风力机支撑结构疲劳损伤评估中的不确定性分析

Uncertainty Analysis in Fatigue Damage Assessment of Wind Turbine Support Structure

风力机支撑结构所处的环境条件复杂,其振动特性和疲劳问题是决定风力机安全运行的关键因素。通过对1.5MW风力机的环境数据和塔底应变进行长期监测,研究风力机设计规范给出的疲劳计算方法中未涵盖的一些关键问题。首先,分析风速与塔底应力的关系。然后,使用雨流计数法和Palmgren-Miner准则,研究在相差不大的风速和风向下,转速对塔底应力和疲劳损伤的影响。结果表明:风力机停机时的塔底应力较叶轮旋转时小得多,产生的疲劳损伤也最小;启停机过程会使塔底应力呈现非平稳特征,强烈影响结构的应力幅值和疲劳损伤。此外,分析代表性样本的不同选择对损伤结果的影响。因此,在疲劳损伤评估时,应更加准确地定义荷载工况并选择合理的代表性样本。

The environmental conditions of the wind turbine support structure are complex,and its vibration characteristics and fatigue degree are the key factors to determine the safe operation of wind turbines.The standard method of fatigue calculation is given in the wind turbine design code.Through the long-term monitoring of the environmental data and tower bottom strain of 1.5MW wind turbine,some key problems not covered in the code are studied.First,the relationship between wind speed and tower bottom stress is analyzed.Then,the rain-flow counting method and Palmgren-Miner criterion are used to study the effects of rotating speed on tower bottom stress and fatigue damage under similar wind speed and direction.The results show that the tower bottom stress during turbine shutdown is much smaller than that during rotation,and its fatigue damage is the smallest.The startup and shutdown process will make the tower bottom stress non-stationary,which will strongly affect the stress amplitude and fatigue damage of the structure.In addition,the influence of different selection of representative samples on damage results is also analyzed.Therefore,the load cases should be defined more accurately and reasonable representative samples should be selected in fatigue damage assessment.