Active distribution network(ADN)is a solution for power system with interconnection of distributed energy resources(DER),which may change the network operation and power flow of traditional power distribution network....Active distribution network(ADN)is a solution for power system with interconnection of distributed energy resources(DER),which may change the network operation and power flow of traditional power distribution network.However,in some circumstances the malfunction of protection and feeder automation in distribution network occurs due to the uncertain bidirectional power flow.Therefore,a novel method of fault location,isolation,and service restoration(FLISR)for ADN based on distributed processing is proposed in this paper.The differential-activated algorithm based on synchronous sampling for feeder fault location and isolation is studied,and a framework of fault restoration is established for ADN.Finally,the effectiveness of the proposed algorithm is verified via computer simulation of a case study for active distributed power system.展开更多
The power system is susceptible to failures,and further interruptions by subsequent outages which may cause extended events in the formed island.Most of the literature reviewed has focused on island formation after th...The power system is susceptible to failures,and further interruptions by subsequent outages which may cause extended events in the formed island.Most of the literature reviewed has focused on island formation after the disconnection of the main grid supply.However,there is still a need to analyze the post-restoration failures to improve the resilience and minimize the pro-longed disconnection of priority customers.The current research investigates the behavior of islanding schemes under secondary collapses and provides an adaptive solution to withstand such severities.A new total active critical node finding methodology is presented which eases the rearrangement of the initially formed island when affected by multiple faults or DG failures.The concept of single islanding with the coordination of multiple DGs is also discussed,in which the DG's power-sharing capacity is not confined to the boundaries of only particular islands.An economic plan is also proposed to select the controlled type DGs to reduce the overall cost of generation by reducing fuel cost.To evaluate the network's effectiveness and robustness,the proposed adaptive method is deployed on an updated IEEE 69-bus distribution system.Index Terms-Active distribution network,distributed generation,multi-objective,post-restoration,single islanding.展开更多
Land degradation affects extensive drylands around the world.Due to long-term misuse,the Israeli Sde Zin dryland site has faced severe degradation.The study objective was to assess the feasibility of passive restorati...Land degradation affects extensive drylands around the world.Due to long-term misuse,the Israeli Sde Zin dryland site has faced severe degradation.The study objective was to assess the feasibility of passive restoration in recovering the site.The study was conducted in four land-units along a preservation-degradation continuum:(1)an area that has not faced anthropogenic disturbances(Ecological land);(2)an area that was proclaimed as a national park in the 1970s(Rehabilitation);(3)an area that was prone,until recently,to moderate anthropogenic pressures(Triangle);and(4)a dirt road that was subjected to long-term off-road traffic(Dirtroad).Soil was sampled and analyzed for its properties.The soil physical quality followed the trend of Ecological land>Rehabilitation>Triangle>Dirtroad.Specifically,high soil salinity in the latter three land-units is attributed to long-term erosional processes that exposed the underlying salic horizons.Herbaceous and shrubby vegetation cover was also monitored.The herbaceous vegetation cover followed the trend of Ecological land(86.4%)>Rehabilitation(40.3%)>Triangle(26.2%)>Dirtroad(2.1%),while the shrubby cover was 2.8%in the Ecological land-unit,and practically zero in the other land-units.It seems that despite the effectiveness of passive restoration in recovering the soil’s physical properties,the recovery of vegetation is limited by the severe soil salinity.展开更多
