Ferroresonance is a complex and little known electrotechnical phenomenon. This lack of knowledge means that it is voluntarily considered responsible for a number of unexplained destructions or malfunctioning of equipm...Ferroresonance is a complex and little known electrotechnical phenomenon. This lack of knowledge means that it is voluntarily considered responsible for a number of unexplained destructions or malfunctioning of equipment. The mathematical framework most suited to the general study of this phenomenon is the bifurcation theory, the main tool of which is the continuation method. Nevertheless, the use of a continuation process is not devoid of difficulties. In fact, to continue the solutions isolats which are closed curves, it is necessary to know a solution belonging to this isolated curve (isolat) to initialise the continuation method. The principal contribution of this article is to develop an analytical method allowing systematic calculation of this initial solution for various periodic ferroresonant modes (fundamental, harmonic and subharmonic) appearing on nonlinear electric system. The approach proposed uses a problem formulation in the frequency domain. This method enables to directly determine the solution in steady state without computing of the transient state. When we apply this method to the single-phase ferroresonant circuits (series and parallels configurations), we could easily calculate an initial solution for each ferroresonant mode that can be established. Knowing this first solution, we show how to use this analytical approach in a continuation technique to find the other solutions. The totality of the obtained solutions is represented in a plane where the abscissa is the amplitude of the supply voltage and the ordinate the amplitude of the system’s state variable (flux or voltage). The curve thus obtained is called “bifurcation diagram”. We will be able to then obtain a synthetic knowledge of the possible behaviors of the two circuits and particularly the limits of the dangerous zones of the various periodic ferroresonant modes that may appear. General results related to the series ferroresonance and parallel ferroresonance, obtained numerically starting from the theoretical and real cases,展开更多
为提高工控系统异常流量检测能力,设计一种结合孤立森林(isolation forest,iForest)和单类支持向量机(one-class support vector machine,OCSVM)的混合算法。采用孤立森林算法检测训练数据中的离群点,将离群点剔除以降低其对单类支持向...为提高工控系统异常流量检测能力,设计一种结合孤立森林(isolation forest,iForest)和单类支持向量机(one-class support vector machine,OCSVM)的混合算法。采用孤立森林算法检测训练数据中的离群点,将离群点剔除以降低其对单类支持向量机决策函数的影响;基于正常数据训练单类支持向量机模型,结合特征选取和参数优化进一步提高异常检测模型的检测率。实验结果表明:在燃气管道数据集上,该算法模型的检测率提高至92.51%,特别是对异常行为的召回率和查准率上升,优化了异常检测模型的性能,满足可靠性要求。展开更多
文摘Ferroresonance is a complex and little known electrotechnical phenomenon. This lack of knowledge means that it is voluntarily considered responsible for a number of unexplained destructions or malfunctioning of equipment. The mathematical framework most suited to the general study of this phenomenon is the bifurcation theory, the main tool of which is the continuation method. Nevertheless, the use of a continuation process is not devoid of difficulties. In fact, to continue the solutions isolats which are closed curves, it is necessary to know a solution belonging to this isolated curve (isolat) to initialise the continuation method. The principal contribution of this article is to develop an analytical method allowing systematic calculation of this initial solution for various periodic ferroresonant modes (fundamental, harmonic and subharmonic) appearing on nonlinear electric system. The approach proposed uses a problem formulation in the frequency domain. This method enables to directly determine the solution in steady state without computing of the transient state. When we apply this method to the single-phase ferroresonant circuits (series and parallels configurations), we could easily calculate an initial solution for each ferroresonant mode that can be established. Knowing this first solution, we show how to use this analytical approach in a continuation technique to find the other solutions. The totality of the obtained solutions is represented in a plane where the abscissa is the amplitude of the supply voltage and the ordinate the amplitude of the system’s state variable (flux or voltage). The curve thus obtained is called “bifurcation diagram”. We will be able to then obtain a synthetic knowledge of the possible behaviors of the two circuits and particularly the limits of the dangerous zones of the various periodic ferroresonant modes that may appear. General results related to the series ferroresonance and parallel ferroresonance, obtained numerically starting from the theoretical and real cases,
文摘为提高工控系统异常流量检测能力,设计一种结合孤立森林(isolation forest,iForest)和单类支持向量机(one-class support vector machine,OCSVM)的混合算法。采用孤立森林算法检测训练数据中的离群点,将离群点剔除以降低其对单类支持向量机决策函数的影响;基于正常数据训练单类支持向量机模型,结合特征选取和参数优化进一步提高异常检测模型的检测率。实验结果表明:在燃气管道数据集上,该算法模型的检测率提高至92.51%,特别是对异常行为的召回率和查准率上升,优化了异常检测模型的性能,满足可靠性要求。
