Performance analysis of speed estimator insensitive to stator resistance at low speed in sensorless induction motor drives

This paper presents the performance analysis of two model reference adaptive system (MRAS) based speed estimator for sensorless field oriented control of induction motor drive at low speeds including zero speed without affecting the stability of the system. Flux based MRAS speed estimator being dependent upon the stator resistance variations, needs to be tracked during the operation of the drive especially at low speeds, which increases the system complexity while proposed steady state reactive power MRAS rotor speed estimator gives the better performance at low speeds including zero speed. Thus scheme is robust to the effect of stator resistance variations in flux MRAS speed estimator. A brief analysis of significance of the speed tuning signal used in MRAS speed estimator is obtained in this paper. The performance of both the method is rigorously verified through tracking capability of the speed estimator especially at low speed in MATLAB/SIMULINK software package.