| The 14 th Five-Year Plan period is important for China to promote the energy development strategy of “four revolutions and one cooperation”.Wind power is an important form of effective utilization of wind energy resources and one of the important supports for China’s sustainable energy development.Its development prospects are very broad.In recent years,wind turbines can be seen everywhere in the inland areas where wind energy resources are abundant in China,but there are also many disadvantages of inland wind turbines,such as being limited by the region,inland wind turbines usually have to be arranged in places where wind energy storage is abundant,and inland wind turbines also affect the lives of nearby residents.China’s offshore wind energy is very rich and has great potential,and it is close to the eastern load center,which makes it convenient to consume locally.Large-scale development of offshore wind power will become one of the important means for China to deepen energy transformation and promote air pollution prevention and control.Offshore wind turbines are subject to more complex environmental loads than inland wind turbines,in addition to wind loads and seismic loads,they are also subject to wave loads.At the same time,for the planning and construction of some offshore wind farms in China’s nearshore areas,the destructive impact of seismic motion on wind turbines needs to be taken into account,but the existing offshore wind turbine design does not consider the impact of seismic motion loads sufficiently.Due to the multi-dimensional spatial characteristics of actual seismic motion loads,the coupling effect of multi-dimensional seismic motion on the structural response of offshore wind turbines cannot be ignored,but there are few studies on the dynamic characteristics of offshore wind turbines under multi-dimensional seismic motion.Therefore,it is necessary to study the dynamic characteristics of offshore wind turbines under multidimensional seismic motion,to provide a reference for the seismic design of offshore wind turbine structures.Considering that 5MW large-scale wind turbines are widely used in China’s offshore wind turbine market,this paper takes this typical large-scale wind turbine structure as the research object and studies the dynamic characteristics of large-scale offshore wind turbine structures under multi-dimensional seismic motion in depth.The main research results include:(1)Solidworks software is used to build a solid model of the 5MW offshore wind turbine,and then the interface between Solidworks and large finite element analysis software is used to complete the import of the solid model of the wind turbine built in Solidworks software into ANSYS,to carry out refined modelling of the complex parts of the wind turbine such as the blades,and to use ANSYS finite element software The model is modal analysed using ANSYS finite element software and the required parameters,such as mass and stiffness of each part of the wind turbine,are extracted for subsequent dynamics modelling.The modal analysis results show that the inherent frequencies of the 5MW wind turbine blade,tower and the wind turbine as a whole are less than 10% of the inherent frequencies of the 5MW wind turbine in FAST.(2)Based on the Lagrange equation,the complex structure of the wind turbine system is simplified into a 14-degree-of-freedom reduced-order structure coupled dynamic model.This model considers the influence of wind load and wave load on the structure and can describe the dynamic response characteristics of the structure more accurately.Secondly,this paper applies the virtual work principle to derive generalized vectors for various loads,including aerodynamic load,hydrodynamic load,seismic load,etc.The simplified offshore wind turbine model in this paper can better shorten calculation time and obtain accurate results under the premise of ensuring structural coupling characteristics and overall accuracy of the model.The theoretical analysis results verify the accuracy of the reduced-order dynamic model.Compared with the model in IEC literature,their natural frequencies differ by no more than 10%.(3)Using MATLAB software,based on the overall simplified coupling model,four different types of seismic motions with amplitudes of 0.15 g are selected.And according to the direction of seismic motion application,apply seismic motion to study the dynamic characteristics of blades and tower tubes,which are the main force-bearing components under multi-dimensional seismic motion.The simulation analysis results show that under multi-dimensional seismic motion,there is a large difference between blade displacement in the flapping direction and blade displacement in the swaying direction.The tip displacement in the flapping direction under four kinds of seismic motions is larger than that in the swaying direction.At the same time,Northridge seismic motion will excite the higher-order frequency of the tower tube.(4)Based on the relevant computational theories of aerodynamics,hydrodynamics and structural dynamics,the corresponding load magnitudes were calculated by combining the wind turbine blade and tower models,and the dynamic response of the wind turbine under the action of wind and wave loads alone,as well as under the action of wind and wave seismic loads,was investigated.The results show that the blade tip displacements due to wind and wave loads are greater than those under the selected ground vibrations in this paper,while the blade vibrations under wind loads are influenced by the overall first-order modalities of the wind turbine.The leaf tip displacements under wind and wave seismic loading are significantly influenced by the wind and wave loads. |
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