新能源、基于模块化多电平换流器的多端柔性直流(modular multilevel converter-based multi-terminal high voltage direct current,MMC-MTDC)以及交流电网之间宽频振荡风险凸出,严重制约MMC-MTDC安全稳定运行和新能源高效消纳。MMC-M...新能源、基于模块化多电平换流器的多端柔性直流(modular multilevel converter-based multi-terminal high voltage direct current,MMC-MTDC)以及交流电网之间宽频振荡风险凸出,严重制约MMC-MTDC安全稳定运行和新能源高效消纳。MMC-MTDC各换流站呈现定交流电压、定直流电压、定功率等异构化控制方式,多端换流站之间又存在强非线性耦合,给系统振荡建模与分析带来挑战。为此,首先提出计及正负序控制的MMC-MTDC控制系统模块化建模方法。然后,针对复杂交直流网架结构,建立计及多端非线性耦合的MMC-MTDC不同断面通用化阻抗模型。最后,以三端MMC-MTDC环网为例,仿真验证通用化阻抗建模的准确性和有效性,并分析多端互联系统及正负序控制对阻抗特性的耦合影响,为新能源基地经MMC-MTDC互联系统振荡分析提供基础。展开更多
Bicycle-sharing system is considered as a green option to provide a better connection between scenic spots and nearby metro/bus stations. Allocating and optimizing the layout of bicycle-sharing system inside the sceni...Bicycle-sharing system is considered as a green option to provide a better connection between scenic spots and nearby metro/bus stations. Allocating and optimizing the layout of bicycle-sharing system inside the scenic spot and around its influencing area are focused on. It is found that the terrain, land use, nearby transport network and scenery point distribution have significant impact on the allocation of bicycle-sharing system. While the candidate bicycle-sharing stations installed at the inner scenic points, entrances/exits and metro stations are fixed, the ones installed at bus-stations and other passenger concentration buildings are adjustable. Aiming at minimizing the total cycling distance and overlapping rate, an optimization model is proposed and solved based on the idea of cluster concept and greedy heuristic. A revealed preference/stated preference （RP/SP） combined survey was conducted at Xuanwu Lake in Nanjing, China, to get an insight into the touring trip characteristics and bicycle-sharing tendency. The results reveal that 39.81% visitors accept a cycling distance of 1-3 km and 62.50% respondents think that the bicycle-sharing system should charge an appropriate fee. The sttrvey indicates that there is high possibility to carry out a bicycle-sharing system at Xuanwu Lake. Optimizing the allocation problem cluster by cluster rather than using an exhaustive search method significantly reduces the computing amount from O（2^43） to O（43 2）. The 500 m-radius-coverage rate for the alternative optimized by 500 m-radius-cluster and 800 m-radius-cluster is 89.2% and 68.5%, respectively. The final layout scheme will provide decision makers engineering guidelines and theoretical support.展开更多
文摘新能源、基于模块化多电平换流器的多端柔性直流(modular multilevel converter-based multi-terminal high voltage direct current,MMC-MTDC)以及交流电网之间宽频振荡风险凸出,严重制约MMC-MTDC安全稳定运行和新能源高效消纳。MMC-MTDC各换流站呈现定交流电压、定直流电压、定功率等异构化控制方式,多端换流站之间又存在强非线性耦合,给系统振荡建模与分析带来挑战。为此,首先提出计及正负序控制的MMC-MTDC控制系统模块化建模方法。然后,针对复杂交直流网架结构,建立计及多端非线性耦合的MMC-MTDC不同断面通用化阻抗模型。最后,以三端MMC-MTDC环网为例,仿真验证通用化阻抗建模的准确性和有效性,并分析多端互联系统及正负序控制对阻抗特性的耦合影响,为新能源基地经MMC-MTDC互联系统振荡分析提供基础。
基金Project(51208261)supported by the National Natural Science Foundation of ChinaProject(12YJCZH062)supported by the Ministry of Education of Humanities and Social Science of ChinaProject(30920140132033)supported by the Fundamental Research Funds for the Central Universities,China
文摘Bicycle-sharing system is considered as a green option to provide a better connection between scenic spots and nearby metro/bus stations. Allocating and optimizing the layout of bicycle-sharing system inside the scenic spot and around its influencing area are focused on. It is found that the terrain, land use, nearby transport network and scenery point distribution have significant impact on the allocation of bicycle-sharing system. While the candidate bicycle-sharing stations installed at the inner scenic points, entrances/exits and metro stations are fixed, the ones installed at bus-stations and other passenger concentration buildings are adjustable. Aiming at minimizing the total cycling distance and overlapping rate, an optimization model is proposed and solved based on the idea of cluster concept and greedy heuristic. A revealed preference/stated preference （RP/SP） combined survey was conducted at Xuanwu Lake in Nanjing, China, to get an insight into the touring trip characteristics and bicycle-sharing tendency. The results reveal that 39.81% visitors accept a cycling distance of 1-3 km and 62.50% respondents think that the bicycle-sharing system should charge an appropriate fee. The sttrvey indicates that there is high possibility to carry out a bicycle-sharing system at Xuanwu Lake. Optimizing the allocation problem cluster by cluster rather than using an exhaustive search method significantly reduces the computing amount from O（2^43） to O（43 2）. The 500 m-radius-coverage rate for the alternative optimized by 500 m-radius-cluster and 800 m-radius-cluster is 89.2% and 68.5%, respectively. The final layout scheme will provide decision makers engineering guidelines and theoretical support.