The increased speed of global change and associated high severity disturbances,in conjunction with the increasing suite of societal expectations on forests,suggest that the timeliness of interventions to encourage the...The increased speed of global change and associated high severity disturbances,in conjunction with the increasing suite of societal expectations on forests,suggest that the timeliness of interventions to encourage the adaptive capacity of ecosystems and to reduce negative impacts in regards to provision of ecosystem services is increasingly relevant.To address this issue,we expand the concept of lag time as used in ecological discussions into a forest management context.In this context,lag times have earlier starting and later ending points and can be separated into different components.These components include the delay till detection,decision making,and implementation,followed by ecological lag time and the time till ecosystem services are provided at acceptable levels.The first three components are influenced by the availability of information,the lack of which can extend lag times.Also,the lengths of components are not simply additive but they interact.For example,treatment preparation due to a quicker detection can lead to shorter decision and implementation lag times.We highlight the benefits of addressing the various components of lag time in forestry operations.Especially when considering adaptive capacity in times of global change,our analysis suggests that all aspects of the forestry sector are challenged to consider how to optimize lag times.Last,we propose that such issues need to be considered with any management action and are especially relevant in discussions whether the best strategy after disturbances or in the light of global change is to adopt a passive approach and let natural ecosystem processes play out on their own or whether active management is better suited to ensure a more rapid and fitting ecosystem response to facilitate the continued provision of ecosystem services.展开更多
Restoration treatments can impact the growth and development of tree seedlings;however, it is often difficult to discern whether responses are driven by changes in microclimate, biotic interactions, or soil properties...Restoration treatments can impact the growth and development of tree seedlings;however, it is often difficult to discern whether responses are driven by changes in microclimate, biotic interactions, or soil properties. To isolate for the latter, we quantified the growth response of four species [Ocotea puberula (Lauraceae);Otoba novogranatensis (Myristicaceae);Pseudolmedia mollis (Moraceae);Senna papillosa (Fabaceae)] grown under similar shade-house conditions in soils collected from 6 - 7 year old active (four species plantation) and passive restoration plots (natural recovery), and nearby reference forest sites in Costa Rica. We also evaluated the role of parent tree by collecting individuals from five mother trees. We measured height, above- and below-ground biomass, and determined root: shoot ratios (RSR). Species differed markedly in their responses. Ocotea, and to a lesser extent Pseudolmedia, were largely driven by parent tree. In contrast, Senna showed a strong soil response for all variables with more growth in active than passive restoration soils;reference forest seedlings were typically intermediate. An interaction suggested that some genotypes are more responsive to different soil properties than others. Otoba had higher soil-driven RSR in both restoration treatments. Surprisingly most soil nutrients, including %N, were similar or significantly lower in active restoration soils, suggesting that seedlings are responding to differences in soil microbial communities or more labile nutrients (e.g., NH4+ and NO3-). Active restoration appears to facilitate the growth of other species by improving certain soil properties. Additionally, genotypes are an important driver of seedling vigor and some species may be more responsive to subtle differences in soil properties than others.展开更多
Restoration of late seral features in second growth Sequoia sempervirens (coast redwood) forests is increasingly important, as so little of the original old-growth remains. Natural recovery is an effective method rest...Restoration of late seral features in second growth Sequoia sempervirens (coast redwood) forests is increasingly important, as so little of the original old-growth remains. Natural recovery is an effective method restoring many late seral features, and does not require the additional disturbance of active management. In order to better understand management impacts on redwood understory abundance and composition, data were collected in naturally recovering stands and in stands that were actively managed with the explicit intent of promoting old-growth characteristics. Ten 10 m diameter plots with three 2 m diameter nested sub-plots were randomly sampled in two sites within each management type. Results indicate that tree canopy cover, native species cover and richness, richness of coast redwood associated species, and the cover of Trillium ovatum (western wake robin) were significantly higher in naturally recovering versus actively managed stands. In addition, several coast redwood associated understory species were exclusively recorded in the naturally recovering stands including: Asuram caudatum (wild ginger), Prosartes hookeri (hooker’s fairybells), Maianthemum racemosum (false solomon seal), Scoliopus bigelovii (fetid adder’s tongue), Viola sempervirens (redwood violet);while only one such species was recorded exclusively in the actively managed stands: Trientalis latifolia (pacific star flower). Natural recovery appeared to support understory recovery more effectively than active forest management in this case.展开更多
