Efficiency and Fault Ride-Through Performance of a Diode-Rectifier- and VSC-Inverter-Based HVDC Link for Offshore Wind Farms

This paper includes a technical feasibility study on the use of an HVDC diode-based rectifier together with an onshore voltage-source converter (VSC) for the connection of large offshore wind farms. A distributed control algorithm for the wind farm is used, where all the wind turbines contribute to the offshore-grid voltage and frequency control while allowing wind turbine optimal power tracking. Moreover, the proposed system shows good fault ride-through performance to solid faults at the onshore connection point, wind-farm ac grid, and HVDC line. The technical feasibility of the proposed solution has been validated by means of detailed PSCAD/EMTDC simulations. The efficiency of the complete system has also been studied and found to compare favorably with that of a VSC-HVDC-inverter station.