated in the inverter dead zone to obtain the compensated d and q axis harmonic voltages; then use a low-pass filter to extract the 5th and 7th current harmonics, and use a proportional-integral controller to suppress the 5th and 7th current harmonics to obtain the suppressed 5th and 7th voltage harmonics; superimpose the fundamental component of the d and q axis current feedback values ​​collected by the sensor module, the dead zone compensation voltage and the obtained suppressed 5th and 7th voltage harmonics to obtain the d and q axis voltages, and use the SVPWM (space vector pulse width modulation) strategy to drive the motor; The torque fluctuation suppression module uses the d-axis and q-axis current feedback values, electrical angles and electrical angular velocity inputs obtained by the sensor module to pre-identify the flux harmonic lookup table and obtain the 5th and 7th permanent magnet flux harmonics; predicts the torque fluctuation based on the magnetic common energy model, designs the optimal stator current reference value to suppress the torque, and uses the proportional resonant controller to control the actual current to follow the current reference value to obtain the 6th harmonic voltage after the torque is suppressed; the fundamental component of the d-axis and q-axis current feedback values ​​obtained by the sensor module and the fundamental current i d0 、i q0 u generated by the PI controller d0 、u q0 The dq axis voltage is obtained by superimposing the 6th harmonic voltage obtained to suppress torque fluctuation, and the motor is driven using the SVPWM strategy.

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