Image deconvolution problems with a symmetric point-spread function arisein many areas of science and engineering. These problems often are solved by theRichardson-Lucy method, a nonlinear iterative method. We first s...Image deconvolution problems with a symmetric point-spread function arisein many areas of science and engineering. These problems often are solved by theRichardson-Lucy method, a nonlinear iterative method. We first show a convergenceresult for the Richardson-Lucy method. The proof sheds light on why the method mayconverge slowly. Subsequently, we describe an iterative active set method that imposesthe same constraints on the computed solution as the Richardson-Lucy method. Computed examples show the latter method to yield better restorations than the RichardsonLucy method and typically require less computational effort.展开更多
智能软开关（soft open point,SOP）是安装于传统联络开关处的电力电子装置,能够快速、准确地控制自身功率流动,改变系统功率分布,进而改善整个配电系统的运行状态。在配电网发生故障并隔离后,SOP可以为失电区域提供有效的电压支撑,提...智能软开关（soft open point,SOP）是安装于传统联络开关处的电力电子装置,能够快速、准确地控制自身功率流动,改变系统功率分布,进而改善整个配电系统的运行状态。在配电网发生故障并隔离后,SOP可以为失电区域提供有效的电压支撑,提高配电系统的供电恢复能力。首先,对SOP的主要功能和数学模型进行阐述,给出考虑SOP的配电网故障恢复流程;其次,提出基于SOP的有源配电网供电恢复模型,这一模型本质上属于大规模非线性规划模型,采用二阶锥规划方法进行模型转化和求解;最后,在IEEE 33节点测试算例上进行分析验证,得到影响SOP供电恢复能力的因素,并在不同的分布式电源条件下进行对比分析,验证所提模型的正确性和有效性。展开更多
柔性软开关(soft open points,SOP)具有端口间的功率连续调节功能,可解决配电网与分布式电源协同运行带来的问题,同时可提升系统可靠性和供电能力。针对当前尚且缺乏具体度量手段量化SOP的配置成效问题,提出了考虑可靠性的含四端SOP有...柔性软开关(soft open points,SOP)具有端口间的功率连续调节功能,可解决配电网与分布式电源协同运行带来的问题,同时可提升系统可靠性和供电能力。针对当前尚且缺乏具体度量手段量化SOP的配置成效问题,提出了考虑可靠性的含四端SOP有源配电网供电能力评估方法。首先,研究了四端SOP的接入拓扑和组网模式,分析了四端SOP在配电网正常运行和故障恢复过程中的控制模式;其次,结合馈线分区理念,研究了四端SOP对配电网故障后不同馈线分区停电时间的影响,构建了含四端SOP有源配电网的故障模式影响分析和负荷削减与转供模型,并提出了可靠性评估方法;再次,以可靠性为约束,建立了含四端SOP有源配电网供电能力评估模型,并提出了求解方法。最后,通过算例验证了所提方法的有效性和实用性。展开更多
基金This paper was supported by the National High Technology Research and Development Program of China(863 Program)(No.2014AA051902).
文摘Active distribution network(ADN)is a solution for power system with interconnection of distributed energy resources(DER),which may change the network operation and power flow of traditional power distribution network.However,in some circumstances the malfunction of protection and feeder automation in distribution network occurs due to the uncertain bidirectional power flow.Therefore,a novel method of fault location,isolation,and service restoration(FLISR)for ADN based on distributed processing is proposed in this paper.The differential-activated algorithm based on synchronous sampling for feeder fault location and isolation is studied,and a framework of fault restoration is established for ADN.Finally,the effectiveness of the proposed algorithm is verified via computer simulation of a case study for active distributed power system.
基金supported in part by the National Natural Science Foundation of China(No.51677003)。
文摘The power system is susceptible to failures,and further interruptions by subsequent outages which may cause extended events in the formed island.Most of the literature reviewed has focused on island formation after the disconnection of the main grid supply.However,there is still a need to analyze the post-restoration failures to improve the resilience and minimize the pro-longed disconnection of priority customers.The current research investigates the behavior of islanding schemes under secondary collapses and provides an adaptive solution to withstand such severities.A new total active critical node finding methodology is presented which eases the rearrangement of the initially formed island when affected by multiple faults or DG failures.The concept of single islanding with the coordination of multiple DGs is also discussed,in which the DG's power-sharing capacity is not confined to the boundaries of only particular islands.An economic plan is also proposed to select the controlled type DGs to reduce the overall cost of generation by reducing fuel cost.To evaluate the network's effectiveness and robustness,the proposed adaptive method is deployed on an updated IEEE 69-bus distribution system.Index Terms-Active distribution network,distributed generation,multi-objective,post-restoration,single islanding.
