| With the high development and utilization of traditional energy sources such as coal,oil and natural gas,the energy issue will become a serious bottleneck restricting the sustainable development of China's economy.As one of the most promising alternative energy sources,wind energy is increasingly being developed and utilized by countries all over the world.Offshore wind energy has a clearer advantage over onshore wind energy.“From land to sea,from shallow to deep,from fixed foundation to floating platform” has become an inevitable trend in the future wind farms construction.The stability of the platform is the basic guarantee for the safe operation of the floating wind turbine.Therefore,it is of great significance to explore the dynamic response characteristics of the floating wind turbine platform.In this paper,four common floating wind turbine platforms are studied,and the dynamic response characteristics of floating wind turbine platforms excited by external environmental loads are studied based on aerodynamics and hydrodynamics.In order to improve the stability of the floating wind turbine platform,some effective improvement measures are proposed,which will provide theoretical and technical support for the development of floating wind turbines in the future.The specific work of the thesis is as follows:1.Based on the blade element moment theory,considering the tip-loss,hub-loss and dynamic stall,the unsteady aerodynamic load solving model of floating wind turbine is established.The secondary development of AQWA is realized by Fortran programming,and the aerodynamic-hydrodynamic of floating wind turbine is established.-Mooring coupled dynamics model and algorithmic solution of the model.2.Based on the radiation/diffraction theory,the frequency-domain hydrodynamic performance of four basic types of floating wind turbine platforms(TLP,Spar,semisubmersible platform and Barge)is studied,and additional mass,radiation damping and first-order wave excitation in frequency domain are obtained.The amplitude-frequency characteristic curve of the force and amplitude response operator(RAO)is studied.The effects of wave incident angle and water depth on the first-order wave excitation force and RAO in frequency domain of the four floating wind turbine platforms are studied.3.Based on the established aerodynamic-hydrodynamic-mooring coupling dynamics model of floating wind turbine,the free-decay curves of four floating wind turbine platforms are obtained through free decay numerical experiments.Natural frequencies in surge,heave and pitch of the four platforms were obatained by adopting the fast fourier transform method.Dynamic characteristics including the motions,mooring line tension and the nacelle surge acceleration in time domain of four platforms under three different working conditions are studied to verify the importance of wind load as well as the coupling effect of wind and wave.And then the surge,heave and pitch dynamic response characteristics of the four platforms both in time and frequency domain are studied,under two different working conditions,including wave only,wind and wave.Furthermore,effect of wave load on dynamic characteristics of the rotor thrust force acting on the floating wind turbine is obtained.At last,considering the coupling effect of wind and wave,effect of the parameters of the catenary mooring system including distance between connection point and free surface,the length and the diameter of the catenary on the the maximum value of platform motions,mooring line tension and nacelle surge vibration acceleration are obtained.4.In order to improve the heave stability of floating wind turbine Spar platform,taking the research experiences of traditional offshore oil and gas area,this paper proposes two methods to install heave plate,including removing materials and adding materials on the main body of Spar.And then effect of heave plate and its installation position on dynamic response of floating wind turbine Spar platform is studied under both normal sea condition and severe sea conditon.5.In order to improve the stability of floating wind turbine platform,the design method of multi-platform array floating wind farm with common mooring system is proposed based on the idea of “tie-in-boat” in the ancient Red Cliff War to enhance the stability of ships.The floating wind farm with 3×3 array Barge platform,3×3,2×2 array Semi-Submersible platform and 3×3 array Spar platform are established and the dynamic response characteristics of them under normal and extreme sea conditions are studied.Because of the problem of excessive yaw and roll response when mooring system is directly linked to the main body of Spar platform,two methods of installing the yaw damper plate and moving the mooring link point out are proposed to improve the stability of floating wind farm platform on Spar platform,and the influence of the yaw damper plate and moving the mooring link point out on the dynamic response characteristics of the floating wind farm platform on Spar platform under normal and extreme sea conditions are researched.6.The conceptual design method of hybrid platform floating wind farm is proposed,the 3×3 array hybrid floating wind farm based on the three-buoy semi-submersible platform,four-buoy semi-submersible platform,Spar platform and Barge platform are established.The yaw response characteristics of hybrid platform floating wind farm under extreme sea conditions are studied when the mooring system is directly linked to the platform.Because of the problem of excessive yaw response caused by the asymmetry of mooring system,a mooring system layout criterion for hybrid floating wind farm is proposed,which is based on the orthogonal arrangement of mooring system according to the largest scale structure.The 3×3 array hybrid floating wind farm based on the Spar platform and Barge platform are established,of which the mooring system is arranged according to the proposed layout criteria,and the dynamic response characteristics of the 3×3 array hybrid platform floating wind farm based on Barge platform and Spar platform under normal and extreme sea conditions are studied... |
PDF Full Text Request