PWM-Based Speed and Position Estimations for Permanent Magnet Synchronous Machines

A novel sensorless rotor position and speed estimator is presented in this study. The method is based on the measurement of the current response to conventional space-vector pulse width modulated voltages (SV-PWM) for PMSM drives applications. Model-Reference Adaptive Systems (MRAS) estimators are often used for sensorless speed estimation. A MRAS typically uses two models: the reference model (voltage model) and the adaptive model (current model). The voltage model in flux-based MRAS uses integration of stator voltages to calculate the stator flux. The pure integrator is usually replaced by a low pass filter; however, this results in phase errors at low frequencies. The position is estimated using oversampling and averaging over a switching SV-PWM cycle, eliminating the need for integrators. Extensive experimental tests are presented to evaluate the performance of the proposed estimator. The results of the experiments demonstrate good performance at various speeds and under various load circumstances, in both motoring and regenerating mode. The proposed method also shows robustness to changes in motor parameters.