Analysis and Comparison of SHE and APOD Harmonic Elimination Strategies in CCS Multilevel Inverters

Abstract

This work defines and compares the characteristics between two modulation strategies Alternative Phase Opposition Disposition (APOD) and Selective Harmonic Elimination (SHE) based on a five-level Cross-Connected Source-Based Multilevel Inverter (CCS-MLI). It has a reduced component count that can be reached through shared switching branches. The CCS-MLI topology has an efficient alternative to conventional H-bridge structures. The baseline harmonic profile can be evaluated by the APOD technique for the first time in this study. The association of SHE method with the Newton-Raphson algorithm to eliminate low-order harmonics by calculating the optimized switching angles. To ensure a fair comparison, MATLAB/Simulink simulations were performed under the same RL load conditions. The results show that the output voltage's THD with APOD is around 34.4%, whereas the SHE-controlled inverter yields a much lower THD of 18.61%, underscoring its higher capability to remove harmonics. The analysis confirms that the SHE approach, while requiring more computational resources, delivers a high-fidelity output waveform, rendering it more appropriate for applications that require stringent power quality standards. The results highlight the possibility of improving the performance of compact multilevel inverters by sophisticated modulation methods.