A filtered back EMF based speed-sensorless induction motor drive

Previous works on back EMF based speed-sensorless induction motor drives generally adopt the MRAS approach, frequently contain model redundancy, and can become unstable in the regenerative mode due to lack of adequate stability analysis and a suitable design method. In this paper, a novel back EMF based speed estimation using an adaptive observer is proposed. Explicit stability conditions are then derived from the stability analysis, based on which a design strategy for the speed estimator is introduced to guarantee the stability for the whole operating conditions including the regenerating mode. The implementation complexity is minimized by the integration of the proposed observer with the vector controller to avoid model redundancy. The feasibility of the proposed system is verified by experiment.