Selective Harmonic Elimination With Optimal DC Sources in Multilevel Inverters Using Generalized Pattern Search

This paper presents the computation of optimal dc sources and switching angles using the generalized pattern search (GPS) optimization method for harmonic elimination in a cascaded multilevel inverter. The goal is to solve nonlinear equations for eliminating low-order harmonics and reaching desired fundamental component. For case study, 5- and 7-level inverters are chosen. The 7-level inverter with equal dc sources and 5-and 7-level inverters with an optimal dc source are applied to eliminate fifth and seventh harmonics. To obtain this goal, MATLAB software is used. Considering simulation results, cost, and simpler implementation, 5-level inverter with an optimized dc source is more effective in all modulation indexes in comparison with 7-level inverter. Also, results demonstrate the superiority of GPS over genetic algorithm (GA) in attaining accurate global minima. For better evaluation of optimizing more dc sources and GPS performance in comparison with GA, 7-level inverter with two optimal dc sources is applied to eliminate fifth, seventh, 11th, and 13th harmonics. Finally, to validate the accuracy of the 5-level inverter with an optimal dc source and GPS performance, the experimental results are provided for a 5-level cascaded H-bridge inverter.