Adaptive stator flux estimator for the induction machine Direct Torque Control

Abstract

The paper presents a new stator flux estimator for the induction machine Direct Torque Control (DTC). The study aims to develop an estimator which gives good stator flux feedback values even when the stator resistor varies with the machine temperature. In DTC algorithm, stator electric equation is usually used to calculate the stator flux error. The value of this error is used with the torque error to determine the optimal voltage space vector that gives a simultaneous changing of the torque and the flux in the desired direction. The accuracy of the DTC depends on the proper calculation of the stator flux. The main objective is to build a stator flux estimator depending on the rotor electric equation. Since the time response of the rotor flux is bigger than the time response of the stator flux, this new estimator is less sensitive to the variation of the rotor resistor. The behaviour of the developed estimator is enhanced in an adaptive way to take into account the variation of the saturation level in the air gap of the induction machine.