Control co-design for floating offshore wind turbines considering aeroelastic–control interactions under platform motions

Floating offshore wind turbines exhibit more intricate bilateral coupling between rotor aeroelasticity and control dynamics than bottom-fixed wind turbines due to the additional degrees of freedom introduced by platform motions. Conventional sequential design approaches implement control after completing the multi-physical system, neglecting these interactions, and often resulting in locally optimal solutions. To address this limitation, the control co-design method is adopted to floating wind turbines in this study. Co-simulations are achieved by parameterizing blade aeroelasticity and the generator torque and blade pitch controls within an integrated aero-hydro-elastic-mooring-control time-domain simulation framework. A case study based on a 10 MW floating wind turbine is conducted using the Non-dominated Sorting Genetic Algorithm II to simultaneously minimize blade mass and maximize annual energy production. The results are analyzed and compared with those from a corresponding control co-design problem for the bottom-fixed case to assess the effect of platform motions. The optimization converges to a Pareto front, with improvements of up to 5.62% in blade mass reduction and 3.33% in power generation increase compared with the baseline design—gains that surpass those observed in the bottom-fixed case. Also, driven by multiple constraints of structural loads and deflections, the control co-design method could mitigate the resonance between blade pitch control and platform pitch motion observed in the baseline model and avoid the additional power loss due to a too low control frequency. These results demonstrate that the control co-design method presents high capability to enhance floating wind turbine performance by coordinating plant and control parameters to avoid resonance, improve wind speed tracking, and mitigate structural loads.