Reduction of torque ripple in direct torque control of induction motor using constant switching frequency operation

This paper proposed simple algorithm for direct flux and torque controlled three phase induction motor drive systems. Proposed method is based on control of decoupled between amplitude and angle of reference stator flux for determining required stator voltage vector. The flux as well as torque errors within the given sampling time are controlled by required stator voltage vector which is evaluated from reference stator flux. The direct torque control is achieved by reference stator flux angle which is generates from instantaneous slip angular frequency and rotor angular frequency. The amplitude of the reference stator flux is kept constant at rated value. This technique gives better performance in three phase induction motor than conventional technique. Simulation results for 3 hp induction motor drive for both proposed and conventional techniques are presented and compared. Results shows that the stator current, flux linkage and torque ripples are decreased with proposed technique. (6 pages)