Nearest level control for improving total harmonic distortion in a 13-level three-phase multilevel inverter

This research investigates the application of nearest level control (NLC) in a three-phase transistor-clamped H-bridge (TCHB) multilevel inverter (MLI) to enhance power quality and reduce harmonic distortion. The TCHB topology offers high perfor-mance with fewer components compared to traditional MLI configurations, making it par-ticularly suitable for renewable energy applications. By operating at fundamental switching frequency, the NLC technique effectively minimizes switching losses while reducing total harmonic distortion (THD). The study includes MATLAB/Simulink-based simulation modeling and experimental validation using dSPACE, tested under varying load conditions. For a 13-level TCHB inverter with equal DC supplies and a modulation index of M = 1, the voltage THD was 5.22% (resistive load) and 5.17% (inductive-resistive load) in simula-tions, which was further reduced to 4.5% and 4.2% in experiments. The NLC technique demonstrated superior harmonic performance and efficiency compared to conventional methods, particularly at higher voltage levels. This study highlights the practical advantages of the TCHB inverter, including reduced component count, simplified control implementa-tion, and enhanced output waveform quality. These findings confirm the potential of the NLC-based TCHB inverter for high-performance motor drives and grid-tied renewable en-ergy systems, positioning it as a promising solution for modern power electronics applica-tions.