Voltage Setting Strategy for 1000-MW Class Dual-Active Bridge Based High-Voltage DC/DC Converter with Failure Cells

In the last decade, many projects of offshore wind farms have been planned and implemented to ensure compliance with government policy, especially in Europe. Some projects adopted HVDC transmission with long-distance submarine cable from offshore to onshore. However, the medium-voltage (MV) collection grid uses AC, not DC. Moreover, the MW rating of wind energy has been increasing over the years. The increase in MW rating has led to an increase in current in the MV collection grid and longer distances between wind turbines. Therefore, it is necessary to have an MVDC collector grid, and an HV DC/DC converter is required to step up the MVDC to the HVDC.This paper describes the impact of voltage fluctuation on a 1000-MW class dual-active bridge (DAB) based high-voltage DC/DC converter. A method of DC voltage setting that can be used when a component of a cell fails is also discussed in this paper.