Sensorless Control Based on Extended-EMF Using Current Oversampling for PMSM

This paper proposes a novel approach to estimate extended electromotive force (EEMF) using current oversampling. By combining the oversampled current with the modeled inverter voltage, it becomes possible to estimate EEMF even during the pulse width modulation (PWM) cycle. This technique enhances the signal-to-noise ratio of the position estimator and improves its accuracy compared to conventional method. Normally, noise effects limit phase-locked loop (PLL) and auto speed regulator (ASR) bandwidth. The proposed method reduces this limitation. Experimental results confirm the proposed method's effectiveness by showing its tolerance to load at low speed, where EEMF is low, and position estimation accuracy is diminished.