Hybrid multilevel converter with dc side H-bridge chain links

Hybrid multilevel converters are more attractive than the traditional multilevel converters, such as modular converters, because they offer all the features needed in a modern voltage source converter based dc transmission system with reduced size and weight, at a competitive level of semiconductor losses. Therefore, this paper investigates the technical feasibility of a hybrid multilevel converter that uses dc side H-bridge chain links, for high-voltage dc and flexible ac transmission systems. Additionally, its operating principle, modulation and capacitor voltage balancing, and control are described. The focus of this paper is on response of the hybrid multilevel converter to ac and dc network faults. Therefore the hybrid multilevel converter with dc side chain links is simulated as one station of point-to-point dc transmission system that operates in an inversion mode, with all the necessary control systems incorporated. The major results and findings of this investigation are presented and discussed.