Harmonics Close-loop Transmission Mechanism And Torsional Vibration Suppression In Permanent Magnet Synchronous Motor

Permanent Magnet Synchronous Motor(PMSM)vector control drive system is widely used in many important mechanical equipment such as vehicles,numerical control machines,robots and underwater vessels.However,torsional vibration of PMSM will increase vibration and damage the stability of the equipment,such leading to the reduction of reliability and service life of the equipment.Reducing the torsional vibration by suppressing the speed harmonics of PMSM is of great significance to the development of manufacturing industry.Therefore,this paper studies the closed-loop transmission mechanism of electrical related harmonics and the torsional vibration control method in PMSM Vector Control drive system.The conclusions are as follows:(1)The transfer functions of PMSM,vector control strategy,inverter,current filter under the d-q axis coordinate system in PMSM vector control derive system are derived.There is a transmission path coupling from the d-q axis stator voltage to the stator current of PMSM.The accuracy of the transfer function calculation can be greatly improved by considering the influence of the d-q axis coupling terms.The influence of space vector pulse width modulation on the voltage command signal in the stationary coordinate system can be regarded as a time delay.In the d-q axis coordinate system,the transfer function of the delay link is the multiplication of the inverse rotation transformation matrix,the delay link's transfer function and the rotation transformation matrix.The accuracy of the deduced results are verified by simulation.The transfer function calculation provides a theoretical basis for the analysis of the harmonic closed-loop transfer characteristics in PMSM vector control drive system.(2)The closed-loop transmission mechanism of dead-time effect related harmonics in the PMSM vector control drive system is deduced,and a motor control parameter optimization method for torsional vibration reduction is proposed accordingly.The mathematical expression of the d-q axis voltage error harmonic caused by the dead-time effect is given.The d-q axis closed-loop transfer function from the voltage error harmonic to the stator current is derived,and the mathematical expressions for the d-q axis stator current and speed harmonics caused by the dead-time effect are obtained.The closed-loop transmission mechanism of the dead-time effect related harmonics reveals the influence of the vector control strategy's closed-loop control on the torsional vibration response,and establishes the correlation between the motor control parameters and the torsional vibration response.Based on this mathematical model,the motor control parameter optimization method for torsional vibration reduction is proposed.The derived expressions of current and speed harmonic are used for calculating the optimization objective function,and the genetic optimization algorithm is used to find the optimal control parameters which minimize the dead-time related current and speed harmonics.The motor control parameter constraint range calculated based on the motor's response speed requirements is used as the constraint condition,and the torsional vibration of PMSM can be reduced just by setting the optimal control parameters of the current and speed controllers.The proposed method does not require complex control algorithms and structural optimization,and is of great significance for engineering application.In simulation and experiment analysis,the proposed method obtaining the optimal control parameters effectively and reduces the torsional vibration accordingly.When the optimal PI parameters are used,the amplitude of the 24^th order speed harmonics is reduced by 73%at the maximum during the experiment.(3)The torsional vibration reduction method based on the real and imaginary harmonic controllers is proposed.The proposed method includes three parts:harmonic extraction,harmonic controller and injection voltage signal reconstruction.In the process of online real-time suppression of speed harmonics,the harmonic controller adjusts the injected voltage harmonics according to the harmonic extraction results,and the injected voltage harmonics are converted into the time domain through signal reconstruction and added into injection voltage command.A real-time order extraction algorithm is proposed,which uses the motor rotation angle signal to construct the Fourier transform operator and extracts the speed harmonic by combining single-point Fourier transform and sliding window together.The calculation burden and complicated parameter adjustment caused by the harmonic extraction algorithm using rotation coordinate transformation and digital filter are avoided.A speed harmonic controller based on the real and imaginary parts of the speed harmonic is designed,which solves the amplitude static deviation problem of the amplitude-phase-based method,and the performance in the speed harmonic suppression is improved.The proposed speed harmonic controller can adjust the speed harmonic directly by the injected voltage harmonic,and the current harmonic controller and current harmonic extraction are no longer required.The difficulty of parameter adjustment and the calculation load are reduced consequently.The proposed torsional vibration reduction method has many advantages such as fast response speed,excellent suppression effect,low calculation effort,and the ability to be applied under variable conditions.In the experiment,the 24^th order speed harmonic's amplitude is reduced by more than 98%by the proposed speed harmonic suppression method.(4)The closed-loop transmission mechanism of injected voltage harmonics in PMSM vector control drive system is deduced,and a method for current and speed harmonics suppressing by harmonic injection based on closed-loop transmission of harmonics in the motor drive system is proposed.The derived transfer function reveals the closed-loop transfer mechanism of injected voltage harmonics in the PMSM vector control drive system.According to the closed-loop transfer function,a harmonic controller is designed.The inverse of the closed-loop transfer relationship matrix is added to the harmonic controller for decoupling the relation between voltage and current harmonics.The failure problem of the existing harmonic injection methods under some operating conditions is solved.In the experiment,besides having similar harmonic suppression ability under the effective working conditions of the existing harmonic injection method,the proposed method can still effectively suppress the current and speed harmonics under the working conditions where the existing method fails.The d axis current harmonic,q axis current harmonic,and speed harmonic are suppressed by 97%,95%,and 97%,respectively.