Injectionless Sensorless Control of Synchronous Reluctance Machine for Zero to Low Speeds Region

An alternative to the high frequency injection approach for sensorless control at zero and low speed region is proposed for synchronous reluctance machines (SyR) using finite-control-set model predictive control (FCS-MPC). The saliency based position estimate aims to exploit the switching current ripple which is pronounced owing to the nature of MPC especially around zero and low speed region due to the minimal back-emf. A demerit of the high frequency injection techniques is the bandwidth hindrance of position observer by the demodulating low pass filter (LPF). In the proposed method, no such filters are required and consequently, high bandwidth is achieved. Guidelines for the calibration of observers are addressed. In addition, the effects of cross-saturation on position estimation is inherently considered. The experimental validation on a 1 kW SyR shows stable operation under torque and speed transients, and proves the feasibility of the proposed technique.