Comparative study of rotor flux estimators sensitivity in the speed sensorless induction motor drive

Motor drives with speed sensors are expensive and less reliable. Therefore there is significant interest in finding software-based methods of controlling induction motors using only stator current and voltage sensors. In a simple typical application, estimation methods for motor flux and speed are used. However, simulation studies and real life applications show that observers, instead of estimators, are more powerful and manageable. This paper shows the differences between these two methods. Simulation results present the advantages of observers over estimators. For the simulation, a model of a field-oriented closed-loop control system for an induction machine was used, together with a speed estimator and flux observer or estimator for comparison purposes.