SELECTIVE HARMONIC ELIMINATION PULSE WIDTH MODULATION (SHEPWM) FOR FIVE-PHASE NINE-LEVEL INVERTER USING IMPROVED WHALE OPTIMIZATION ALGORITHM

The multilevel inverter (MLI) is a well-known DC-AC converter system that can be used to convert renewable energy sources into industrial power sources. Compared to single-phase or three-phase MLI, five-phase MLI provide better output in terms of quality, efficiency and power. The harmonics in the MLI output voltage degrade the system's performance and reliability. Selected harmonic elimination pulse width modulation (SHEPWM) switching techniques are used to remove the lower order harmonics and lower the total harmonic distortion (THD). In recent years, a rapid evolution of optimization algorithms such as particle swarm optimization (PSO) algorithm, the genetic algorithm (GA) and whale optimization algorithm (WOA) are used to solve a complex equation such as SHEPWM non-linear equations. However, these algorithms were easy to fall into premature convergence and could not give the best result during the exploration and exploitation stage. In this paper, the improved whale optimization algorithm (IWOA), which is an improved version of the WOA is used as it has a better balance of exploration and exploitation which avoid premature convergence and is able to provide better results. The IWOA used to solve the non-linear equations for a five-phase nine-level inverter, and the results were compared to WOA, GA, and PSO for the whole modulation indexes (M). In comparison to all optimizations, the results indicate that the IWOA has a higher probability of reaching the global optimal. The proposed method efficiently computes the required switching angles for various M and eliminated the desired low order harmonics. The results show that the fifth, seventh, and eleventh harmonics have been removed from the output voltage of the five-phase, nine- level Cascaded H-Bridge Multilevel Inverter (CHBMLI).