Dynamic Load Analysis of the Tower Structure of a Floating Wind Turbine Under Random Wind and Wave Excitation by Detuning Blade Pitch Controller Proportional Gains

Abstract

This paper carried out coupled non-linear aero-hydro-servo-elastic simulations of a semisubmersible floating wind turbine under normal and severe sea states at various wind speeds. The NREL 5MW turbine was modeled by the SIMO-RIFLEX module in SESAM with hydrodynamic gathered by the WADAM code. A taut leg mooring system with redundancy was applied to account for the relatively shallow water site in the South China Sea. By detuning KP, the proportional gain coefficient of the blade-pitch controller, the platform motions and dynamic load effects on tower structure were investigated. It was found that the reduction of KP mitigates the load effects on tower top and base connections in certain load conditions. The motion performance of the platform was improved to some extent. The generator power output, as well as the fluctuation, were analyzed. Finally, suggestion on detailed blade pitch gains tuning according to specific wind speed and sea state was given.