Evaluation of the positioning capability of a novel concept design of dynamic positioning-assisted mooring systems for floating offshore wind turbines

Based on the improved positioning capability from using dynamic positioning assisted mooring system (DPAM) in offshore drilling floating platforms, this paper proposes the application of DPAM to floating offshore wind turbines (FOWTs), aiming to improve the traditional redundant mooring positioning (MP) system. The novel concept design principle is that the traditional MP is optimized to meet the positioning requirements under working sea conditions, while the dynamic positioning (DP) system is activated to assist the MP during only extreme sea conditions. To evaluate the DPAM system positioning capability, a fully coupled kinetic model of a FOWT with DPAM is built in MATLAB/Simulink, and the dynamic responses are analysed in the time domain. Only the low-frequency motions of the FOWT in the horizontal plane are considered in the design of DP control strategies, and the DP is turned on when the mooring line tension reaches the maximum allowable breaking limit. The results show that, compared with traditional MP, our proposed novel conceptual DPAM design leads to significant reductions in the total amount of steel and mooring radius of the DPAM system while maintaining a similar positioning capability under extreme sea conditions.