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International Conference on power system Technology (powerCON)

作者： Yunfeng Cheng Chao Lu Kun Men Liang Tu the State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghual University Beijinz P.R. China the Academy of China Southern Power Grid Guangzhou P.R. China

China's electrical grid has installed more than 2500 sets of phasor measurement unit (PMU), covering almost all the 500 kV and above and part of the 220 kV substations, which in sure observable of the ultra-high voltage power network and provide mass data for system analysis. However, PMU measurements may contain bad data and the precision of measurements especially phase need to be further improved. state estimation is an effective method to deal with data contaminated by noise and bias. Therefore, it's of great significance to study the PMU-only state estimation (POSE) problem. The real number equations based on the rectangular coordinate system and weighted least squares (WLS)algorithm are the general method to solve the POSE problem at present, which need to convert phasors into their real and imaginary parts, thus enlarging the size of the coefficient matrix which decreases the computational efficiency. In this paper, complex number equations for the POSE problem are established and the complex number weighted least squares (CWLS) estimation model is built to solve the equation directly in the complex domain which needs no phasor converting. The error characteristics of PMU measurements in the complex domain are analyzed in depth which give a guidance of choosing weights and illustrate the robustness of the CWLS to phase. Test results demonstrate the contrast analysis between the CWLS and the WLS from the perspectives of estimation time, estimation accuracy and adaptability to different error levels, which shows that the performances of the CWL Sare better than the WLS. The robustness of the CWLS to phase is also showed in the tests.

关键词： Phasor measurement units Measurement errors Measurement uncertainty Phase measurement Current measurement Voltage measurement Equations

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Simplified mathematical model of inter-turn short circuit of field windings in hydro-generators and its application

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Science China(Technological Sciences) 2013年第4期56卷 898-909页

作者： HAO LiangLiang WU JunYong SUN YuGuang WANG XiangHeng School of Electrical Engineering Beijing Jiaotong University State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University

Inter-turn short circuit of field windings is a common electrical fault of *** is an important method of investigating the fault and providing data support for fault ***,huge numbers of pole pairs and damper loops in large hydro-generators would lead to lengthy calculation time,hindering scientific research and engineering *** deal with this problem,we analyze a theoretical basis for a damper winding simplified model and then propose an equivalent treatment *** the analysis of steady-state current harmonic characteristics of generators with different stator winding configurations during the fault,the simplified models suitable for steady-state calculation are derived from two aspects,namely,additional rotor harmonic current frequency characteristics and the relationship of the amplitude as well as the phase of each branch current of the *** calculation and experimental results of the two simplified models are then compared to verify the models' correctness.A calculation example of the Three Gorges left bank VGS generator shows few deviations between the calculation results of the simplified model and the original ***,the calculation time using the simplified model is 1/1500 that using the original model,which provides a more effective tool for on-line fault ***,the sensitivity-verification application of the fault-monitoring scheme based on the stator steady-state unbalanced current RMS is *** result shows that the scheme can monitor two-turn short circuits of field windings in the Three Gorges generator and provide high sensitivity.

关键词： hydro-generator field windings inter-turn short circuit simplified model on-line monitoring

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Design optimization of ferrite rings for VFTO mitigation

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IEEE Transactions on power Delivery 2014年第99期PP卷 1-1页

作者： He, Jiaxi Guan, Yonggang Liu, Weidong Chen, Weijiang Li, Zhibing Department of Electrical Engineering State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing100084 China State Grid Corporation of China Beijing100031 China China Electric Power Research Institute Beijing100192 China

Very-fast transient overvoltage (VFTO)-related problems are raising growing concerns in China with the development of ultra-high voltage. The practice of fitting ferrite rings on gas-insulated switchgear busbars for VFTO mitigation has long been proposed but few investigations on its design optimization were conducted. Based on theoretical analysis of the simplified model, the optimal damping condition of ferrite rings is proposed, which is conducive to the type selection. The number of rings to be employed to ensure visible suppressing effects is given through simulations and the influence of the saturation is discussed. Impact on the power frequency is analyzed to be negligible. Finally, comparisons aremade between the theoretical conclusions and existing experiment results, which approve the optimal damping condition and agree with the number of rings to be employed. © 2014 IEEE.

关键词： Electric switchgear

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Simplified equivalent models of large-scale wind power and their application on small-signal stability

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Journal of Modern power systems and Clean Energy 2013年第1期1卷 58-64页

作者： Nan DING Zongxiang LU Ying QIAO Yong MIN State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua UniversityBeijing 100084China

With the rapid growth of grid-connected wind power penetration level,it is necessary to study the impacts of wind power on power system *** small-signal stability of power systems with large-scale wind power is explored using the eigenvalue analysis method.A prototype sample system,the two-synchronous-generator system with a wind farm,is proposed for theoretical ***,simplified models of wind turbines(WTs)and the corresponding equivalent models of wind farms are *** kinds of typical WT models,i.e.,squirrel cage induction generator,doubly-fed induction generator,and permanent magnet synchronous generator are ***,based on the simplified equivalent models,effects of large-scale wind farms on the electromechanical oscillation modes(EOMs)of synchronous systems are *** results indicate that wind farms of the three kinds of WTs have positive effects on ***,long transmission lines connecting wind farmto the systemmay produce negative effects on the small-signal stability of the system.

