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Measured Impedance and Threshold Value of Electrode Line Impedance Supervision Based Protection in HVDC Transmission System

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Journal of Modern Power Systems and Clean Energy 2023年第4期11卷 1294-1304页

作者： Qiang Sun Bin Li jiawei he Ye Li Key Laboratory of Smart Grid of Ministry of Education Tianjin UniversityTianjinChina State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of TechnologyTianjinChina

At present,electrode line impedance supervision(ELIS)based protection is widely used to detect faults on grounding electrode lines,which are indispensable elements of high-voltage direct current(HVDC)*** existing theoretical analysis of measured impedance is based on lumped line model and the threshold value is generally set according to engineering experience,which have caused the dead zone problem and even ***,a study on measured impedance of ELIS-based protection and its threshold value selection method is carried out to solve this *** this study,the expressions of measured impedance under normal operation and fault conditions are deduced based on rigorous and accurate line *** on the expressions,the characteristics of the measured impedance are calculated and *** the characteristics of the measured impedance,the applicability of the protection with the traditional threshold value is further discussed and the distribution of the dead zone can be ***,the method to calculate the threshold value of ELIS-based protection is *** a proper threshold value selected by the proposed method,the dead zone of ELIS-based protection is effectively eliminated,and the protection can identify all types of faults even with large transition *** studies on PSCAD/EMTDC have been conducted to verify the conclusion.

关键词： Grounding electrode line electrode line impedance supervision(ELIS)based protection measured impedance characteristic threshold value selection

Black Phosphorus/Nanocarbons Constructing a Dual-Carbon Conductive Network for High-Performance Sodium-Ion Batteries

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Transactions of Tianjin University 2022年第2期28卷 132-143页

作者： Leping Dang jiawei he Hongyuan Wei School of Chemical Engineering and Technology Tianjin UniversityTianjin 300072China

Black phosphorus has been recognized as a prospective candidate anode material for sodium-ion batteries(SIBs)due to its ultrahigh theoretical capacity of 2596 mA·h/g and high electric conductivity of≈300 S/***,its large volume expansion and contraction during sodiation/desodiation lead to poor cycling *** this work,a BP/graphite nanoparticle/nitrogen-doped multiwalled carbon nanotubes(BP/G/CNTs)composite with a dual-carbon conductive network is successfully fabricated as a promising anode material for SIBs through a simple two-step mechanical milling *** unique structure can mitigate the eff ect of volume changes and provide additional electron conduction pathways during ***,the formation of P–O–C bonds helps maintain the intimate connection between phosphorus and carbon,thereby improving the cycling and rate *** a result,the BP/G/CNTs composite delivers a high initial Coulombic efficiency(89.6%)and a high specific capacity for SIBs(1791.3 mA·h/g after 100 cycles at 519.2 mA/g and 1665.2 mA·h/g after 100 cycles at 1298 mA/g).Based on these results,the integrated strategy of one-and two-dimensional carbon materials can guide other anode materials for SIBs.

关键词： Sodium-ion batteries Anode material Black phosphorus Ball milling Carbon conductive network

A review of the protection for the multi-terminal VSC-HVDC grid

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Protection and Control of Modern Power Systems 2019年第1期4卷 251-261页

作者： Bin Li jiawei he Ye Li Botong Li School of Electrical and Information Engineering Tianjin UniversityTianjin300072China

The multi-terminal VSC-HVDC grid is believed to be widely applied in the future power system. The dc line protection is the key technique for operation security and power supply reliability of the dc grid. In this paper, the single-ended protections, namely, the traveling-wave based protection and transient-variable based protection, as well as the pilot protections, mainly including the directional pilot protection and current differential protection, are discussed in detail. With the analyzed protections, the effective main and back-up protection strategy can be configured for the dc line in multi-terminal VSC-HVDC grid.

