Slip frequency correction based on torque observer for induction machine indirect vector control system

The performance of induction motor vector control is easily impacted by the variation of motor parameters. To overcome the effect of rotor time constant changing, a field orientation real-time correction method of rotor flux accurate orientation based on torque observer is proposed in this paper. The slip frequency is compensated directly by applying a PI regulator which uses the difference produced by the two torque observers in dq and αβ reference frame respectively when there´s a flux directional deviation. The coupling of dq-axis current caused by the rotor time constant change, and the influence exerted by the directional deviation on rotor flux and torque observer are analyzed. Since this method directly observes the stator flux without involving the rotor resistance, the accuracy of correction can be effectively ensured. Besides, this method is very simple in structure and easily to be implemented in industrial application. Simulation results have verified the effectiveness of the new proposed method.