High Voltage Gain Three-Level DC–DC Converter With Switched-Capacitor Technique for DC Wind Farms

All-dc offshore wind power collection and transmission is a prospective scheme for long-distance large-scale offshore wind power development, in which wind turbine medium-voltage dc/dc is one of the key technologies. In this article, a three-level series resonant switched-capacitor active-fault interface dc/dc converter is proposed. Switched-capacitor modules are applied instead of full-bridge rectification to improve the boost capability, which can reduce submodules in input-parallel-output-series topology and reduce the size, weight, and cost. The active-fault interface circuit can still operate normally when some submodules fail, thus improving the system's reliability. The proposed converter has dc short-circuit fault-blocking capability. By adopting a three-level structure, with automatic antibias capability, the switching voltage stress is reduced with a high power quality. An LC series resonance circuit is added to realize soft switching. The electrical isolation and fault isolation are considered. The steady-state operation, voltage relationship, current and voltage stress, power dissipation of each component, and parameter design of the converter have been analyzed and derived in detail, respectively. The results from the simulation and physical experiment verify the validity of the proposed dc/dc converter.