Automatic Identification of Modal Parameters of Wind Turbine Towers Under Harmonic Excitation
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摘要: 运行工况下风力发电机组的周期性激励会产生与结构模态频率相近的谐波干扰,将影响结构基本模态的振动水平及动力参数的识别。为了在运行过程中有效连续监测塔筒振动状态,提出了一种基于势能凝聚层次聚类(PHA)的协方差驱动随机子空间法(Cov-SSI)与概率密度函数法(PDF)相结合的风机塔筒模态参数自动识别方法。通过现场振动响应测试,首先采用Cov-SSI法初步识别塔筒结构模态参数;其次,引入PHA法改进稳定图,定义频率与模态置信准则(MAC)距离矩阵进行清洗、聚类,实现自动化分离不同阶模态;最后将聚类簇信息通过PDF法判定并剔除谐波模态。结果表明:所提方法能有效分离并剔除谐波分量,实现风机塔筒运行模态参数的自动化识别,对风电机组安全运行自动化实时监测具有较好的工程应用价值。Abstract: The periodic excitation of wind turbines under operating conditions will generate harmonic disturbances with similar frequencies to the structural modes, which will affect the vibration level of the fundamental modes of the structure and the identification of the dynamic parameters. In order to effectively and continuously monitor the tower vibration status during operation, the covariance-driven stochastic subspace identification (Cov-SSI) method based on potential hierarchical agglomerative clustering (PHA) combined with the probability density function (PDF) was proposed for the automatic identification of modal parameters of wind turbine towers. Through the on-site vibration response test, the Cov-SSI method was firstly used to initially identify the tower structure modal parameters; secondly, the PHA method was introduced to improve the stability diagram, and the frequency and modal confidence criterion (MAC) distance matrix was defined for cleaning and clustering to automate the separation of different orders of modes; finally, the information of the clustered clusters was used to determine and eliminate the harmonic modes by the PDF method. The results showed that the proposed method could effectively separate and eliminate the harmonic components, realize the automatic identification of the modal parameters of wind turbine towers under operation, and provide a good engineering application value for the automated real-time monitoring of wind turbine safety operation.
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