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China International Conference on Electricity Distribution, CICED

作者： He He Shaneng Xu Minghao Wen State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China Quanzhou Power Supply Company of State Grid Quanzhou China

Taking into account the error caused by differential, two factors' impact on the distance protection algorithm after equal transfer processes are studied, including the sampling rate and cut-off frequency of the low-pass filter. It comes to a conclusion that increasing the sampling rate can reduce the error caused by differential and cutting down the cut-off frequency can reduce the variance of the least square method, which is verified by the ATP simulation and dynamic physical simulation results. Combined with the simulation results, the impact caused by the length of data window is studied by analyzing the performances of the proposed algorithm. By optimizing the sampling rate, the cutoff frequency, and the length of data window, the distance measuring error can be achieved within 5% at approximately 10ms after the fault occurrence.

关键词： Abstracts Equations Cutoff frequency

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Novel faulty feeder identification scheme in the neutral in-effectively grounded distribution networks

Novel faulty feeder identification scheme in the neutral in-...

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12th IET International Conference on Developments in Power System Protection, DPSP 2014

作者： Lin, Xiangning Kursan, Ivan Sun, Jinwen Li, Zhengtian Zheng, Rongjin Bo, Zhiqian Xuv, Jianfei Weiv, Zhongkang State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University ofScience and Technology Wuhan 430074 China Fujian University of Technology No 3 Xueyuan Road University Town Minhou Fuzhou City Fujian Province China Xuji group corporation State Grid Beijing 100000 China State Grid Jibei Electric Power Company Limited Beijing 100053 China

ISBN: (纸本)9781849198349

The selection of the faulty feeder in the case of single phase-to-earth fault in a Neutral Un-effectively Grounded System (NUGS) has been one of the conventional problems of distribution network. The compensation method is introduced to highlight the difference of the zero-sequence admittances between the faulted feeder and the sound feeder. In this way, the setting of the criterion becomes feasible. The on-site requirement to the protection is also involved in this paper. A variety of simulation tests were carried out by virtue of ATP software. The results demonstrate that this algorithm is immune to the variation of network structures and parameters, fault conditions, and fault resistance etc. The successful rate of feeder selection is proved to be improved to a great extent.

关键词： Electric power distribution

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Accurate single-ended data based fault location method for multi-source and multi-branch distribution network

Accurate single-ended data based fault location method for m...

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12th IET International Conference on Developments in Power System Protection, DPSP 2014

作者： Lin, Xiangning Kursan, Ivan Sun, Jinwen Li, Zhengtian Zheng, Rongjin Bo, Zhiqian Xu, Jianfei Wei, Zhongkang State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan 430074 China Fujian University of Technology No3 Xueyuan Road University Town Minhou Fuzhou City Fujian Province China Xuji Group Corporation State Grid Beijing 100000 China State Grid Jibei Electric Power Company Limited Beijing 100053 China

ISBN: (纸本)9781849198349

A novel single-ended traveling wave fault location method applicable to the distribution network with multiple branches is presented in this paper. The method only depends on the arrival times of the initial aerial-mode and zero-mode travelling wave, and it is not affected by structure of a distribution system itself. Therefore, good results can be achieved for precise fault locating in multi-source and multi-source distribution networks. Furthermore, the impacts of different factors on the fault location accuracy are investigated. The feasibility and effectiveness of the presented method is verified by PSCAD/EMTDC simulation results.

关键词： Antennas

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Stability of DC-link voltage affected by phase-locked loop for DFIG-based wind turbine connected to a weak AC system

Stability of DC-link voltage affected by phase-locked loop f...

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International Conference on Electrical Machines and Systems (ICEMS)

作者： Dong Wang Jiabing Hu Yunhui Huang Ningbo Wang Qiang Zhou State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China Wind Power Technology Center of Gansu Electric Power Corporation Lanzhou China

The paper investigates the stability of DC-link voltage, in electromagnetic time scale, of doubly fed induction generator (DFIG) based wind turbine attached to a weak AC system. In weak AC system, the dynamic of phase-locked loop (PLL) is coupled with DFIG converters' control. A reduced order model is proposed for stability analysis of DFIG DC-link voltage. Eigenvalue analysis shows that PLL, active power control (APC) and reactive power control (RPC) of rotor side converter (RSC) mainly participate in dominant oscillation mode of control system. The interactions between PLL and RSC control damage the stability of DC-link voltage in weak grid. Synchronizing and damping components defined by PLL are presented for stability analysis physically. Each control's contribution to synchronizing and damping components is analyzed for different grid strengths and PLL gains. It clearly illustrates how PLL and RSC control interact leading to system instability. Time domain simulation of a detailed model was carried out to verify the validity of the analysis above.

