Quantifying the effects of high-speed shaft braking on the substructural dynamics of monopile offshore wind turbines

Abstract

ABSTRACT This paper investigates the effects of high-speed shaft braking (HSB) on the substructural dynamics of monopile-type offshore wind turbines. By incorporating blade aerodynamics, generator-torque control, monopile structural dynamics, and the HSB control, the main dynamics of the offshore wind turbine are analyzed. Dynamic simulations of a monopile 5 MW offshore wind turbine by utilizing a high-fidelity aeroelastic offshore wind turbine model are used to provide detailed results. Orthogonal experiments are also conducted using the Taguchi method for different levels of the HSB control. The results reveal that the roll/sway displacements of the monopile and the side-to-side shear force of the tower-top/yaw bearing experience amplitude vibrations (around 20% of the rated value) due to the HSB control. The HSB control not only changes the instantaneous dynamic loads (more than 25% of the rated values) on the blades but also can interact with the normal wind turbine control. Therefore, the HSB control should be carefully designed and applied when the offshore wind turbine is in normal operation since incorrect HSB control may excite large oscillations.