基金funded by the Nature and Parks Authority,and laboratory works was funded by the Israel Science Foundation(ISF)Grant No.602/21The Dead Sea and Arava Science Center is supported by the Ministry of Science and Technology。
文摘Land degradation affects extensive drylands around the world.Due to long-term misuse,the Israeli Sde Zin dryland site has faced severe degradation.The study objective was to assess the feasibility of passive restoration in recovering the site.The study was conducted in four land-units along a preservation-degradation continuum:(1)an area that has not faced anthropogenic disturbances(Ecological land);(2)an area that was proclaimed as a national park in the 1970s(Rehabilitation);(3)an area that was prone,until recently,to moderate anthropogenic pressures(Triangle);and(4)a dirt road that was subjected to long-term off-road traffic(Dirtroad).Soil was sampled and analyzed for its properties.The soil physical quality followed the trend of Ecological land>Rehabilitation>Triangle>Dirtroad.Specifically,high soil salinity in the latter three land-units is attributed to long-term erosional processes that exposed the underlying salic horizons.Herbaceous and shrubby vegetation cover was also monitored.The herbaceous vegetation cover followed the trend of Ecological land(86.4%)>Rehabilitation(40.3%)>Triangle(26.2%)>Dirtroad(2.1%),while the shrubby cover was 2.8%in the Ecological land-unit,and practically zero in the other land-units.It seems that despite the effectiveness of passive restoration in recovering the soil’s physical properties,the recovery of vegetation is limited by the severe soil salinity.
基金funding from the Deutsche Forschungsgemeinschaft (DFG),project ID 422010107,reference number UP 14/1 through the Freiburg Research Collaboration Programme
文摘The increased speed of global change and associated high severity disturbances,in conjunction with the increasing suite of societal expectations on forests,suggest that the timeliness of interventions to encourage the adaptive capacity of ecosystems and to reduce negative impacts in regards to provision of ecosystem services is increasingly relevant.To address this issue,we expand the concept of lag time as used in ecological discussions into a forest management context.In this context,lag times have earlier starting and later ending points and can be separated into different components.These components include the delay till detection,decision making,and implementation,followed by ecological lag time and the time till ecosystem services are provided at acceptable levels.The first three components are influenced by the availability of information,the lack of which can extend lag times.Also,the lengths of components are not simply additive but they interact.For example,treatment preparation due to a quicker detection can lead to shorter decision and implementation lag times.We highlight the benefits of addressing the various components of lag time in forestry operations.Especially when considering adaptive capacity in times of global change,our analysis suggests that all aspects of the forestry sector are challenged to consider how to optimize lag times.Last,we propose that such issues need to be considered with any management action and are especially relevant in discussions whether the best strategy after disturbances or in the light of global change is to adopt a passive approach and let natural ecosystem processes play out on their own or whether active management is better suited to ensure a more rapid and fitting ecosystem response to facilitate the continued provision of ecosystem services.
文摘Restoration treatments can impact the growth and development of tree seedlings;however, it is often difficult to discern whether responses are driven by changes in microclimate, biotic interactions, or soil properties. To isolate for the latter, we quantified the growth response of four species [Ocotea puberula (Lauraceae);Otoba novogranatensis (Myristicaceae);Pseudolmedia mollis (Moraceae);Senna papillosa (Fabaceae)] grown under similar shade-house conditions in soils collected from 6 - 7 year old active (four species plantation) and passive restoration plots (natural recovery), and nearby reference forest sites in Costa Rica. We also evaluated the role of parent tree by collecting individuals from five mother trees. We measured height, above- and below-ground biomass, and determined root: shoot ratios (RSR). Species differed markedly in their responses. Ocotea, and to a lesser extent Pseudolmedia, were largely driven by parent tree. In contrast, Senna showed a strong soil response for all variables with more growth in active than passive restoration soils;reference forest seedlings were typically intermediate. An interaction suggested that some genotypes are more responsive to different soil properties than others. Otoba had higher soil-driven RSR in both restoration treatments. Surprisingly most soil nutrients, including %N, were similar or significantly lower in active restoration soils, suggesting that seedlings are responding to differences in soil microbial communities or more labile nutrients (e.g., NH4+ and NO3-). Active restoration appears to facilitate the growth of other species by improving certain soil properties. Additionally, genotypes are an important driver of seedling vigor and some species may be more responsive to subtle differences in soil properties than others.
