Mooring Actuation for Stabilization of Floating Offshore Wind Turbines

Abstract

Abstract. The oscillatory motion of floating offshore wind turbines (FOWTs) under erratic sea conditions negatively impacts power generation efficiency, increases structural fatigue loading, and reduces system longevity. While individual blade pitch control can be used to regulate rotor speed and stabilize platform dynamics, it imposes significant mechanical loads on the pitch actuators. To alleviate this burden, mooring line actuation (MLA) offers a promising complementary strategy. This paper investigates the potential and challenges of mooring line actuation for dynamic stabilization of FOWTs. Two platform configurations-a spar-buoy and a tension-leg platform (TLP)-are modeled and validated. For TLP, a tuned mass damper (TMD) strategy is examined as a benchmark for comparative stabilization performance. A comprehensive controllability investigation is conducted to evaluate the effectiveness of MLA in influencing platform degrees-of-freedom (DOFs). Based on these insights, a linear quadratic regulator (LQR) controller is designed to modulate mooring line lengths and associated tensions for active stabilization. Numerical simulations reveal that MLA provides significantly greater stabilization benefits for the TLP configuration compared to the spar-buoy. This underscores the importance of integrated control co-design (CCD) to improve MLA performance, especially for platforms with lower inherent controllability. Across a range of operational scenarios, the proposed MLA strategy demonstrates effective simultaneous surge and pitch suppression with minimal mooring line actuation, offering a viable path toward load-reducing, performance-enhancing control architectures in next-generation FOWTs.