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

Abstract

The invention discloses a torque ripple suppression method and control device based on permanent magnet flux linkage harmonic identification, and the method comprises an online identification process and a torque ripple suppression process, and is used for suppressing the torque ripple of a built-in 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 a harmonic component extraction step; the torque ripple suppression process comprises the steps of inputting a pre-recognized flux linkage harmonic lookup table to obtain fifth and seventh permanent magnet flux linkage harmonics, predicting torque ripple according to a magnetic co-energy model, outputting an optimal stator current reference value, obtaining sixth harmonic voltage for suppressing the torque ripple, and driving the motor by using an SVPWM strategy after a fundamental component and a harmonic component are superposed.

Description

Technical Field

[0001] The present invention belongs to the field of permanent magnet synchronous motor control, and in particular relates to a method and a control device for suppressing torque fluctuations of a permanent magnet synchronous motor based on online identification of permanent magnet flux harmonics. Background Art

[0002] Permanent magnet synchronous motors have the advantages of compact structure, high power density, high air gap flux and high torque-to-inertia ratio. They are widely used in high-precision AC servo, electric vehicle drive, wind power generation and other systems. In practical applications, due to design compromises and manufacturing tolerances, the permanent magnet flux of the motor is not sinusoidal and there are permanent magnet flux harmonics. When the motor is working, the permanent magnet flux harmonics interact with the current to produce torque harmonics. Torque fluctuations will cause vibration and noise in the motor system, and may even damage mechanical structural parts such as the shaft, which has an adverse effect on applications in high-precision applications and will also affect the riding experience of passengers in the field of electric vehicles.

[0003] Gu Xin et al. proposed a harmonic current suppression method. The closed-loop harmonic current detection system extracts the harmonic current, and finally uses the deadbeat current prediction control strategy to generate a compensation voltage for suppressing the harmonic current (Harmonic Current Suppression Strategy of Permanent Magnet Synchronous Motor Based on Deadbeat Current Prediction Control, Transactions of China Electrotechnical Society, 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 and online scheme for identifying permanent magnet flux harmonics (A Sinusoidal Current Control Strategy Based on Harmonic Voltage Injec-tion 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 harmonics, a torque harmonic is generated by injecting current harmonic components into the stator to offset the torque fluctuation caused by the permanent magnet flux harmonics. The reference value of the injected current harmonics is related to parameters such as the permanent magnet flux harmonics. If the parameters such as the permanent magnet flux harmonics are inaccurate, the injected current harmonics will be inaccurate and the purpose of suppressing torque fluctuations cannot be achieved. As a nonlinear function, the permanent magnet flux harmonics will change with the load of the motor. At present, the methods for obtaining permanent magnet flux harmonics are all calculated by offline reverse dragging, without considering the impact of motor load changes on flux harmonics. Summary of the invention

[0005] The purpose of the present invention is to provide a method and control device for suppressing torque fluctuation of a permanent magnet synchronous motor based on online identification of permanent magnet flux harmonics, which is used to suppress torque fluctuation of a built-in permanent magnet synchronous motor. In view of the torque fluctuation problem caused by flux harmonics of permanent magnets in permanent magnet synchronous motors, and considering that the flux harmonics of permanent magnets will change with the load of the motor, the voltage equations in the 5th and 7th synchronous rotating coordinate systems containing inverter dead zone terms are used to identify the flux harmonics of permanent magnets. The flux harmonics obtained by identification are used to predict torque fluctuations and calculate the current harmonic reference value used to suppress torque fluctuations, thereby improving the stability of the system torque output and having strong robustness.

