A Modular Multilevel Converter With Integrated Energy Dissipation Equipment for Offshore Wind VSC-HVDC System

VSC-HVDC technology has great application prospects in the field of offshore wind system. In order to realize the capability of fault ride through of offshore wind VSC-HVDC system, this paper proposes a modular multilevel converter with integrated energy dissipation equipment (IEDE-MMC), which combines the complementary advantages of MMC and DC chopper. The working process of the short-time pulse of the energy dissipation equipment provides an opportunity for the use of low current switch devices, and it shares the water-cooling system, control-protection system and energy-supply system with the MMC submodule, which eliminates the independent systems required by the traditional DC chopper, providing an economic and reliable solution for the problem of fault ride through. The simulation results of 400 MW/±150 kV VSC-HVDC system verify the fault ride through capability of IEDE-MMC, and the peak value of DC voltage is less than 1.1 p.u., which meets the requirements of the system. Finally, the manufacturing cost and floor area of IEDE-MMC are analyzed. Compared with the scheme of adding DC chopper outside MMC, the IEDE-MMC cost is reduced by 22%, and the total floor area is reduced by 35%.