地震作用下风力机时频域动态响应特性分析

摘要

To analyze the seismic load impact on the structure dynamic response of large-scale wind turbine,model cosidering the wind turbine platform and soil interaction based on Wolf theory was set up.Structure dynamic response of the NREL 5 MW wind turbine on start-up,normal operating,yawing motion and emergency shutdown conditions were predicted through FAST tool.Due to the nonlinear and non-stationary characteristics of the time-domain aero-elastic response of wind turbine on seismic and turbulence inflow condition,the Hilbert-Huang transform (HHT) method was applied to obtain the time-frequency characteristics for analyzing the multi-load coupling mechanism.The results show that the influence on tower-top deflection of seismic loading should be taken to consideration,the influence on side to side direction shouldn't be neglected even more.Earthquake load is the main excitation load for tower-top vibration which is far more important than the aerodynamics.The characteristic vibrational frequency of tower is the first order natural frequency.Seismic loading enhance the magnitude of first order natural frequency and second harmonic frequency obviously.The fact should be considered in tower structural designing.%为研究地震载荷对大型风力机结构动力学响应的影响,基于Wolf方法建立风力机基础与土地的耦合模型,在FAST软件中仿真了NREL 5 MW风力机开机启动、正常运行、偏航和紧急停机等工况下的结构动力学响应.针对风力机气动弹性响应在地震和湍流风联合作用时典型的非线性和非平稳特点,通过希尔伯特-黄变换(Hilbert-Huang Transform)分析风力机塔顶位移时频域响应特性.结果表明:地震载荷对塔顶位移的影响不可忽略,尤其是对侧向位移的影响,同时地震载荷是塔顶振动的主要激励,气动载荷影响几乎可以忽略;塔架一阶固有频率为塔顶振动特征频率,地震载荷明显增大固有频率响应幅值,且增大了其二倍频处的响应,塔架结构抗震设计时应考虑这一现象.