Improved Flux Estimation Technique For Direct Torque control of Induction Motor Drives

Abstract

Induction motors are the starting point to design an electrical drive system which is widely used in ma ny
industrial applications. In recently various speed control technique are used. But the direct torque control (DTC) scheme
being one of the most recent steps in this direction. This scheme provides excellent properties of regulation without
rotational speed feedback. In this control scheme the electromagnetic torque and stator flux magnitude are estimated
with only stator voltages and currents and this estimation does not depend on motor parameters except for the stator
resistance. Literature review has been done to study the recent improvements in DTC scheme especially in low speed
range operation to improved flux estimation and reduce the torque ripple problem.
The conventional direct torque controlled scheme used voltage model for flux estima tion but this model estimate
inaccurate flux at lower speed. So due to inaccurate flux estimation DTC drive give poor performance by distortion of
stator current and torque ripple. So here I have present another model for flux estimation which gives best DTC drive
performance at lower speed.