实际电力系统中,公共连接点(point of common coupling,PCC)处的设备投退、无功补偿设备投切、系统供电方式调整等运行方式变化所引起的背景谐波电压波动与系统谐波阻抗变化具有随机性,导致传统方法准确性受到影响。提出了一种考虑系统...实际电力系统中,公共连接点(point of common coupling,PCC)处的设备投退、无功补偿设备投切、系统供电方式调整等运行方式变化所引起的背景谐波电压波动与系统谐波阻抗变化具有随机性,导致传统方法准确性受到影响。提出了一种考虑系统运行方式变化的多谐波源责任划分方法。首先,基于相关性分析进行用户侧主导波动数据筛选;其次,基于密度聚类(density-based spatial clustering of applications with noise,DBSCAN)算法对系统谐波阻抗数据进行分类;最后,基于背景谐波电压分类迭代的思想实现更为精确的系统侧谐波阻抗估计,并进行后续谐波责任划分。仿真算例结果表明该方法能够较好地抑制背景谐波电压波动和系统侧阻抗变化带来的影响,得出较精确的系统侧谐波阻抗值和更准确的谐波责任划分结果。展开更多
A study of shock train self-excited oscillation in an isolator with background waves was implemented through a wind tunnel experiment.Dynamic pressure data were captured by high-frequency pressure measurements and the...A study of shock train self-excited oscillation in an isolator with background waves was implemented through a wind tunnel experiment.Dynamic pressure data were captured by high-frequency pressure measurements and the flow field was recorded by the high-speed Schlieren technique.The shock train structure was mostly asymmetrical during self-excited oscillation,regardless of its oscillation mode.We found that the pressure discontinuity caused by background waves was responsible for the asymmetry.On the wall where the pressure at the leading edge of the shock train was lower,a large separation region formed and the shock train deflected toward to the other wall.The oscillation mode of the shock train was related to the change of wall pressure in the oscillation range of its leading edge.The oscillation range and oscillation intensity of the shock train leading edge were affected by the wall pressure gradient induced by background waves.When located in a negative pressure gradient region,the oscillation of the leading edge strengthened;when located in a positive pressure gradient region,the oscillation weakened.To find out the cause of self-excited oscillation,correlation and phase analyses were performed.The results indicated that the instability of the separation region induced by the leading shock was the source of perturbation that caused self-excited oscillation,regardless of the oscillation mode of the shock train.展开更多
The changes of numeraire can be used as a very powerful tool in pricing contingent claims in the context of a complete market.By using the method of numeraire changes to evaluate convertible bonds when the value of fi...The changes of numeraire can be used as a very powerful tool in pricing contingent claims in the context of a complete market.By using the method of numeraire changes to evaluate convertible bonds when the value of firm,and those of zero-coupon bonds follow general adapted stochastic processes in this paper,using Ito theorem and Gisanov theorem.A closed-form solution is derived under the stochastic volatility by using fast Fourier transforms.展开更多
文摘实际电力系统中,公共连接点(point of common coupling,PCC)处的设备投退、无功补偿设备投切、系统供电方式调整等运行方式变化所引起的背景谐波电压波动与系统谐波阻抗变化具有随机性,导致传统方法准确性受到影响。提出了一种考虑系统运行方式变化的多谐波源责任划分方法。首先,基于相关性分析进行用户侧主导波动数据筛选;其次,基于密度聚类(density-based spatial clustering of applications with noise,DBSCAN)算法对系统谐波阻抗数据进行分类;最后,基于背景谐波电压分类迭代的思想实现更为精确的系统侧谐波阻抗估计,并进行后续谐波责任划分。仿真算例结果表明该方法能够较好地抑制背景谐波电压波动和系统侧阻抗变化带来的影响,得出较精确的系统侧谐波阻抗值和更准确的谐波责任划分结果。
基金supported by the National Natural Science Foundation of China(Nos.11972139 and 51676204)。
文摘A study of shock train self-excited oscillation in an isolator with background waves was implemented through a wind tunnel experiment.Dynamic pressure data were captured by high-frequency pressure measurements and the flow field was recorded by the high-speed Schlieren technique.The shock train structure was mostly asymmetrical during self-excited oscillation,regardless of its oscillation mode.We found that the pressure discontinuity caused by background waves was responsible for the asymmetry.On the wall where the pressure at the leading edge of the shock train was lower,a large separation region formed and the shock train deflected toward to the other wall.The oscillation mode of the shock train was related to the change of wall pressure in the oscillation range of its leading edge.The oscillation range and oscillation intensity of the shock train leading edge were affected by the wall pressure gradient induced by background waves.When located in a negative pressure gradient region,the oscillation of the leading edge strengthened;when located in a positive pressure gradient region,the oscillation weakened.To find out the cause of self-excited oscillation,correlation and phase analyses were performed.The results indicated that the instability of the separation region induced by the leading shock was the source of perturbation that caused self-excited oscillation,regardless of the oscillation mode of the shock train.
基金supported by the National key scientific instrument and Equipment Development Program of China under Grant No.2012YQ220119Anhui Provincial Natural Science Foundation under Grant No.1308085 MF93+1 种基金the Fundamental Research Foundation for the Central Universities under Grant No.2013HGXJ0223National Natural Science Foundations of China under Grant No.11201108
文摘The changes of numeraire can be used as a very powerful tool in pricing contingent claims in the context of a complete market.By using the method of numeraire changes to evaluate convertible bonds when the value of firm,and those of zero-coupon bonds follow general adapted stochastic processes in this paper,using Ito theorem and Gisanov theorem.A closed-form solution is derived under the stochastic volatility by using fast Fourier transforms.
