To address the challenges of fault line identification and low detection accuracy of wave head in Fault Location(FL)research of distribution networks with complex topologies,this paper proposes an FL method of Multi-B...To address the challenges of fault line identification and low detection accuracy of wave head in Fault Location(FL)research of distribution networks with complex topologies,this paper proposes an FL method of Multi-Branch distribution line based on Maximal Overlap Discrete Wavelet Transform(MODWT)combined with the improved Teager Energy Operator(TEO).Firstly,the current and voltage Traveling Wave(TW)signals at the head of each line are extracted,and the fault-induced components are obtained to determine the fault line by analyzing the polarity of the mutation amount of fault voltage and current TWs.Subsequently,the fault discrimination mark is calculated based on the fault-induced line-mode current and the zero-mode voltage,with the fault type determined by comparing each mark’s value against the fault discrimination table,transforming the FL problem in complex topology into a single-line FL problem.Finally,the fault voltage TW is extracted fromthe fault line,and the wave head detection method based on MODWT combined with improved TEO is used to precisely identify the arrival instants of both the first TW wave head and its first reflection at each line terminal,and then the FL result is calculated by applying the double-ended TW ranging formula that removes the influence of wave velocity.Simulation results demonstrate that the proposed method accurately identifies the fault line and types of faults occurring and maintains the ranging accuracy within 0.5%under various fault scenarios.展开更多
This paper presents a photonic crystal(PhC)line-defect slow-light waveguide modified by resonant rings.We introduce resonant rings into the line defect,constructing a slow-light waveguide with high normalized delay ba...This paper presents a photonic crystal(PhC)line-defect slow-light waveguide modified by resonant rings.We introduce resonant rings into the line defect,constructing a slow-light waveguide with high normalized delay bandwidth product(NDBP)and low group velocity dispersion(GVD).We simulate,analyze,and optimize the structural parameters of this slow-light waveguide using the finite difference time domain(FDTD)method,theoretically achieving a maximum group index of 3.7,maximum bandwidth of 15.6 nm,and maximum NDBP of 0.4416 for slow-light effect.The resonant ring-modified PhC slow-light waveguide designed in this paper exhibits GVD lower than the order of 10^(−20)s^(2)/m over a normalized frequency range from 0.3554 to 0.4175.This study is expected to provide theoretical references for the study of slow-light buffering devices based on PhCs with high NDBP values.展开更多
In this paper, the efficiencies of two production lines, one is with commonly, the other is with separately buffer capacities are compared, the result is that the former one is better than the latter
According to the glacial landforms and deposits with the optically stimulated luminescence （OSL）dating results, two glacial stages of the last glacial cycle （LGC） and Late Glacial were identified. The Late Glacial...According to the glacial landforms and deposits with the optically stimulated luminescence （OSL）dating results, two glacial stages of the last glacial cycle （LGC） and Late Glacial were identified. The Late Glacial stage （Meteorological Station glacier advance） took place about 11 ka （11.3±1.2 ka）, and the last glacial maximum （LGM）, named Black Wind Mouth glacier advance, occurred at 20 ka （20.0±2.1 ka）. Based on the Ohmura＇s formula in which there is a relationship between summer （JJA） atmospheric temperature （T） and the annual precipitation （P） at ELA, the present