Research On Offshore Wind Turbine Monopile Tower Seismic Dynamic Response And Vibration Reduction Control

The tower is the key structure supporting the turbine and the nacelle in the wind power system.China's wind energy rich areas are mainly distributed in the Eurasian seismic belt and the circum-Pacific seismic belt.The wind turbine in earthquake disaster is very likely to earthquake damage during the service time,in addition.In addition,offshore wind turbine tower will be under cyclic wave load,and be more prone to failure or collapse.The large offshore monopile wind turbine was chosen as the research object.The modal truncation method and multi-body system dynamics theory were adapted to set up wind turbine simulation model.Based on Kaimal turbulent wind spectrum model and the JONSWAP wave spectrum model respectively,the tower dynamic response is calculated under the different water depths and different intensity earthquake,and the nonlinear dynamics method to analyze response time series.Furthermore,the TMD damping effect of vibration of tower is studied.Conclusion are as followes:1.When PGA of earthquake is 0.15 g,tower top acceleration response,tower displacement and tower bending moment is gradually increasing with the deepening of the water depth.The transverse tower bending moment respomse at 40 m deep water is most acute.And,30 m deep water wind turbine tower lateral bending response acceleration are small.With 20 m deep water,wind turbine tower acceleration response is more intense.For 20 m and 40 m deep water support structure,tower structure strength weak reason shear force has larger ascension.Wind-earthquke coupling effect will aggravate the top acceleration and bending moment responses.2.The responses of tower top displacement,acceleration and tower base bending moment increase with the strengthening of earthquake intensity,but the increase of tower top displacement is small.And the response of transverse tower top acceleration affected by earthquake is more obvious than that in the direction of flow.The influence of seismic load on the response of tower footing moment in the direction of incoming flow is slightly greater than that of transverse tower footing moment.In terms of the overall structure of the tower,when the earthquake intensity is small,the tower displacement of the wind turbine is mainly controlled by turbulent wind load.With the increase of the earthquake intensity,the control load of the tower displacement changes into the earthquake load,and the relationship between displacement and height changes from non-linear to linear.Under the action of seismic load,the acceleration response of the tower at different heights increases greatly.At the same time,the response peak appears at the height of the tower at 80 m,while the acceleration of the support structure and the top of the tower increases less.Under the action of earthquakes of different intensities,the peak values of shear force responses of towers at different heights have great differences,while the part with the largest increase of bending moment responses of towers appear at the bottom of the tower,and the bending moment responses at different heights show certain nonlinearity.According to the formula of moment load of tower provided by IEC,a model of nonlinear tower load presented in this paper is more accurate.3.Under the combined action of turbulent wind and earthquake with PGA of 0.15 g,the displacement response of the tower top of wind turbines in different water depths presents nonlinear dynamic characteristics.The characteristics increase with the deepening of water entry depth.At the same time,the nonlinear characteristics of the displacement response of the tower top of the wind turbine will first increase and then decrease slightly with the increase of the earthquake intensity.The nonlinear characteristics of tower vibration response considering soil structure coupling effect are obvious by p-y curve method.4.When the PGA is 0.3 g,under the earthquake coupled with the turbulent wind,the TMD damping device has a good effect on the vibration control of the tower top with a water depth of 20 m,and a general effect on the vibration control of the tower top with a water depth of 30 m and 40 m.TMD has the most obvious control effect on tower top displacement and tower foundation bending moment in the direction of incoming flow when the earthquake acts alone,but insufficient control on tower top vibration and tower foundation load caused by turbulent wind.