Shutdown load of offshore monopile wind turbine under typhoon conditions

Abstract The performance and safety of wind turbines, which are important renewable energy facilities, are affected by many factors. Among them, the performance of the wind turbine in the face of extreme weather conditions is critical. Due to the complexity of the typhoon’s structure, the load of the wind turbine varies greatly in different life cycles. At present, there is a lack of research on the load of the wind turbine during the whole process of typhoon transit in China. Based on the comprehensive consideration of the current research on typhoons, this paper first uses the relationship between complex exponential function and trigonometric function combined with fast Fourier transform to simulate the three-dimensional wind speed time history of typhoons. Second, the Monin-Obukhov similarity theory is used to decompose the typhoon power spectrum. Finally, we take the NERL 5MW wind turbine as an example and use the improved BEM theory to analyze the whole process load of the wind turbine during the typhoon transit. The typhoon transit simulation method used in this paper can well reproduce the actual situation of typhoon transit. When the typhoon is in the front and back wall stages of the typhoon eye, the energy in the low-frequency band is significantly higher than that in the front and back wall stages of the vortex periphery. In the stage of typhoon transit, the front and rear walls of the typhoon eye have the greatest influence on the wind turbine blades. In addition, it is also found that no matter which stage in the life cycle of the typhoon, the bending moment of wind turbine blades is always dominated by the flapping bending moment.