基于VMD-HHT方法的水电机组启动过渡过程振动信号分析研究

为了解决水电机组启动过渡过程振动信号特征频率提取困难问题，采用一种较新的处理非线性非平稳信号自适应方法---变分模态分解（VMD），并用于葛洲坝某台机组启动过渡过程振动信号分析。通过Hilbert-Huang（HHT）变换对VMD分解得到的各固有模态函数（IMF）进行瞬时频率计算，得出相应Hilbert谱图，并将结果与经验模态分解（EMD）方法进行对比。结果表明：经VMD分解后，机组启动过渡过程振动信号各分量频率变化与机组转速时变规律吻合良好，能够有效提取特征频率，较EMD具有更好的自适应性，分析结果更加准确有效，能够更好的揭示水电机组过渡过程信号中的振动规律。

Analysis of the Hydropower Unit Vibration Signal in the Start Transient Process Based on VMD-HHT Method

In order to solve the issue that the characteristic frequencies of vibration signals during the transient process of a hydropower unit was difficult to extract , the variational mode decomposition (VMD) method, a relatively new self-adaptive method for processing non-linear and non-stationary signals,was adopted to investigate the vibration signals during the transient process of a hydropower unit in the Gezhouba power plant. The Hilbert-Huang transform (HHT) was used to calculate the instantaneous frequency of each intrinsicmode functions(IMF) decomposed by VMD to arrive at the corresponding Hilbert spectrum. The results showed great consistency between the frequency change of each component and the time-dependent rule of the rotational speed . This suggested that VMD was capable of extracting characteristic frequencies to facilitate the analysis of vibration characteristics. Compared with the empirical mode decomposition (EMD), the VMD outperformed in self-adaptivity. It provided more accurate and effective analysis results and better demonstrations of the vibration rule during the transient process of the hydropower unit.