Permanent magnet synchronous motor stability control method

Abstract

The invention relates to the technical field of motor control, and particularly discloses a permanent magnet synchronous motor stability control method, which comprises the following steps of: adjusting parameters of a PI regulator 1 and a PI regulator 2 to enable feedback dq axis current of a motor to follow given; a harmonic extraction module is operated, current harmonics of all times are obtained, harmonic currents id.xth and iq.xth are obtained through calculation, and x is an odd number which is not three times; calculating to obtain an effective value is.xth of each current harmonic wave; when is.xth is larger than the judgment threshold value delta I, the enabling coefficient Mx is equal to 1; when is.xth is smaller than or equal to the judgment threshold value delta I, the enabling coefficient Mx is equal to 0; adding a harmonic processing module, and operating the permanent magnet synchronous motor; operating a harmonic extraction module, and adjusting a gain coefficient Kx according to the distribution condition of each current harmonic; according to the invention, the current harmonics of each time of the motor are effectively combed, the current harmonics of the motor are reduced in a targeted manner, the torque ripple is reduced, and the stability of motor control is improved.

Description

Technical Field

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

[0002] The existing permanent magnet synchronous motor current loop control mostly adopts PI regulator and its improved scheme. The permanent magnet synchronous motor current loop control method based on PI control is a traditional PI control method. The traditional PI control method has a simple structure, but does not realize the decoupling control of the permanent magnet synchronous motor. The feedback decoupling control method and the feedforward decoupling control method are based on the PI control method. They both subtract a compensation amount equal to the coupling amount from the output of the PI regulator to offset the dq axis coupling term.

[0003] The feedback decoupling control method uses the feedback value of the motor current to calculate the compensation amount, and the feedforward decoupling control method uses the given value of the motor current to calculate the compensation amount. Both methods rely on the accuracy of the motor parameters and will be affected by the changes in the motor parameters, causing the control effects of the feedforward decoupling and feedback decoupling to deviate due to the changes in the motor parameters. When there are a large number of harmonics in the motor current, the prior art 1 cannot suppress the harmonics well, and the motor will have a large torque pulsation.

[0004] In order to improve the stability of permanent magnet synchronous motor control, reduce torque pulsation in the permanent magnet synchronous motor control process, and reduce current harmonics, the present invention proposes a permanent magnet synchronous motor stability control method with multiple current harmonic reduction, which is applied to the current loop controller of the motor control algorithm to solve the problem that the existing permanent magnet synchronous motor current loop control cannot suppress harmonics well, and then the motor will have large torque pulsation. Summary of the invention

[0005] In view of the problems existing in the prior art, an object of the present invention is to provide a permanent magnet synchronous motor stability control method.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a permanent magnet synchronous motor stability control method, comprising the following steps: S1, without adding harmonic processing module, running the permanent magnet synchronous motor to rated working condition; S2, adjust the parameters of PI regulator 1 and PI regulator 2 to make the feedback dq axis current of the motor follow the given value; S3. Run the harmonic extraction module to obtain the harmonic current of each current harmonic calculation i d.xth and i q.xth , where x is an odd number that is not a multiple of 3; S4. Calculate the effective value of each current harmonic is.xth , the calculation formula is as follows: ; S5. Compare i s.xth and judgment threshold ΔI, when i s.xth When it is greater than the judgment threshold ΔI, the enabling coefficient Mx is equal to 1; when i s.xth When it is less than or equal to the judgment threshold ΔI, the enabling coefficient Mx is equal to 0; S6. Add the harmonic processing module, run the permanent magnet synchronous motor, and the gain coefficient Kx defaults to 1; S7, running the harmonic extraction module, and adjusting the gain coefficient Kx according to the distribution of each current harmonic.

[0007] Preferably, the stator current of the permanent magnet synchronous motor in S1 is i a 、i b The stator current is detected by the current sensor. i a 、i b The current is obtained by 3s / 2s conversion i α and i β , current i α and i β The feedback current is obtained by 2s / 2r transformation i d and i q , the rotor electrical angle of the permanent magnet synchronous motor i r and the motor electrical angular velocity oh r The bus voltage value is measured by the rotary transformer. u dc Measured by a voltage sensor.