关键词： Phase locked loops Voltage control Stability analysis Power system stability Damping Oscillators Mathematical model

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Stability of Interacting Grid-Connected Power Converters

Stability of Interacting Grid-Connected Power Converters

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IEEE International Symposium on Circuits and Systems

作者： Cheng Wan Meng Huang Chi K. Tse Xinbo Ruan State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China Department of Electronic and Information Engineering The Hong Kong Polytechnic University Kowloon Hong Kong

ISBN: (纸本)9781479934331

The power grid in a typical micro distribution system is non-ideal, presenting itself as a voltage source with significant impedance. Thus, grid-connected converters interact with each other via the the non-ideal grid. In this study, we consider the practical scenario of voltage-source converters connected to a three-phase voltage source with significant impedance. We show that stability can be compromised in the interacting converters. Specifically, the stable operating regions in selected parameter space may be reduced when grid-connected converters interact under certain conditions. In this paper, we develop bifurcation boundaries in the parameter space with respect to Hopf-type instability. A small-signal model in the dq-frame is adopted to analyze the system using an impedance-based approach. Moreover, results are presented in design-oriented forms so as to facilitate the identification of variation trends of the parameter ranges that guarantee stable operation.

关键词： voltage source power conversion unit parameter space methods Converters Power grids three-phase voltage dispensing system impedance

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DC voltage control and power dispatch study of a five-terminal DC grid based on average-value VSC model

DC voltage control and power dispatch study of a five-termin...

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International Conference on Power System technology (POWERCON)

作者： Kai Wang Xiaobo Hu Wei Sun Haishun Sun Ke Zhang State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan Hubei Province China China Electric Power Research Institute Beijing China

DC grids based on voltage source converters (VSCs) are proposed for integrating large windfarms and delivering remote energy source power through long distance. A number of DC voltage control and power dispatch strategies are presented by researchers to guarantee the power transmission flexibility and capacity of such DC grids. Various options for ensuring satisfactory steady-state and dynamic-state system characteristics are discussed in the paper. A novel control strategy is proposed to achieve the goal of both precise DC voltage tracking under normal operation and steady control mode conversion after slack-bus terminal loss. PSCAD/EMTDC simulations on a five-terminal DC grid with four onshore VSC terminals and one offshore VSC terminal during wind power variation and onshore VSC terminal loss are presented to show the robust performance of the proposed control strategy. Further studies on the loss of master terminal during severe fault are provided to validate the positive effect of dynamic braking resistor (DBR).

关键词： Voltage control Power conversion Power systems Steady-state Resistors Distributed Bragg reflectors

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Design of a nonlinear excitation controller using synergetic control theory

Design of a nonlinear excitation controller using synergetic...

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IEEE PES Asia-Pacific Power and Energy engineering Conference (APPEEC)

作者： Ping Zhao Jiebin Zhuo Zhenxing Li Wei Yao Shaorong Wang College of Electrical Engineering & New Energy China Three Gorges University Yichang China State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology(HUST) Wuhan China

ISBN: (纸本)9781479975389

This paper proposes an improved synergetic excitation controller (ISEC) for synchronous generator in order to not only improve transient stability but also obtain good voltage regulation performances of power systems. According to the control objective, a manifold is chosen as a linear combination of the deviation of generator terminal voltage, rotor speed and active power for the synthesis of the synergetic excitation controller. Then the control law of the conventional synergetic excitation controller (CSEC) is deduced based on the nonlinear model of the synchronous generator. The influences of controller parameters on control performance and its selection principle are also discussed. Compared with CSEC, an adaption strategy is proposed for ISEC to vary the control parameter in order to improve the performances of the voltage regulation and transient stability under various operating conditions. Case studies are undertaken on a single-machine infinite-bus (SMIB) power system. Simulation results show the ISEC can provide better damping and voltage regulation performances in comparison with the CSEC and conventional power system stabilizer.

