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Numerical Analysis of Space Charge Characteristics in Low-density Polyethylene Nanocomposite Under External DC Electric Field

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高电压技术 2013年第8期39卷 1813-1820页

作者： ZHOU Yuanxiang ZHANG Ling SHA Yanchao TIAN Jihuan State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing 100084 China ABB Corporate Research Center Beijing 100015 China

The dynamic characteristics of space charge in nanocomposite of low-density polyethylene (LDPE) mixed with inorganic nano- fillers. Different from previous qualitatively theoretical works, we investigated the influence of trap depth, trap volume charge density and injection barrier height on the space charge and the electric field distribution in the nanocomposite under a DC external electric field (100 MV/m) systematically and quantificationally, through numerical simulations based on a bipolar charge transport model. The simulation re- sults showed that, the increase of trap depth would severely distort the balanced electric field distribution with the highest and the lowest electric field of 119 MV/m and 47 MV/m, respectively. It is concluded that the introduction of nanofillers creates more deep traps, which would block space charges by capturing most of them in the vicinity of electrode and hence reduce the local electric field largely. Further theoretical analysis of the simulation indicates that both the high permittivity and the low local electric field of the nanocomposite contri- buted to the increase of injection barrier height, and almost no charge could overcome an injection barrier higher than 1.25 eV. At last, a mechanism of space charge suppression in the LDPE nanocomposite was presented.

关键词：纳米复合材料低密度聚乙烯直流电场空间电荷电荷特性数值分析无机纳米填料陷阱深度

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Comparison of two basic structures in magnetically-coupled resonant wireless power transfer

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Diangong Jishu Xuebao/Transactions of China Electrotechnical Society 2013年第SUPPL.2期28卷 18-22页

作者： Zhang, Yiming Zhao, Zhengming Yuan, Liqiang Lu, Ting State Key Lab. of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing 100084 China

Wireless power transfer (WPT) has been a research focus in recent decades. Based on magnetically-coupled resonant WPT (MCR-WPT), this paper made a comparison of two basic structures in MCR-WPT: the two-coil structure and the four-coil structure. Their equivalent circuits were built. To illuminate the difference between these two structures, the input impedance, the transfer efficiency, and the load matching were studied and tested by experimental results. The conclusion is drawn that without reducing the transfer efficiency, the addition of the source coil and the load coil in the four-coil structure makes it easier to match the source and the load than the two-coil structure.

关键词： Magnetic resonance

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On dispatching power systems with significant wind generation using disturbance feedbacks

On dispatching power systems with significant wind generatio...

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Chinese control Conference (CCC)

作者： Wei Wei Shengwei Mei Feng Liu State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing Beijing CN

With the rapid development of renewable energies, especially wind power, how to manage unexpected generation variations economically and reliably in dispatch has become crucial for modern power systems. To address this issue, this paper presents an affine disturbance feedback robust dispatch (ADF-RD) methodology for power systems with large scale wind power integration in the framework of adjustable robust optimization (ARO). This methodology divides the dispatching process into pre-dispatch and re-dispatch. Pre-dispatch decision immunizes against all possible realizations of uncertainties in a set, while re-dispatch which can be regarded as a feedback will be adaptively adjusted using an affine function with respect to the realized uncertainty in real time. The ADF-RD methodology is applied to an hourly ahead dispatch (HAD) problem. The effectiveness and efficiency of the proposed ADF-RD methodology are demonstrated by numerical experiments carried on a five-bus system.

关键词： Uncertainty Wind power generation Wind forecasting Wind farms Load flow power transmission lines

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A massive grid-connected power accumulator battery testing system using hybrid AC-DC microgrid

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Diangong Jishu Xuebao/Transactions of China Electrotechnical Society 2014年 29卷 449-453页

作者： Long, Bo Sun, Hongbin Wang, Bin Yao, Shuqing Fang, Xu Yao, Gaoxiang University of Electronic Science and Technology Chengdu610054 China State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing100084 China Bohai New Century Machinery Manufacturing Co. Ltd. TianJin300280 China

