Laboratory experiments are conducted to study the probability distribution of surface elevation for wind waves and the convergence is discussed of the Gram-Charlier series in describing the surface elevation distribut...Laboratory experiments are conducted to study the probability distribution of surface elevation for wind waves and the convergence is discussed of the Gram-Charlier series in describing the surface elevation distribution. Results show that the agreement between the Gram-Charlier series and the observed distribution becomes better and better as the truncated order of the series increases in a certain range, which is contrary to the phenomenon observed by Huang and Long (1980). It is also shown that the Gram-Charlier series is sensitive to the anomalies in the data set which will make the agreement worse if they are not preprocessed appropriately. Negative values of the probability distribution expressed by the Gram-Charlier series in some ranges of surface elevations are discussed, but the absolute values of the negative values as well as the ranges of their occurrence become smaller gradually as more and mote terms are included. Therefore the negative values will have no evident effect on the form of the whole surface elevation distribution when the series is truncated at higher orders. Furthermore, a simple recurrence formula is obtained to calculate the coefficients of the Gram-Charlier series in order to extend the Gram-Charlier series to high orders conveniently.展开更多
随机潮流能够比较全面地反映系统运行状态,对电网安全性风险评估起到重要作用。现有的随机潮流计算方法中,结合半不变量和Gram-Charlier展开级数的方法可快速且准确地计算节点电压和支路潮流的概率密度函数(probability distribution fu...随机潮流能够比较全面地反映系统运行状态,对电网安全性风险评估起到重要作用。现有的随机潮流计算方法中,结合半不变量和Gram-Charlier展开级数的方法可快速且准确地计算节点电压和支路潮流的概率密度函数(probability distribution function,PDF)以及累积分布函数(cumulative distribution function,CDF)。以受时域和地域不均匀分布影响的系统当前运行状态为基础构造预想事故集,将全概率理论与半不变量法随机潮流相结合,提出一种考虑电网静态安全风险的随机潮流算法。对IEEE RTS 96节点实验系统的计算表明,该算法可快速、准确地评估系统当前运行状态的静态安全风险,具有实际应用价值。展开更多
发电机组的随机故障停运对电力系统潮流计算产生影响,应用传统半不变量法计算概率潮流(probabilistic power flow,PPF)将产生较大误差。提出一种考虑离散分布输入变量的半不变量法PPF计算方法。针对服从离散分布的发电机注入功率采用多...发电机组的随机故障停运对电力系统潮流计算产生影响,应用传统半不变量法计算概率潮流(probabilistic power flow,PPF)将产生较大误差。提出一种考虑离散分布输入变量的半不变量法PPF计算方法。针对服从离散分布的发电机注入功率采用多点线性化方法,减小潮流方程线性化误差。同时,引入阈值分析策略,提高计算效率。最后,综合运用A型Gram-Charlier级数和C型Gram-Charlier级数拟合状态变量的概率分布。对IEEE-RTS 24节点系统进行仿真,验证了算法的准确性和实用性。结果表明:所提PPF计算方法具有较高的精度,并保持一定的计算效率。展开更多
基金This project was financially supported by the National Nature Science Foundation of China(Grant No.49876012,49976003)
文摘Laboratory experiments are conducted to study the probability distribution of surface elevation for wind waves and the convergence is discussed of the Gram-Charlier series in describing the surface elevation distribution. Results show that the agreement between the Gram-Charlier series and the observed distribution becomes better and better as the truncated order of the series increases in a certain range, which is contrary to the phenomenon observed by Huang and Long (1980). It is also shown that the Gram-Charlier series is sensitive to the anomalies in the data set which will make the agreement worse if they are not preprocessed appropriately. Negative values of the probability distribution expressed by the Gram-Charlier series in some ranges of surface elevations are discussed, but the absolute values of the negative values as well as the ranges of their occurrence become smaller gradually as more and mote terms are included. Therefore the negative values will have no evident effect on the form of the whole surface elevation distribution when the series is truncated at higher orders. Furthermore, a simple recurrence formula is obtained to calculate the coefficients of the Gram-Charlier series in order to extend the Gram-Charlier series to high orders conveniently.
文摘随机潮流能够比较全面地反映系统运行状态,对电网安全性风险评估起到重要作用。现有的随机潮流计算方法中,结合半不变量和Gram-Charlier展开级数的方法可快速且准确地计算节点电压和支路潮流的概率密度函数(probability distribution function,PDF)以及累积分布函数(cumulative distribution function,CDF)。以受时域和地域不均匀分布影响的系统当前运行状态为基础构造预想事故集,将全概率理论与半不变量法随机潮流相结合,提出一种考虑电网静态安全风险的随机潮流算法。对IEEE RTS 96节点实验系统的计算表明,该算法可快速、准确地评估系统当前运行状态的静态安全风险,具有实际应用价值。
文摘发电机组的随机故障停运对电力系统潮流计算产生影响,应用传统半不变量法计算概率潮流(probabilistic power flow,PPF)将产生较大误差。提出一种考虑离散分布输入变量的半不变量法PPF计算方法。针对服从离散分布的发电机注入功率采用多点线性化方法,减小潮流方程线性化误差。同时,引入阈值分析策略,提高计算效率。最后,综合运用A型Gram-Charlier级数和C型Gram-Charlier级数拟合状态变量的概率分布。对IEEE-RTS 24节点系统进行仿真,验证了算法的准确性和实用性。结果表明:所提PPF计算方法具有较高的精度,并保持一定的计算效率。