关键词： Multi-terminal VSC-HVDC grid Traveling-wave based protection Transient-variable based protection Directional pilot protection Current differential protection

Homogenizing interfacial shear stress in brick-and-mortar structured composites via gradient modulus for enhanced mechanical properties

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Acta Mechanica Sinica 2024年第6期40卷 115-124页

作者： Yang Gao jiawei he Jie Jiang Jianping Zuo School of Mechanics and Civil Engineering China University of Mining and Technology(Beijing)Beijing100083China

Inspired by nature,various biomimetic materials have been synthesized for enhanced mechanical properties,among which composites with brick-and-mortar structures attract the most *** such bio-inspired composites,the matrix layer mainly functions to transfer load between bricks through shearing,while the shear stress in the matrix is not uniform but highly concentrated on the interface ends,which tends to initiate cracks and evoke interface delamination in *** enhance the composites’resistance to interface delamination,we propose to homogenize the shear stress by adopting a matrix with a gradient modulus.A theoretical solution to the optimal gradient modulus of the matrix layer is obtained,followed by computational ***,composites with such functionally graded matrices are further demonstrated to possess higher elastic limits,higher resilience,and flaw tolerance than the uniform *** results of this paper should be of great value to the design and synthesis of advanced structural materials for superior mechanical performance.

关键词： Stress concentration Interface delamination Brick-and-mortar structure Composite

DC fault analysis for modular multilevel converter-based system

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Journal of Modern Power Systems and Clean Energy 2017年第2期5卷 275-282页

作者： Bin LI jiawei he Jie TIAN Yadong FENG Yunlong DONG Key Laboratory of Smart Grid of Ministry of Education Tianjin UniversityTianjinChina NR Electric NanjingChina

DC fault protection is the key technique for the development of the DC distribution and transmission system. This paper analyzes the transient characteristics of DC faults in a modular multilevel converter(MMC) based DC system combining with the numerical method. Meanwhile,lots of simulation tests based on MATLAB/Simulink are carried out to verify the correctness of the theoretical analysis. Finally, the technological difficulties of and requirements for the protection and isolation are discussed to provide the theoretical foundation for the design of dc fault protection strategy.

关键词： DC system DC fault analysis DC fault protection Modular multilevel converter

Direction Protection Based on Time-domain Travelling Wave for Flexible MTDC Grid

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CSEE Journal of Power and Energy Systems 2023年第4期9卷 1414-1424页

作者： Ye Li Bin Li jiawei he Huijie Lyu Wenbo Wang Zhongrun Xie State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of TechnologyTianjin 300132China the Key Laboratory of Smart Grid of Ministry of Education Tianjin UniversityTianjin 300072China he Key Laboratory of Smart Grid of Ministry of Education Tianjin UniversityTianjin 300072China Key Laboratory of Smart Grid of Ministry of Education Tianjin UniversityTianjin 300072China.

Fault direction identification is important for dc protection,which cannot only be used in directional pilot pro-tection,but also plays an important role in non-unit protection(for excluding backward faults).Direction criteria based on i and di/dt have been utilized in LCC-HVDC system ***,the reliability and sensitivity of the protection are significantly influenced by fault transition resistance and line distribution *** a flexible MTDC grid,boundary char-acteristics of the DC inductor can be utilized to judge the fault *** when the DC inductor is only installed at converter outlet,this kind of direction protection cannot ***,this paper analyzes the frequency characteristic of the fault traveling wave(TW)*** this basis,the direction protection based on the time-domain TW is proposed,which is immune from frequency-dependence line *** with existing direction protection,it has higher operation reliability and sensitivity,and is independent of the line ***,the feasibility and superiority of the designed direction protection are verified by simulation cases based on PSCAD/*** Terms-Frequency-dependent characteristic,operation sensitivity,operation reliability,traveling-wave based direction protection.

关键词： Frequency-dependent characteristic operation sensitivity operation reliability traveling-wave based direction protection.

Research on DC Protection Strategy in Multi-Terminal Hybrid HVDC System

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Engineering 2021年第8期7卷 1064-1075页

作者： Yuping Zheng jiawei he Bin Li Tonghua Wua Wei Dai Ye Li State Key Laboratory of Smart Grid Protection and Control State Grid Electric Power Research Institute(NARI Group Corporation)Nanjing 211106China Key Laboratory of Smart Grid of Ministry of Education Tianjin UniversityTianjin 300072China College of Energy and Electrical Engineering Hohai UniversityNanjing 210098China

