Variable Frequency Operation for Future Offshore Wind Farm Design: A Comparison with Conventional Wind Turbines

Recent developments of offshore power grid demonstrations in European waters at substantial distances from the onshore grid have accelerated the demand to look at high voltage DC power transmission (HVDC) as an alternative topology to traditional high voltage AC methods [1]. Current VSC-HVDC technology can realise the integration of a centralised power converter to control the speed of a cluster of turbines, thus reducing the number of power converters from the farm and therefore potentially increasing reliability and lowering power loss. This paper will primarily concentrate on the benefits of variable frequency operation of a wind farm using a centralised VSC-HVDC converter and comparing its performance to 50 Hz Type 4 wind turbines. The analysis will incorporate measured wind data form Irish offshore locations and will provide a detailed power loss methodology for the wind farm components with annual energy capture results for both variable and fixed frequency approaches.