A Geometric Series Based Nearest Level Modulation Scheme for Multilevel Inverter

Multilevel inverters are the best suitable power electronics converters over conventional two/three-level inverters to provide high power quality ac waveforms. However, the quality of the ac power highly depends on the modulation scheme employed by the multilevel inverter. The use of a low-switching frequency modulation scheme is strongly emphasized over a high-switching frequency modulation scheme because of numerous advantages such as lesser power loss, lower switching stress, improved converter efficiency and enhanced converter lifetime. This paper presents a variant of the Nearest Level Modulation scheme, which is based on the geometric nature of variation of MLI switching angles. Hence, the proposed NLM scheme is termed as Geometric-NLM (G-NLM). A seven-level symmetric CCS-MLI topology is taken for the case study, and the proposed modulation scheme is implemented on it. Matlab/Simulink is used to carry out the simulation, and the results are presented. The G-NLM is found to have reduced the voltage THD and improved other MLI parameters compared to the conventional NLM scheme.