High-Precision Sensorless Optimal Commutation Deviation Correction Strategy of BLDC Motor with Asymmetric Back EMF

Due to the asymmetry of the actual back electromotive force (back EMF), the performance of the conventional commutation deviation correction method degrades in sensorless control of the brushless direct current (BLDC) motor. This article proposes a high-precision sensorless optimal commutation deviation correction strategy, which considers the asymmetry problems of the back EMF. First, this article discusses the optimal commutation issues and the internal power factor angle based commutation deviation correction method. Then, given the issue of the nonsinusoidal phase current integration and the asymmetric back EMF, a dual improved second-order generalized integrator with a positive sequence component extractor (DISOGI-PSCE) is proposed. The DISOGI-PSCE can effectively deal with the dc component and harmonics in flux-linkage and current integration, as well as the asymmetry of the back EMF. Finally, experimental tests are performed on a magnetically suspended control moment gyroscope BLDC motor, which verified the effectiveness of the proposed high-precision sensorless optimal commutation deviation correction method.