Performance Evaluation of a Sensorless Induction Motor Drive at Very Low and Zero Speed Using a MRAS Speed Observer

Model Reference Adaptive System (MRAS) represents one of the most attractive and popular solutions for sensorless control of AC drives. However, the performance of this scheme deteriorates when approaching the zero speed zone. This paper presents an experimental evaluation of the performance of MRAS speed observer when working at very low and zero speed. Results are obtained when applied to an indirect vector control induction motor drive in both open loop and sensorless modes of operation. Since the focus here is on operation around and at zero speed under both no-load and loading operating conditions, this represents a useful contribution to the literature. Results show the deterioration in the performance of the estimation scheme at very low and zero speed especially when load is applied.