GWO-NR Hybrid Method for Selective Harmonic Elimination in Multilevel Inverter for Distributed Energy Systems

This article presents a hybrid method to solve the selective harmonic elimination (SHE) problem for an adaptive DC bus multilevel inverter (MLI) topology. The proposed hybrid method combines the Grey wolf optimization (GWO) technique and Newton-Raphson (NR) numerical method which drastically minimizes the computational time and further improves the accuracy of the SHE solution. The technique is essentially divided into two stages. In the exploration stage, GWO explores the entire search space of SHE problem and provides initial values of switching angles for a given modulation index with a fast rate of exploration. In the exploitation stage, the NR method uses these initial switching angles as input to iteratively determine the optimum value of the firing angles. This GWO-inspired iterative methodology is implemented on a hybrid MLI topology for photovoltaic (PV) system applications. The performance of proposed SHE method is compared with recently developed metaheuristic SHE techniques based on some key performance indices. From an application point of view, the 11-Level MLI is tested on a PV battery-based stand-alone system to determine the effectiveness of the proposed method in MATLAB/Simulink environment. Finally, a small-scale experimental prototype is developed to validate the proposed method. The simulation and experimental results have been shown to demonstrate the effectiveness of GWO-NR SHE method in terms of excellent control over the targeted harmonics and fast dynamic control in the standalone PV system.