Topologies comparison of multi-cell Medium Frequency Transformer for offshore farms

New European objectives have increased the interest about offshore tidal current farm. High Voltage Direct Current (HVDC) connection is used for distribution from farm to shore and traditionally local distribution is achieved by an AC grid. Nevertheless, energy conversion station with high volume power density is really interesting in offshore applications and even more in subsea context. Local DC distribution grid could be considered because of the different interests in term of weight and size of DC-DC converter thanks to Medium Frequency Transformer (MFT). This paper presents a comparison of different topologies for a tidal current farm test bench near PaimpolBrehat in France. MF DC-DC converter topologies are compared using factors as: costs, losses, weights, sizing, availability, number of cells and single or three-phase transformers. For a 8 MVA tidal farm, 4×2 MVA single phase DC-DC converters appears to be the cost-effective solution.