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2nd IET Renewable power generation Conference, RPG 2013

作者： He, F. Zhao, Z. Yuan, L. Lu, T. State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781849197588

This paper proposes a hierarchical control scheme for parallel grid-connected PV inverters with a common dc bus. Droop control and group coordination are implemented to achieve equal power sharing between inverters as well as zero steady-state error for dc voltage regulation. The implementation is specifically designed for distributed control to promote modularization and system reliability. Experimental results have verified that the proposed scheme is effective.

关键词： Electric power transmission networks

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Functionality identification for the testing systems with large-scale highly-concentrated wind power integration by long-distance transmission lines

Functionality identification for the testing systems with la...

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IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT Europe)

作者： Jiabing Hu Yunhe Hou Feng Liu Yongning Chi Shuanglei Feng Haiyan Tang Guobing Song Xiaoming Yuan State Key Lab of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China Department of Electrical and Electronic Engineerig The University of Hong Kong Hong Kong China State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China China Electric Power Research Institute Beijinz China Department of Electrical Engineering Xi’ an Jiaotong University Xi'an China

ISBN: (纸本)9781479977215

Large-scale, highly-concentrated wind power integrated into grids through long transmission lines will bring significant challenges to power system operation during steady-state and dynamic processes. Tremendous research has been conducted in this critical area. However, few, if any available testing systems have been established to meet the requirements of the research on different time-scales. The objective of this paper is to identify the functionality requirements of the testing systems for the comprehensive studies, which covers different time-scale problems of power systems. For this purpose, the realistic Gansu power grids in China and wind farms in Jiuquan area are selected. As a typical power grid with large-scale highly-concentrated wind power integration by long-distance transmissions, the characteristics of the selected wind farms and power grid are discussed first. Two simplified systems are constructed associated with the major characteristics. The critical functionality requirements of the testing systems for different research purposes, i.e., system planning, operation, control, and protection, are identified. As the first step, this paper scopes the key requirements and, ultimately, a complete testing system is expected.

关键词： Wind power generation power system stability Stability analysis Testing Wind farms Frequency control power grids

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Air-gap magnetic field distribution and inductance characteristics in a long primary sectional powered variable pole pitch linear induction motor

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Qinghua Daxue Xuebao/Journal of Tsinghua University 2014年第9期54卷 1161-1165and1172页

作者： Mu, Shujun Chai, Jianyun Sun, Xudong Wang, Shanming State Key Lab. of Security Control and Simulation of Power Systems and Large Scale Generation Equipments Department of Electrical Engineering Tsinghua University Beijing100084 China

This study investigated the air-gap magnetic field distribution and inductance characteristics of a long primary sectional powered variable pole pitch linear induction motor (VPPLIM). A one-dimensional analytical model and a 2-D finite element model were used to analyze the air-gap magnetic field distribution in the VPPLIM with harmonic fields for uniformly accelerating the mover with a typical AC supply. The air-gap magnetic field distribution was used to develop analytical expressions for the self-and mutual-inductances of the motor and their characteristics. The analytical expressions are verified by the finite element simulations. ©, 2014, Press of Tsinghua University. All right reserved.

关键词： Inductance

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A fast transient simulation model of DFIG based on the piecewise averaging method

A fast transient simulation model of DFIG based on the piece...

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2nd IET Renewable power generation Conference, RPG 2013

作者： Feng, G. Xu, Y. Chen, Y. Gao, H. Chen, L. State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781849197588

Due to the power electronic devices in doubly fed induction generators (DFIG), it is very time consuming to simulate the electromagnetic transients of DFIG using its detailed model. Thus it is necessary to have appropriately simplified model of DFIG that maintains desirable accuracy. In this paper, the piecewise averaged model of PWM converters is introduced and applied to the modelling of DFIG. The proposed model divides the simulation time interval into switching periods and recalculates the averaged state equations of PWM converters in each switching cycle. In addition, a predictorcorrector based EMTP algorithm is designed to iteratively solve the model. Instead of treating switching events at the time points when they happen, the new algorithm solves all the switching instants in a switching cycle at the same time, which avoids frequency modification of the system conductance matrix and speeds up EMT simulations of DFIG. simulation results of a single-machine infinity bus system with a DFIG show that the proposed model and algorithm can achieve satisfactory accuracy and efficiency.

关键词： Equations of state

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Pattern analysis of future HVDC grid development

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2014年第34期34卷 6007-6020页

作者： Yao, Liangzhong Wu, Jing Wang, Zhibing Li, Yan Lu, Zongxiang China Electric Power Research Institute Haidian District Beijing100192 China State Key Lab of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China

The development of high voltage direct current (HVDC) grid is an effective approach to implement the large-scale long-distance power transmission, the large-scale renewable energy integration and accommodation, and the safe and stable operation of the interconnected AC grids. This paper reviewed the latest research progresses of DC transmission technologies, summarized the characteristics of DC grid, and discussed the current research status of DC grid. Then a typical topology of HVDC grid considering the integration of large-scale renewable generations over different regions was proposed. The technical requirements of such a HVDC grid was studied and refined accordingly. Furthermore, new types of key equipment, new control and protection technologies, reliability evaluation methods and standard system of such a HVDC grid were analyzed and the present research foundations and the future research directions of these relevant technologies were stated. It provides a technical reference for future research and construction of the DC grid in China. © 2014 Chin. Soc. for Elec. Eng.

关键词： HVDC power transmission

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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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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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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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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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