A Optimized Capacitor Voltage Balance Strategy using Binary Number Sorting Algorithm for Modular Multilevel Converter

Abstract

Capacitor voltage balancing strategy for Submodules (SMs) is one of the key technologies for modular multi-level converters(MMC). The conventional strategy has the problems of large computation and high switching frequency of devices. In order to solve these problems, a mark and operation voltage balancing strategy (MOVBS) is proposed. This strategy marks SMs with two different labels according to the amplitude of capacitor voltage of SMs and current direction of arms, then do sorting and selecting operations to SMs based on the marking results. It reduces sorting times, switching frequency and power loss of devices. For capacitor voltage sorting process, a binary radix sorting algorithm(BRSA) is proposed to improve sorting speed and efficiency of MOVBS. Finally, the feasibility and effectiveness of the MOVBS is verified with a 11-level MMC-HVDC simulation model created in Matlab/Simulink.