[0008] Preferably, the motor given torque of the permanent magnet synchronous motor is , motor given torque The given current is output through the maximum torque current ratio MTPA module and , stator current i a 、i b and rotor electrical angle i ris the input of the harmonic extraction module, and the output of the harmonic extraction module is the harmonic current i d.xth and i q.xth .

[0009] Preferably, the feedback current i d 、i q , given current , , harmonic current i d.xth 、i q.xth And the motor electrical angular velocity oh r As the input of the current loop controller, the current loop controller outputs the command voltage u d and u q , command voltage u d and u q , motor electrical angular velocity oh r , rotor electrical angle i r and bus voltage u dc As the input of the PWM modulation module, the PWM modulation module outputs six PWM pulse signals to drive the inverter to work and control the operation of the permanent magnet synchronous motor.

[0010] Preferably, the algorithm of the current loop controller is as follows: given current With feedback current i d The difference after the filter is used as the input of PI regulator 1, and the output of PI regulator 1 is u d1 ; Given current With feedback current i q The difference after the filter is used as the input of PI regulator 2, and the output of PI regulator 2 is u q1 ; Feedback current i d , i q With given current , And the motor electrical angular velocity oh rAs the input of the decoupling controller, the decoupling controller adopts the feedforward decoupling method or the feedback decoupling method, and the output of the decoupling controller is u dj and u qj .

[0011] Preferably, the harmonic extraction module in S3 extracts the xth current harmonic by coordinate transformation, and the current harmonic when x is 5 is extracted by stator current i a 、i b Calculate the current i α and i β ; Through current i α 、i β and the rotor electrical angle i r Calculate the harmonic current i d.xth and i q.xth , the calculation formula is as follows: ; in, i c = -i a - i b ; .

[0012] Preferably, the harmonic processing module in S6 includes a target current Multiple current harmonics i d.xth The difference after the filter is used as the input of PI regulator three, and the output of PI regulator three is u d.xth ; Target current and i q.xth The difference after the filter is used as the input of PI regulator 4, and the output of PI regulator 4 is u q.xth ; Target current and target current Generally set to 0.

[0013] Preferably, the output of the PI regulator three is u d.xth The product of the gain coefficient Kx and the enable coefficient Mx is the compensation voltage under this harmonic. ud1.xth , the output of PI regulator 4 is u q.xth The product of the gain coefficient Kx and the enable coefficient Mx is the compensation voltage under this harmonic. u q1.xth ; The sum of the compensation voltage under each harmonic is Δ u d and Δ u q； The harmonic voltage processing module processes multiple harmonics simultaneously.

[0014] Preferably, the compensation voltage Δ u d , decoupling controller output u dj The output of the PI regulator u d1 The sum is the current loop controller d-axis output command voltage u d ; Compensation voltage Δ u q , decoupling controller output u qj The output of the PI regulator u q1 The sum is the q-axis output command voltage of the current loop controller u q .

[0015] The present invention has the following beneficial effects: The permanent magnet synchronous motor stability control method designed in the present invention effectively sorts out the various current harmonics of the motor, reduces the motor current harmonics in a targeted manner, thereby reducing torque pulsation and improving the stability of motor control.

[0016] The permanent magnet synchronous motor stability control method designed in the present invention has strong versatility and can be adjusted according to different working conditions.

[0017] The permanent magnet synchronous motor stability control method designed by the present invention has small calculation amount, no complicated calculation and occupies few resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a block diagram of permanent magnet synchronous motor control strategy.

[0019] Figure 2 It is the control flow chart of the current loop controller.

[0020] Figure 3 It is an implementation flow chart of the permanent magnet synchronous motor stability control method. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely further describe the technical solutions in the embodiments of the present invention. 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.

[0022] With the increasing requirements for energy conservation and emission reduction in recent years, the development of efficient and energy-saving motor control systems is of great significance in reducing operating costs. Permanent magnet synchronous motors have been widely used in the field of electric vehicles due to their advantages such as high efficiency, high power density, high torque density ratio, and compact structure. However, permanent magnet synchronous motors are multivariable control objects with nonlinear and strong coupling characteristics. Changes in motor parameters, external disturbances, and unpredictable factors during operation increase the uncertainty of control and affect the control performance of permanent magnet synchronous motors. Torque oscillation may even occur under some working conditions.

