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2nd International Conference on Vulnerability and Risk Analysis and Management, ICVRAM 2014 and the 6th International Symposium on Uncertainty Modeling and Analysis, ISUMA 2014

作者： Li, H.S. Ma, Y.Z. Cao, Z. Key Lab. of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicles Nanjing University of Aeronautics and Astronautics Nanjing210016 China State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University Wuhan430072 China

ISBN: (纸本)9780784413609

Subset Simulation provides an efficient and robust method to estimate the failure probabilities at small probability levels for a single failure mode defined by the system response concerned. However, estimating failure probabilities of multiple stochastic responses using a single run of Subset Simulation remains quite a challenging task in structural reliability analysis. To address this problem, this study develops a generalized Subset Simulation (GSS) approach, in which a unified intermediate event is defined to drive the simulation procedure progressively approaching multiple failure regions, and estimate the corresponding failure probabilities simultaneously. The sorting difficulty arising in the multiple stochastic responses is bypassed by the definition of the unified intermediate event. Finally, two representative examples are used to demonstrate the performance of the proposed GSS approach. © 2014 American Society of Civil Engineers.

关键词： Reliability analysis

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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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A method for in vivo detection of abnormal subepidermal tissues based on dielectric properties

A method for in vivo detection of abnormal subepidermal tiss...

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作者： Zhang, Liang Liu, Peiguo Dong, Xiuzhen Zhou, Dongming Shi, Xuetao College of Science National University of Defense Technology Changsha Hunan410073 China State Key Lab. of Complex Electromagnetic Environ. Effects on Electronics and Information System National University of Defense Technology Changsha Hunan410073 China Faculty of Biomedical Engineering Fourth Military Medical University Xi'an Shaanxi710032 China

In this paper, a convenient and noninvasive scanning imaging method using microwave frequency band for abnormal subepidermal tissues detection is proposed in the aim to improve diagnosis and prognosis in clinical environments. This method is based on the reflective detection technology with coaxial probe that is used to measure the dielectric properties of tissues. An improved equivalent circuit and simulated annealing algorithm (SA) were used in this work to analyze the dielectric properties of tissues. Computational simulations incorporating a simplified model of subcutaneous hemorrhage described in this work were used to evaluate this method. The dielectric properties data of tissues in the model of simulation is derived from the literature. The simulation results demonstrated the potential of this method to detect abnormal subepidermal tissues conveniently and expose them in the image accurately. © 2014 - IOS Press and the authors.

关键词： Tissue

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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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Organic light-emitting diodes fabricated on nanostructured AZO: A low-cost way towards enhanced light extraction for large area lighting application

Organic light-emitting diodes fabricated on nanostructured A...

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2014 SID International Symposium

作者： Jiang, Yibin Li, Guijun Li, He Chen, Shuming Kwok, Hoi-Sing Department of Electronic and Computer Engineering State Key Lab on Advanced Displays and Optoelectronics Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong Department of Electrical and Electronic Engineering South University of Science and Technology of China Shenzhen 518055 China

Organic light-emitting diodes (OLEDs) were fabricated on nanostructured aluminum doped zinc oxide (AZO). The nanostructured AZO was formed by selectively etching as- prepared AZO film. The nanostructured AZO serves not only as low-cost indium-free anode but also as internal light extraction structure. OLEDs on it showed a 25.7% efficiency enhancement compared to the conventional ones. © 2014 SID.

关键词： Zinc oxide

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Modelling of Multilayer Graphene (MLG)-Based Structures at Different Temperatures

Modelling of Multilayer Graphene (MLG)-Based Structures at D...

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IEEE International Symposium on electromagnetic Compatibility

作者： Da-Wei Wang Wen-Sheng Zhao Hong-Ke Ma Wenchao Chen Wen-Yan Yin Centre for Optical and Electromagnetic Research State Key Lab of MOI Zhejiang University Hangzhou 310058 China Microelectronics CAD Centre Hangzhou Dianzi University Hangzhou 310018 China Science and Technology on High Power Microwave Lab Institute of Applied Electronics CAEP Mianyang 621900 China Centre for Electromagnetic Environment and Compatibility Research Department of Information Science and Electronic Engineering Zhejiang University Hangzhou 310058 China

ISBN: (纸本)9781479966172

A FDTD method with the conformal modification is proposed to study electromagnetic properties of multilayer graphene (MLG). The vector fitting technique is employed to change the MLG conductivity model into an appropriate form for the FDTD implementation by an auxiliary differential equation formulation. Some numerical results are presented with the accuracy of our developed algorithm validated by comparing our results to the analytical ones, and the effects of layer number of MLG in the MLG-based structures as well as operating temperature are examined in detail.

关键词： Multilayer graphene (MLG) ADE-FDTD method vector fitting technique temperature

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