Nowadays, the network mode of the most energy recovery power battery testing instruments adopts AC-microgrid, which has the drawbacks of low energy recovery efficiency, complicated power circuit topology, cumbersome of the control algorithms. Aiming at these issues, a hybrid AC-DC microgrid system which is based on the power battery testing system has been put forward in this paper. The proposed scheme is composed by an energy storing system, a bidirectional DC-DC converter for test experiment, the grid-side loads, compared with conventional scheme, the proposed scheme has the merits of higher energy recovery efficiency, simplified power circuit for testing instruments. ©, 2014, Diangong Jishu Xuebao/Transactions of China Electrotechnical Society. All right reserved.

关键词： DC-DC converters

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A large-scale reactive power optimization method based on gaussian penalty function with discrete control variables

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2013年第4期33卷 68-76页

作者： Li, Zhigang Wu, Wenchuan Zhang, Boming Guo, Qinglai State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Haidian District Beijing 100084 China

Reactive power optimization with discrete control variables can be formulated as a mixed-integer nonlinear programming problem, which is a typical NP-hard problem in mathematics. This paper proposed a Gaussian penalty function based approach to handle discrete variables, in which the discrete variables were relaxed to continuous variables. The properties of the optimization model with Gaussian penalty function, as well as how it could be affected by parameters, were discussed. Then a practical algorithm combining nonlinear interior point method and a heuristic parameters tuning strategy was developed to solve the optimization problem. Finally, numerical experiments were taken on different systems, including IEEE standard systems and several real power systems with varying scales, to verify the robustness and practicability of the proposed method. © 2013 Chinese Society for Electrical Engineering.

关键词： IEEE Standards

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Fast evaluation of the lightning electromagnetic field in the time domain with an adaptive piecewise approximation of channel base current

Fast evaluation of the lightning electromagnetic field in th...

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作者： Lee, Jae-Bok Zou, Jun Li, Mo Chang, Sughun Electrical Environment Research Center Korea Electrotechnology Research Institute Changwon Korea Republic of State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing China

Purpose - A fast algorithm is proposed to calculate the lightning electromagnetic field over a perfectly conducting earth surface. Design/methodology/approach - The channel base current is approximated by a number of sub-domain quadratic functions using the proposed adaptive sampling technique, and the derivative and integral of the channel base current with respect to time can be analytically expressed. With the help of these approximations, the ideal electromagnetic field of the lightning channel can be evaluated along the lightning channel with respect to the height. Findings - The computational time can be greatly reduced using the proposed approach to evaluate the electromagnetic field of a lightning channel in the time domain. Originality/value - The adaptive sampling technique is a general-purposed approach, which can be potentially used in other applications to fit a function with the minimal number of intervals. © Emerald Group Publishing Limited.

关键词： Electromagnetic fields

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A non-iterative affine arithmetic methodology for interval power flow analysis of transmission network

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2013年第19期33卷 76-83页

作者： Ding, Tao Bo, Rui Guo, Qinglai Sun, Hongbin Wu, Wenchuan Zhang, Boming State Key Lab. of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China Midwest ISO St. Paul 55108 United States

power flow exhibits uncertainty when power injections randomly fluctuate. The variables of power flow problem are correlated through the constraints set forth by power flow equations. Affine arithmetic can effectively overcome the correlation and therefore is adopted in this paper. In order to improve the computational efficiency, non-iterative method was proposed, which can transform the interval power flow problem into optimization problems. Linear programming, nonlinear programming and quadratic programming optimization models were established to obtain intervals of nodal voltage magnitude, phase angle, branch active power and reactive power, respectively. simulation results of 9-bus and 57-bus test system show that the power flow interval obtained by the proposed algorithm is nearly the same as that by iterative algorithms, whereas the branch power flow results are better. The interval power flow problem can be solved quickly and efficiently with time complexity approximately O(m3). As well, parallel computing can be implemented to achieve promising improvement in computation time. © 2013 Chinese Society for Electrical Engineering.

关键词： Quadratic programming

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Calculation of surface electric field on UHV transmission lines under lightning stroke

Calculation of surface electric field on UHV transmission li...

