Abstract
There is a significant interaction between wind and earthquakes for large-scaled wind turbines due to an aeroelastic effect. This study evaluates the accuracy of an uncoupled method extensively utilized to analyze the seismic response of wind turbines at the operational state. Initially, the oscillation of the blade for the National Renewable Energy Laboratory (NREL) 5 MW wind turbine excited by wind and wind-earthquake combination, respectively, is compared using the fully coupled method to verify the assumption in this uncoupled method. Subsequently, the influence of ground motions on the aerodynamic loadings of the rotor is discussed to evaluate the interaction between wind and earthquake loads. In addition, the accuracy of the uncoupled method is assessed by comparing the analysis results of the coupled and uncoupled methods, where different mean wind speed and equivalent aerodynamic damping ratio are considered. The results indicate that the oscillation velocity of blades and thrust on the rotor are significantly influenced by ground motions. Moreover, the amplitude of thrust variations caused by earthquakes increases monotonously with the oscillation velocity amplitude of blade-root. The errors between the two models are beyond the engineering margins for some earthquakes, such that it is difficult to optimize a consistent aerodynamic damping in the uncoupled model to accurately predict the seismic response of wind turbines.
Highlights
As the primary form of wind energy utilization, wind power can fulfill the global energy demand and reduce CO2 emissions [1]
The dynamic response of the National Renewable Energy Laboratory (NREL) 5 MW wind turbine excited by wind and earthquake loads was investigated, and the results revealed the fundamental role of seismic loads in the reliability and economics of wind turbines [11]
The accuracy of the uncoupled method predicting the seismic response of wind turbines was investigated in this study
Summary
As the primary form of wind energy utilization, wind power can fulfill the global energy demand and reduce CO2 emissions [1]. The computational costs of the coupled method may be significant due to the randomness of wind and earthquakes, and the existing aeroelastic code for wind turbines had very limited ability to model the support structure and foundation These shortcomings of the coupled method promoted the development of the uncoupled analysis method. On the basis of these studies, an improved uncoupled method was proposed [30], where the aerodynamic forces of the blade nodes for each time step were computed by the AeroDyn code and the structural model of the wind turbine is established by the commercial finite element software ABAQUS. This method was initially used to evaluate the seismic fragility of the NREL 5 MW wind turbine for different mean wind speeds This method was implemented in the GH BLADED software and assessed by comparisons between the coupled and uncoupled analysis results [31,32,33].
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