摘要
电力系统实测低频振荡信号的主要特点为:振荡模式出现的时间不确定,持续的时间不确定,振幅带有阻尼特性且随时间变化。因此,在对低频振荡信号进行参数辨识之前,应判别是否发生了持续、稳定的低频振荡。但现在认可度较高的低频振荡分析方法并不对此进行判别,缺乏真实性。基于此,本文提出了电力系统低频振荡监测的Duffing振子可停振动系统法。Duffing振子可停振动状态的改变对周期扰动高度敏感,同时对随机微小扰动却十分不敏感。根据这个特点将量测信号输入到可停振动系统中,得到其相轨迹。随机微小扰动的相轨迹聚焦为一点,为可停振动状态,弱阻尼模式的低频振荡和强迫功率振荡相轨迹存在"低频振荡吸引子",而负阻尼的低频振荡的相轨迹存在"低频振荡排斥子"。因此,根据相轨迹的状态改变,可以判断是否存在稳定的低频振荡信号,是哪种模式的低频振荡,以及模式的阻尼特性。为快速准确地告警、合理选择振荡抑制措施及快速抑制振荡提供依据。该方法通过可视化的方法展现振荡过程和特性,利用其提取的对数平衡距可以对相轨迹进行定量分析,为低频振荡监测提供了一种新的分析方法。
The measurement signals are represented as a typical nonlinear and non-stationary random process. The main characteristics of low-frequency oscillation （LFO） lie in that, both the appearance time of oscillation mode and the lasting time are uncertain, and the amplitude damping changes with time. Therefore, before parameter identification, whether the sustained and stable LFO is or not should be determined. The high approval methods for LFO analysis are not suitable for such situation. Then, a new method is proposed to monitor LFO based on order stopping oscillation system of duffing oscillator. The state of order stopping oscillation system of duffing oscillator is highly sensitive to periodic perturbation while it is quite insensitive to random small perturbation. The measured data used as the excitation （input signal）, were put into order stopping oscillation system, and then the phase trajectories of system were obtained. Small perturbations＇ phase trajectory converged to the focal point, whose state is order stopping oscillation. The existence of LFO attractor was obtained by phase trajectory of weak damping mode and forced oscillation, javascript：void（0）;while LFO caused by negative damp existed LFO repellor. Thus, according to the change of phase trajectory, whether there is a steady-state LFO can be judged, and the mode and damping characteristic can also be judged correctly. It is very significant in fast and accurate alarming, rationally selecting the oscillation suppression measures, and quickly suppressing the oscillation. Processing and characteristics of LFO were showed by using the method of graphic visualization, and then logarithm distance with equilibrium point provides a method of quantitative analysis.
出处
《电工技术学报》
EI
CSCD
北大核心
2015年第20期159-167,共9页
Transactions of China Electrotechnical Society
关键词
Duffing振子可停振动系统
低频振荡监测
吸引子
排斥子
Order stopping oscillation system of dulling oscillator, low-frequency oscillation monitoring, attractor, repellor
