Overview of High-Power Medium-Frequency DC/DC Converter Topologies for Wind Turbines Interfaced to a MVDC Collection Grid

Remote offshore wind power plants are expected to be connected via HVDC systems to the main grids. The extension of single point-to-point HVDC systems into meshed HVDC grids is discussed actively. This leads the integration of DC technology into the collection grid of the wind farm to gain interest and relevance. Using DC technology in the collection grid demands the wind turbine systems to have a DC output, preferably in medium voltage. This paper investigates power converter topologies for DC wind turbines, especially DC/DC converter topologies comprising a Medium Frequency (MF) transformer. The MF transformer is an essential element to provide a galvanic isolation between the MVDC grid and the generator side. The topologies are compared on the basis of number of components, control, cost, redundancy and size. The topology A results as the most suitable configuration based on the evaluation.