Abstract
Carrier based SPWM techniques are the simplest and widely reported methods in the literature when it comes to controlling Modular Multilevel Converter (MMC) for high or medium voltage applications. In this paper, various multilevel SPWM techniques for MMC are simulated, analyzed and compared with each other. The conventional half bridge submodule (SM) is considered here for the study. The effect of the SM capacitance on the output voltage waveform is also analyzed and the optimal value of the capacitance is found out. Differences in the quality of output voltage between traditional phase disposition (PD) PWM and the proposed unipolar PD PWM have been observed and their comparative performances are shown based on 8-SM per phase MMC structure in the simulation results. Closed loop control of grid connected MMC is also validated by simulation study and then superiority of the unipolar PD PWM in comparison to any other carrier based SPWM technique is established.
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