This paper aims to study a new grey prediction approach and its solution for forecasting the main system variable whose accurate value could not be collected while the potential value set could be defined. Based on th...This paper aims to study a new grey prediction approach and its solution for forecasting the main system variable whose accurate value could not be collected while the potential value set could be defined. Based on the traditional nonhomogenous discrete grey forecasting model（NDGM）, the interval grey number and its algebra operations are redefined and combined with the NDGM model to construct a new interval grey number sequence prediction approach. The solving principle of the model is analyzed, the new accuracy evaluation indices, i.e. mean absolute percentage error of mean value sequence（MAPEM） and mean percent of interval sequence simulating value set covered（MPSVSC）, are defined and, the procedure of the interval grey number sequence based the NDGM（IG-NDGM） is given out. Finally, a numerical case is used to test the modelling accuracy of the proposed model. Results show that the proposed approach could solve the interval grey number sequence prediction problem and it is much better than the traditional DGM（1,1） model and GM（1,1） model.展开更多
柔性软开关(soft open point, SOP)能够实现配电网的柔性互联与潮流的动态调节,从而优化配电资源的配置与调度。换流器可以在故障时输出正负序电流来提供电压支撑并提高自身的故障穿越能力,从而改善不对称接地故障的负载电压。然而采用...柔性软开关(soft open point, SOP)能够实现配电网的柔性互联与潮流的动态调节,从而优化配电资源的配置与调度。换流器可以在故障时输出正负序电流来提供电压支撑并提高自身的故障穿越能力,从而改善不对称接地故障的负载电压。然而采用开环计算的方案易受实际工况影响,采用传统负序电压闭环的支撑效果较差。因此文中在传统负序电压外环的基础上进行改进,控制负序电流的幅值以抑制负序电压,控制负序电流的相位以优化抑制效果。为提高逆变器容量利用率并限制有功波动,文中提出正负序电流限幅的综合方案,并通过PSCAD仿真软件依据实际配电网参数搭建短路工况进行仿真。结果验证该控制策略可以有效改善故障时的电压表现,提高逆变器低压穿越能力,具有更高的实际可应用性。展开更多
Aligning Exposure Limits for Contact Currents with Exposure Limits for Electric Fields Robert Kavet1 and Richard A.Tell2(1.Kavet Consulting LLC,4455 Worden Way,Oakland,CA 94619;2.Richard Tell Associates,Inc.,10037 Lon...Aligning Exposure Limits for Contact Currents with Exposure Limits for Electric Fields Robert Kavet1 and Richard A.Tell2(1.Kavet Consulting LLC,4455 Worden Way,Oakland,CA 94619;2.Richard Tell Associates,Inc.,10037 Long Meadow Road,Madison,AL 35756.)Abstract:The Institute for Electrical and Electronic Engineers(IEEE)and the International Commission on Non-ionizing Radiation Protection(ICNIRP)have established limits for exposures to electromagnetic fields across the 0-300 GHz(non-ionizing)spectrum,including limits on contact currents(CC)specified by IEEE for 0-110 MHz(ICNIRP issued a CC“guidance level”).展开更多
基金supported by the National Natural Science Foundation of China(7090104171171113)the Aeronautical Science Foundation of China(2014ZG52077)
文摘This paper aims to study a new grey prediction approach and its solution for forecasting the main system variable whose accurate value could not be collected while the potential value set could be defined. Based on the traditional nonhomogenous discrete grey forecasting model（NDGM）, the interval grey number and its algebra operations are redefined and combined with the NDGM model to construct a new interval grey number sequence prediction approach. The solving principle of the model is analyzed, the new accuracy evaluation indices, i.e. mean absolute percentage error of mean value sequence（MAPEM） and mean percent of interval sequence simulating value set covered（MPSVSC）, are defined and, the procedure of the interval grey number sequence based the NDGM（IG-NDGM） is given out. Finally, a numerical case is used to test the modelling accuracy of the proposed model. Results show that the proposed approach could solve the interval grey number sequence prediction problem and it is much better than the traditional DGM（1,1） model and GM（1,1） model.
文摘柔性软开关(soft open point, SOP)能够实现配电网的柔性互联与潮流的动态调节,从而优化配电资源的配置与调度。换流器可以在故障时输出正负序电流来提供电压支撑并提高自身的故障穿越能力,从而改善不对称接地故障的负载电压。然而采用开环计算的方案易受实际工况影响,采用传统负序电压闭环的支撑效果较差。因此文中在传统负序电压外环的基础上进行改进,控制负序电流的幅值以抑制负序电压,控制负序电流的相位以优化抑制效果。为提高逆变器容量利用率并限制有功波动,文中提出正负序电流限幅的综合方案,并通过PSCAD仿真软件依据实际配电网参数搭建短路工况进行仿真。结果验证该控制策略可以有效改善故障时的电压表现,提高逆变器低压穿越能力,具有更高的实际可应用性。
文摘Aligning Exposure Limits for Contact Currents with Exposure Limits for Electric Fields Robert Kavet1 and Richard A.Tell2(1.Kavet Consulting LLC,4455 Worden Way,Oakland,CA 94619;2.Richard Tell Associates,Inc.,10037 Long Meadow Road,Madison,AL 35756.)Abstract:The Institute for Electrical and Electronic Engineers(IEEE)and the International Commission on Non-ionizing Radiation Protection(ICNIRP)have established limits for exposures to electromagnetic fields across the 0-300 GHz(non-ionizing)spectrum,including limits on contact currents(CC)specified by IEEE for 0-110 MHz(ICNIRP issued a CC“guidance level”).
