Modeling And Analysis Of Structural Load And Motion Characteristics Of Floating Offshore Wind Turbine

With the development of wind turbine technology,the remaining wind farm on land which can be developed is becoming less and less.Then developing the wind farm in the sea will become an inevitable trend in the future.Considering the limit of some offshore fisheries,military and some other actual conditions,it's meaningful to develop floating offshore wind turbines in the deep sea.Professor Heronemus of the University of Massachusetts has proposed a design concept for deep sea floating wind turbines in 1972.Floating platform with six degrees is applied to floating offshore wind turbines which is different from the wind turbines on land and in the shallow sea.However,the load and movement characteristics of the floating offshore wind turbines are more complicated in the complex service environment.It doesn't only bear the wind load,but also bear the complicated wave load.So it limits the practical application of the floating offshore wind turbines.Therefore,the 1.2MW floating offshore wind turbine is taken as the object for research in this paper.Aiming to figure out the load model and the method to analyze the movement characteristics of the floating offshore wind turbines,Simulation model of the blade and support structure for wind turbine is constructed and the dynamic characteristics of the blade of the floating wind turbine and the motion characteristics of the platform are analyzed in the model.The main work of this paper is as follows:(1)Aiming at the 1.2MW scale wind turbine,a novel dynamic analysis model is presented to research the blade loads and dynamic characteristics.In this model,the blade flexible deformation is considered,the whole blade is divided into a plurality of unit,and the relative rotation between the adjacent units is considered.A nacelle coordinate system,a rotation shaft coordinate system,and a blade coordinate system are employed to describe the wind turbine.In SIMULINK circumstance,the blade inertial load calculation model,centrifugal force load calculation model,gravity load calculation model and aerodynamic load are established.the load and motion characteristics is grasped through the numerical simulation analysis of blade load and motion characteristics of wind turbine.(2)The relations of the wind and wave is considered.The wind and wave load model of the offshore floating wind turbines is established based on the aerodynamics theory and wave mechanics theory.Three typical force models of wind turbine under extreme service conditions are discussed and it is taken as the base of parameter design.When the ratio of diameter to wavelength of pressure tank is less than 0.2,it is viewed as a small scale structure.The Morison equation is introduced for load analysis.When the ratio of diameter to wavelength of pressure tank is more than 0.2,it is viewed as a large scale structure.The introduction of MacCamyFuchs formula for load analysis.(3)The multi-load model of wind load,wave load and gravity load during the operation of the floating wind turbine is analyzed and established.The motion process is divided into a combination of translational and rotational.The method of reciprocal iterative solution is used to solve the motion.Finally,the input wind model,blade(wind wheel)model,floating platform model and other sub-models are integrated in the whole model of wind turbines in the Simulink environment to perform numerical simulation analysis.The simulation results show that the operating load and motion characteristics of floating wind turbines can be effectively analyzed.It is helpful to understand its operating mechanism and can provide a reference for the design and control floating offshore wind turbine.