| Compared with the traditional electric excitation synchronous motor,the permanent magnet synchronous motor has the advantages of simple structure,small volume,light weight,small loss and high operating efficiency,as well as simple shape and size optimization design of the motor.However,due to the non-linear factors such as dead zone time and tube pressure drop in the inverter during the operation of permanent magnet synchronous motor,time harmonics will be introduced.On the other hand,the air gap magnetic field distortion of the motor body will cause tooth slot effect and magnetic saturation effect,and these factors will introduce space harmonics.The existence of time harmonics and space harmonics will bring high-order harmonic current,which will cause the torque ripple of the motor,bring vibration and noise to the system,reduce the working efficiency,affect the speed control of the motor,and limit its use range.Therefore,it is of practical significance to suppress the harmonic current of permanent magnet synchronous motor and reduce the torque ripple to improve production efficiency and economic development.Based on the working principle and basic structure of permanent magnet synchronous motor,the mathematical model of permanent magnet synchronous motor is established by using coordinate transformation principle and power conservation principle.The vector control method of permanent magnet synchronous motor is introduced briefly.On this basis,the causes of harmonic generation of PMSM are analyzed in detail,the mathematical model of harmonic current in DQ coordinate system and the voltage regulation equation of PMSM are established,and the relationship between harmonic current and torque ripple is deduced.The results show that the fifth and seventh harmonic currents mainly affect the torque ripple of PMSM.In this paper,the harmonic current compensation method is proposed to offset the harmonic components generated during the operation of the motor and to suppress the torque ripple.MATLAB/Simulink and finite element analysis software were respectively used to build a permanent magnet synchronous motor system simulation model for comparative simulation analysis.Through the analysis of the simulation data,when the ideal permanent magnet synchronous motor model is used,the phase current THD value decreases from13.12% to 5.58% before and after the harmonic current compensation algorithm is added.The 5th harmonic current content decreases from 10.37% to 0.3264%,the 7th harmonic current content decreases from 6.935% to 0.2179%,and the torque ripple decreases from0.3744N·m to 0.1113N·m.When using FEM permanent magnet synchronous motor model simulation,the THD value of phase current decreases from 13.20% to 3.77%,the content of 5th harmonic current decreases from 10.63% to 1.405%,and the content of 7th harmonic current decreases from 7.108% to 0.7745% before and after adding harmonic current compensation algorithm.Torque ripple decreases from 0.4448 N·m to 0.1158 N·m.Both methods can effectively reduce the content of 5th and 7th harmonic current,increase the sine degree of current waveform,and reduce the electromagnetic torque ripple of motor.On the basis of simulation analysis,the hardware experiment platform of PMSM speed control system is designed and built with DRV8301 digital motor control suite as the core.Through this platform,the harmonic compensation algorithm is used to restrain the torque ripple.The experimental results verify that the algorithm can effectively reduce the harmonic current content and achieve the purpose of restraining the torque ripple. |
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