Optimal PWM for Minimization of Total Harmonic Current Distortion in High-Power Induction Motors Using Genetic Algorithms

This study presents a powerful application of genetic algorithm (GA) for the minimization of the total harmonic current distortion (THCD) in high-power induction motors fed by voltage source inverters, based on an approximate harmonic model. That is, optimal pulse patterns (switching angles) are determined to have the THCD minimized and the fundamental output voltage regulated concurrently. As the minimization of THCD corresponds to the minimization of harmonic copper losses of the motor windings, GA optimization technique has been utilized, in comparison with conventional optimization methods due to its capabilities of searching the entire solution space with more probability of finding the global optimum solution. Necessarily in this case, the fundamental frequency must be considered constant for the purpose of defining a sensible optimization problem. Switching angles are accomplished up to 12, in which for more than this number of switching angles, space vector pulsewidth modulation (SVPWM) method, is preferred to optimal PWM method. Indeed, in high-power machines, the feeding scheme is a combination of optimal PWM and SVPWM