Design and Loss Analysis of a Medium-Voltage DC-DC Converter Intended for Offshore Wind Farms

In the last decade, many projects of offshore wind farms have been planned and conducted to compliant each government policy. To increase the energy yield, attention has been paid to the replacement from AC collection grid to DC collection grid. At the moment, many applications such as electric vehicles and DC power supplies have adopted an isolated DC-DC converter with low-loss magnetic material. However, the low-loss magnetic material has the limitation of the size and shape. Therefore, such magnetic material cannot be used directly for high-power application. This paper discusses suitable designs for a 10 MW 1 kV/+/- 25 kV DC-DC converter, focusing on the use of low-loss magnetic materials. The discussion deals with system structure, circuit topology, phase number, semiconductor devices, and transformer structure. The loss analysis conducted by computer simulation and theoretical analysis verifies that the medium-voltage DC-DC converter can achieve the efficiency of 98.5% with the submodule-based structure, the three-phase dual active bridge topology, the hybrid pair of 5th- and 6th-generation IGBTs, the shell-type transformer, the nanocrystalline core, and the switching frequency of 1.5 kHz.