| Accompanying the development and progress of science and technology in China,the demand for energy has been increasing.The development and utilization of traditional nonrenewable energy sources are often accompanied by environmental pollution and high costs.Therefore,the promotion of the development and utilization of new and renewable energy sources is a trend that must be followed.Among various renewable energy sources,wind energy has attracted widespread attention due to its characteristics of being widely distributed,pollution-free,abundant and renewable.At present,the main form of wind energy utilization is through wind turbines for wind power generation.On the one hand,the efficiency and stability of wind power generation are largely affected by the complex and changeable wind conditions;on the other hand,with the rapid development of the wind power industry,the installation sites of wind turbines gradually coincide with active earthquake zones,making it possible for wind turbines to be subjected to seismic loads during their working life.Therefore,the study of dynamic response of wind turbines is of great importance.This paper studies the dynamic response of wind turbines,focusing particularly on the effects of earthquakes and wind loads on structures,as well as the Soil-Structure Interaction(SSI)effect.The NREL 5MW wind turbine is taken as the research object,and a wind turbine model with a fixed foundation is built using the ANSYS Workbench platform.The dynamic response of the wind turbine structure under different characteristic earthquake and wind load intensities is analyzed through fluid-solid coupling simulation.Using the Winkler foundation beam model,an appropriate single pile foundation is selected,and a model considering the SSI effect is established using the p-y curve method recommended in the API specification.Considering that the calculation cost of load coupling effects between earthquake and pulsating wind loads is too high in fluid-solid coupling analysis,this paper uses the transfer matrix method to further analyze the dynamic response of the wind turbine tower through theoretical derivation.After summarizing and analyzing the results using the above methods,the following conclusions are obtained:(1)In the modal analysis of wind turbines,the SSI effect will cause changes in the tower’s natural vibration characteristics.The first-order natural frequency drops by approximately 8%,and the second-order natural frequency drops by approximately 15%.Neglecting the SSI effect when the natural vibration characteristics change significantly will lead to distorted dynamic response results.(2)The displacement response at the top of the tower is mainly affected by wind loads.When the average wind speed increases from 5m / s to 11.4m / s,the displacement can increase from about 0.04 m to about 0.5m.The structural stiffness decreases due to the SSI effect,and the displacement at the top of the tower increases by 0.05 m to 0.15 m under different working conditions.The maximum relative increase in each working condition can exceed 20%.(3)The peak acceleration response of the structure is mainly affected by seismic loads.In the steady-state wind condition,the amplification factor of acceleration is mostly around 1.0.After introducing the pulsating wind,the amplification factor of acceleration is generally about0.2 higher than that of the steady-state wind condition.The SSI effect will to some extent reduce the acceleration response at the top of the tower,and the magnitude of the decrease is related to the intensity of the earthquake motion.(4)The average value of the base moment response is mainly affected by wind loads.The change in the intensity and characteristics of the seismic motion will not have a significant effect on the average value of the base moment response.When the wind speed is low,the change in the seismic motion will cause the peak moment value at the base to increase by up to60 MNm.The SSI effect can reduce the peak moment response by up to 20 MNm,and the average value will decrease by about 10 MN,the relative decline of the peak and average response is in the range of 10% to 20%.(5)The variation law of the base shear response under steady-state wind conditions is similar to that of the base moment response.In the conventional model,the increase in wind load will cause a slight decrease in the base shear response,n most working conditions,the decrease is less than 10%。While in the model considering the SSI effect,it will slightly increase,the change amplitude is similar to that in the conventional model.The SSI effect will reduce the base shear response of the structure,with the maximum reduction being 0.5 MN.However,in working conditions with strong pulsating wind and small seismic loads,there will be a slight increase,the lifting amplitude is about 0.15 MN.(6)From the research in this paper,we can know that the coupling effect between ground motion and wind load and the influence of SSI effect on the structure should be fully considered when designing the tower of wind turbine.The laws of wind load and SSI effect on various dynamic responses of structures in different working conditions are not clear.When carrying out design work,different working conditions should be calculated separately.The more comprehensive and complex working conditions of design load can not reveal the response laws under simple working conditions. |