theoretical equilibrium line altitude （ELAt） in Changbai Mountains was 3380±100 m. Six methods of accumulation-area ratio （AAR）, maximum elevation of lateral moraines （MELM）, toe-to headwall altitude ratios （THAR）, the terminal to summit altitudinal （TSAM）, the altitude of cirque floor （CF）, and the terminal to average elevation of the catchment area （Hofer） were used for calculation of the former ELAs in different stages. These methods provided the ELA for a range of 2250-2383 m with an average value of 2320±20 m during the LGM, which is 200 m higher than the value of previous investigation. The snowlines during the Late Glacial are 2490 m on northern slope, and 2440 m on western slope. The results show that the snowline on northern slope is 50 m higher than that on western slope during the Late Glacial, and the average snowline is 2465m. The/kElP, values were more than 1000 m during the LGM, and about 920 m lower than now during the Late Glacial stage respectively. Compared with Taiwan Residents and Japanese mountains in East Asia during the LGM, the effect of the uplift on ELA in Changbai Mountains during the glaciations （i.e. 20 m uplift in the LGM and 11 m in the Late Glacial） is not obvious.展开更多
Using flexible damping technology to improve tunnel lining structure is an emerging method to resist earthquake disasters,and several methods have been explored to predict mechanical response of tunnel lining with dam...Using flexible damping technology to improve tunnel lining structure is an emerging method to resist earthquake disasters,and several methods have been explored to predict mechanical response of tunnel lining with damping layer.However,the traditional numerical methods suffer from the complex modelling and time-consuming problems.Therefore,a prediction model named the random forest regressor(RFR)is proposed based on 240 numerical simulation results of the mechanical response of tunnel lining.In addition,circle mapping(CM)is used to improve Archimedes optimization algorithm(AOA),reptile search algorithm(RSA),and Chernobyl disaster optimizer(CDO)to further improve the predictive performance of the RFR model.The performance evaluation results show that the CMRSA-RFR is the best prediction model.The damping layer thickness is the most important feature for predicting the maximum principal stress of tunnel lining containing damping layer.This study verifies the feasibility of combining numerical simulation with machine learning technology,and provides a new solution for predicting the mechanical response of aseismic tunnel with damping layer.展开更多
电力需求的增长和系统容量的提升对输配电电缆的传输容量和运行可靠性提出了更高的要求,有效利用高压直流(high voltage direct current,HVDC)电缆线路的动态增容潜力对于实现电力资源优化配置具有重要意义。通过有限元分析(finite elem...电力需求的增长和系统容量的提升对输配电电缆的传输容量和运行可靠性提出了更高的要求,有效利用高压直流(high voltage direct current,HVDC)电缆线路的动态增容潜力对于实现电力资源优化配置具有重要意义。通过有限元分析(finite element analysis,FEA)方法建立了不同敷设环境中高压直流电缆线路的暂态热场及电场模型,仿真分析了电缆在多种典型动态负荷下的温度分布及绝缘电场特性,研究发现:相比于架空及土壤直埋敷设,隧道敷设的HVDC电缆系统热响应时间常数达到数百小时,因此具有更好的动态增容能力。论文以隧道中敷设为例,通过相应FEA模型反演计算了不同初始负荷与应急时长下直流电缆的允许最大过负荷电流,给出了针对HVDC电缆线路短时动态增容能力的评估方法,并对直流电缆线路动态增容过程中的暂态电热特性进行了分析。结果表明:初始负荷率高,应急持续时间长,绝缘电导率温度敏感性强的高压XLPE直流电缆在动态增容过程中场强变化幅度大,应予以特别关注;初始负荷率不超过50%的隧道敷设双极直流电缆线路,单级可在1.5倍额定电流下安全运行2 h。该结果可为工程中HVDC电缆线路动态增容与优化调度提供理论指导。展开更多
基于可控电网换相型换流器(controllable line commutated converter,CLCC)的高压直流输电技术避免了常规直流换相失败问题,为高压直流馈入电网提供了崭新途径。文章揭示CLCC高压直流输电系统的故障响应机理,对比CLCC与电网换相型换流...基于可控电网换相型换流器(controllable line commutated converter,CLCC)的高压直流输电技术避免了常规直流换相失败问题,为高压直流馈入电网提供了崭新途径。文章揭示CLCC高压直流输电系统的故障响应机理,对比CLCC与电网换相型换流器、电压源型换流器等直流输电技术的功率特性差异。针对CLCC可控换流的技术特点,提出一种基于最大触发角提升的CLCC优化控制方法,改善了CLCC的故障响应特性,提升了受端电网交流电压的恢复速度。最后,基于PSD-PSModel电力系统仿真软件,建立送受端电网机电暂态和CLCC直流电磁暂态的混合仿真模型,验证理论分析的准确性和优化控制的有效性。展开更多
基金funded by the project of Guizhou Power Grid Co.,Ltd.Guiyang Power Supply Bureau(No.GZKJXM20232317).
