为解决交流配电系统存在设备负载率低、冗余度大、故障后恢复供电时间长等问题,提出了一种基于柔性直流的不间断电力交换器(uninterrupted power hub,UPH),并利用电压源换流器将多个配电变电站互联,以实现变电站间负载率均衡、负荷转供...为解决交流配电系统存在设备负载率低、冗余度大、故障后恢复供电时间长等问题,提出了一种基于柔性直流的不间断电力交换器(uninterrupted power hub,UPH),并利用电压源换流器将多个配电变电站互联,以实现变电站间负载率均衡、负荷转供等功能。论文分析了UPH的主要运行方式和控制策略,并通过数字仿真分析了UPH的控制性能。研究结果表明,通过设置固定与变电站连接及灵活在各个变电站切换这2种换流器,并合理配置其容量,UPH可比传统互联方案节省较大的换流器总体容量,是柔性直流技术提升配电网设备利用率和可靠性的一种新方案。论文研究可为柔性直流技术在配电系统中的应用提供参考。展开更多
多种新能源发电的接入和负荷容量的快速增长,使得配、用电系统短路电流限制问题突出,同时大量重要负荷对电压骤降为代表的电能质量问题非常敏感,严重的话会退出正常运行并造成巨额经济损失。基于谐振开关的并联型统一电能质量控制器(Shu...多种新能源发电的接入和负荷容量的快速增长,使得配、用电系统短路电流限制问题突出,同时大量重要负荷对电压骤降为代表的电能质量问题非常敏感,严重的话会退出正常运行并造成巨额经济损失。基于谐振开关的并联型统一电能质量控制器(Shunt-unified Power Quality Controller,S-UPQC)利用触发导通晶闸管形成的并联谐振电路构造出可快速切换的开关,既能对线路故障电流进行快速抑制,又可当电网电压骤降时将敏感负荷与故障电网快速隔离,依靠自身储能为负荷提供不间断供电。此外,S-UPQC还具有动态无功和谐波补偿的能力。针对S-UPQC典型算例建立的PSCAD/EMTDC电磁暂态仿真模型,验证了有效性。结果表明,发生电压骤降时S-UPQC切换时间不超过1.5 ms,发生线路短路时,故障电流可在半个周波内被有效抑制。展开更多
This paper investigates the problem of stability analysis for a class of incommensurate nabla fractional order systems.In particular,both Caputo definition and Riemann-Liouville definition are under consideration.With...This paper investigates the problem of stability analysis for a class of incommensurate nabla fractional order systems.In particular,both Caputo definition and Riemann-Liouville definition are under consideration.With the convex assumption,several elementary fractional difference inequalities on Lyapunov functions are developed.According to the essential features of nabla fractional calculus,the sufficient conditions are given first to guarantee the asymptotic stability for the incommensurate system by using the direct Lyapunov method.To substantiate the efficacy and effectiveness of the theoretical results,four examples are elaborated.展开更多
文摘为解决交流配电系统存在设备负载率低、冗余度大、故障后恢复供电时间长等问题,提出了一种基于柔性直流的不间断电力交换器(uninterrupted power hub,UPH),并利用电压源换流器将多个配电变电站互联,以实现变电站间负载率均衡、负荷转供等功能。论文分析了UPH的主要运行方式和控制策略,并通过数字仿真分析了UPH的控制性能。研究结果表明,通过设置固定与变电站连接及灵活在各个变电站切换这2种换流器,并合理配置其容量,UPH可比传统互联方案节省较大的换流器总体容量,是柔性直流技术提升配电网设备利用率和可靠性的一种新方案。论文研究可为柔性直流技术在配电系统中的应用提供参考。
文摘多种新能源发电的接入和负荷容量的快速增长,使得配、用电系统短路电流限制问题突出,同时大量重要负荷对电压骤降为代表的电能质量问题非常敏感,严重的话会退出正常运行并造成巨额经济损失。基于谐振开关的并联型统一电能质量控制器(Shunt-unified Power Quality Controller,S-UPQC)利用触发导通晶闸管形成的并联谐振电路构造出可快速切换的开关,既能对线路故障电流进行快速抑制,又可当电网电压骤降时将敏感负荷与故障电网快速隔离,依靠自身储能为负荷提供不间断供电。此外,S-UPQC还具有动态无功和谐波补偿的能力。针对S-UPQC典型算例建立的PSCAD/EMTDC电磁暂态仿真模型,验证了有效性。结果表明,发生电压骤降时S-UPQC切换时间不超过1.5 ms,发生线路短路时,故障电流可在半个周波内被有效抑制。
基金supported by the National Natural Science Foundation of China under Grant No.62273092the Science Climbing Project under Grant No.4307012166+3 种基金the Anhui Provincial Natural Science Foundation under Grant No.1708085QF141the Fundamental Research Funds for the Central Universities under Grant No.WK2100100028the General Financial Grant from the China Postdoctoral Science Foundation under Grant No.2016M602032the fund of China Scholarship Council under Grant No.201806345002。
文摘This paper investigates the problem of stability analysis for a class of incommensurate nabla fractional order systems.In particular,both Caputo definition and Riemann-Liouville definition are under consideration.With the convex assumption,several elementary fractional difference inequalities on Lyapunov functions are developed.According to the essential features of nabla fractional calculus,the sufficient conditions are given first to guarantee the asymptotic stability for the incommensurate system by using the direct Lyapunov method.To substantiate the efficacy and effectiveness of the theoretical results,four examples are elaborated.
