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2nd Annual Conference on Electrical and control Engineering, ICECE 2011

作者： Li, Dapeng Wang, Shouxiang Zhan, Jie Zhao, Yishu Key Laboratory of Power System Simulation and Control Tianjin University Ministry of Education Tianjin 300072 China State Grid of China Technology College Shandong Jinan 250002 China

ISBN: (纸本)9781424481637

The requirement for power supply reliability and power quality has been increasing. When a fault occurs in distribution networks, fast locating and isolating the fault, restoring the power, and reducing outage time and area are becoming more and more crucial. The concept of fast self-healing has been proposed, which is also the requirement for smart grid development. In this paper, a self-healing reconfiguration technique is proposed for smart distribution networks with insertion of distributed generations (DGs). And a tree structure algorithm based on heuristic rules is proposed. Islands formed by DGs are used to deal with fault isolation and power restoration after a fault occurs. The effectiveness of the proposed algorithm is verified using a 26 bus bars test system with DGs. © 2011 IEEE.

关键词： Distributed power generation

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Reactive power optimization of power system based on improved particle swarm optimization

Reactive power optimization of power system based on improve...

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International Conference on Electric Utility Deregulation and Restructuring and power Technologies

作者： Wang, Hao Jiang, Huilan Xu, Ke Li, Guodong Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University Tianjin 300072 China Tianjin Electric Power Corporation Technology Center Tianjin 300384 China

ISBN: (纸本)9781457703638

Reactive power optimization is a nonlinear, multivariable, multi-constrained programming problem, which makes the optimization process complicated. In this paper, based on the characteristics of reactive power optimization, a mathematical model of reactive power optimization, including comprehensive consideration of the practical constraints and reactive power regulation means for optimization, is established. Also particle swarm optimization (PSO) has been studied, and the method based on improved particle swarm optimization for reactive power is going to be taken in this paper. Optimization for the IEEE 14-bus system proves that the improved PSO algorithm used in this paper for reactive power optimization is effective. The algorithm is simple, convergent and of high quality for optimization, and thus suitable for solving reactive power optimization problems, with some application prospect. © 2011 IEEE.

关键词： Reactive power

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Harmonic analysis of the interconnection of wind farm

Harmonic analysis of the interconnection of wind farm

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2011 International Conference on Electric and Electronics, EEIC 2011

作者： Wang, Jidong Du, Xuhao Li, Guodong Yang, Guanqing Key Laboratory of Power System Simulation and Control Ministry of Education Tianjin University Tianjin 300072 China Tianjin Electric Power Science Research Institute Tianjin 300022 China

ISBN: (纸本)9783642216961

With the large-scale wind farms accessing systems continuously and a wide range of variable speed wind turbines' application, the harmonic problems caused by the interconnection of wind farms have got more and more attention. This paper analyzes the harmonic mechanism caused by wind farms connected with the grid;based on Dig SILENT / power Factory simulation platform, establishes a permanent magnet direct drive wind turbine model. Finally, the harmonic simulation of an actual example for a wind farm connected with the grid is given in this paper. simulation results show that the second harmonic current of the wind farm accessing point and the third harmonic current of point of common coupling are exceeded, which should be suppressed;the contents of other harmonics are in the allowed range of Chinese National Standard. © 2011 Springer-Verlag Berlin Heidelberg.

关键词： Harmonic analysis

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Experimental research of the upward leader inception from transmission line

Experimental research of the upward leader inception from tr...

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2011 7th Asia-Pacific International Conference on Lightning, APL2011

作者： Zeng, Rong Li, Zhizhao Yu, Zhanqing Zhuang, Chijie State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781457714665

Electro-Geometric Model (EGM) has been applied widely all over the world to evaluate the lightning shielding failure of transmission line. But with the increase of operation voltage to 1000 kV and tower height to more than 100 meters, some shortcomings of the traditional EGM model were found by many researchers. Leader Progression Model (LPM) was proposed to solve these problems. But some fundamental works, such as when the upward leader initiates and how it propagates, is still indistinct. An experiment was designed and implemented in this paper to simulate the electric field circumstance near the test transmission line while the lightning downward leader approached. The upward leader from the test transmission line was clearly observed. The inception voltage and characteristics was analyzed. The streamer and leader initiated from the ground wire and conductor bundle were compared. The experiment results show that the leader initiating from the ground wire is more active in the inception stage. The velocity of the upward leader acquired is about 1.2-3.0 cm/μs. © 2011 IEEE.

关键词： Electric lines

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Research on earthing schemes in LV microgrids

Research on earthing schemes in LV microgrids

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2011 International Conference on Advanced power system Automation and Protection, APAP 2011

作者： Li, BoTong Li, YongLi Ma, Tao Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University Tianjin 300072 China Junliangcheng Power Co. Ltd. China Huadian Tianjin 300300 China

ISBN: (纸本)9781424496198

For the access of green distributed generation(DG), LV microgrid is an important direction of development nowadays. Because the LV microgirds are in direct contact with users, so how to design its earthing scheme is the first thing to think about in order to guarantee personal safety and reliable operation of the equipments. Earthing schemes of LV mircrogrids are studied in the paper and how it works properly is presented. The principles of neutral earthing modes of microgrid is given according to standard IEC60364 and DGs neutral earthing mode is discussed under different operation modes. How the traditional protection modes of TN and TT are used in LV microgrids is studied. Considering the dispersion and variety of DGs and energy storage devices, combined earthing mode of TN and TT is proposed as a reasonable way for microgrids. © 2011 IEEE.

