Spectral Model of Offshore Wind Turbines and Vibration Control by Pendulum Tuned Mass Dampers

Offshore wind turbines (OWTs) are complex systems that may experience excessive vibrations due to winds, waves, rotor torque, or seismic loads during the operation. Tuned mass dampers (TMDs) have been a widely used vibration passive control device in structures, including wind turbines. The TMD works as a damper that transfers the kinetic energy from the main structure to a secondary mass usually attached to the hub. The spectral element method (SEM) is suitable for analyzing dynamic structural problemss with accuracy and low computational cost. This paper presents a monopile wind turbine fitted with a pendulum-TMD (PTMD) modeled by spectral elements. An optimum pendulum design is performed through the genetic algorithm technique. The wind turbine selected is a National Renewable Energy Lab (NREL) monopile 5 MW baseline wind turbine fitted with a PTMD, subjected to winds and waves simulated as random spectra in the analysis. Numerical results show the efficiency of the proposed spectral model and the optimum PTMD design for the OWT under random excitation.