Analyzing the Relationship Between Minimum THD and Nearest Level Waveforms in Multilevel Inverters

Reducing Total Harmonic Distortion (THD) is essential for improving power quality and ensuring compliance with standards in modern power systems. While multilevel converters inherently help reduce THD due to their staircase output waveform, additional THD reduction techniques are often required to meet stringent regulatory requirements. Existing approaches in the literature largely rely on numerical optimization techniques, which impose significant computational burdens and may yield sub-optimal solutions. This paper establishes a direct analytical relationship between the minimum THD switching signals and Nearest Level Modulation (NLM) which is not reported in the literature. Then equations are developed to derive explicit equations for determining the optimal switching angles to achieve minimum THD. The proposed method eliminates the limitations of existing numerical or optimization-based approaches, offering a more efficient and precise solution for THD minimization in multilevel converters.