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

[0007] A method for suppressing torque fluctuation 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 according to the sampled stator current to obtain the d and q axis stator voltages and stator currents; wherein the d 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 a 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 also includes calculating the harmonic amplitude of the permanent magnet flux linkage based on the suppressed 5th and 7th voltage harmonics obtained in step 4, and calculating the harmonic amplitude of the permanent magnet flux linkage based on the fundamental current feedback value i d 、i q , 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 (ii): Input the feedback value obtained by sampling 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 the torque fluctuation according to the magnetic common energy model, output 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 to obtain the 6th harmonic voltage used to suppress the torque fluctuation;

[0018] Step (iii): The fundamental component obtained in step (i) and the fundamental current i obtained in step (ii) are d0 、i q0 u generated by the PI controller d0 、u q0 The superimposed dq axis voltage is obtained by superimposing the sixth harmonic voltage for suppressing torque fluctuation obtained in step (ii), 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: using a current sensor and an encoder to perform sampling measurement, and calculating and obtaining 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 a 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] In the formula, are the d-axis and q-axis stator voltages after the 5th and 7th voltage harmonics are transformed by the 5th and 7th synchronous rotating coordinates; 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 of the 5th and 7th current harmonics after 5th and 7th synchronous rotating coordinate transformation respectively; L d , L q is the d-axis and q-axis inductance, ψ d5 , q5 , d7 , q5 are the d-axis and q-axis flux of the 5th and 7th harmonic flux, 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 and q axis voltage components generated in the inverter dead zone, which are preset parameter values. Furthermore, during the online identification process, the 5th and 7th voltage harmonics generated by the inverter dead zone are compensated in step 2: 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,

[0025] Furthermore, the permanent magnet flux harmonic amplitude is calculated based on the suppressed 5th and 7th voltage harmonics obtained in step 4, specifically including:

[0026] 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

[0027]

[0028]

[0029] In the formula, the time derivative of the flux harmonic is very small and can be ignored, so the voltage equation can be transformed into

[0030]

[0031]

[0032] Calculation of flux harmonics

[0033]

[0034]

[0035]

[0036] Where Ψ5 and Ψ7 are the 5th and 7th harmonic amplitudes of permanent magnet flux linkage respectively.

[0037] 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, and the control device comprises a sensor module and a control circuit, wherein the sensor 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 comprises an online identification module and a fluctuation suppression module;

[0038] 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 in 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;

[0039] 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 obtains the 5th and 7th permanent magnet flux harmonics; predicts the torque fluctuation according to the magnetic common energy model, designs the optimal stator current reference value to suppress the torque, and uses a proportional resonance (PR) controller to control the actual current to follow the current reference value, and obtains 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 which suppresses torque fluctuation, and the motor is driven using the SVPWM strategy.

[0040] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0041] The present invention aims to solve the problem that the permanent magnet flux harmonics will change with the motor load during the process of suppressing torque fluctuations in a built-in permanent magnet synchronous motor with non-sinusoidal permanent magnet flux. The permanent magnet flux harmonics are identified using voltage equations in the 5th and 7th synchronous rotating coordinate systems containing inverter dead zone terms, and the identified permanent magnet flux harmonics are used to predict torque fluctuations and calculate current harmonics for suppressing torque fluctuations. Compared with other methods for measuring permanent magnet flux harmonics offline, the online identification of permanent magnet flux harmonics can adapt to load changes, and the calculated current harmonic reference value for suppressing torque fluctuations is also more accurate. This method is proposed on the basis of analyzing the torque fluctuations caused by permanent magnet flux harmonics, can improve the stability of torque output, and has strong robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A block diagram of an online identification process in a method for suppressing torque fluctuations of a permanent magnet synchronous motor by online identification of permanent magnet flux harmonics according to the present invention;

[0043] 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;

[0044] Figure 3 A flowchart 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;

[0045] 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

[0046] In order to make the purpose, technical solution, beneficial effects and significant progress of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is 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.

[0047] A method for suppressing torque fluctuation of a permanent magnet synchronous motor by online identification of permanent magnet flux harmonics includes an online identification process and a fluctuation suppression process.

[0048] Among them, Figure 1 , Figure 3 As shown, 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 using a PI controller.

[0049] Step 1: Use the voltage equations in the 5th and 7th synchronous rotating coordinate systems containing the inverter dead zone term to identify the permanent magnet flux harmonics

[0050] S11: using a current sensor and an encoder to perform sampling measurement to obtain information such as the stator current, electrical angle, and electrical angular velocity of the permanent magnet synchronous motor;

[0051] The three-phase stator winding of the motor usually adopts a star connection mode. Under ideal conditions, the winding is symmetrically distributed, so the motor back electromotive force waveform is half-wave symmetrical, that is, the winding back electromotive force waveform does not contain even harmonics, and the three-phase nth harmonic currents differ by 2nπ / 3. Therefore, the stator harmonic current can be expressed as: 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, the 5th harmonic component and the 7th harmonic component of the three-phase stator current of the stator, θ1θ5θ7 are the initial phase angles of the fundamental component, the 5th harmonic component and the 7th harmonic component of the three-phase stator current of the stator.

