Minimization of Torque Ripple in Induction Motor Drive by Optimal Harmonic Elimination

Cascaded H-Bridge Multilevel Inverter (CH-MLI) is rich in output voltage harmonics. If MLI's poly-phase output voltage is fed directly as input to drive an induction motor, there is great change in the performance of the motor output. To reduce the lower order harmonics in CH-MLI, a novel selective harmonic elimination method is proposed in this paper. The proposed Cross-Entropy (CE) optimization is implemented to find the optimal switching angle of CH-MLI. The switching angles determined are generated by sinusoidal pulse width modulation in MATLAB based simulation. The performance of CE optimized 11-level CH-MLI connected to an induction motor drive is compared with existing optimization methods. The torque ripple and total harmonics distortion (THD) comparisons are studied. Moreover, Cross-Entropy optimization algorithm simulation results are found superior to the other algorithms in reducing the THD as well as a reduced torque ripple. Using CE optimization technique about 14.45% reduction in torque ripple is attained and 19.14% reduction in THD is found.