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Journal of Modern Power Systems and Clean Energy 2018年第3期6卷 509-520页

作者： Chul-Ho NOH Chul-Hwan KIM Gi-Hyeon GWON Yun-Sik OH College of Information and Communication Engineering Sungkyunkwan University

The increasing importance of energy efficiency has led to several studies related to the construction of a reliable low voltage DC(LVDC) distribution system.Specifically, studies on a protection scheme that considers the fault characteristics of an LVDC distribution system are essential to improve system reliability. When compared to a conventional distribution system, the most distinct feature of an LVDC distribution system is the existence of a capacitive discharge current from converters under a fault condition that results in the prompt operation of protection devices. Therefore, this study involves proposing a precise and rapid technique to identify the fault section in an LVDC distribution system. The technique involves two stages, namely: an analysis stage to analyze the capacitive discharge current and a decision stage to identify the fault section based on the fault type. A detailed discussion of each step is presented and its feasibility is verified based on the results of simulations with an ElectroMagnetic Transients Program and MATLAB~?.

关键词： Capacitive discharge current Fault section identification Fault type identification Low voltage DC distribution system

On the Cegrell Classes Associated to a Positive Closed current

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Chinese Annals of Mathematics,Series B 2019年第4期40卷 567-584页

作者： Mohamed ZAWAY Department of Mathematics Faculty of Sciences Ad DwadimiShaqra University Department of Mathematics Faculty of Science of Gabes University of Gabes

The aim of this paper is to study the operatoron■ on some classes of plurisubharmonic (psh) functions, which are not necessary bounded, where T is a positive closed current of bidimension (q, q) on an open set ? of C^n. The author introduces two classes F_p^T (?) and■ and shows first that they belong to the domain of definition of the operator■. Then the author proves that all functions that belong to these classes are C_T-quasi-continuous and that the comparison principle is valid for them.

关键词： Positive closed current Plurisubharmonic function Capacity Monge-Ampère Operator

Flexible unbalanced control with peak current limitation for virtual synchronous generator under voltage sags

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Journal of Modern Power Systems and Clean Energy 2018年第1期6卷 61-72页

作者： Tianwen ZHENG Laijun CHEN Yan GUO Shengwei MEI State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Qinghai Key Lab of Efficient Utilization of Clean Energy New Energy Photovoltaic Industry Research Center Qinghai University

Virtual synchronous generator(VSG)is gridfriendly for integrating distributed generations(DGs)since it can emulate the operation mechanism of traditional synchronous generator(SG).However,the traditional VSG control strategy,which is mainly suitable for balanced voltage conditions,may lead to power oscillations,current unbalance and even overcurrent under unbalanced voltage sags.To overcome this difficulty,a flexible unbalanced control with peak current limitation for VSG under unbalanced operating conditions is proposed.Based on the basic VSG control algorithm,the control strategy integrates two novel control modules,which are current reference generator(CRG)and power reference generator(PRG).The proposed control strategy can flexibly meet different operation demands,which includes current balancing,constant active or reactive power.And the injected currents are kept within safety values for a better utilization of the VSG power capacity.Furthermore,the experimental platform is built.Experimental results demonstrate the validness and effectiveness of the proposed control strategy.

关键词： Virtual synchronous generator Unbalanced control current reference generator Power reference generator Voltage sags

Ground magnetic characteristics of the storm-time ring current Asymmetry

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Science China Earth Sciences 2008年第5期51卷 686-693页

作者： WU YingYan XU WenYao CHEN GengXiong CHEN Bo LIU XiaoCan Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100029China Graduate University of Chinese Academy of Sciences Beijing 100049China

Using the minute data of the H component of geomagnetic field from the 20°E magnetic meridian chain and the 30°N magnetic latitudinal chain, the temporal evolution characteristics of the equatorial ring current during the storm on November 7-10, 2004 are studied. It is indicated that the UT-MLT and UT-MLAT graphics extremely exhibit the local time distribution, latitudinal variation and temporal evo- lution of the H component. The results show: (1) The UT-MLT contour clearly shows the increasing of the H component mostly around noon during the initial phase, representing the geomagnetic effect from the magnetopause current system. During the main phase, most negative values of the H com- ponent appear around the dusk-side, indicating the dawn-dusk asymmetric distribution of the ring cur- rent. (2) The contour of UT-MLAT suggests the latitudinal variation of the H component decreasing with the enhancement of the latitudes during geomagnetic storm, which is in good agreement with the Dst index. The latitudinal variations provide a new sight for describing the temporal characteristics of the intensity of the storm-time ring current. (3) Both the contours of UT-MLT and UT-MLAT are useful to monitor the space-time distribution of the equatorial ring current.

关键词： geomagnetic storm ring current dawn-dusk asymmetry latitudinal variation

A novel hybrid FEM-BEM method for 3D eddy current field calculation using current density J

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Science China(Technological Sciences) 2003年第1期46卷 41-48页

作者：刘志珍王衍章贾智平孙英明 School of Electrical Engineering Shandong University Jinan 250061 China Department of Science and Technology Shandong University Jinan 250061 China School of Computer Science and Technology Shandong University Jinan 250061 China Center of Computer Jinan University Jinan 250002 China Correspondence should be addressed to Liu Zhizhen

This paper introduces a novel hybrid FEM-BEM method for calculating 3D eddy cur-rent field. In the eddy current region, the eddy current density J is solved by the finite element method (FEM) which is discretized by brick finite element mesh, while in the eddy current free re-gion, the magnetic field intensity H is solved by the boundary element method (BEM) which is dis-cretized by rectangular boundary element mesh. Under the boundary conditions, an algebraic equation group is obtained that only includes J by eliminating H. This method has many advan-tages over traditional ones, such as fewer variables, more convenient coupling between the FEM and the BEM and wider application to multiply-connected regions. The calculated values of two models are in good agreement with experimental results. This shows the validity of our method.

