Reduction of Torque Ripple in Direct Torque Control for Induction Motor Drives Using Decoupled Amplitude and Angle of Stator Flux Control

Abstract

This paper proposes design and implementation of a direct torque controlled induction motor drive system. The method is based on decouple control of the amplitude and the angle of the stator flux reference for determining the reference stator voltage vector in generating the PWM output voltage for induction motors. The objective is to reduce electromagnetic torque ripple and stator flux droop which result in a decrease in current distortion at steady state. The proposed technique is based on the relationship between the instantaneous slip angular frequency and rotor angular frequency in adjustment of the stator °ux angle reference. The amplitude of the reference stator flux is always kept constant at rated value. The system has been implemented to verify its capability such as torque and stator °ux responses, stator phase current distortion both during dynamic and steady state with load variation, and low speed operation.