A novel commutation correction method for high-speed PM brushless dc motor

The phase current of permanent magnet brushless dc (BLDC) motor lags the phase electromotive force (EMF) with the traditional commutation method, especially during high-speed operations. To overcome this problem, a novel commutation correction method is proposed in this paper. In the proposed method, the phase current lag angle is detected indirectly by detecting the phase difference between the rotor flux and the integral of the phase current. Since the detected phase difference can be reduced to zero through closed-loop control, the commutation point can be accordingly corrected. This commutation point correction method can increase the voltage utilization, achieve higher torque and extend the speed range with simple control. Also, it is effective within the entire operating speed range and load range. Basic principle and implementation of the new commutation point correction method will be presented in this paper, and sufficient simulation results will be given to validate the effectiveness and superiority of the control strategy.