Commutation Point Optimization Method for Sensorless BLdc Motor Control Using Vector Phase Difference of Back EMF and Current
Haifeng Zhang, Lirong Deng, Haitao Li, Shiqiang Zheng, Hao Jin, Baodong Chen
Abstract
Commutation error is a crucial factor that reduces the efficiency of brushless dc (BLdc) motors. This article presents a commutation point optimization method for a sensorless BLdc motor. First, the sources of commutation error under position sensorless control are analyzed, and a conclusion is drawn that the phase difference between the back electromotive force vector and phase current vector equals the total commutation error. Second, a fundamental waveform extractor is used to eliminate the influence of harmonics on the equivalent commutation error. Third, the phase difference of the fundamental waveforms is extracted by a combined phase-locked loop, and the real-time commutation error is obtained consequently. Finally, accurate commutation is achieved by compensating for the phase difference, and experimental results on a reaction flywheel prototype evaluate the presented method.