文摘Restoration of late seral features in second growth Sequoia sempervirens (coast redwood) forests is increasingly important, as so little of the original old-growth remains. Natural recovery is an effective method restoring many late seral features, and does not require the additional disturbance of active management. In order to better understand management impacts on redwood understory abundance and composition, data were collected in naturally recovering stands and in stands that were actively managed with the explicit intent of promoting old-growth characteristics. Ten 10 m diameter plots with three 2 m diameter nested sub-plots were randomly sampled in two sites within each management type. Results indicate that tree canopy cover, native species cover and richness, richness of coast redwood associated species, and the cover of Trillium ovatum (western wake robin) were significantly higher in naturally recovering versus actively managed stands. In addition, several coast redwood associated understory species were exclusively recorded in the naturally recovering stands including: Asuram caudatum (wild ginger), Prosartes hookeri (hooker’s fairybells), Maianthemum racemosum (false solomon seal), Scoliopus bigelovii (fetid adder’s tongue), Viola sempervirens (redwood violet);while only one such species was recorded exclusively in the actively managed stands: Trientalis latifolia (pacific star flower). Natural recovery appeared to support understory recovery more effectively than active forest management in this case.
基金We would like to thank the referees for comments.This work was supported by PRIN-MIUR-Cofin 2008 project,GNCS-INDAM,an OBR Research Challenge Grant,and NSF grant DMS-1115385.
文摘Image deconvolution problems with a symmetric point-spread function arisein many areas of science and engineering. These problems often are solved by theRichardson-Lucy method, a nonlinear iterative method. We first show a convergenceresult for the Richardson-Lucy method. The proof sheds light on why the method mayconverge slowly. Subsequently, we describe an iterative active set method that imposesthe same constraints on the computed solution as the Richardson-Lucy method. Computed examples show the latter method to yield better restorations than the RichardsonLucy method and typically require less computational effort.
文摘智能软开关（soft open point,SOP）是安装于传统联络开关处的电力电子装置,能够快速、准确地控制自身功率流动,改变系统功率分布,进而改善整个配电系统的运行状态。在配电网发生故障并隔离后,SOP可以为失电区域提供有效的电压支撑,提高配电系统的供电恢复能力。首先,对SOP的主要功能和数学模型进行阐述,给出考虑SOP的配电网故障恢复流程;其次,提出基于SOP的有源配电网供电恢复模型,这一模型本质上属于大规模非线性规划模型,采用二阶锥规划方法进行模型转化和求解;最后,在IEEE 33节点测试算例上进行分析验证,得到影响SOP供电恢复能力的因素,并在不同的分布式电源条件下进行对比分析,验证所提模型的正确性和有效性。
文摘柔性软开关(soft open points,SOP)具有端口间的功率连续调节功能,可解决配电网与分布式电源协同运行带来的问题,同时可提升系统可靠性和供电能力。针对当前尚且缺乏具体度量手段量化SOP的配置成效问题,提出了考虑可靠性的含四端SOP有源配电网供电能力评估方法。首先,研究了四端SOP的接入拓扑和组网模式,分析了四端SOP在配电网正常运行和故障恢复过程中的控制模式;其次,结合馈线分区理念,研究了四端SOP对配电网故障后不同馈线分区停电时间的影响,构建了含四端SOP有源配电网的故障模式影响分析和负荷削减与转供模型,并提出了可靠性评估方法;再次,以可靠性为约束,建立了含四端SOP有源配电网供电能力评估模型,并提出了求解方法。最后,通过算例验证了所提方法的有效性和实用性。
