Robust speed identification for speed-sensorless vector control of induction motors

This paper describes a new approach to estimating induction motor speed from measured terminal voltages and currents for speed-sensorless vector control. The proposed approach is based on observing the instantaneous reactive power of the motor. The estimated speed is used as feedback in an indirect vector control system. The described technique is very simple and robust to variations of motor parameters. The new approach is not dependent upon the knowledge of the value of the stator resistance, nor is it affected by stator resistance thermal variations. Furthermore, pure integration of sensed variables, in principle, is not required at all. Therefore, this new method can achieve much wider bandwidth speed control than previous tacholess drives. The effectiveness is verified by simulation and experiment