关键词： Voltage control Power system stability Rotors Transient analysis Generators Damping

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Thermal Analysis of a Toroidal Field Model Magnet with HTS Wires

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Physics Procedia 2014年 58卷 240-243页

作者： X. Deng H. Liu L. Ren Y. Zhang Y. Xu X. Zhao Y. Tang State Key Laboratory of Advanced Electromagnetic Engineering and Technology (R&D Center of Applied Superconductivity Huazhong University of Science and Technology) 1037 Luoyu Road Wuhan 430074 P. R. China

A HTS toroidal magnet will be fabricated to study the application of HTS wires in tokamak. This magnet consists of 12 D-shaped coils using commercial YBCO tape. It is expected to work at 20 K or below for the purpose of getting a high toroidal magnetic field. The critical current of this magnet is 316.5 A and the working current of this magnet is 220 A. This system is cooled by the conduction-cooling method with two GM cryoc olers. This paper gives the cooling down analysis and the stability analysis of this magnet. The result shows the pre-cooling time is 14 hours and the magnet is stable in a specific fault condition.

关键词： HTS totoidal field AC loss thermal analysis

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Partial equilibrium prediction of solidification and carbide precipitation in Ti-added high Cr cast irons

Partial equilibrium prediction of solidification and carbide...

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作者： Zhang, Hongwei Liu, Qiang Shibata, Hiroyuki Wang, Qiang Jönsson, Pär He, Jicheng Nakajima, Keiji Northeastern University Key Laboratory of Electromagnetic Processing of Materials Shenyang 110004 China KTH Royal Institute of Technology Department of Materials Science and Engineering SE-100 44 Stockholm Sweden Tohoku University Institute of Multidisciplinary Research for Advanced Materials 2-1-1 Katahira Aoba-ku Sendai 980-8577 Japan

Carbide precipitation and eutectic phase transformation during solidification of Fe-C-Cr-Ti-Mn-Mo-Ni- Si Ti-added high-chromium cast irons (HCCIs) were studied numerically and experimentally by the help of Partial Equilibrium approximation, DSC thermal analyses and EDX analyses. The main carbides formed during the solidification are distinguished as MC, primary M7C3 and eutectic M7C3 from their distinguished constitution, while other researchers didn't distinguish the primary and eutectic M 7C3carbide. Through comparing the prediction of Partial Equilibrium approximation with DSC thermal analysis measurement, the precipitation sequence of the eutectic structure in HCCIs is clarified to follow the sequence of FCC prior to the eutectic M7C3, although they were usually expected to precipitate simultaneously. The hardness index of the HCCIs is evaluated quantatively by summation of the contributions of the Vickers hardness of MC, primary M7C3 and eutectic M 7C3 carbides with predicted precipitation amount and composition / constitution. The effects of C, Ti and Cr contents on the precipitation sequence, the amount and the composition of carbides as well as the hardness of the HCCIs are discussed deeply. Finally, the validity of Partial Equilibrium approximation is shown in prediction of the solidification in multicomponent system with large amount of precipitated carbides. © 2014 ISIJ.

关键词： Eutectics

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Research the length of the positive corona using the digital image processing technology

Research the length of the positive corona using the digital...

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Conference on Electrical Insulation and Dielectric Phenomena, (CEIDP)

作者： Qizheng Ye Xingwang Li Yu Hu Yi Sun State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China Electric Power Research Institute of Guangdong Power Grid Corporation Guangdong China

This paper presents an experimental study of dc air discharge in a point-line electrode system. The digital image processing technology presented in our previously paper is used to calculate the length of the positive corona. The calculated results of the mean gray level, the standard deviation of the gray levels and the coefficient of variation which is the ratio of the standard deviation to the mean gray level, show that the jump location of the coefficient of variation is the end point of the corona and can be used as an index of the length of corona. With an increase of the voltage, the length of corona increases and the positive corona mingles with the negative corona at last. Compared with the other methods, the method is not only effective but also simple in the quantitative analysis the length of the corona.

关键词： Image processing Corona

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