Dynamic analysis of floating wind turbines subjected to deterministic wind gusts

A wind turbine converts kinematic energy to electrical energy, and can be designed from onshore to offshore operation, then from shallow water to deep water. Compared to onshore wind turbines, floating wind turbines face more complicated environment conditions. To guarantee stability of floating wind turbines in various environment conditions, extreme wind and wave loads should be studied. This thesis focuses on the dynamic response in time domain under extreme deterministic wind gusts, in a return period of 50 years, for which simulations are carried out in order to assess the turbine’s performance and build a database: softwares SIMA, FAST and Matlab are used for the task. Based on equations of motion of platform, a simplified dynamic wind turbine model inspired by the DTU 10-MW RWT is built in Matlab to study extreme response subjected to deterministic gusts defined in DNV-OSJ103: Design of Floating Wind Turbine Structures. The simple model includes generator torque and a blade pitch control system converted from the NREL 5-MW turbine source code in FAST, written in Fortran. Extreme loads on the mooring system can be assessed by surge and pitch offsets of the platform in the output. Contrasting results from SIMA and Matlab and analyzing different gust shapes, the extreme (worst) deterministic gust are found