Research on speed sensorless vector control of induction motor based on stator flux orientation

The stator flux for speed sensorless vector control is estimated by integration of back EMF. But the drift, initial value and distortion problems of pure integrator often cause orientation inaccurateness. In this paper, a novel integration method using a kind of saturable feedback is presented. And the limiting level used in saturable feedback is adjustable according to the estimated speed of induction motor. This algorithm can be used to accurately measure the motor flux including its magnitude and phase angle over a very wide speed range. The usefulness of the proposed scheme is successfully demonstrated by simulation and actual system experiments based on ADMCF328 DSP.