风电场并网后将对电力系统运行产生一系列影响。传统半不变量法计算概率潮流(probabilistic power flow,PPF)通常仅考虑风速随机性,可能导致分析结果偏离客观实际。提出一种计及参数模糊性的半不变量法PPF计算方法。针对风速和负荷的随...风电场并网后将对电力系统运行产生一系列影响。传统半不变量法计算概率潮流(probabilistic power flow,PPF)通常仅考虑风速随机性,可能导致分析结果偏离客观实际。提出一种计及参数模糊性的半不变量法PPF计算方法。针对风速和负荷的随机性及模糊性,建立随机模糊不确定性模型,采用基于增量法的模糊潮流求得状态变量数字特征的可能性分布。同时,计及风速模糊相关性,通过模糊化半不变量法的解析法拟合得到状态变量各阶半不变量三角模糊置信区间。最后,运用Gram-Charlier级数拟合状态量的模糊概率分布。对改进IEEE 14节点系统以及江苏南京78节点等值系统的实际数据进行测试,验证了算法的有效性、准确性及实用性,并具体分析了风速模糊相关性对系统运行特性的影响。展开更多
In order to fully interpret and describe damage mechanics, the origin and development of fuzzy stochastic damage mechanics were introduced based on the analysis of the harmony of damage, probability, and fuzzy members...In order to fully interpret and describe damage mechanics, the origin and development of fuzzy stochastic damage mechanics were introduced based on the analysis of the harmony of damage, probability, and fuzzy membership in the interval of [0,1]. In a complete normed linear space, it was proven that a generalized damage field can be simulated through β probability distribution. Three kinds of fuzzy behaviors of damage variables were formulated and explained through analysis of the generalized uncertainty of damage variables and the establishment of a fuzzy functional expression. Corresponding fuzzy mapping distributions, namely, the half-depressed distribution, swing distribution, and combined swing distribution, which can simulate varying fuzzy evolution in diverse stochastic damage situations, were set up. Furthermore, through demonstration of the generalized probabilistic characteristics of damage variables, the cumulative distribution function and probability density function of fuzzy stochastic damage variables, which show β probability distribution, were modified according to the expansion principle. The three-dimensional fuzzy stochastic damage mechanical behaviors of the Longtan rolled-concrete dam were examined with the self-developed fuzzy stochastic damage finite element program. The statistical correlation and non-normality of random field parameters were considered comprehensively in the fuzzy stochastic damage model described in this paper. The results show that an initial damage field based on the comprehensive statistical evaluation helps to avoid many difficulties in the establishment of experiments and numerical algorithms for damage mechanics analysis.展开更多
Conjunction of two probability laws can give rise to a possibility law. Using two probability densities over two disjoint ranges, we can define the fuzzy mean of a fuzzy variable with the help of means two random vari...Conjunction of two probability laws can give rise to a possibility law. Using two probability densities over two disjoint ranges, we can define the fuzzy mean of a fuzzy variable with the help of means two random variables in two disjoint spaces.展开更多
目的本文提出一种新颖的基于模糊同质直方图和数据融合技术的彩色图像分割算法。方法首先计算图像的同质特征和同质直方图,然后检测出直方图的峰值点对RGB彩色图像各层进行初始分割,最后计算各基色彩色图像的概率分配函数,使用基于正交...目的本文提出一种新颖的基于模糊同质直方图和数据融合技术的彩色图像分割算法。方法首先计算图像的同质特征和同质直方图,然后检测出直方图的峰值点对RGB彩色图像各层进行初始分割,最后计算各基色彩色图像的概率分配函数,使用基于正交和的Dempster-Shafer(DS)理论合并规则进行图像融合,得到最终的彩色分割图像。结果选用人工合成和多种医学图像进行仿真实验。定性分析表明基于本文算法的分割图像对比度和清晰度均最优,且图像中细胞边界清晰完整,细胞数量真实可靠;定量评估结果显示基于本文算法的图像分割敏感度均最高,显著优于现存的基于目标点到原型成员之间距离的优良模型(Model for Membership Functions,MMFD)和高斯分布假设和直方图阈值(Model Mass Function Method Based on the Assumption of Gaussian Distribution,MMFAGD)算法,且基于同质直方图优于FCM(Fuzzy C-Means)和HCM(Hard C-Means)产生的概率分配函数。结论基于模糊同质直方图的DS证据理论是一种可行的彩色图像分割算法,不仅能获得优质、稳定、准确的彩色分割图像,而且优越于其他现存的分割算法。展开更多
