Harmonic Minimization using a Cascaded Multilevel Converter for a Standalone Renewable Energy System

Abstract

Effective power conversion is necessary when integrating photovoltaic (PV) systems into the electrical grid to manage high voltages, minimize switch stress, and improve power quality while reducing the need for intensive filtering. The advantages of multilevel inverters (MLIs), especially cascaded H-Bridge (CHB) designs, in lowering electromagnetic interference (EMI) and increasing efficiency have made them essential for renewable energy systems. This work proposes a DC-AC-DC-AC converter system with seven-level and thirteen-level topologies. The seven-level converter system is designed and simulated in MATLAB/Simulink using phase-shifted pulse-width modulation (PSPWM) and level-shifted pulse-width modulation (LSPWM) to analyze total harmonic distortion (THD) and determine the best modulation technique for a grid-connected standalone system. The study finds that the thirteen-level converter showed improved power quality and system efficiency, with a significant decrease in THD to 0.43 % after filtering. Real-time simulation on the OPAL-RT platform confirms the adaptability and efficacy of the presented approach in real-world situations. Furthermore, incorporating more reliable and compact medium-frequency transformers supports environmental sustainability by enhancing energy efficiency, reducing material consumption, and supporting modularity for easier maintenance.