谐波干扰下海上风机结构工作模态识别

Operational modal identification of an offshore wind turbine structure under harmonic interference

针对海上风力发电机组高转速叶轮对风机结构会造成强烈的周期性激励,而该强谐波作用往往会淹没响应中的结构模态信息,增加识别结构工作模态参数难度问题,以某海上风电试验样机振动响应原型观测信号为研究对象,采用基于改进特征系统实现法(Eigensystem Realization Algorithm,ERA)与概率密度函数法(Probability Density Function,PDF)结合的工作模态识别方法及判定思路,剔除不同工况下转频、倍频谐波成分干扰,实现风机结构多阶工作模态参数有效识别。该方法不仅能有效避免谐波干扰以获取结构的真实工作模态,同时对海上风机结构运行安全性实时在线监测、评估具有较好的工程适用性。

It is difficult to identify the operational modal parameters of an offshore wind turbine structure accurately because the structural modal information in its responses is buried by the strong recurring harmonic excitation induced from the wind turbine＇s impeller with high rotating speed. In order to solve the problem of structural operational modal identification, a method combining the modified eigensystem realization algorithm （ERA） with the probability density function （PDF） was proposed here. Subsequently, the interference coming from the rotating frequencies and frequency multiplication was eliminated and the effective identification for the multi-operatlonal modal parameters of a certain offshore wind turbine test prototype was achieved based on the measured signals under different operational conditions. It was shown that this approach can not only avoid the strong harmonic interference so as to obtain the real structural operational modes effectively, but also has a better engineering applicability in online real-time monitoring and evaluation of the structural operational security for offshore wind turbine structures.