Performance enhancement of a 15-level reduced-switch MLI through THD reduction using hybrid metaheuristic optimization techniques

This paper aims to minimize total harmonic distortion (THD) in a reduced-switch multilevel inverter using an advanced hybrid optimization framework. A 15-level asymmetric multilevel inverter (MLI) with a binary-weighted (1:2:4) DC source configuration is considered the test platform because it balances power quality and hardware complexity with only seven active switches, three DC sources, and three diodes. While such reduced-switch topologies are not new in the field, their harmonic performance can be critically limited by the selection of the optimal switching angles. To address this issue, Selective Harmonic Elimination Pulse Width Modulation (SHEPWM) has been adopted, where a hybrid metaheuristic optimization algorithm solves the nonlinear transcendental equations- Enhanced Whale Optimization Algorithm (EWOA), Adaptive Particle Swarm Optimization-Newton Raphson (APSO-NR), Particle Swarm Optimization-Genetic Algorithm (PSO-GA) and Harris Hawks-Differential Evolution (HH-DE). The main contribution of this paper is the systematic comparison and implementation of these hybrid algorithms using a single SHEPWM scheme, analyzing their convergence behaviour, statistical performance, and harmonic minimization. From the simulation studies, the HHDDE algorithm achieved the fastest convergence rate and a THD of 5.33%, with current THDs below 3%, ensuring compliance with the IEEE-519 harmonic standards without external filtering.