Wind turbine earthquake analysis using conical beam finite element formulation

Wind energy is one of the most promising renewable energy sources that can reduce greenhouse gas emissions and fossil fuel dependence. Wind turbines are usually installed in areas with high wind potential, which may also coincide with regions prone to seismic activity. So, to ensure the safety and reliability of wind turbines under earthquake load, it is necessary to perform seismic analysis and design, taking into account the aerodynamic, structural, and control aspects of the wind turbine system. In this paper, tower dynamic behavior of ۵MW NREL benchmark wind turbine is modeled using Lagrange equations with linearly tapered conical cross section beam element based on Timoshenko beam model. Then the proposed dynamic model is used to perform dynamic spectrum analysis to calculate the seismic loads exerted on wind turbine towers due to earthquake. The aerodynamic loads applied to the NREL ۵MW wind turbine at different operational condition according to Germanischer Lloyd (GL) guideline is calculated using FAST software. Then aerodynamic bending moments and seismic moments are combined and the resulted bending moments are used to obtain the safety factor of the structure along its heights against earthquake. The results indicate that this tower can withstand the earthquake occurrences in type III ground of Iran regions and the smallest safety factor is equal to ۱.۱۸.

Keywords:

dynamical behavior , forced vibration , tapered beam element , Aerodynamic load calculation , seismic analysis.