[0023] Considering the factors of induced electromotive force harmonics and current harmonics, the electromagnetic torque of the permanent magnet synchronous motor can be expressed as (1)

[0024] In the formula, T 0 is the average torque, T 6. T 12 and T 18 They are 6th, 12th and 18th pulsating torques respectively. T 6. T 12 and T 18 Can be expressed as ; (2) ; (3) (4)

[0025] In the formula, E 1 is the fundamental wave of the induced electromotive force, E 5 、E 7 、E 11 ......are the 5th, 7th, 11th harmonics of the induced electromotive force, I 1 is the fundamental wave of stator current, I 5. I 7. I 11 ......are the 5th, 7th, 11th harmonics of the stator current respectively.

[0026] The spatial distribution of the permanent magnet magnetic field or stator winding of a permanent magnet synchronous motor cannot be completely sinusoidal. Due to the influence of manufacturing tolerances, it is difficult to obtain an ideal sinusoidal magnetic field distribution, so the waveform of the induced electromotive force will definitely be distorted. Here we focus on analyzing the torque ripple caused by current harmonics.

[0027] Assuming that the induced electromotive force is a sine wave, the induced electromotive force only contains the fundamental component E 1. The remaining components E 5. E 7. E 11 , E 13 , E 17 , E 19 ......is 0, the torque ripple equations (2)~(4) can be simplified to ; (5) ; (6) (7)

[0028] It can be seen that the 6nth torque pulsation is generated by the (6n+1)th and (6n–1)th current harmonics. Reducing the 5th, 7th, 11th, 13th, etc. harmonics of the stator current can effectively reduce the torque pulsation of the motor.

[0029] In order to reduce the stator current harmonics of the motor, the present invention proposes a multiple current harmonic reduction method, which is applied in the current loop of the motor control. The control block diagram is shown in FIG. Figure 1 shown.

[0030] Stator current of permanent magnet synchronous motor i a 、i b The stator current is detected by the current sensor. i a 、i b The current is obtained by 3s / 2s conversion i α and i β , current i α and i β The feedback current is obtained by 2s / 2r transformation i d and i q , the rotor electrical angle of the permanent magnet synchronous motor i rand the motor electrical angular velocity oh r The bus voltage value is measured by the rotary transformer. u dc Measured by a voltage sensor.

[0031] The motor torque setting of permanent magnet synchronous motor is , motor given torque Output given current through Maximum Torque Per Ample (MTPA) module and , stator current i a , i b and rotor electrical angle i r is the input of the harmonic extraction module, and the output of the harmonic extraction module is the harmonic current i d.xth and i q.xth . x represents 5, 7, 11, 13, 17, 19, etc., which are odd numbers that are not multiples of 3.

[0032] Feedback current i d 、i q , given current , , harmonic current i d.xth , i q.xth And the motor electrical angular velocity oh r As the input of the current loop controller, the current loop controller outputs the command voltage u d and u q , command voltage u d and u q , motor electrical angular velocity oh r , rotor electrical angle i r and bus voltage u dc As the input of the PWM modulation module, the PWM modulation module outputs six PWM pulse signals to drive the inverter to work and control the operation of the permanent magnet synchronous motor.

[0033] The harmonic extraction module extracts the 5th, 7th, 11th, 13th, 17th, and 19th current harmonics through coordinate transformation. Taking the 5th current harmonic as an example, Formula 8 uses the stator current i a 、i b Calculate the current i α and i β Formula 9 uses the current i α , i β and the rotor electrical angle i r Calculate the harmonic current i d.xth and i q.xth .

[0034] (8) in, i c = -i a - i b .

[0035] (9) Similarly, according to this method, the 7th, 11th, 13th, 17th, 19th and other high-frequency current harmonics can be obtained.

[0036] The block diagram of the current loop controller is as follows: Figure 2 shown.

[0037] Given current and i d The difference after the filter is used as the input of PI regulator 1, and the output of PI regulator 1 is u d1 ; Given current and i q The difference after the filter is used as the input of PI regulator 2, and the output of PI regulator 2 is u q1 The filter is mostly a low-pass filter, but other filters can also be used. The filter parameters can be modified during software debugging.

