Improved rotor flux estimator for sensorless induction motor

An improved rotor flux estimator based on voltage model was proposed for speed sensorless field-oriented vector controlled induction motor drives. In order to eliminate direct current (DC) drift and saturation problems of pure integrator for back electromotive force, an improved programmable low-pass filter (LPF) rotor flux estimator was proposed to replace the pure integrator. However, introduction of the LPF estimator may cause magnitude, phase errors, and decrease in estimation performance. A compensator was designed to reduce the magnitude and phase error introduced from the LPF estimator. The validity of the proposed rotor flux estimator is verified by speed sensorless field-oriented vector controlled 11 kW induction motor drive.