文摘To address the challenges of fault line identification and low detection accuracy of wave head in Fault Location(FL)research of distribution networks with complex topologies,this paper proposes an FL method of Multi-Branch distribution line based on Maximal Overlap Discrete Wavelet Transform(MODWT)combined with the improved Teager Energy Operator(TEO).Firstly,the current and voltage Traveling Wave(TW)signals at the head of each line are extracted,and the fault-induced components are obtained to determine the fault line by analyzing the polarity of the mutation amount of fault voltage and current TWs.Subsequently,the fault discrimination mark is calculated based on the fault-induced line-mode current and the zero-mode voltage,with the fault type determined by comparing each mark’s value against the fault discrimination table,transforming the FL problem in complex topology into a single-line FL problem.Finally,the fault voltage TW is extracted fromthe fault line,and the wave head detection method based on MODWT combined with improved TEO is used to precisely identify the arrival instants of both the first TW wave head and its first reflection at each line terminal,and then the FL result is calculated by applying the double-ended TW ranging formula that removes the influence of wave velocity.Simulation results demonstrate that the proposed method accurately identifies the fault line and types of faults occurring and maintains the ranging accuracy within 0.5%under various fault scenarios.
基金supported by the Graduate Student Innovation Fund of Xi’an Shiyou University(No.YCS21211087).
文摘This paper presents a photonic crystal(PhC)line-defect slow-light waveguide modified by resonant rings.We introduce resonant rings into the line defect,constructing a slow-light waveguide with high normalized delay bandwidth product(NDBP)and low group velocity dispersion(GVD).We simulate,analyze,and optimize the structural parameters of this slow-light waveguide using the finite difference time domain(FDTD)method,theoretically achieving a maximum group index of 3.7,maximum bandwidth of 15.6 nm,and maximum NDBP of 0.4416 for slow-light effect.The resonant ring-modified PhC slow-light waveguide designed in this paper exhibits GVD lower than the order of 10^(−20)s^(2)/m over a normalized frequency range from 0.3554 to 0.4175.This study is expected to provide theoretical references for the study of slow-light buffering devices based on PhCs with high NDBP values.
文摘In this paper, the efficiencies of two production lines, one is with commonly, the other is with separately buffer capacities are compared, the result is that the former one is better than the latter
基金National Natural Science Foundation of China,No.40571016
文摘According to the glacial landforms and deposits with the optically stimulated luminescence （OSL）dating results, two glacial stages of the last glacial cycle （LGC） and Late Glacial were identified. The Late Glacial stage （Meteorological Station glacier advance） took place about 11 ka （11.3±1.2 ka）, and the last glacial maximum （LGM）, named Black Wind Mouth glacier advance, occurred at 20 ka （20.0±2.1 ka）. Based on the Ohmura＇s formula in which there is a relationship between summer （JJA） atmospheric temperature （T） and the annual precipitation （P） at ELA, the present theoretical equilibrium line altitude （ELAt） in Changbai Mountains was 3380±100 m. Six methods of accumulation-area ratio （AAR）, maximum elevation of lateral moraines （MELM）, toe-to headwall altitude ratios （THAR）, the terminal to summit altitudinal （TSAM）, the altitude of cirque floor （CF）, and the terminal to average elevation of the catchment area （Hofer） were used for calculation of the former ELAs in different stages. These methods provided the ELA for a range of 2250-2383 m with an average value of 2320±20 m during the LGM, which is 200 m higher than the value of previous investigation. The snowlines during the Late Glacial are 2490 m on northern slope, and 2440 m on western slope. The results show that the snowline on northern slope is 50 m higher than that on western slope during the Late Glacial, and the average snowline is 2465m. The/kElP, values were more than 1000 m during the LGM, and about 920 m lower than now during the Late Glacial stage respectively. Compared with Taiwan Residents and Japanese mountains in East Asia during the LGM, the effect of the uplift on ELA in Changbai Mountains during the glaciations （i.e. 20 m uplift in the LGM and 11 m in the Late Glacial） is not obvious.
