An analysis of induction motor speed sensorless control using the extended EMF estimation

Induction motor speed sensorless control, which can be used in electric vehicles, allowing operation at low and zero speed, optimizing torque response and efficiency, is presented in the paper. The magnitude and orientation angle of the rotor flux of the induction motor are determined by the output of the closed-loop rotor flux observer based on the calculation of the extended electromotive force of machine. The proposed stator flux oriented control scheme is robust to parameter variations and external disturbances. Both, observer and controller, utilize the continuous sliding mode and Lyapunov theory. A smooth transition into the field weakening region and the full utilization of the inverter current and voltage capability are thus made possible. The produced torque is a continuous output variable of control. The reference tracking performance is demonstrated by experiments. Also the frequency analysis of the operation together with the proposal of parameter setting method is given.