Model reference adaptive system pseudoreduced-order flux observer for very low speed and zero speed estimation in sensorless induction motor drives

Sensorless induction motor (IM) drives are widely used in industry for their reliability and flexibility, particularly in hostile environment. However, the performance of many of previously developed observer based speed sensors in very low speeds of IM drives was not satisfactory. The authors have proposed and developed a model reference adaptive system (MRAS) based sensorless induction motor drive, which has high performance in very low speeds. In this novel scheme, an adaptive pseudoreduced-order flux observer (APFO) is used instead of the adaptive full-order flux observer (AFFO). In comparison with the AFFO, this method consumes less computational time, and provides a better speed estimation at very low speeds. This paper presents the theory, modelling, simulation and experimental results of the proposed MRAS pseudoreduced-order flux observer based sensorless field-oriented induction motor drives.