Deployment of an Adaptable Sensorless Commutation Technique on BLDC Motor Drives Exploiting Zero Sequence Voltage

This paper introduces an improved signal processing technique of zero sequence voltage (ZSV) with the scope of position sensorless commutation of a BLDC motor drive system. Rotor position information is extracted in the proposed technique from ZSV. This signal includes all time intervals where back electromagnetic force (EMF) zero crossings (ZCs) occur, from which the commutation instants are determined. This technique exploits maximally flat group delay of Bessel low-pass filters for switching noise suppression. This attribute leads to a speed-independent time displacement of ZSV. The fundamental frequency of ZSV is determined through a median-filtering algorithm, which is required for a dynamic rate limiter that eliminates erroneous ZCs. In sequence, a pulse train is generated by the detected ZCs of the emerged signal and properly shifted to determine the correct commutation instants. The proposed technique ensures a wide operational speed range for the drive system. A theoretical analysis of the drive system is presented, considering a BLDC motor with nonideal back-EMF. Experimental results presented in this paper validate the effectiveness and robustness of the proposed position sensorless commutation technique under various operational conditions.