PSC-PWM Scheme for Modular Multilevel Converters with Highly-reduced Carrier Numbers and Low Control Complexity

Abstract

The Modular Multilevel Converter (MMC) has been recently accepted as an advantageous choice for high-voltage applications. However, for extending this topology to higher voltages, the number of its submodules should be increased. On the other hand, using high-frequency carrier-based modulation schemes is very popular for voltage-source converters; since they provide improved output quality, and don’t involve complex calculations. When this strategy is employed for MMCs, the number of carriers would increase for more submodules, and the control complexity and required memory become more as result. Moreover, synchronizing several carriers is another issue. In this paper, a novel PSC-PWM scheme with low control complexity is proposed. The number of carriers employed in the designed scheme is always two, and independent of the submodule numbers. Despite this fact, the benefits of the conventional PSC-PWM, like the excellent harmonic content for different operating points, are completely remained. The performance of the proposed method is validated through conducting simulations in the MATLAB/Simulink environment.