[0038] Feedback current i d 、i q With given current , And the motor electrical angular velocity oh r As the input of the decoupling controller, the decoupling controller adopts the feedforward decoupling method or the feedback decoupling method, and the output of the decoupling controller is u dj and u qj .

[0039] Figure 2 The dotted line is the harmonic processing module. Multiple current harmonics i d.xth The difference after the filter is used as the input of PI regulator three, and the output of PI regulator three is u d.xth ; Target current and i q.xth The difference after the filter is used as the input of PI regulator 4, and the output of PI regulator 4 is u q.xth The filter is usually a low-pass filter, but other filters can also be used. The filter parameters can be modified during software debugging. Target current and target current Generally set to 0.

[0040] The output of PI regulator three is u d.xth The product of the gain coefficient Kx and the enable coefficient Mx is the compensation voltage under this harmonic. u d1.xth , the output of PI regulator 4 is u q.xth The product of the gain coefficient Kx and the enable coefficient Mx is the compensation voltage under this harmonic. u q1.xth ; The sum of the compensation voltage under each harmonic is Δ u d and Δ u q； The harmonic voltage processing module processes multiple harmonics simultaneously.

[0041] The harmonic voltage processing module can process multiple harmonics at the same time, such as the 7th, 11th, 13th, 17th, 19th, etc., which can be added according to actual needs.

[0042] Compensation voltage Δ u d , decoupling controller output u dj The output of the PI regulator u d1 The sum is the current loop controller d-axis output command voltageu d ; Compensation voltage Δ u q , decoupling controller output u qj The output of the PI regulator u q1 The sum is the q-axis output command voltage of the current loop controller u q .

[0043] The harmonic distribution of the motor is mainly low-order, and the 5th and 7th harmonics are generally larger. However, under some specific motors or specific working conditions, the harmonic distribution of the motor current will be different. Therefore, the method proposed in the present invention needs to be processed accordingly according to the specific situation during the actual application. The implementation flow chart is as follows Figure 3 shown.

[0044] (1) Without adding the harmonic processing module, the permanent magnet synchronous motor is operated to the rated operating condition; (2) Adjust the parameters of PI regulator 1 and PI regulator 2 so that the feedback dq axis current of the motor follows the given value; (3) Run the harmonic extraction module to obtain the harmonic current of each current harmonic calculation i d.xth and i q.xth , where x is an odd number that is not a multiple of 3; (4) Calculate the effective value of each current harmonic i s.xth , the calculation formula is as follows: ; (5) Comparison i s.xth and judgment threshold ΔI, when i s.xth When it is greater than the judgment threshold ΔI, the enabling coefficient Mx is equal to 1; when i s.xth When it is less than or equal to the judgment threshold ΔI, the enabling coefficient Mx is equal to 0; (6) Add the harmonic processing module, run the permanent magnet synchronous motor, and the gain coefficient Kx defaults to 1; (7) Run the harmonic extraction module and adjust the gain factor Kx according to the distribution of each current harmonic.

[0045] The present invention is not limited to the above-mentioned implementation modes, and anyone should be aware of the structural changes made under the enlightenment of the present invention, and all those having the same or similar technical solutions as the present invention fall within the protection scope of the present invention.

[0046] The techniques, shapes, and structural parts not described in detail in the present invention are all well-known techniques.

Claims

1. A permanent magnet synchronous motor stability control method, characterized in that: The following steps are involved: S1, without adding harmonic processing module, running the permanent magnet synchronous motor to rated working condition; S2, adjust the parameters of PI regulator 1 and PI regulator 2 to make the feedback dq axis current of the motor follow the given value; S3. Run the harmonic extraction module to obtain the harmonic current of each current harmonic calculation i d.xth and i q.xth , where x is an odd number that is not a multiple of 3; S4. Calculate the effective value of each current harmonic i s.xth , the calculation formula is as follows: ； S5. Compare i s.xth and judgment threshold ΔI, when i s.xth When it is greater than the judgment threshold ΔI, the enabling coefficient Mx is equal to 1; when i s.xth When it is less than or equal to the judgment threshold ΔI, the enabling coefficient Mx is equal to 0; S6. Add the harmonic processing module, run the permanent magnet synchronous motor, and the gain coefficient Kx defaults to 1; S7, running the harmonic extraction module, and adjusting the gain coefficient Kx according to the distribution of each current harmonic.

