A Grouping Strategy Based on Prime Factorization for Capacitor Voltage Balancing of the Modular Multilevel Converter

The modular multilevel converter (MMC) is attractive for high-power applications because of the advantages of its high modularity and high power quality. This paper proposes a prime factorization-based grouping strategy for capacitor voltage balancing of MMC. With prime factors arranged from the largest to the smallest, the computation burden has been reduced significantly, which is proved mathematically. Then, a 401-level MMC adopting the proposed grouping strategy is implemented and evaluated in the PSCAD/EMTDC environment. Simulation results confirm the effectiveness of the proposed strategy for capacitor voltage balancing performance under both steady and dynamic states. And by comparing with conventional sorting algorithm, it can be concluded that the prime factorization pattern can significantly improve the simulation efficiency. Finally, the switching frequency of the proposed algorithm is discussed.