FUZZY DIRECT TORQUE CONTROL OF PMSM WITH STATOR FLUX ESTIMATION AND COMPENSATION

Abstract

In this paper we are dealing with the direct torque control and its limitations. DTC suffers in the low speeds due to the effect of changes in stator resistance on the flux measurements. To improve the system performance (PMSM) at low speeds a fuzzy resistance estimator is proposed to eliminate the error due to change in stator resistance. The stator current error caused by the change in stator resistance of the induction at constant flux and torque commands is used by the fuzzy estimator for correcting the stator resistance used by the controller to match machine resistance. The fuzzy controller computation speed is a key factor to obtain fast torque control. Flux position, error in flux magnitude and error in torque are used as fuzzy state variables. Fuzzy rules are determined by observing the vector diagram of flux and current. To enable DTC to be applied at low speed while the stator flux estimation compensation has been developed. The simulation results show the effectiveness of the new control strategy.