A Novel Method of Reducing Commutation Torque Ripple for Brushless DC Motor Based on Cuk Converter

In this paper, based on Cuk converter, a novel commutation torque ripple reduction strategy is proposed for the brushless DC motor. Output modes (buck-boost mode and boost mode) of the Cuk converter during the 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 noncommutated 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 the pulse amplitude modulation (PAM) method without the inverter pulse width modulation chopping, which 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. The experimental results verify the correctness of the theory and the effectiveness of the proposed approach.