Sensorless Drive for Salient Synchronous Motors Based on Direct Fitting of Elliptical-Shape High-Frequency Currents

The article deals with a position sensorless control for synchronous motor drive with an ease tuning procedure and a reduced number of tunable parameters. The rotating high-frequency (HF) signals injection is implemented and the elliptical shape of the HF-induced current trace is fitted by means of the least square (LS) algorithm. The ellipse tilt is related to the rotor position and the latter is estimated by processing the fitted coefficients of the ellipse mathematical equation. The proposed LS algorithm processes the measured currents, without the need to filter them as occurs in conventional injection methods. Furthermore, no motor parameters are required to tune the proposed rotor position observer. The method was validated throughout several experimental tests performed on an interior permanent magnet synchronous motor.