Rotor flux angle tracking controller for sensorless induction motor drives

A controller structure is proposed for the tracking of the rotor flux angle in a speed sensorless induction motor. The method is based on the fundamental-wave induction motor model that is augmented with the mechanical dynamics. A low-frequency current test signal is injected into the stator winding, and the response of the stator voltage is used to produce an error signal that can be controlled to zero by forcing the current signal into the direction of the rotor flux. The validity of the method down to zero stator frequency and speed is confirmed by the results of simulations and experiments.