LAUSR

Existing methods of compensation of commutation instants are generally developed based on the assumption that the back electromotive force (EMF) is trapezoidal wave and the three-phase windings are symmetrical. But this is not the fact. The actual back EMF waveform and commutation ripple would make the conventional methods disabled. According to the actual back EMF waveforms, the relationship between commutation point shift and the difference of dc-link current, which is sampled at the points before and after commutation, is analyzed. Based on this relationship, a novel self-compensation method of commutation error is proposed, which can be used both in sensorless motor and in hall sensor-based motor. As the shift phase is obtained through analytical method, fast convergence speed can be achieved. Furthermore, the influences caused by the freewheeling of turn-off phase inductance and the unbalanced three-phase windings are analyzed and removed. At last, the validity of the proposed self-compensation method is verified through experimental results.