Influence of control strategy on FOWT global performance by aero-elastic-control-floater-mooring coupled dynamic analysis
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2014. The International Society of Offshore and Polar Engineers. More FOWTs (floating offshore wind turbines) are to be installed in the near future as relevant regulations and technological hurdles are reduced. In the present study, a numerical prediction tool has been developed for the fully coupled dynamic analysis of FOWTs in time domain, including aero-loading, tower elasticity, blade-rotor dynamics and control, mooring dynamics, and platform motions, so that the influence of rotor-control dynamics on the hull-mooring performance and vice versa can be assessed. The developed coupled analysis program is applied to OC3-Hywind spar design with 5 MW turbine. In case of spar-type floaters, the control strategy may significantly influence the hull, tower/blade, and mooring dynamics due to the possibility of control-induced instability/resonance causing resonant hull motions. Therefore, it is important to use a proper control strategy without such problems at the penalty of slight overshoot in power outputs. In this regard, the global performances of two different control strategies-conventional and modified control strategies-are systematically compared to better understand the subtle coupling effects between the blade-pitch angle and shaft controls and hull motions. The developed technology and numerical tools are readily applicable to any types of floating wind farms in any combinations of irregular waves, dynamic winds, and steady currents.