[0052] The obtained stator harmonic current data is converted into d-axis and q-axis stator currents according to the principle of abc / dq coordinate transformation; the obtained motor electrical angle θ is differentiated to obtain the electrical angular velocity ω in the synchronous rotating coordinate system. e .

[0053] S12: Extract the 5th and 7th current harmonics i in a 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:

[0054]

[0055]

[0056] In the formula, are the d-axis and q-axis stator voltages after the 5th and 7th voltage harmonics are transformed by the 5th and 7th synchronous rotating coordinates; 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 of the 5th and 7th current harmonics after 5th and 7th synchronous rotating coordinate transformation respectively; L d , L q is the d-axis and q-axis inductance, ψd5 , q5 , d7 , q5 are the d-axis and q-axis flux of the 5th and 7th harmonic flux, 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 and q axis voltage components generated in the inverter dead zone, which are preset parameter values.

[0057] Step 2: Dead-zone voltage harmonic compensation

[0058] Calculate the error △U of the three-phase voltage caused by the dead time a , △U b , △U c , the formula is:

[0059] Among them, i a 、i b 、i c For the three-phase current extracted by the current sensor, the sign function is defined as:

[0060]

[0061] The voltage error △U caused by the inverter dead zone a △U b △U c In the 5th and 7th synchronous rotation coordinate system, it is expressed as V dead_d5 、V dead_q5 、V dead_d7 、V dead_q7 ;

[0062] 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 ;

[0063]

[0064] 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:

[0065] 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 ;

[0066] The multiple synchronous rotation d, q coordinate transformation method is used to extract the harmonic components.

[0067] The transformation matrix of transforming the abc coordinate system into the synchronous rotating coordinate system corresponding to the 5th and 7th harmonics is:

[0068]

[0069]

[0070] After transformation, the expression of the motor stator current in the 5th and 7th synchronous rotating coordinate systems can be obtained as follows:

[0071]

[0072]

[0073] 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.

[0074] From the above formula, it can be seen that in the synchronous 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 synchronous 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.

[0075] The DC component in the 5th and 7th synchronous rotating coordinate systems is obtained by filtering with a low-pass filter.

[0076]

[0077]

[0078] 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 、ud7 、u q7 ;

[0079] 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

[0080]

[0081]

[0082] The fundamental component in the sampled d and q axis current feedback values, the voltage harmonics used to compensate for the inverter dead zone in step 2, and the voltage harmonics used to control the current harmonics in step 4 are superimposed to obtain the d and q axis voltages, and the SVPWM (space vector pulse width modulation) strategy is used to drive the motor.

[0083] Step 5: Use the deformed voltage equation (14) and equation (15) to calculate the permanent magnet flux harmonic amplitudes Ψ5 and Ψ7, specifically including:

[0001] In the formula, the time derivative of the flux harmonic is very small and can be ignored, so the voltage equation can be transformed into

[0002]

[0003]

[0004] Substitute equation 16 and equation 17 into the following formula to calculate the 5th and 7th permanent magnet flux harmonic amplitudes Ψ5 and Ψ7:

[0005]

[0006]

[0007]

[0008] 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.

[0009] like Figure 2 , Figure 4 As shown, the torque fluctuation suppression process specifically includes:

[0010] Step (1): Re-collect the d-axis and q-axis current feedback values ​​i of the permanent magnet synchronous motor by using the method of step S11 in the online identification process.d0 、i q0 , electrical angle θ, electrical angular velocity ω e ;

[0011] Step (ii): Input the feedback value obtained by sampling into the pre-identified flux harmonic lookup table generated in step 6 to extract the 6th current harmonic i d6 and i q6 ; Predict torque fluctuations based on the magnetic energy model and design the optimal stator current reference value To suppress torque, the proportional resonant (PR) controller is used to control the actual current to follow the current reference value.