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作者： Yu, Zhanqing Li, Qian Zeng, Rong He, Jinliang Zhang, Yong Li, Zhizhao Zhuang, Chijie Liao, Yongli State Key Lab of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China Department of Mathematical Sciences Tsinghua University Beijing 100084 China Electric Power Research Institute China Southern Power Grid Guangzhou China

Lightning is the major cause of interruptions in power transmission lines. Ultra-high voltage (UHV) AC transmission line has been put into operation in China. Due to the large tower height up to 90 m and the high operation voltage up to 1000 kV, the shielding failure probability increase obviously. Nowadays the leader progression model is an advanced method to evaluate the shielding failure probability of transmission lines. The surface electric field is the key issue for lightning failure analyzing, because the upward leader inception mainly depends on the surface electric field. In this paper, the lightning leader model is introduced. A charge simulation method based piecewise linear function is adopted to analyze the surface electric field on phase conductors and ground wires. The influence factors, such as operation voltage, lightning peak current, lightning down leader position, protection angle, on surface electric field were analyzed. © 2012 Elsevier B.V. All rights reserved.

关键词： Electric lines

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Numerical Analysis of Space Charge Characteristics in Low-density Polyethylene Nanocomposite under External DC Electric Field

Numerical Analysis of Space Charge Characteristics in Low-de...

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中国物理学会第十八届全国静电学术会议

作者： ZHOU Yuanxiang ZHANG Ling SHA Yanchao TIAN Jihuan State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University ABB (China) Limited Universal

In this work, we are interested in space charge dynamics characteristics in the low-density polyethylene(LDPE) nanocomposite mixed with some mass fraction of inorganic nanofillers. Different with all previous qualitatively theoretical works, numerical simulation based on the bipolar charge transport model was performed to systematically investigate the influence of trap depth, trap concentration, and injection barrier height on the space charge and electric field distributions under DC external electric field of 100 k V/mm. Our simulation results showed that increasing the trap depth would severely distort the electric field distribution at the balanced status with the highest and lowest electric field of 119 k V/mm and 47 k V/mm, respectively. Due to the introduction of nanofillers, more deep traps were created and blocked the space charge movement, capturing most of space charge in the vicinity of the electrode and largely declining the local electric field further. In addition, our theoretical analysis also showed both the high permittivity and low local electric field contributed to the increase of injection barrier height. Once the injection barrier height surpassed 1.25 e V, there was almost no charge that could overcome the injection barrier. At last, a mechanism of space charge suppression in the LDPE nanocomposite was presented.

关键词： LDPE nanocomposite space charge bipolar charge transport model trap depth Schottkyinjection barrier height

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Resistance Characteristics of Arc in Long Air Gap

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高电压技术 2013年第8期39卷 1881-1885页

作者： YU Zhanqing YU Junjie ZENG Rong CHEN He PENG Xiang State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China Maintenance and Test Center of EHV Power Transmission Company China Southem Power Grid Co. Ltd. Guangzhou 510663 China

Arc resistance is an important parameter for characterizing long arcs in air, and its laboratory testing is of importance for accurate arc modeling of electromagnetic transient caused by short circuit fault. Therefore, we constructed an experimental system to study the cha- racteristics of long AC arc in air. Driven by currents of 10 kA or 40 kA (root mean square value), the system produces arcs with different initial lengths of 1 m, 2 m and 4 m, and the movement of the arcs are captured by a high-speed camera. After performing experiments using the system, we carried out analysis and comparisons of the arc resistance of arcs with different lengths and different currents, as well as a study of the relationship between the macro-morphology and the resistance of the arcs. Conclusions were drawn from the experimental re- sults: the arc voltage had obvious saturation characteristics; the arc resistance increased with the increase of arc length and the decrease of current; the arcs bended or extended significantly in time and the peak arc voltage within a single cycle increased correspondingly; the arcs had voltage and current in the same phase. In the end, a formula of arc resistance based on the experiment results is derived.

关键词：耐电弧性电阻特性空气间隙实验室测试电流驱动实验系统初始长度电弧电压

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