PWM Switching Delay Correction Method for High-Speed Brushless DC Drives

Abstract

For high-speed brushless DC (BLDC) drives, the switching-to-fundamental frequency ratio is usually insufficient. As a result, the commutation errors caused by PWM switching delay are significant, which means the power switches will take action at inaccurate instants. This will cause low-frequency current oscillations and produce additional losses. In addition, the conventional commutation PWM method will cause accumulative errors in the sensorless operation and will further lead to instability issues in the high-speed region. In order to suppress these influences, a novel carrier-synchronized commutation PWM strategy is proposed in this paper. It shows that the proposed strategy can eliminate the commutation error caused by PWM switching delay. In addition, the instability phenomenon can be avoided and the current control performance is greatly improved. Finally, the proposed strategy is verified by simulation and experiments on a 78 000-r/min BLDC drive platform.