Data envelopment analysis （DEA） is an effective non-parametric method for measuring the relative efficiencies of decision making units （DMUs） with multiple inputs and outputs. In many real situations, the internal...Data envelopment analysis （DEA） is an effective non-parametric method for measuring the relative efficiencies of decision making units （DMUs） with multiple inputs and outputs. In many real situations, the internal structure of DMUs is a two-stage network process with shared inputs used in both stages and common outputs produced by the both stages. For example, hospitals have a two-stage network structure. Stage 1 consumes resources such as information technology system, plant, equipment and admin personnel to generate outputs such as medical records, laundry and housekeeping. Stage 2 consumes the same set of resources used by stage 1 （named shared inputs） and the outputs generated by stage 1 （named intermediate measures） to provide patient services. Besides, some of outputs, for instance, patient satisfaction degrees, are generated by the two individual stages together （named shared outputs）. Since some of shared inputs and outputs are hard split up and allocated to each individual stage, it needs to develop two-stage DEA methods for evaluating the performance of two-stage network processes in such problems. This paper extends the centralized model to measure the DEA efficiency of the two-stage process with non split-table shared inputs and outputs. A weighted additive approach is used to combine the two individual stages. Moreover, additive efficiency decomposition models are developed to simultaneously evaluate the maximal and the minimal achievable efficiencies for the individual stages. Finally, an example of 17 city branches of China Construction Bank in Anhui Province is employed to illustrate the proposed approach.展开更多
输入串联输出并联型(input-series output-parallel,ISOP)直流变换器广泛应用于能源互联网中的直流电网场景,其关键问题在于解决系统模块间输入电压不均衡。为此,结合谐振型和移相型双有源桥(dual active bridge,DAB)变换器,提出一种具...输入串联输出并联型(input-series output-parallel,ISOP)直流变换器广泛应用于能源互联网中的直流电网场景,其关键问题在于解决系统模块间输入电压不均衡。为此,结合谐振型和移相型双有源桥(dual active bridge,DAB)变换器,提出一种具备自适应均压能力的混合型模块化ISOP型直流变换器,系统同时具备谐振型DAB的高效率和移相型DAB的灵活控制能力。通过在DAB源端的滞后桥臂中点增设无源的LC谐振支路,该谐振支路与相邻子模块的2个半桥模块共同构成非隔离型双有源半桥,以此来实现系统输入电压的自适应均衡。此外,提出一种低电压穿越(low voltage ride-through,LVRT)方法,在DAB前端连接电压调整模块,模块内部的高频变压器的副边串联电感,当系统输入输出侧发生电压跌落时具备故障穿越的能力,提高系统的暂态可控性。最后,在MATLAB/SIMULINK环境下搭建模型进行验证,可以证明系统的自适应均压性能及故障穿越方法的有效性。展开更多
针对输入串联输出并联双有源桥(dual active bridge,DAB)变换器子模块内部参数不匹配导致的功率不平衡,以及单移相(single phase shift,SPS)控制下变换器工作效率低的问题,该文基于拓展移相(extended phase shift,EPS)控制提出一种扰动...针对输入串联输出并联双有源桥(dual active bridge,DAB)变换器子模块内部参数不匹配导致的功率不平衡,以及单移相(single phase shift,SPS)控制下变换器工作效率低的问题,该文基于拓展移相(extended phase shift,EPS)控制提出一种扰动均压(disturbance voltage sharing,DVS)控制策略。通过建立EPS控制下的电流应力解析模型,求解最优电流应力对应下的内外移相比组合。进一步,设计逐级扰动方案,通过扰动模块的外移相比,对各模块内部参数失配时的输入电压进行补偿。DVS控制策略在实现串并联模块间功率平衡的前提下,降低变换器电流应力,从而提升变换器的工作效率。此外,由于无需在每个控制环路中增设输入电压传感器,系统结构更为简化,硬件成本更低。最后,通过仿真和实验验证了所提控制策略的正确性和有效性。展开更多
输入串联输出并联(inputseriesoutputparallel,ISOP)双有源桥(dualactivebridge,DAB)变换器的输入均压(input voltage sharing,IVS)主动控制策略存在控制系统复杂和传感器数量较多的问题。相反地,无源调控方法的控制系统简单,因而具有...输入串联输出并联(inputseriesoutputparallel,ISOP)双有源桥(dualactivebridge,DAB)变换器的输入均压(input voltage sharing,IVS)主动控制策略存在控制系统复杂和传感器数量较多的问题。相反地,无源调控方法的控制系统简单,因而具有明显的优势。基于无源均压思想,提出一种适用于共占空比控制的基于耦合电容的ISOP-DAB变换器的输入电压自平衡拓扑结构,通过耦合电容使得子模块的高频链环节产生电气耦合,从而实现子模块输入电压的均衡。进一步,给出含有耦合电容的ISOP-DAB变换器的简化等效电路,并进行理论分析与推导,得到子模块输入母线电压偏差及耦合电容电流与变换器硬件参数的关系。理论计算表明该拓扑在子模块参数存在较大的偏差时仍然具有较好的IVS能力。最后,仿真和实验结果验证该拓扑的可行性和有效性。展开更多
直流变压器是互联网数据中心(Internet Data Center,IDC)配电系统的重要单元,其技术水平影响着整个IDC配电系统的运营水平。以逻辑链路控制(Logical Link Control,LLC)谐振变换器为基础单元模块,以输入串联、输出并联为拓扑结构,设计了...直流变压器是互联网数据中心(Internet Data Center,IDC)配电系统的重要单元,其技术水平影响着整个IDC配电系统的运营水平。以逻辑链路控制(Logical Link Control,LLC)谐振变换器为基础单元模块,以输入串联、输出并联为拓扑结构,设计了一款基于IDC配电系统的直流变压器。首先介绍了直流变压器系统的拓扑结构,并分析了其均压均流特性;其次又提出了一种三环控制策略,主要对直流变压器系统进行均压均流控制,该策略可以使系统稳定输出额定电压,并使系统具有良好的均压均流效果;最后设计一款10 kV/400 V的直流变压器系统,实验表明该系统运行效果良好,具有较高的稳定性和调节能力。展开更多
基金Acknowledgments The authors thank the editors and two anonymous referees for their helpful comments and suggestions that substantially improved the quality of this work. This research has been supported by grants from National Natural Science Foundation of China （71224001） and China Postdoctoral Science Foundation funded project （2015M571135）.