[0012] Magnetic co-energy model:

[0013] where t e is the total torque generated by the permanent magnet synchronous motor, including DC component and 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 is the dq-axis permanent magnet flux and current vector, t cog is the cogging torque, K P =3P / 2 and P is the pole pair number, "×" is defined as [ab]×[cd] T = cross product of ad-bc. Here, the harmonics in the inductance and the cogging torque are ignored. From the magnetic common energy model, it can be seen that the torque harmonics depend on the harmonics of the permanent magnet flux and the stator current.

[0014] 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 Respectively expressed in the form of Fourier series:

[0015]

[0016]

[0017]

[0018] The above parameters are defined as follows:

[0019] 1)Ψ0 is the average permanent magnet flux on the d-axis, ψ d6 ,q6 is the 6th harmonic of permanent magnet flux linkage of d and q axes; d6 and q6 is the amplitude of the sixth harmonic component of the dq axis magnetic flux;

[0020] 2)I d0 and I q0 is the average current of dq axis; 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 stator current in the dq axis, φ d6 and φ q6 is the phase angle of the corresponding stator current harmonic;

[0021] Design the optimal stator current reference value To suppress the torque. And use the proportional resonant (PR) controller to control the actual current to follow the current reference value

[0022] The stator harmonic current used to minimize torque ripple will cause 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 current, that is, to minimize the square of the harmonic current amplitude, as follows:

[0023]

[0024] By solving the two objectives of minimizing torque harmonics and minimizing motor harmonic current losses, the stator harmonic current amplitude can be obtained. and phase angle

[0025]

[0026]

[0027]

[0028]

[0029] Where L Δ =L d -L q

[0030] The implementation diagram of harmonic current injection is as follows: Figure 2 shown.

[0031] The dq-axis reference current includes the DC component of the torque command for motor control and the harmonic component for minimizing torque ripple.

[0032] Two independent controllers are used to control the actual current to follow the reference current: 1) a PI controller for DC current control; 2) a proportional resonant (PR) controller for harmonic current control.

[0033] Then, the outputs of the PI and PR controllers are added to form the dq-axis reference voltage, which is fed back to the voltage source inverter to minimize the torque ripple of the motor drive.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. The non-essential improvements, adjustments or replacements made by those skilled in the art based on the contents of this specification are all within the scope of protection required by the present invention.

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 according to the sampled stator current to obtain the d and q axis stator voltages and stator currents; wherein the d 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 a 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 also includes calculating the permanent magnet flux harmonic amplitude based on the suppressed 5th and 7th voltage harmonics obtained in step 4, and calculating the harmonic amplitude of the permanent magnet flux based on 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 (ii): Input the feedback value obtained by sampling 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 the torque fluctuation according to the magnetic common energy model, output 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 to obtain the 6th harmonic voltage used to suppress the torque fluctuation; Step (iii): The fundamental component obtained in step (i) and the fundamental current i obtained in step (ii) are d0 、i q0 u generated by the PI controller d0 、u q0 The dq axis voltage is obtained by superimposing the sixth harmonic voltage for suppressing torque fluctuation obtained in step (ii), and the motor is driven using the SVPWM strategy.

2. The method for suppressing torque fluctuations based on permanent magnet flux harmonic identification according to claim 1 is characterized in that: Step 1 in the online identification process specifically includes: S11: using a current sensor and an encoder to perform sampling measurement, and calculating and obtaining 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 a 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: In the formula, are the d-axis and q-axis stator voltages after the 5th and 7th voltage harmonics are transformed by the 5th and 7th synchronous rotating coordinates; 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 of the 5th and 7th current harmonics after 5th and 7th synchronous rotating coordinate transformation respectively; L d , L q is the d-axis and q-axis inductance, ψ d5 , q5 , d7 , q5 are the d-axis and q-axis flux of the 5th and 7th harmonic flux, 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 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 is 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 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 in 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 obtains the 5th and 7th permanent magnet flux harmonics; predicts the torque fluctuation according to the magnetic common energy model, designs the optimal stator current reference value to suppress the torque, and uses a proportional resonant controller to control the actual current to follow the current reference value, and obtains 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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