针对含增强型死区的单水电机组电力系统,结合相图法和非光滑分岔理论分析负荷参数对超低频频率振荡(ultra-low frequency oscillation,ULFO)的影响,揭示其发生ULFO的数学机理之一是C-分岔。具体如下:首先,介绍分区域光滑系统(非光滑系统...针对含增强型死区的单水电机组电力系统,结合相图法和非光滑分岔理论分析负荷参数对超低频频率振荡(ultra-low frequency oscillation,ULFO)的影响,揭示其发生ULFO的数学机理之一是C-分岔。具体如下:首先,介绍分区域光滑系统(非光滑系统)的边界平衡点分岔(boundary equilibrium bifurcation,BEB)和非光滑分岔理论,说明一般动力系统振荡的原因之一是不同光滑系统切换相关的非光滑分岔;其次,给出含增强型死区的单水电机组电力系统的简单数学模型;再次,分析不同负荷扰动下系统平衡点从有到无的分岔特性;最后,结合时域和相图,讨论不同负荷扰动、有/无增强型死区时,扰动后系统的动力学特性。由分析结果可知除不存在平衡点外,系统轨线在大范围收敛到极限环,对应负荷参数出现C型非光滑分岔,是电网出现ULFO的机理之一。展开更多
该文从切换型振荡角度,分析负阻尼情形下死区或限幅参与的频率振荡,说明负阻尼下超低频频率振荡(ultra-low frequency oscillation,ULFO)的机理之一是切换型振荡,并揭示了含死区和限幅的单机水电系统在突变负荷扰动下的超低频频率振荡...该文从切换型振荡角度,分析负阻尼情形下死区或限幅参与的频率振荡,说明负阻尼下超低频频率振荡(ultra-low frequency oscillation,ULFO)的机理之一是切换型振荡,并揭示了含死区和限幅的单机水电系统在突变负荷扰动下的超低频频率振荡可对应分段光滑连续系统的单次穿越型类Hopf非光滑分岔。首先,介绍分段光滑连续系统边界平衡点分岔(boundary equilibrium bifurcation,BEB)、类Hopf分岔和单次穿越型类Hopf分岔;其次,给出单水电机组电力系统的非光滑动力系统模型;然后,对比分析有/无死区和限幅(切换边界)时,单机系统负阻尼时频率振荡的差异,初步说明稳定的持续振荡与限幅和死区切换边界相关,无法单纯使用负阻尼或传统Hopf分岔来解释;进一步,借助广义Jacobi矩阵,说明有死区或限幅边界作用的切换型振荡对应的是发生单次穿越型类Hopf分岔;最后,分析突变负荷扰动下单机系统的平衡点、扰动后轨迹的非光滑分岔特性,说明单次穿越型类Hopf分岔是伴随着稳定结点穿越边界变为不稳定焦点的类Hopf分岔。展开更多
A coupled neural system with multiple delays has been investigated. The number of equilibrium points is analyzed. It implies that the neural system exhibits a unique equilibrium and three ones for the different values...A coupled neural system with multiple delays has been investigated. The number of equilibrium points is analyzed. It implies that the neural system exhibits a unique equilibrium and three ones for the different values of coupling weight by employing the pitchfork bifurcation of the trivial equilibrium point. Further, the local asymptotical stability of the trivial equilibrium point is studied by analyzing the corresponding characteristic equation. Some stability criteria involving multiple delays and coupling weight are obtained. The results show that the neural system exhibits the delay-independent and delay-dependent stability. Increasing delay induces stability switching between resting state and periodic motion in some parameter regions of coupling weight. In addition, the criterion for the global stability of the trivial equilibrium is also derived by constructing a suitable Lyapunov functional. Finally, some numerical simulations are taken to support the theoretical results.展开更多
文摘针对含增强型死区的单水电机组电力系统,结合相图法和非光滑分岔理论分析负荷参数对超低频频率振荡(ultra-low frequency oscillation,ULFO)的影响,揭示其发生ULFO的数学机理之一是C-分岔。具体如下:首先,介绍分区域光滑系统(非光滑系统)的边界平衡点分岔(boundary equilibrium bifurcation,BEB)和非光滑分岔理论,说明一般动力系统振荡的原因之一是不同光滑系统切换相关的非光滑分岔;其次,给出含增强型死区的单水电机组电力系统的简单数学模型;再次,分析不同负荷扰动下系统平衡点从有到无的分岔特性;最后,结合时域和相图,讨论不同负荷扰动、有/无增强型死区时,扰动后系统的动力学特性。由分析结果可知除不存在平衡点外,系统轨线在大范围收敛到极限环,对应负荷参数出现C型非光滑分岔,是电网出现ULFO的机理之一。
文摘该文从切换型振荡角度,分析负阻尼情形下死区或限幅参与的频率振荡,说明负阻尼下超低频频率振荡(ultra-low frequency oscillation,ULFO)的机理之一是切换型振荡,并揭示了含死区和限幅的单机水电系统在突变负荷扰动下的超低频频率振荡可对应分段光滑连续系统的单次穿越型类Hopf非光滑分岔。首先,介绍分段光滑连续系统边界平衡点分岔(boundary equilibrium bifurcation,BEB)、类Hopf分岔和单次穿越型类Hopf分岔;其次,给出单水电机组电力系统的非光滑动力系统模型;然后,对比分析有/无死区和限幅(切换边界)时,单机系统负阻尼时频率振荡的差异,初步说明稳定的持续振荡与限幅和死区切换边界相关,无法单纯使用负阻尼或传统Hopf分岔来解释;进一步,借助广义Jacobi矩阵,说明有死区或限幅边界作用的切换型振荡对应的是发生单次穿越型类Hopf分岔;最后,分析突变负荷扰动下单机系统的平衡点、扰动后轨迹的非光滑分岔特性,说明单次穿越型类Hopf分岔是伴随着稳定结点穿越边界变为不稳定焦点的类Hopf分岔。
基金supported by the National Natural Science Foundation of China(Grant Nos.11202068&11572224)the University Key Teacher Foundation for Youths of Henan Province(Grant No.2014GGJS-076)the Key Technologies Research Project of Henan Province(Grant No.152102210089)
文摘A coupled neural system with multiple delays has been investigated. The number of equilibrium points is analyzed. It implies that the neural system exhibits a unique equilibrium and three ones for the different values of coupling weight by employing the pitchfork bifurcation of the trivial equilibrium point. Further, the local asymptotical stability of the trivial equilibrium point is studied by analyzing the corresponding characteristic equation. Some stability criteria involving multiple delays and coupling weight are obtained. The results show that the neural system exhibits the delay-independent and delay-dependent stability. Increasing delay induces stability switching between resting state and periodic motion in some parameter regions of coupling weight. In addition, the criterion for the global stability of the trivial equilibrium is also derived by constructing a suitable Lyapunov functional. Finally, some numerical simulations are taken to support the theoretical results.