Abstract
In floating offshore wind turbine-generator systems, wind and wave variations cause platform pitching motion and increase fatigue loads. A feedforward control based on the preview of the inflow wind speed to the wind turbine is combined with a gain-scheduling feedback control of the generator speed to stabilize platform motion and reduce dynamic load variations at high wind speeds. In this feedforward control, the blade pitch is manipulated in response to the previewed wind speed so that the generator speed is maintained at the rated value. An aero-elastic-hydro-control coupled simulation using the developed feedback-feedforward controller is performed for a 5-MW floating offshore wind turbine-generator system. The simulation results under turbulent wind fields and irregular wave height variations reveal that the stabilization of the platform motion and the reduction in the dynamic load variations at the tower base and blade root as well as the low-speed shaft are achieved by using the spatial mean wind speed as the previewed wind speed. Moreover, the impact of the previewing error of the inflow wind speed with high-frequency turbulence on the control performances is clarified.
