Research and design of speed control for high speed sensorless brushless DC motor with commutation compensation

This paper presents the design and implementation of a high speed sensorless brushless DC motor (BLDCM) drive with commutation compensation. The back electromotive force (EMF) detection using three phase terminal voltage is implemented to detect the rotor position, in order to filter the high frequency switching signals, a low pass filter is applied in the back EMF detection circuits, the cut-off frequency of the low pass filter is determined by the speed range and switch signal's frequency. The hysteresis caused by the low pass filter has a linear relationship with the frequency of the back EMF. Thus, the proposed control method is aimed to correct the commutation instant with an angle compensation in the whole speed range. The compensation angle is obtained from the detection circuits' parameters and the back EMF frequency. The simulation and experiment results showed that this method has excellent performances with large load disturbance in whole speed range.