文摘风电场并网后将对电力系统运行产生一系列影响。传统半不变量法计算概率潮流(probabilistic power flow,PPF)通常仅考虑风速随机性,可能导致分析结果偏离客观实际。提出一种计及参数模糊性的半不变量法PPF计算方法。针对风速和负荷的随机性及模糊性,建立随机模糊不确定性模型,采用基于增量法的模糊潮流求得状态变量数字特征的可能性分布。同时,计及风速模糊相关性,通过模糊化半不变量法的解析法拟合得到状态变量各阶半不变量三角模糊置信区间。最后,运用Gram-Charlier级数拟合状态量的模糊概率分布。对改进IEEE 14节点系统以及江苏南京78节点等值系统的实际数据进行测试,验证了算法的有效性、准确性及实用性,并具体分析了风速模糊相关性对系统运行特性的影响。
基金supported by the National Natural Science Foundation of China(Grant No51109118)the China Postdoctoral Science Foundation(Grant No20100470344)+1 种基金the Fundamental Project Fund of Zhejiang Ocean University(Grant No21045032610)the Initiating Project Fund for Doctors of Zhejiang Ocean University(Grant No21045011909)
文摘In order to fully interpret and describe damage mechanics, the origin and development of fuzzy stochastic damage mechanics were introduced based on the analysis of the harmony of damage, probability, and fuzzy membership in the interval of [0,1]. In a complete normed linear space, it was proven that a generalized damage field can be simulated through β probability distribution. Three kinds of fuzzy behaviors of damage variables were formulated and explained through analysis of the generalized uncertainty of damage variables and the establishment of a fuzzy functional expression. Corresponding fuzzy mapping distributions, namely, the half-depressed distribution, swing distribution, and combined swing distribution, which can simulate varying fuzzy evolution in diverse stochastic damage situations, were set up. Furthermore, through demonstration of the generalized probabilistic characteristics of damage variables, the cumulative distribution function and probability density function of fuzzy stochastic damage variables, which show β probability distribution, were modified according to the expansion principle. The three-dimensional fuzzy stochastic damage mechanical behaviors of the Longtan rolled-concrete dam were examined with the self-developed fuzzy stochastic damage finite element program. The statistical correlation and non-normality of random field parameters were considered comprehensively in the fuzzy stochastic damage model described in this paper. The results show that an initial damage field based on the comprehensive statistical evaluation helps to avoid many difficulties in the establishment of experiments and numerical algorithms for damage mechanics analysis.
文摘Conjunction of two probability laws can give rise to a possibility law. Using two probability densities over two disjoint ranges, we can define the fuzzy mean of a fuzzy variable with the help of means two random variables in two disjoint spaces.
文摘目的本文提出一种新颖的基于模糊同质直方图和数据融合技术的彩色图像分割算法。方法首先计算图像的同质特征和同质直方图,然后检测出直方图的峰值点对RGB彩色图像各层进行初始分割,最后计算各基色彩色图像的概率分配函数,使用基于正交和的Dempster-Shafer(DS)理论合并规则进行图像融合,得到最终的彩色分割图像。结果选用人工合成和多种医学图像进行仿真实验。定性分析表明基于本文算法的分割图像对比度和清晰度均最优,且图像中细胞边界清晰完整,细胞数量真实可靠;定量评估结果显示基于本文算法的图像分割敏感度均最高,显著优于现存的基于目标点到原型成员之间距离的优良模型(Model for Membership Functions,MMFD)和高斯分布假设和直方图阈值(Model Mass Function Method Based on the Assumption of Gaussian Distribution,MMFAGD)算法,且基于同质直方图优于FCM(Fuzzy C-Means)和HCM(Hard C-Means)产生的概率分配函数。结论基于模糊同质直方图的DS证据理论是一种可行的彩色图像分割算法,不仅能获得优质、稳定、准确的彩色分割图像,而且优越于其他现存的分割算法。
