Multi-objective optimization of a negative stiffness vibration control system for offshore wind turbines

A systematic multi -objective optimization approach is presented for designing vibration control systems for monopile Offshore Wind Turbines (OWT) under the combined actions of wind and wave. An extended configuration of the KDamper (EKD) is employed, with second -order tower phenomena and soil-structure interaction effects taken into account. A holistic approach is employed to design an optimal EKD by considering competing objectives and limitations, such as engineering requirements, manufacturing specifications, available budget, and uncertainties in the design parameters. A global sensitivity analysis is conducted to identify the influence of each parameter of the OWT-EKD system on performance. Subsequently, a global multi -objective optimization is employed to explore the trade-off between conflicting objectives (Pareto front) and demonstrate that the EKD effectively operates even without specific components (e.g., dampers). In accounting for the uncertainties involved, such as manufacturing tolerances and environmental conditions, a robust analysis on a bi-objective Pareto front is performed, leading to the selection of EKD designs that exhibit superior average performance. The numerical results demonstrate the improvement in the peak tower dynamic response and the effective damping compared to a conventional Tuned Mass Damper comprising 20 times higher mass.