Research on Torque Ripple Suppression of Open-Winding BLDCM Based on Zero Vector

Brushless DC motors (BLDCM) are widely utilised due to their simple mechanical structure and high power density. To enhance energy efficiency, environmental sustainability and control flexibility, open-winding brushless DC motors (OW-BLDCM) have been introduced. Direct torque control (DTC) is an efficient control strategy for BLDCM; however, the nonsinusoidal back electromotive force and phase-off operation characteristics of OW-BLDCM present fundamental theoretical challenges for its implementation. This paper investigates these challenges from both mechanistic and physical perspectives. The commutation current paths under zero-voltage vector conditions are analysed, and an optimised zero-voltage vector selection strategy is proposed to prevent simultaneous three-phase conduction and phase current reversal, thereby mitigating commutation torque ripple. Additionally, a duty-cycle control algorithm is introduced to further reduce torque ripple within each sector. Experimental results demonstrate that the proposed zero-voltage vector strategy effectively reduces torque ripple by 27.8% by eliminating undesirable current behaviours. Further application of the duty-cycle control algorithm achieves an additional 26.9% reduction in torque ripple. These findings validate the theoretical analysis and confirm the effectiveness of the proposed method, providing a solid foundation for the future application of modern control strategies in OW-BLDCM.