Research On Harmonic Current Suppression Strategy Of Open-winding Nine-phase Permanent Magnet Synchronous Moto

Open winding topology has higher output power,more flexible power supply selection mode,and more diverse output combinations,so it is widely used in the field of multiphase motors.To improve the utilization of fundamental current,the stator of multi-phase openwinding PMSM mostly adopts concentrated full-pitch winding.However,due to the influence of harmonic back EMF and nonlinear factors of the inverter,there are many harmonic currents in stator winding of the motor,which will seriously affect the operation of the motor.Therefore,to reduce the impact of harmonic current of the motor and propose an effective harmonic current suppression strategy,aiming at improving the performance of the ship large capacity multiphase PMSM,the paper researches the nine-phase open-winding PMSM to find the impact of harmonic current on the motor and the harmonic source from inverter and motor.Firstly,the harmonic voltage output of full-bridge inverter with bipolar SPWM and frequency doubling unipolar SPWM are analyzed.The relationship between nonlinear factors and output voltage of inverter which working in different condition is analyzed.According to the mathematical model of the PMSM in the d-q coordinate,the influence of the harmonic component of the back EMF of the motor on the harmonic current is studied.Based on the harmonic characteristics of inverter output voltage and motor,combined harmonic detection with synchronous reference frame phase-locked loop(SRF-PLL),an improved harmonic current suppression strategy is proposed.The SRF-PLL is used to track the harmonic voltage output by the inverter due to various nonlinear factors,with the back EMF of the motor,the feedforward compensation voltage is applied to the harmonic current closed-loop control.The amplitude and frequency characteristics of SRF-PLL and QPR controller are analyzed by using Bode diagram,and it is confirmed that SRF-PLL with lowpass filter(LPF)can effectively suppress the switching frequency voltage component,and the characteristic of QPR controller is analyzed.Finally,the simulation and experimental results verified the correctness of the above theoretical analyse and the effectiveness of the harmonic current suppression method is also verified.