Torque Ripple Reduction For PM Brushless DC Motor Based On Cuk Converter

Brushless DC motors have been widely used in aerospace,precision instruments,medical electronics and other fields,because of their simple structure,high reliability and high power density.However,the torque ripple can make the vibration and noise,which restricts its application in the high performance speed control system and the high precision position servo control system.The current methods still face a series of problems and challenges in suppressing the torque ripple and commutation torque ripple caused by free-wheeling current in the non-commutation state.This paper aims to solve the torque ripple and extend the application field of brushless DC motor to the high performance and high precision system.With the development of power electronics technology,DC-DC converter topology,modulation and control technology have been greatly developed.Based on Cuk converter,a novel commutation torque ripple reduction strategy is proposed for brushless DC motor(BLDCM)in this paper.Output modes(buck-boost mode and boost mode)of the Cuk converter during commutation period and normal conduction period are altered by designing a mode selection circuit,which can reduce commutation torque ripple over the entire speed range.During the commutation period,Cuk converter operates in the boost mode to step up the input voltage of three-phase bridge inverter and then meet the voltage demand of commutation period,such that the commutation torque ripple can be reduced by keeping the non-commutated current steady.In order to improve the utilization rate of the converter,during the normal conduction period,Cuk converter operates in the buck-boost mode and the input voltage of three-phase bridge inverter is regulated by adopting PAM(Pulse Amplitude Modulation)method without the inverter PWM chopping,which torque ripples are eliminated in normal conduction region,and can reduce the voltage spike damage to the motor windings caused by turn-on/off of MOSFET in the inverter and simplify the program of modulation method further.Based on the above theory,the simulation is carried out to verify the feasibility of the proposed method.The control system is set up taking TMS320F28335 as the core part,and the design of the control strategy is applied to the brushless DC motor control system.The experimental results verify the correctness of the theory and the effectiveness of the proposed approach.