Harmonics analysis and simulation of NLM in MMC

Selecting inter-phase circulation, up and lower bridge arm current, and AC output voltage wave of the inverter as research objects, this paper analysed harmonic components in Modular Multilevel Converter (MMC) in Nearest Level Modulation (NLM) when MMC is used as inverter. With theoretical deduction, this paper points out that the up and lower bridge arm current mainly contains DC current component, fundamental component and second harmonic component, inter-phase circulation contains only even harmonic, AC output voltage wave contains only odd harmonic components. Finally, the derivation results are simulated and verified by 11-level PWM converter model (See Fig.1 and Fig.2) based on Matlab/Simulink.