| The offshore floating wind turbine is an increasingly emerging technology in the field of ocean engineering.The design and construction of offshore floating wind turbines is intrisincally multiple disciplinary,which involves aerodynamics,hydrodynamics,wind turbine system control and structural dynamics.In order to accelerate the development of China’s offshore wind power industry,it is of great necessity to propose innovative floating wind turbine system,and analyze its coupled dynamic response characteristics for structural design and optimization purpose.In this study,a new type steel truss floating foundation was proposed for offshore wind turbine,which combines the main advantages of Spar and semi-submersible floating foundation.And this paper designs and optimizes the truss foundation floating wind turbine.Based on the coupled analysis theory of wind turbine aerodynamic-hydrodynamic-structured dynamic-wind turbine system control,its coupled dynamic response under the ocean wind-wave conditions was studied.(1)According to the parameters of the truss foundation floating wind turbine designed initially,considering the influence of the diameter of the pontoon,the diameter of the heave plate,and the distance between the pontoon and the central axis on the truss foundation hydrodynamic performance,a parametric analysis was carried out.And the dimensional parameters of the truss foundation were optimized based on the results.According to the Morison equation and potential flow theory,the frequency domain method was used to calculate the frequency domain hydrodynamic parameters of the truss foundation floating wind turbine,including wave force(moment),additional mass,potential flow damping and motion RAO(Response amplitude operator).The calculation results show that the natural periods of the heave RAO,pitch RAO and roll RAO of the designed truss foundation floating wind turbine are about 23 s,20s,and 20 s,which are larger than the typical wave period,which can avoid resonance and have good wave resistance.(2)The coupled dynamic model of wind turbine-tower-floating foundation-mooring system was established,and the motion responses of the truss foundation floating wind turbine and Spar foundation floating wind turbine compared and analyzed.The results showed that: In the three translational degrees of freedom,the truss foundation floating wind turbine and the Spar foundation floating wind turbine correspondingly smaller,and the performance is equivalent;in the three degrees of freedom of rotation of pitch,roll and yaw,the truss foundation floating wind turbine performance is better than the Spar foundation floating wind turbine,especially the pitch and roll performance,the former has better stability.B y simulating the dynamic response of the floating fan system with different wind speeds and waves under normal sea conditions,the results show that the sway and heave motion of the truss foundation floating wind turbine is mainly caused by wind load;the pitch motion is affected by the wind speed and wave.the amplitude of the pitching motion is the largest under the rated wind speed,and the heave motion is more affected by the change of the wave.The effects of different environmental incident angles on the dynamic response of the truss foundation floating wind turbine were analyzed.The results show that the heave and surge responses of the truss foundation floating wind turbine are less affected by the change of wind wave incident angle;The sway,pitch and roll response is greatly affected by the incident angle of the wind and waves.when the load direction is not along the axis of symmetry,the yaw is slightly larger,which is related to the geometric shape of the truss foundation.The dynamic response of the truss foundation floating wind turbine under the environmental sea conditions of 1 year and 50 years is studied.The results show that the heave response amplitude of the truss foundation floating wind turbine meets ± 3.5m under two extreme sea conditions.pitch response meets the requirements of average pitch angle less than 5 ° and dynamic pitch angle less than 15 °.Due to the symmetry of the truss foundation floating wind turbine,its pitch response under both extreme sea conditions is small.(3)With the typhoon as the background,the wind speed time-history data under three conditions of strong typhoon,typhoon transit and steady strong wind were simulated.The results show that the wind speed under strong typhoon and typhoon transit conditions has strong non-stationarity and relatively weak non-stationarity,the average wind speed and direction change continuously with time.The coupled dynamic response of the truss foundation floating wind turbine under three working conditions of strong typhoon,typhoon transit and steady strong wind was simulated,and the influence of non-stationary wind speed on its dynamic response was analyzed.The results show that: The load and motion response of the bottom of the tower of the floating wind turbine fluctuate greatly under strong typhoon and typhoon transit conditions,which is consistent with the external wind speed change trend;due to the continuous change of the wind direction of the non-stationary wind,it will cause a large torque at the bottom of the tower,the floating wind turbine will produce a greater response to the yaw motion. |
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