Dynamics And Structural Strength Of TLP Wind Turbine System Considering Spoke Dimention

As one of thecommercial prospects renewable energy,wind powerhas attracted attention around the world.The wind resource of Chinaranks third only after the United States and Russia,including 253 GW onshore wind resource and 750 GW offshore wind resource.With the continuous development of wind energy utilization,the onshore wind resources will slowly deplete.Offshore wind power due to its advantages such as stable high speed,low turbulence strength and the ability to reduce the visual pollution,is becoming the main direction of the future wind energydevelopment.In thecountries with rich offshore wind energy,most of the sites are located in 30 meterswater depth or more,but the traditional fixed supporting structure over this water depthhas poor economy,so that floating wind turbine supporting structure has become a hot research topic.Based on industry background and direction,floating offshoring wind-turbine considering tension leg(FOWT-TLP)structure as an object,using numerical simulation and experimental method to researchspoke dimension effects to FOWTTLP dynamic response,second order hydrodynamic response to FOWT-TLP dynamic response,the tension leg platform structural strength,and the new type of tension leg platform,the main contents and results are following:The investigation of the spoke dimension effect on FOWT-TLP system dynamic response.The 5MW wind turbine modelsof National Renewable Energy Laboratory are used to perform the analysis by full coupling numerical simulation methods.Six different floating tension leg wind turbine systems have been studied.At the same time,one 1:80 scaled test has been carried out at the wave tank laboratory of Harbin Institute of Technology(HIT)consideringdifferent cases.Numerical simulations show that the spoke dimensioncannot be ignored,since it can help to improve the hydrodynamic added mass and damping,and reduce the exciting force,but have a small effect on the surge dynamics.By experiment with specific conditions,the beneficial effects for spoke dimension to the surge and sway displacement response are verified.It shows that an optimal size under certain conditionsexits,and the wave –wind conditions of the second order coupled hydrodynamic loads on floating wind turbine system can not be ignored.The investigation on the FOWT-TLP systems dynamic response considering the second-order hydrodynamic effects and spoke dimension.Sea Fem software was used to perform the response calculationof the six degrees of freedom of the FOWT-TLP system when considering the second-order hydrodynamic effects and spoke dimension.It shows that onlyconsidering the first-order hydrodynamic the displacement and rotational freedom will lead to some bias;roll angle,pitch and roll moment are sensitive to theeffectsof the second-order hydrodynamic.It can also reduce the force of the tension leg mooring system that parallels to the wave direction.Investigation on thestrength of the TLP structure.By using MIT-TLPmodels and considering certain conditions,the effects of the different thickness,the connection part in the top,the internal horizontal and vertical stiffeners,spoke dimension connection and connection angel have been investiagated.A novel method to reduce the structure weightis developed,providing references for the future structural layout and design.Performance evaluation and experimental study of the HIT-TLP structure.Based on a full life-cycle initial design qualification and former research,HIT-TLP structure has been proposed for the NREL 5MW wind turbine.The First and second order hydrodynamic calculation are considered and they are compared with MITTLP structure.The layoutinside thestructure and calculation of the whole strength are carried out.A 1:80 model tank test at the HIT wave tank laboratory is designed and tested.The comparison of numerical calculations shows that reasonable spoke dimensioncan help to reduce the second-order hydrodynamic loads on the dynamic response of the system.The experimental results show that better dynamic performance can be observed when using the new floating tension leg structure system.At the same time,it was found that in the combination of some special case under certain conditions,the response from the external load with its own rotation coupling is higher than those from loading under the extreme conditions.