基金Project(2023YFB2390400)supported by the National Key R&D Programs for Young Scientists,ChinaProjects(U21A20159,52079133,52379112,52309123,41902288)supported by the National Natural Science Foundation of China+5 种基金Project(2024AFB041)supported by the Hubei Provincial Natural Science Foundation,ChinaProject(QTKS0034W23291)supported by the Key Laboratory of Water Grid Project and Regulation of Ministry of Water Resources,ChinaProject(2023SGG07)supported by the Visiting Researcher Fund Program of State Key Laboratory of Water Resources Engineering and Management,ChinaProject(2022KY56(ZDZX)-02)supported by the Key Research Program of FSDI,ChinaProject(SKS-2022103)supported by the Key Research Program of the Ministry of Water Resources,ChinaProject(202102AF080001)supported by the Yunnan Major Science and Technology Special Program,China。
文摘Using flexible damping technology to improve tunnel lining structure is an emerging method to resist earthquake disasters,and several methods have been explored to predict mechanical response of tunnel lining with damping layer.However,the traditional numerical methods suffer from the complex modelling and time-consuming problems.Therefore,a prediction model named the random forest regressor(RFR)is proposed based on 240 numerical simulation results of the mechanical response of tunnel lining.In addition,circle mapping(CM)is used to improve Archimedes optimization algorithm(AOA),reptile search algorithm(RSA),and Chernobyl disaster optimizer(CDO)to further improve the predictive performance of the RFR model.The performance evaluation results show that the CMRSA-RFR is the best prediction model.The damping layer thickness is the most important feature for predicting the maximum principal stress of tunnel lining containing damping layer.This study verifies the feasibility of combining numerical simulation with machine learning technology,and provides a new solution for predicting the mechanical response of aseismic tunnel with damping layer.
文摘电力需求的增长和系统容量的提升对输配电电缆的传输容量和运行可靠性提出了更高的要求,有效利用高压直流(high voltage direct current,HVDC)电缆线路的动态增容潜力对于实现电力资源优化配置具有重要意义。通过有限元分析(finite element analysis,FEA)方法建立了不同敷设环境中高压直流电缆线路的暂态热场及电场模型,仿真分析了电缆在多种典型动态负荷下的温度分布及绝缘电场特性,研究发现:相比于架空及土壤直埋敷设,隧道敷设的HVDC电缆系统热响应时间常数达到数百小时,因此具有更好的动态增容能力。论文以隧道中敷设为例,通过相应FEA模型反演计算了不同初始负荷与应急时长下直流电缆的允许最大过负荷电流,给出了针对HVDC电缆线路短时动态增容能力的评估方法,并对直流电缆线路动态增容过程中的暂态电热特性进行了分析。结果表明:初始负荷率高,应急持续时间长,绝缘电导率温度敏感性强的高压XLPE直流电缆在动态增容过程中场强变化幅度大,应予以特别关注;初始负荷率不超过50%的隧道敷设双极直流电缆线路,单级可在1.5倍额定电流下安全运行2 h。该结果可为工程中HVDC电缆线路动态增容与优化调度提供理论指导。
文摘基于可控电网换相型换流器(controllable line commutated converter,CLCC)的高压直流输电技术避免了常规直流换相失败问题,为高压直流馈入电网提供了崭新途径。文章揭示CLCC高压直流输电系统的故障响应机理,对比CLCC与电网换相型换流器、电压源型换流器等直流输电技术的功率特性差异。针对CLCC可控换流的技术特点,提出一种基于最大触发角提升的CLCC优化控制方法,改善了CLCC的故障响应特性,提升了受端电网交流电压的恢复速度。最后,基于PSD-PSModel电力系统仿真软件,建立送受端电网机电暂态和CLCC直流电磁暂态的混合仿真模型,验证理论分析的准确性和优化控制的有效性。
