类噪声环境下基于滑动相干谱的强迫振荡检测方法研究

Research on detection of forced power oscillation based on ambient excitation and sliding coherence method

电力系统中时刻存在负荷投切等环境激励,使得系统响应表现为类似噪声的小幅波动。如果强迫功率振荡的幅值较小,很容易淹没在类噪声信号中。本文推导了类噪声环境下电力系统强迫功率振荡解析表达式,从数学角度阐释了类噪声环境下强迫振荡的机理特性。在深入分析类噪声环境下小幅强迫振荡频谱特征的基础上,提出了基于滑动相干谱法(SCM)的小幅强迫功率振荡检测方法。首先采集得到两组发电机有功功率类噪声响应数据,计算得到对应的自功率谱密度和互功率谱密度,从而计算得到两组数据的幅值平方相干函数值,进而通过对所得幅值平方相干函数值的量化比较,检测出淹没在类噪声信号中的小幅强迫功率振荡。IEEE 4机2区域系统和16机68节点系统验证了所提检测方法的可行性及有效性。

Small fluctuations caused by random changes of loads exist continuously in power grid,which are referred as ambient excitation. If the magnitude of forced oscillation is small,it might be hidden in the ambient excitation. This paper derives the mathematical expression of forced power oscillation under the ambient excitation and explains the mechanism of forced oscillation from a mathematical point of view. Based on the profound analysis of the spectral characteristics,a method for forced power oscillation detection on the basis of sliding coherence method is proposed. Firstly,the ambient data by the WAMS are obtained. Then,they are calculated to obtain the corresponding power spectral density and cross power spectral density,further get the coherent result. Finally,forced power oscillation with small magnitude can be detected by quantized comparison of the coherent results. The method is proved to be effective and feasible by the simulation analysis of IEEE 4-machine 2-area system and 16-machine68-bus system.