Transient voltage stability analysis(TVSA)of power systems is one of the most computationally challenging tasks in dynamic security assessment.To reduce the complexity of TVSA,this paper proposes an improved expanding...Transient voltage stability analysis(TVSA)of power systems is one of the most computationally challenging tasks in dynamic security assessment.To reduce the complexity of TVSA,this paper proposes an improved expanding annular domain(improved EAD)algorithm to estimate the domain of attraction(DA)of power systems containing multiple induction motors(IMs),whose improvements are concerned with relaxing the restriction on critical value and simplifying iteration steps.The proposed algorithm can systematically construct Lyapunov function for lossy power systems with IMs and their slip constraints.First,the extended Lyapunov stability theory and sum of squares(SOS)programming are presented,which are powerful tools to construct Lyapunov function.Second,the internal node model of IM is developed by an analogy with that of a synchronous generator,and a multi-machine power system model by eliminating algebraic variables is derived.Then,an improved EAD algorithm with SOS programming is proposed to estimate the DA for a power system considering the slip constraint of IM.Finally,the superiority of our method is demonstrated on two modified IEEE test cases.Simulation results show that the proposed algorithm can provide a better estimated DA and critical clearing slip for power systems with multiple IMs.展开更多
显示器电磁木马是通过控制计算机屏幕电磁辐射达到窃取信息目的的一种新型木马。当前的主流防护思想是用软件防护代替较为成熟但造价昂贵的硬件防护机制,然而目前软防护思想大多侧重于理论方法的探索,在实现机制上相对比较复杂。针对显...显示器电磁木马是通过控制计算机屏幕电磁辐射达到窃取信息目的的一种新型木马。当前的主流防护思想是用软件防护代替较为成熟但造价昂贵的硬件防护机制,然而目前软防护思想大多侧重于理论方法的探索,在实现机制上相对比较复杂。针对显示器电磁木马的工作特点提出了Soft-TEMPEST防护机制,设计了显示器电磁木马的ADFA(API Detection and Frequency Analysis)检测方法。该方法通过API函数序列的周期性挖掘分析,结合对屏幕像素信息的傅里叶变换及频谱分析,达到检测出木马进程的目的。测试结果表明,该方法能够成功检测出多种显示器电磁木马,而且原理简单,方便投入使用。展开更多
无间隙金属氧化物避雷器的雷电残压特性、雷电动作负载特性是避雷器雷电保护特性的核心特征,这些特性和作用的雷电波有很大关系。利用电磁暂态分析程序EMTP—ATP建立了典型750 k V变电站雷电计算模型,依据国内外捕获的雷电波特征参数统...无间隙金属氧化物避雷器的雷电残压特性、雷电动作负载特性是避雷器雷电保护特性的核心特征,这些特性和作用的雷电波有很大关系。利用电磁暂态分析程序EMTP—ATP建立了典型750 k V变电站雷电计算模型,依据国内外捕获的雷电波特征参数统计结果,雷电流的波头约为1μs^5μs,波长约为20μs^100μs,选取了有代表性的5种雷电侵入波波形,即1/20μs、1/100μs、2.6/50μs、5/20μs、5/100μs。研究了不同雷电侵入波对避雷器放电电流的影响。展开更多
基金supported by the Department of Science,and Technology of Guangdong Province under Grant No.2023 A1515240019。
文摘Transient voltage stability analysis(TVSA)of power systems is one of the most computationally challenging tasks in dynamic security assessment.To reduce the complexity of TVSA,this paper proposes an improved expanding annular domain(improved EAD)algorithm to estimate the domain of attraction(DA)of power systems containing multiple induction motors(IMs),whose improvements are concerned with relaxing the restriction on critical value and simplifying iteration steps.The proposed algorithm can systematically construct Lyapunov function for lossy power systems with IMs and their slip constraints.First,the extended Lyapunov stability theory and sum of squares(SOS)programming are presented,which are powerful tools to construct Lyapunov function.Second,the internal node model of IM is developed by an analogy with that of a synchronous generator,and a multi-machine power system model by eliminating algebraic variables is derived.Then,an improved EAD algorithm with SOS programming is proposed to estimate the DA for a power system considering the slip constraint of IM.Finally,the superiority of our method is demonstrated on two modified IEEE test cases.Simulation results show that the proposed algorithm can provide a better estimated DA and critical clearing slip for power systems with multiple IMs.
文摘显示器电磁木马是通过控制计算机屏幕电磁辐射达到窃取信息目的的一种新型木马。当前的主流防护思想是用软件防护代替较为成熟但造价昂贵的硬件防护机制,然而目前软防护思想大多侧重于理论方法的探索,在实现机制上相对比较复杂。针对显示器电磁木马的工作特点提出了Soft-TEMPEST防护机制,设计了显示器电磁木马的ADFA(API Detection and Frequency Analysis)检测方法。该方法通过API函数序列的周期性挖掘分析,结合对屏幕像素信息的傅里叶变换及频谱分析,达到检测出木马进程的目的。测试结果表明,该方法能够成功检测出多种显示器电磁木马,而且原理简单,方便投入使用。
文摘无间隙金属氧化物避雷器的雷电残压特性、雷电动作负载特性是避雷器雷电保护特性的核心特征,这些特性和作用的雷电波有很大关系。利用电磁暂态分析程序EMTP—ATP建立了典型750 k V变电站雷电计算模型,依据国内外捕获的雷电波特征参数统计结果,雷电流的波头约为1μs^5μs,波长约为20μs^100μs,选取了有代表性的5种雷电侵入波波形,即1/20μs、1/100μs、2.6/50μs、5/20μs、5/100μs。研究了不同雷电侵入波对避雷器放电电流的影响。
