Medium-voltage DC/DC converter for offshore wind collection grid

A novel modular DC/DC converter with input-series-input-parallel output-series connection to realise a DC collection power network for large-scale wind farms is presented. The proposed topology uses interconnection of multiple modular cells with low rated voltage and power to enable operation with high voltage at the input and output. Low rated power of individual modules in the proposed DC/DC converter permits the use of a high-frequency ac link, resulting in a significant reduction in transformer size and weight, which makes deployment of DC collection networks in offshore wind farm applications more feasible and effective. In addition, a robust control scheme is developed to ensure power sharing between practical modules with parameter mismatch and during transient conditions. Small- and large-signal analyses are performed in order to deduce the control structure for the converter input and output stages. Simulation and experimental results demonstrate and validate the proposed converter and associated control scheme.