Improving power stability in floating offshore wind turbines through control systems: an aero-hydro-servo-elastic study

Floating offshore wind turbines (FOWTs) exhibit significant potential for renewable energy generation. However, due to the six-degree-of-freedom (6DoF) motions of their platforms, they experience greater inflow wind speed variations than bottom-fixed turbines. This variability poses challenges to power output stability, underscoring the critical role of advanced control systems. Building upon our previous extensive studies on FOWT dynamics, this research investigates the coupled dynamic responses of FOWTs equipped with generator torque and blade pitch controllers. A fully coupled aero-hydro-servo-elastic analysis framework, integrated with Computational Fluid Dynamics (CFD), is employed to simulate a spar-type FOWT under diverse wind speeds and sea states. The study analyses key parameters including aerodynamic loads, aeroelastic blade deformation, platform motions, mooring tensions, and wake field characteristics, focusing on the controllers’ impact on energy performance and structural dynamics. Results demonstrate that the controllers effectively mitigate aerodynamic load fluctuations and enhance power output when wind speeds exceed the rated value. While the controllers increase platform motion at high wind speeds, they significantly suppress motion responses under severe wave conditions. An inverse relationship is observed between wake velocity modifications and average aerodynamic power variations due to controller interventions. Notably, except at a high wind speed of 18 m/s, the controllers amplify turbulence intensity within the wake, particularly in the proximal wake region (x/D < 3). These insights contribute to optimizing control strategies for FOWTs, enhancing their efficiency and reliability in renewable energy generation under varying operational conditions.