Concept And Global Dynamic Response Research Of Multi-MW SPAR-type FOWT

Due to the increasingly shortage of global energy resources and serious problems such as environmental pollution and climate warming caused by the fiercer use of fossil fuels,wind energy has drawn more and more attention as a clean and renewable energy.The offshore has rich wind energy and wide space,which attracting many scholars to study the floating wind turbine.In order to realize the scale application of floating wind turbines in medium depth sea areas and solve the problem of energy shortages,this paper designs a new 6MW spar-type floating offshore wind turbine for water depth conditions of 100 meters.Firstly,the current situation and prospects of the development of wind power industry at home and abroad are introduced.The current research on offshore wind turbines by domestic and foreign scholars is reviewed.Then,the various load calculation principles of offshore floating wind turbines in the ocean environment are introduced and the motion equation of wind turbine in the time domain is listed.The wet surface model and free surface model of 6MW spar FOWT are established by Genie and Patranpre modules in Sesam software.Hydrod module acquires Wamit files including hydrodynamic coefficients,the first-order wave excitation force under different frequencies and different directions and quadratic transfer function.The full-coupled dynamic response of the FOWT is simulated by FAST,a gas-liquid-solid-elastic numerical software,to investigate its working stability and survivability.Under the working conditions,the key structure,the motion response of the platform and the tension force of the mooring line are calculated and analyzed respectively.In the extreme sea condition,the effects of the second-order mean wave force and the secondorder slow wave drift force on the motion response of the platform,mooring tension force and nacelle acceleration are discussed respectively.The numerical simulation results indicate that the coupling effect between surge and pitch was evident.The platform motion response mainly depends on the wind load,while the wave load changes the heave motion of the platform near the equilibrium position.A greater motion response will be stimulated by the same wind and wave direction.The yaw motion of the platform becomes more obvious when the angle between the wind and the wave increases,while the other DOFs motion are affected little by the wave direction.Moreover,the delta-line mooring system could avoid excessive yaw response and the phenomenon of mooring line winding.The maximum mooring force is below the breaking tension and safe operation of the FOWT could be ensured by the mooring system.Finally,the 6MW spar-type FOWT possesses favorable global dynamic performance and the whole system has an excellent survivability in the harsh sea conditions.