An alternative sensorless field orientation method

This paper proposes a sensorless vector control method to achieve field orientation in induction motor drive systems. The field orientation strategy is based on the concept of varying the stator frequency with respect to a slip difference. A general equation for calculating the slip in any reference frame is developed. A reduced order discrete rotor flux observer with small sensitivity to rotor resistance and slip variations is used. The whole control system operates in a synchronously rotating frame. Only stator voltages and currents are sensed. A different approach in implementing this method through a frequency PID is also presented. Simulation results are used to verify the validity of the proposed alternative sensorless field orientation technique