Wind-induced Vibration Time Domain Analysis Of A Wind Turbine Tower Considering The Blade System

Wind power has received extensive attention as a green,renewable energy source.The emergence of wind turbines plays a significant role in the utilization of wind resources.The tower is a supporting structure of a wind generator and has the characteristics of large flexibility,low natural frequency,and low damping,and bears the full weight of the wind turbine and also receives the wind load from the nacelle and the wind wheel and its own wind load.Due to the frequent action of wind loads,the wind turbine tower is prone to fatigue failure.In the previous wind turbine tower wind-induced vibration response analysis,the blade system was often simplified and only its mass and torque inertia were considered.However,based on the conventional method,the role of the blade system in the tower vibration is neglected,and the wind-induced vibration response analysis of the wind turbine tower is not comprehensive enough.This paper adopts theoretical analysis and numerical simulation method to perform wind-induced vibration fatigue time domain analysis on the wind turbine tower considering the blade system.The specific research work and corresponding results are as follows:(1)Based on the wind load basic theory of wind turbine tower,numerical simulation of the fluctuating wind load on the wind turbine tower is carried out to obtain the equivalent wind load time course along each point of the tower height;the simulation is carried out using the modified leaf momentum theory.The wind turbine pneumatic load program lays the foundation for the transient analysis of the wind-induced vibration response of wind turbine towers.(2)Taking NREL 5MW wind turbine tower as the research object,finite element software is used to establish the finite element model of the wind turbine tower structure.The modal analysis of the finite element model of the tower considering the blade is discussed and analyses the influence of the blade system on the natural vibration frequency of the structure.The wind-induced vibration response of the tower structure considering the blade system is analyzed and the role of blade system in wind vibration response of tower is analyzed.(3)Study wind speed response analysis of towers with different wind speeds,understand the influence of wind speed on the towers of wind turbines,and compare displacement time-history curves at tower tops of wind turbine tower structures with different damping ratios.The results show that structural dampers are good for tower winds.The influence of the horizontal swinging displacement is very significant,and only slight damping can make the tower avoid swinging back and forth greatly.In the design of the wind turbine tower,the influence of structural damping needs to be taken into account to control the structural displacement response.(4)Taking the wind speed from the wind turbine cut-in speed to the cut-out speed range as the target sample,numerically simulate the wind load of the corresponding grade,and calculate the probabilistic characteristics and wind load effect of the wind turbine tower design using the Weibull distribution.Based on the finite element calculation results of the wind turbine tower,combined with the S-N curve provided by the relevant design specifications,based on the Miner linear cumulative damage criterion,predicts the fatigue life of the most unfavorable part of the wind turbine tower under wind load.