关键词： conductor, eddy current density, magnetic field intensity, 3D eddy current field, FEM, BEM, coupling.

Unsteady magnetic reconnection in non-periodic multiple current sheets

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Chinese Science Bulletin 1998年第3期43卷 245-249页

作者： Yifan Liu Xiaohu Wang Huinan Zheng Shui Wang Univ Sci & Technol China Dept Earth & Space Sci Hefei 230026 Peoples R China

The process of magnetic reconnection in non_periodic three_layer current sheets is studied numerically by using two_dimensional magnetohydrodynamic simulation. The results show that unlike periodic current sheets, it ... 详细信息

关键词： multiple current sheets magnetic reconnection numerical simulation.

Recent TCP(Tidal current Power) projects in Korea

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Science China(Technological Sciences) 2010年第1期53卷 57-61页

作者： Chul Hee JO Kang Hee LEE Yu Ho RHO School of Engineering Inha University253Yonghyun-DongNam-GuIncheon 402-751Republic of Korea Graduate School Department.of Naval Architecture & Ocean EngineeringInha University253Yonghyun-DongNam-GuIncheon 402-751Republic of Korea

Having strong current on the west coast with up to 10 m tidal range in Korea,there are many suitable and applicable locations for TCP(Tidal current Power) application in Korea.Not only the west coast,but also the south west regions having narrow channels between islands creating fast ocean stream are suitable for TCP.The first TCP application in Korea is 1 MW helical VAT(Vertical Axis Turbine) device installed in Wooldolmog area in 2008.The first HAT(Horizontal Axis Turbine) TCP device of 25 KW was developed and installed in cooling water weir of Samchonpo power plant in 2008.Furthermore,a 100 kW prototype HAT TCP device is being planned to be installed in Daebang strait in 2009.Another big project would be Inchon TCP farm of 200 MW on the west coast in Korea.The consortium of 5 members was formed in April,2009.This site will be the largest TCP site in the world.The paper describes recent TCP projects in Korea with background and environmental conditions of the projects.

关键词： TCP(Tidal current Power) ocean energy renewable energy clean energy HAT(Horizontal Axis Turbine) VAT(Vertical Axis Turbine)

Analytical study of the effect of the geometrical parameters during the interaction of regular wave-horizontal plate-current

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Acta Oceanologica Sinica 2019年第5期38卷 10-20页

作者： Smail Naasse Meriem Errifaiy Chakib Chahine Laboratory Physics of Polymers and Critical Phenomena Hassan Ⅱ University Casablanca

The present work is an analytical study of the influence of geometrical parameters, such as length, thickness and immersion of the plate, on the reflection coefficient of a regular wave for an immersed horizontal plate in the presence of a uniform current with the same direction as the propagation of the incident regular wave. This study was performed using the linearized potential theory with the evanescent modes while searching for complex roots to the dispersion equation that are neither pure real nor pure imaginary. The results show that the effects of the immersion and the relative length on the reflection coefficient of the plate are accentuated by the presence of the current, whereas the plate thickness practically does not have an effect if it is relatively small.

关键词： current regular wave evanescent modes reflection dispersion equation complex roots geometrical parameters

Ni/_n-SiO_2 Composite Coating Prepared by Brush Plating with Pulse current

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稀有金属材料与工程 2012年第S1期41卷 414-417页

作者： Tan Jun1,Wu Di2,Yao Qiong3,Fan Wenchao1 1 National Key Laboratory for Remanufacturing,Academy of Armored Forces Engineering,Beijing 100072,China 2 Key Laboratory of Surface Engineering,Academy of Armored Forces Engineering,Beijing 100072,China 3 Xichang Satellite Launching Center,Xichang 615000,China Acad Armored Forces Engn Natl Key Lab Remfg Beijing 100072 Peoples R China Acad Armored Forces Engn Key Lab Surface Engn Beijing 100072 Peoples R China Xichang Satellite Launching Ctr Xichang 615000 Peoples R China

Nickel and silicon dioxide nanoparticle composite coatings were prepared by brush plating with direct and pulse current.The surface morphology,microstructure,hardness and wear resistance of the coatings were investigated by scanning electron microscope(SEM),transmission electron microscope(TEM),mirohardness tester and ball-on-disk tribotester.The results show that the technical parameters,pulse current,duty circle and frequency,are of great influence on the growth of crystalline and properties of the coating.Compared with the coating plated with direct current,the coatings plated with pulse currents have smaller nanocrystalline,contain more SiO2 nanoparticle and have higher hardness and wear resistance.

关键词： nano composite coating electrodeposition pulse current brush plating

Electron surfing acceleration in a current sheet of flares

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Science China(Physics,Mechanics & Astronomy) 2009年第11期52卷 1810-1812页

作者： WANG DeYu1 & LU QuanMing2 1 Purple Mountain Observatory, Nanjing 210008, China 2 School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China Purple Mountain Observatory Nanjing China School of Earth and Space Sciences University of Science and Technology of China Hefei China

A model of electron acceleration in a current sheet of flares is studied by the analytical approximation solution and the test particle simulation. The electron can be trapped in a potential of propagating electrostatic wave. The trapped electron moving with the phase velocity vp of wave may be effectively accelerated by evc p× Bz force along the outflow direction in the current sheet, if a criterion condition K > 0 for electron surfing acceleration is satisfied. The electron will be accelerated continuously until the electron detrap from the wave potential at the turning point S.

关键词： electron acceleration electrostatic wave current sheet