关键词： Earthing schemes LV microgrids Neutral earthing Protection earthing Stray current

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Mathematical models of the system-level safe operational areas of power electronic converters in plug-in hybrid electric vehicles

Mathematical models of the system-level safe operational are...

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作者： Wang, Xuesong Bai, Hua Zhao, Zhengming Yuan, Liqiang China Power Engineering Consulting Group Corporation Beijing 100011 China Kettering University Flint MI 48504 United States State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing 100084 China

With the development of plug-in hybrid electric vehicles (PHEVs), power electronics plays an increasingly important role in electric power train systems. The economic and reliable design of these power electronic systems, e.g., dc/ac inverter and battery charger, will be the inward search to popularize electric vehicles. As an extension of system-level safe operational areas (SSOAs) proposed in our previous literature, this paper details the criteria and mathematical models of SSOA for a battery charger and a three-phase two-level dc/ac inverter. Operational areas were established based on the SSOA. Thermal characteristics of the semiconductor devices, operational modes, and load characteristics were enclosed to enhance the mathematical models. Experiments on a 5-kW charger and a 55-kW/380-VAC inverter validated the effectiveness of SSOA. © 2011 IEEE.

关键词： Metals

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power system Operational Reliability Equivalent Modeling and Analysis Based on the Markov Chain

Power System Operational Reliability Equivalent Modeling and...

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IEEE International Conference on power system Technology

作者： Yong Wang Xueshan Han Ying Ding Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of Education(Shandong University) Jinan Shandong Province China State Grid of China Technology College Jinan Shandong Province China

Aiming at the disadvantage of Monte Carlo simulation method in slow convergence and using a great number of computation resources, this paper, based on analytical approach, builds a quick power system operational reliability analyzing model. From the viewpoint of operation, this model which is based on Markov chain, assumes that equipment failure rate follows exponential distribution. Its core content includes three aspects. Firstly, a convenient criterion, used to divide power system operation into three states, and the corresponding state-space transition expression are proposed for engineering application. Secondly, Markov state transition probability matrix is obtained based on power system operation historical data (or simulation data sample). Thirdly, based on state transition probability matrix and current operating state of power system, state transition probability, steady state probability and the mean time to first failure can be acquired very quickly. Example analysis using RBTS-BUS6 system, testified the Markov property of power system state transition and the efficiency of this study.

关键词： Markov chain power system Reliability assessment Reliability prediction

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power Quality Improvement for Mircrogrid in Islanded Mode

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Procedia Engineering 2011年 23卷 174-179页

作者： Gao Xiaozhi Li Linchuan Chen Wenyan Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University Tianjin 300072 China

The aim of this paper is to analyze and improve the power quality of island microgrid assuming that the distributed generators could meet the load active power requirement. The main power quality problems through analysis are the harmonics caused by power-electronic devices and voltage variation caused by high reactive power requirement. Based on economy and compensation performance, a combined system constructed by SVC and SAPF is designed to improve the power quality of microgrid in this paper, in which SAPF is adopted near the microsource to mitigate harmonic currents and SVC near the load to compensate reactive power so as to relieve the voltage variation. simulation results show the effectiveness of the combined system.

关键词： v/f control scheme microgrid power quality APF SVC

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A neutral-point potential balancing algorithm for five-level ANPC converters

A neutral-point potential balancing algorithm for five-level...

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International Conference on Electrical Machines and systems (ICEMS)

作者： Kui Wang Yongdong Li Zedong Zheng State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing China

Five-level active neutral-point-clamped (ANPC) converter is a newly emerging topology which can overcome the drawbacks of traditional neutral-point clamped (NPC) converters and flying-capacitor (FC) converters. Its dc-link is subdivided into two equal parts and the main problem is the neutral-point (NP) potential balancing. In this paper, a NP potential balancing algorithm based on zero-sequence voltage injection is presented. By calculating the NP currents of all key zero-sequence voltages, the most appropriate zero-sequence voltage is selected to generate the demanded NP current. Moreover, by further limiting the span of injected zero-sequence voltages, the NP balancing algorithm can make the two IGBTs connected in series operate at fundamental frequency. A three-phase five-level ANPC inverter prototype was built up and experimental results are presented to verify the validity of this algorithm.

关键词： Capacitors Electric potential Switches Voltage control Inverters Insulated gate bipolar transistors Heuristic algorithms

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simulation of Shunt Active power Filter Using Modified SVPWM control Method

Simulation of Shunt Active Power Filter Using Modified SVPWM...

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The 2011 International Conference on Electric and Electronics (EEIC 2011)

作者： Jidong Wang Guanqing Yang Kun Liu Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University

Space vector pulse width modulation(SVPWM) was widely used in inverter control for the advantages of fixed switching frequency, full utilization of DC-link voltage and better control precision. In recent years, SVPWM is gradually applied in the control method of active power filter(APF) as the APF mains is just one invert. The voltage vectors are composed based on the α-β axis in traditional SVPWM however, in this paper one x-y composed reference axis at 60 degree angles from each other is used instead. Compared with traditional method, the principle of the method is relatively simple and easy to implement. At the same time PI regulator is adopted for the DC-link voltage control. Finally simulation results show that the APF has a better compensation effect using this control method.

关键词： active power filter(APF),space vector PWM,PI control,simulation

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