DC voltage balancing control of large-scale modular multilevel cascade converter

The modular multilevel cascade converter is one of the most practical solutions for high-voltage, large-capacity utility applications. As the number of the series connected submodules increases, the DC voltage balancing control becomes difficult. Problems of the conventional balancing method, when used in those large-scale modular multilevel cascade converter, has been analyzed. A new balancing control strategy has been proposed. Comparative experiments have been carried out on a real 35kV/40MVA cascade multilevel converter to verify effectiveness of the presented balancing control scheme.