A stable back-EMF MRAS-based sensorless low-speed induction motor drive insensitive to stator resistance variation

It is well-documented that back-EMF MRAS-based speed sensorless induction motor drives can suffer from instability problems especially at low-speed operation, and that MRAS schemes using flux estimation suffer from drift problems associated with direct integration. Sensorless IM drives are also sensitive to stator resistance mismatch, particularly at low speeds. Novel stable MRAS speed and stator resistance estimators based on back-EMF quantities, and which are capable of being operated simultaneously, are proposed. Full details of the theoretical foundation and of the design procedure are given. The stability of the estimators is assured by appropriate location of the closed-loop poles of the estimators. Extensive simulation and experimental investigations have been performed to verify the stability of the proposed estimators in the motoring, generating and braking modes of operation.