Abstract
Due to the existence of rotor and tower, the floating offshore wind turbine (FOWT) is subjected to greater wind heeling moment than the conventional floating platform, which would cause significant pitch motion and bring great challenge to the structural safety and power generating efficiency. Moreover, the dynamic cable used for power transmission is sensitive to the horizontal motion of floating platform. Thus, it is essential to inhibit the pitch and horizontal motions of FOWT. The FOWT is connected to the seabed by a mooring system to resist the motions, while the conventional mooring system mainly resists the horizontal motion. In this article, an innovative type of mooring system was proposed to resist the pitch and horizontal motions simultaneously, by dividing the fairleads into two groups at different depths. The motion responses and structural loads of FOWTs were calculated and compared under the effects of the conventional and innovative mooring systems. In addition, the restoring forces and moments of two mooring systems were also given to better verify the motion-inhibiting performances. According to the results, the innovative mooring system was able to significantly reduce the pitch and surge motions of FOWT.
Highlights
With the development of offshore wind power, it is inevitable for the application of floating offshore wind turbines (FOWTs)
It was found in the research that the average power generating efficiency increased with the frequency of pitch motion, while the average aerodynamic thrust did the opposite
Compared with the fixed-type offshore wind turbine, the Innovative Type of Mooring System average aerodynamic thrust coefficients of FOWT were reduced in the full wind speed range
Summary
With the development of offshore wind power, it is inevitable for the application of floating offshore wind turbines (FOWTs). Based on the aforementioned research, it could be confirmed that the global pitch motion could be reduced by improving the blade pitch control algorithm It might be unsteady under the complicated environmental conditions and reduce the power extraction of wind turbine. The horizontal motion of FOWT and load distribution of dynamic cable under the failure of one mooring line were calculated and analyzed by Bae et al (2017) and Li et al (2018). Different from the conventional type, the proposed innovative mooring system was able to inhibit the horizontal and pitch motions of FOWT simultaneously. It was noticeable that the restoring stiffness of innovative mooring system in the pitch DOF was much greater than the conventional type, which meant that it could help to significantly reduce the pitch motion. Obtaining the elastic and mass parameters of each element, the structural dynamics under the influences of external loads could be solved
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