A Novel Medium-Voltage Hybrid-Cascaded DC-DC Converter With DC Fault-Blocking Capability and Reduced Switch Capacity

In this article, a medium-voltage nonisolated dc-dc converter with dc fault-blocking capability is proposed. The converter is designed to connect two high-voltage dc networks with varying voltage levels. The proposed converter is composed of a string of cascaded modules and two sets of series-connected switches. The cascaded modules have all the merits of modular design, and the series-connected switches avoid dynamic balancing issues due to the zero-voltage switching feature. The single-string structure of the proposed converter helps reduce the number of switches, power losses, and volume. The power efficiency of the converter is evaluated to be as high as 99.3%. The feasibility of the proposed converter is verified via 32-kV 22.5-MW simulations and 240-V 1.45-kW experiments.