Improved Modular Multilevel Converter Modulation Strategy

In this paper, for the modulation strategy of modular multilevel converter (MMC), we focus on the step-wave modulation technique and the nearest-level-approximation modulation strategy, and propose an improved nearest-level-approximation (NLC) modulation method. By optimizing the sub-module (SM) capacitor parameters and refining the step voltage values, the harmonic components can be effectively reduced and the quality of the output voltage waveform can be improved. A three-phase MMC model with seven-level sine wave output voltage is constructed by MATLAB/Simulink simulation platform to verify the effectiveness of the improved NLC modulation strategy.