The variability of the output power of distributed renewable energy sources(DRESs)that originate from the fastchanging climatic conditions can negatively affect the grid stability.Therefore,grid operators have incorpo...The variability of the output power of distributed renewable energy sources(DRESs)that originate from the fastchanging climatic conditions can negatively affect the grid stability.Therefore,grid operators have incorporated ramp-rate limitations(RRLs)for the injected DRES power in the grid codes.As the DRES penetration levels increase,the mitigation of high-power ramps is no longer considered as a system support function but rather an ancillary service(AS).Energy storage systems(ESSs)coordinated by RR control algorithms are often applied to mitigate these power fluctuations.However,no unified definition of active power ramps,which is essential to treat the RRL as AS,currently exists.This paper assesses the various definitions for ramp-rate RR and proposes RRL method control for a central battery ESS(BESS)in distribution systems(DSs).The ultimate objective is to restrain high-power ramps at the distribution transformer level so that RRL can be traded as AS to the upstream transmission system(TS).The proposed control is based on the direct control of theΔP/Δt,which means that the control parameters are directly correlated with the RR requirements included in the grid codes.In addition,a novel method for restoring the state of charge(So C)within a specific range following a high ramp-up/down event is proposed.Finally,a parametric method for estimating the sizing of central BESSs(BESS sizing for short)is developed.The BESS sizing is determined by considering the RR requirements,the DRES units,and the load mix of the examined DS.The BESS sizing is directly related to the constant RR achieved using the proposed control.Finally,the proposed methodologies are validated through simulations in MATLAB/Simulink and laboratory tests in a commercially available BESS.展开更多
Purpose: This paper aims to provide a systematic analysis of challenges and responses of the imminent open access-based environment so as to enable sound development of open access(OA) resource strategies.Design/metho...Purpose: This paper aims to provide a systematic analysis of challenges and responses of the imminent open access-based environment so as to enable sound development of open access(OA) resource strategies.Design/methodology/approach: A systematic and evidence-based analysis is used to discover, identify, and contextualize the factors that relate or interact. A challenge metric for the overall context and additional frameworks or alternative lists is used for the detailed analysis.Findings: Research libraries are facing a reality conflict between the traditional library solution and the OA solution. New resource strategies are needed but have to be based on an open knowledge infrastructure and a systematic analysis of factors and alternatives. Support for OA publishing is becoming a major task and complicated capabilities involved call for libraries to play a central role. Hybrid collection development should be in place to take full advantages of the open world while ensuring reliable and trusted retrieval, reuse, and preservation.Research limitations: The research covers main developments in US and European countries mostly in scientific fields and for scholarly papers.Practical implications: There are already evidences for sound OA resource policies. With the imminent dominance of OA resources, research libraries should and can set up their OA resource strategies.Originality/value: The paper suggests a factor metric as an analysis framework, presents rationale lists and policies to support OA publishing, and proposes a hybrid collection strategy to plan for collection development, retrieval, and preservation.展开更多
基金part of and supported by the European UnionHorizon 2020 project“EASY-RES”with G.A.:764090。
文摘The variability of the output power of distributed renewable energy sources(DRESs)that originate from the fastchanging climatic conditions can negatively affect the grid stability.Therefore,grid operators have incorporated ramp-rate limitations(RRLs)for the injected DRES power in the grid codes.As the DRES penetration levels increase,the mitigation of high-power ramps is no longer considered as a system support function but rather an ancillary service(AS).Energy storage systems(ESSs)coordinated by RR control algorithms are often applied to mitigate these power fluctuations.However,no unified definition of active power ramps,which is essential to treat the RRL as AS,currently exists.This paper assesses the various definitions for ramp-rate RR and proposes RRL method control for a central battery ESS(BESS)in distribution systems(DSs).The ultimate objective is to restrain high-power ramps at the distribution transformer level so that RRL can be traded as AS to the upstream transmission system(TS).The proposed control is based on the direct control of theΔP/Δt,which means that the control parameters are directly correlated with the RR requirements included in the grid codes.In addition,a novel method for restoring the state of charge(So C)within a specific range following a high ramp-up/down event is proposed.Finally,a parametric method for estimating the sizing of central BESSs(BESS sizing for short)is developed.The BESS sizing is determined by considering the RR requirements,the DRES units,and the load mix of the examined DS.The BESS sizing is directly related to the constant RR achieved using the proposed control.Finally,the proposed methodologies are validated through simulations in MATLAB/Simulink and laboratory tests in a commercially available BESS.
文摘Purpose: This paper aims to provide a systematic analysis of challenges and responses of the imminent open access-based environment so as to enable sound development of open access(OA) resource strategies.Design/methodology/approach: A systematic and evidence-based analysis is used to discover, identify, and contextualize the factors that relate or interact. A challenge metric for the overall context and additional frameworks or alternative lists is used for the detailed analysis.Findings: Research libraries are facing a reality conflict between the traditional library solution and the OA solution. New resource strategies are needed but have to be based on an open knowledge infrastructure and a systematic analysis of factors and alternatives. Support for OA publishing is becoming a major task and complicated capabilities involved call for libraries to play a central role. Hybrid collection development should be in place to take full advantages of the open world while ensuring reliable and trusted retrieval, reuse, and preservation.Research limitations: The research covers main developments in US and European countries mostly in scientific fields and for scholarly papers.Practical implications: There are already evidences for sound OA resource policies. With the imminent dominance of OA resources, research libraries should and can set up their OA resource strategies.Originality/value: The paper suggests a factor metric as an analysis framework, presents rationale lists and policies to support OA publishing, and proposes a hybrid collection strategy to plan for collection development, retrieval, and preservation.