Multi-terminal hybrid high-voltage direct current(HVDC)systems have been developed quickly in recent years in power transmission ***,for voltage-source converter(VSC)stations in hybrid HVDC systems,no direct current(DC)filters are *** addition,the DC reactor is also not installed at the line end because the DC fault can be limited by the converter *** means that the boundary element at the line end is absent,and the single-ended protections used in line commutated converter(LCC)based HVDC(LCC-HVDC)systems or VSC-HVDC systems cannot distinguish the fault line in multi-terminal hybrid HVDC *** paper proposes a novel singleended DC protection strategy suitable for the multi-terminal hybrid HVDC system,which mainly applies the transient information and active injection concept to detect and distinguish the fault *** with the single-ended protections used in LCC-HVDC and VSC-HVDC systems,the proposed protection strategy is not dependent on the line boundary element and is thus suitable for the multiterminal hybrid HVDC *** corresponding simulation cases based on power systems computer aided design(PSCAD)/electromagnetic transients including DC(EMTDC)are carried out to verify the superiority of the proposed protection.

关键词： Multi-terminal hybrid HVDC system Single-ended protection Transient information Active injection

Anti-colon cancer activity of water-soluble polysaccharides extracted from Gloeostereum incarnatum via Wnt/β-catenin signaling pathway

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Food Science and Human Wellness 2021年第4期10卷 460-470页

作者： jiawei he Anhui Yang Xuyu Zhao Yang Liu Shuyan Liu Di Wang Engineering Research Center of Chinese Ministry of Education for Edible and Medicinal Fungi Jilin Agricultural UniversityChangchun 130118China School of Life Sciences Jilin UniversityChangchun 130012China

The incidence rate of colon cancer ranks the third among malignant tumors *** incarnatum(GI),a fungus with homology of medicine and food,has multiple pharmacological *** was investigated in this study that the anti-colon cancer effect of polysaccharides purifi ed from GI(GIPS)in ApcMinC/Gpt mice(an in situ colon cancer mouse model).Eight-week administration with GIPS at doses of 30 or 90 mg/kg strongly inhibited tumor growth including the reduction on numbers and the suppression of the size without infl uencing the animals’body weight and organ *** to the proteomics performing by antibody array,among 308 detected cytokines,GIPS significantly regulated 89 of *** with vehicle-treated mice,GIPS effectively reduced the levels of interleukin(IL)-1β,IL-4,IL-6,IL-17,IL-22,tumor necrosis factor(TNF)-α,matrix metalloproteinase(MMP)-2,and enhanced the levels of IL-15 and IL-18 in serum and/or colon tissues,which suggested its anti-inflammation of *** suppressed nuclear aggregation of β-catenin,affected the expression of WNT1 and related proteins,thereby regulated the activation of the Wnt ***,GIPS can inhibit the growth of colon cancer,at least partially,via inhibiting the Wnt/β-catenin signaling pathway.

关键词： Gloeostereum incarnatum Water-soluble polysaccharides Colon cancer Wnt/β-catenin

Fast Distance Protection Scheme for Wind Farm Transmission Lines Considering R-L and Bergeron Models

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Journal of Modern Power Systems and Clean Energy 2023年第3期11卷 840-852页

作者： Zepeng Hu Bin Li Yuping Zheng Tonghua Wu jiawei he Bin Yao Yaru Sheng Wei Dai Xindong Li Electrical Engineering and Automation Tianjin UniversityTianjinChina State Key Laboratory of Smart Grid Protection and Control NARI Group CorporationNanjingChina

The distributed capacitance of the line becomes larger as the scale of wind farms,the transmission voltage level,and the transmission distance ***,the error of the traditional time-domain distance protection scheme based on the R-L model,which ignores the distributed capacitance of the line,becomes ***,the error of the time-domain fault location method based on the R-L model,especially the maximum error range,is theoretically analyzed in this *** this basis,a novel fault location method based on the RL and Bergeron models is ***,a fast time-domain distance protection scheme is *** the proposed scheme,the error in the fitting calculation is used to construct a weight matrix,and an algorithm for solving the time-domain differential equations is designed to improve the calculation speed and *** with the traditional frequency-domain distance protection scheme,the proposed scheme is independent of the power supply characteristics;thus,it is suitable for wind farm transmission *** addition,compared with the traditional method based on the R-L model,the proposed scheme effectively avoids the negative influence of the distributed capacitance of the line,which significantly improves the operating *** types of faults are simulated by PSCAD/EMTDC to verify the effectiveness and superiority of the proposed scheme.

关键词： Transmission line R-L model time-domain distance protection wind farm