Torque ripple reduction of BLDC motor based on DC bus voltage automatic selection circuit and neutral point clamped three-level inverter control

Abstract

The torque ripple of Brushless direct current motor (BLDCM) mainly depends on the commutation torque ripple, while the commutation torque ripple mainly depends on the current fluctuation during commutation. In this paper, the cause of current fluctuation during commutation is analyzed, and an automatic selection circuit based on DC bus voltage and a neutral-point-clamped (NPC) three-level inverter controller is proposed. The motor winding is guaranteed to bear half of the DC bus voltage, and the duty cycle is calculated so that the DC bus voltage at the moment of phase change is in a certain relationship with the back electromotive force (EMF) of the circuit, thus suppressing the current ripple during phase change and achieving the purpose of suppressing torque ripple during phase change.