Ellipse Fitting Technique Based Sensorless Control for SynRM Using Rotating Square Voltage Injection

This paper proposes a rotating square voltage injection (RSVI) based sensorless method for synchronous reluctance motor (SynRM). The proposed method injects a high-frequency (HF) rotating square voltage into the stator winding and extracts the fundamental and HF-induced currents without any filter. The elliptical shape of the HF-induced current trajectory is fitted using the least squares (LS) method. Based on the relationship between the ellipse tilt and the rotor position, the fitting coefficients of the elliptical current trajectory are used to estimate the rotor position by quadrature phase-locked loop (Q-PLL). The proposed position estimation method has a simple tuning procedure and does not require motor parameters. Furthermore, to improve the accuracy, the distortion of the elliptical current trajectory due to non-zero speed and position estimation error due to magnetic saturation are analyzed and compensated. Finally, the effectiveness of the proposed method is verified by carrying out simulations on a 3-kW SynRM.