2. The permanent magnet synchronous motor stability control method according to claim 1, characterized in that: The stator current of the permanent magnet synchronous motor in S1 i a 、i b The stator current is detected by the current sensor. i a 、i b The current is obtained by 3s / 2s conversion i α and i β , current i α and i β The feedback current is obtained by 2s / 2r transformation i d and i q , the rotor electrical angle of the permanent magnet synchronous motor θ r and the motor electrical angular velocity ω r The bus voltage value is measured by the rotary transformer. u dc Measured by a voltage sensor.

3. The permanent magnet synchronous motor stability control method according to claim 2, characterized in that: The motor given torque of the permanent magnet synchronous motor is , motor given torque The given current is output through the maximum torque current ratio MTPA module and , stator current i a 、i b and rotor electrical angle θ r is the input of the harmonic extraction module, and the output of the harmonic extraction module is the harmonic current i d.xth and i q.xth .

4. The permanent magnet synchronous motor stability control method according to claim 2, characterized in that: The feedback current i d and i q ， Given current , , harmonic current i d.xth 、i q.xth And the motor electrical angular velocity ω r As the input of the current loop controller, the current loop controller outputs the command voltage u d and u q , command voltage u d and u q , motor electrical angular velocity ω r , rotor electrical angle θ r and bus voltage u dc As the input of the PWM modulation module, the PWM modulation module outputs six PWM pulse signals to drive the inverter to work and control the operation of the permanent magnet synchronous motor.

5. The permanent magnet synchronous motor stability control method according to claim 4, characterized in that: The algorithm of the current loop controller is as follows: Given the current With feedback current i d The difference after the filter is used as the input of PI regulator 1, and the output of PI regulator 1 is u d1 ; Given current With feedback current i q The difference after the filter is used as the input of PI regulator 2, and the output of PI regulator 2 is u q1 ; Feedback current i d 、i q With given current , And the motor electrical angular velocity ω r As the input of the decoupling controller, the decoupling controller adopts the feedforward decoupling method or the feedback decoupling method, and the output of the decoupling controller is u dj and u qj .

6. The permanent magnet synchronous motor stability control method according to claim 1, characterized in that: The harmonic extraction module in step S3 extracts the xth current harmonic by coordinate transformation, and the current harmonic when x is 5 is obtained by stator current. i a 、i b Calculate the current i α and i β ; Through current i α and i β and the rotor electrical angle θ r Calculate the harmonic current i d.xth and i q.xth , the calculation formula is as follows: ； in, i c = -i a - i b ; 。 7. The permanent magnet synchronous motor stability control method according to claim 1, characterized in that: The harmonic processing module in step S6 includes a target current Multiple current harmonics i d.xth The difference after the filter is used as the input of PI regulator three, and the output of PI regulator three is u d.xth ; Target current and i q.xth The difference after the filter is used as the input of PI regulator 4, and the output of PI regulator 4 is u q.xth ; Target current and target current Generally set to 0.

8. The method for controlling the stability of a permanent magnet synchronous motor according to claim 7, characterized in that: The output of the PI regulator three is u d.xth The product of the gain coefficient Kx and the enable coefficient Mx is the compensation voltage under this harmonic. u d1.xth , the output of PI regulator 4 is u q.xth The product of the gain coefficient Kx and the enable coefficient Mx is the compensation voltage under this harmonic. u q1.xth ; The sum of the compensation voltage under each harmonic is Δ u d and Δ u q； The harmonic voltage processing module processes multiple harmonics simultaneously.

9. The method for controlling the stability of a permanent magnet synchronous motor according to claim 8, characterized in that: The compensation voltage Δ u d , decoupling controller output u dj The output of the PI regulator u d1 The sum is the current loop controller d-axis output command voltage u d ; Compensation voltage Δ u q , decoupling controller output u qj The output of the PI regulator u q1 The sum is the q-axis output command voltage of the current loop controller u q .

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