Closed loop control strategy to correct the commutation error of high-speed magetically suspended brushless dc motors without position sensor

This paper analyzes the exact expression of the non-commutation phase current considering the commutation error in PAM modulation mode of high-speed magnetically suspended brushless DC motor based on the line-to-line back-EMFs and points out that the commutation process of high-speed motor is very short. Then this paper proposes a new closed loop control method to correct the commutation error according to this conclusion. The method takes the equivalent phase current integration of non-commutation phase within the range of 30° before and after the commutation as the target and takes the phase current integration difference of non-commutation phase as the feedback amount, and corrects the commutation error automatically through the PI regulator. Applying the optimal hysteresis transition between '90-α' and '150-α' ensures the reliable correction of the commutation error. The experimental results show that this closed loop commutation correction strategy realizes the real-time compensation for the commutation error within the scope of 3 2000r/min.