Research On PMSM Harmonic Current Suppression Strategy Based On Voltagre Compensation Method

The permanent magnet synchronous motor AC servo system is very suitable for driving applications with high precision requirements.In these cases,the stator current waveform of the motor is required to have high smoothness and small torque ripple.However,due to the strong nonlinearity of the inverter and the distortion of the air gap magnetic field during PMSM operation,the stator current of the PMSM contains a large number of higher harmonics and induces large torque ripple.Therefore,it is important to research the control strategy for suppressing current harmonics to improve the performance of the control system.Firstly,the causes of PMSM harmonic current are analyzed.The mathematical model of PMSM harmonic considering harmonic current is established.The method of suppressing current harmonic is researched.Aiming at the problem that the traditional voltage compensation method uses low-pass filter to extract DC quantity,dynamic response time is long and steady-state error is large,the closed-loop current average method is proposed to extract the DC component,the rapidity and stability of the system is improved.However,the voltage compensation method based on the closed-loop current average method requires four coordinate transformations and six PI controllers to adjust the parameters,and the calculation process and parameter adjustment are complicated.In order to reduce the complexity of the algorithm,a voltage compensation method based on the second-order generalized integrator is proposed.The cascaded second-order generalized integrator is connected in parallel with the current-loop PI controller,and the cascaded second-order generalized integrator is used to extract the d-axis and q-axis current six times.Harmonic component,this method does not need coordinate transformation and only requires two PI regulators,which greatly reduces the calculation amount of the system and saves the storage space.Secondly,two kinds of voltage compensation algorithms are simulated.By analyzing the current and torque spectrum,it is found that the total THD of phase A current decreases from 9.05%to 5.28%and the sixth of torque ripple decreases from 0.094Nm to 0.044Nm when adopting the voltage compensation method based on the closed-loop current average method.the total THD of phase A current decreases from 9.05%to 2.85%;and the sixth of torque ripple decreases from 0.094Nm to 0.017Nm when adopting the voltage compensation method based on cascaded second-order generalized integrator.The simulation results verify the effectiveness of the two voltage compensation algorithm.Finally,the two voltage compensation algorithms are verified on the PMSM servo drive experimental platform,and the phase current waveform and spectrum are analyzed.The following conclusions are obtained:using the voltage compensation method based on the closed-loop current average method,the percentage of the 5th harmonic amplitude to the fundamental wave is reduced from 45%to 30%,and the percentage of the 7th harmonic amplitude to the fundamental wave is reduced from 42%to 26%;using the voltage compensation method based on the cascaded second-order generalized integrator,the percentage of the 5th harmonic amplitude to the fundamental wave is reduced from 45%to 24%,and the percentage of 7th harmonic amplitude to the fundamental wave is reduced from 42%to 22%.Experimental results show that both voltage compensation algorithms can effectively suppress current harmonics.