A comparison of insulated DC-DC converters for HVDC off-shore wind farms

To produce cleaner electrical energy, a lot of European countries have decided to develop off shore wind farms. To connect these wind farms to the grid, an HVDC link seems to be the best solution when the distance is important. Actually, the wind turbines generate a low frequency AC voltage and they are connected to the HVDC line with LCCs or VSCs. The solution proposed in this paper consists in taking out the intermediate medium voltage AC stage of the wind farm. For the power transmission, the medium voltage DC is directly stepped-up by insulated DC-DC converters operating at a medium frequency (10 kHz) in order to reduce the size of the passive components (mainly the transformer). Considering the characteristics of 10 kV SiC devices, this paper proposes a comparison of three topologies suitable for this application. The study takes into consideration the sizing of the passive components (transformers, capacitors...), the transformer losses, the semiconductor losses and the global efficiency.