Design of MRAS-based Observer in Speed Sensorless Induction Motor Drive

This paper deals with the design of MRAS-based observer in speed sensorless induction motor drive. The option of reference coordinate of current model is focused on, for there exists an unstable region when the model is expressed in discrete form. An option of voltage model and current model in stationary and synchronous coordinate respectively, is proposed to allow the system to run stable in the whole speed range. Meanwhile, detailed analysis is made of designing an improved integrator with PI adaptive feedback term correction to solve the pure integrator problems in voltage model, which also aids in improving the MRAS-based speed sensorless drive performance in low speed region. In addition, the design method of speed PI adaptive law is proposed in this paper to allow the estimated speed follow well with the practical one dynamically and steadily. Finally, simulation results confirm the analysis made above.