A stable MRAS-based sensorless vector control induction motor drive at low speeds

Many MRAS based sensorless vector control induction motor schemes discussed in the literature. The MRAS based on flux estimation scheme suffers from the problems of using pure integration. On the other hand, those based on back-EMF or on current estimation become unstable in the generating mode of operation due to incomplete satisfaction of stability conditions, especially at low speeds. In this paper, a novel stable MRAS speed estimator based on current estimation is proposed. The stability is assured following a design procedure based on linear control theory. Simulations and experimental investigation have been performed to verify the stability of the proposed estimators.