文摘Data envelopment analysis （DEA） is an effective non-parametric method for measuring the relative efficiencies of decision making units （DMUs） with multiple inputs and outputs. In many real situations, the internal structure of DMUs is a two-stage network process with shared inputs used in both stages and common outputs produced by the both stages. For example, hospitals have a two-stage network structure. Stage 1 consumes resources such as information technology system, plant, equipment and admin personnel to generate outputs such as medical records, laundry and housekeeping. Stage 2 consumes the same set of resources used by stage 1 （named shared inputs） and the outputs generated by stage 1 （named intermediate measures） to provide patient services. Besides, some of outputs, for instance, patient satisfaction degrees, are generated by the two individual stages together （named shared outputs）. Since some of shared inputs and outputs are hard split up and allocated to each individual stage, it needs to develop two-stage DEA methods for evaluating the performance of two-stage network processes in such problems. This paper extends the centralized model to measure the DEA efficiency of the two-stage process with non split-table shared inputs and outputs. A weighted additive approach is used to combine the two individual stages. Moreover, additive efficiency decomposition models are developed to simultaneously evaluate the maximal and the minimal achievable efficiencies for the individual stages. Finally, an example of 17 city branches of China Construction Bank in Anhui Province is employed to illustrate the proposed approach.
文摘输入串联输出并联型(input-series output-parallel,ISOP)直流变换器广泛应用于能源互联网中的直流电网场景,其关键问题在于解决系统模块间输入电压不均衡。为此,结合谐振型和移相型双有源桥(dual active bridge,DAB)变换器,提出一种具备自适应均压能力的混合型模块化ISOP型直流变换器,系统同时具备谐振型DAB的高效率和移相型DAB的灵活控制能力。通过在DAB源端的滞后桥臂中点增设无源的LC谐振支路,该谐振支路与相邻子模块的2个半桥模块共同构成非隔离型双有源半桥,以此来实现系统输入电压的自适应均衡。此外,提出一种低电压穿越(low voltage ride-through,LVRT)方法,在DAB前端连接电压调整模块,模块内部的高频变压器的副边串联电感,当系统输入输出侧发生电压跌落时具备故障穿越的能力,提高系统的暂态可控性。最后,在MATLAB/SIMULINK环境下搭建模型进行验证,可以证明系统的自适应均压性能及故障穿越方法的有效性。
文摘针对输入串联输出并联双有源桥(dual active bridge,DAB)变换器子模块内部参数不匹配导致的功率不平衡,以及单移相(single phase shift,SPS)控制下变换器工作效率低的问题,该文基于拓展移相(extended phase shift,EPS)控制提出一种扰动均压(disturbance voltage sharing,DVS)控制策略。通过建立EPS控制下的电流应力解析模型,求解最优电流应力对应下的内外移相比组合。进一步,设计逐级扰动方案,通过扰动模块的外移相比,对各模块内部参数失配时的输入电压进行补偿。DVS控制策略在实现串并联模块间功率平衡的前提下,降低变换器电流应力,从而提升变换器的工作效率。此外,由于无需在每个控制环路中增设输入电压传感器,系统结构更为简化,硬件成本更低。最后,通过仿真和实验验证了所提控制策略的正确性和有效性。
文摘输入串联输出并联(inputseriesoutputparallel,ISOP)双有源桥(dualactivebridge,DAB)变换器的输入均压(input voltage sharing,IVS)主动控制策略存在控制系统复杂和传感器数量较多的问题。相反地,无源调控方法的控制系统简单,因而具有明显的优势。基于无源均压思想,提出一种适用于共占空比控制的基于耦合电容的ISOP-DAB变换器的输入电压自平衡拓扑结构,通过耦合电容使得子模块的高频链环节产生电气耦合,从而实现子模块输入电压的均衡。进一步,给出含有耦合电容的ISOP-DAB变换器的简化等效电路,并进行理论分析与推导,得到子模块输入母线电压偏差及耦合电容电流与变换器硬件参数的关系。理论计算表明该拓扑在子模块参数存在较大的偏差时仍然具有较好的IVS能力。最后,仿真和实验结果验证该拓扑的可行性和有效性。
文摘直流变压器是互联网数据中心(Internet Data Center,IDC)配电系统的重要单元,其技术水平影响着整个IDC配电系统的运营水平。以逻辑链路控制(Logical Link Control,LLC)谐振变换器为基础单元模块,以输入串联、输出并联为拓扑结构,设计了一款基于IDC配电系统的直流变压器。首先介绍了直流变压器系统的拓扑结构,并分析了其均压均流特性;其次又提出了一种三环控制策略,主要对直流变压器系统进行均压均流控制,该策略可以使系统稳定输出额定电压,并使系统具有良好的均压均流效果;最后设计一款10 kV/400 V的直流变压器系统,实验表明该系统运行效果良好,具有较高的稳定性和调节能力。