关键词： Wind turbine(WT) Small-signal stability Electromechanical oscillation mode(EOM) Simplified model Equivalent model

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Discussion on tower shunt coefficient of UHV DC transmission line under lightning stroke

Discussion on tower shunt coefficient of UHV DC transmission...

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International Conference on Lightning Protection (ICLP)

作者： S Chen J Hu B Zhang Y Yin M Hua State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China China Electric Power Research Institute Beijing China Tibet Electric Power Research Institute Lhasa China

ISBN: (纸本)9781479935451

The development of UHV transmission technology brings longer transmission distance, higher towers and more complicated terrain along the transmission lines, which make the shunt performance of transmission line under lightning stroke more diversiform compared to conventional ones. This paper discusses the effects of factors, such as lightning current waveform, footing resistance, transmission line span etc., on the shunt coefficient of UHV DC transmission lines, which is of great significance for setting out lightning-proof measures as well as the location of lightning stroke point. It is referred that lightning current waveform especially its front time as well as tower footing resistance plays a significant role in determine of the tower shunt coefficient under lightning stroke. As the results indicates, the shunt coefficient of ground wire gets larger as the footing resistance increases while it decreases first and then increases as the front time of the lightning current waveform increases. The shunt coefficient of tower is just the opposite.

关键词： EMTDC Educational institutions Poles and towers Wires Wide area networks Lightning

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A GPU-based Parallel simulation Platform for Large-scale Wind Farm Integration

A GPU-based Parallel Simulation Platform for Large-scale Win...

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IEEE PES Transmission and Distribution Conference and Exposition

作者： Haixiang Gao Ying Chen Yin Xu Zhitong Yu Laijun Chen State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University School of Electrical Engineering and Computer Science Washington State University

ISBN: (纸本)9781479936571

Due to the energy crisis of the next fifty years, an increasing number of large-scale wind farms are integrating into power systems. Parallel simulation platforms are indispensable to evaluate the effects of wind farm integration. A GPU-based parallel simulation platform is constructed in this paper to test the feasibility of simulating integration systems on GPU. By adopting previous research work such as averaged model and improved EMTP algorithm, models and algorithm of the platform are firstly introduced. Then the hardware and software architecture of the platform are put forward, which combine CPU configuration and GPU computing. Finally, a wind farm with different numbers of DFIGs are used to test the performance of the platform. Results show that the platform has excellent accuracy, efficiency and scalability. The work of this paper proves the feasibility to simulate wind farm integrating dynamics adopting GPU and its potential to reach tremendous efficiency and scalability.

关键词： power system simulation power system modelling

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Three-phase steady-state models for distributed generators

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2014年第10期34卷 1509-1518页

作者： Ju, Yuntao Wu, Wenchuan Zhang, Boming Guo, Kunya Wang, Yingnan State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China Liaoning Provincial Power Grid Corp. Shenyang Power Supply Company Shenyang 110021 Liaoning Province China

Low voltage distribution network usually operates under three-phase unbalanced conditions. And the distributed generators (DGs), integrated with distribution network, show different behaviors under different control strategies for unbalanced operating scenarios. For accurate three-phase power flow analysis, detailed three-phase DG models are needed. A unified technique was proposed to formulate the three-phase models for different DGs (include synchronous generator, induction generator, power electronic interface generator, doubly fed induction generator). Comparisons between the proposed models and existing models were also presented in this paper and the models were proved to be right. The proposed approach is suitable for distributed generator unbalanced analysis and is also suitable to model flexible alternative current transmission (FACT) devices. © 2014 Chin. Soc. for Elec. Eng.

关键词： Distributed power generation

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Interval economic dispatch model with uncertain wind power injection and spatial branch and bound method

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2014年第22期34卷 3707-3714页

作者： Ding, Tao Guo, Qinglai Bo, Rui Zhang, Liping 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 Beijing100084 China Midwest ISO St. Pau55108 United States Department of Mathematical Science Tsinghua University Haidian District Beijing100084 China

power injection becomes stochastic due to large-scale wind power integration into power grid, which greatly challenges the traditional power grid. If the uncertainty is modelled using the interval number, the solution of economic dispatch model can also be represented as an interval number. To achieve the precise upper and lower bound, two deterministic programming models were deduced: the optimistic solution can be obtained by an optimistic model using linear programming, whereas the pessimistic solution achieved by a pessimistic model is an NP-hard problem, which can be transformed into a bilinear programming by duality theory. Then a linear relaxation technology, spatial branch and bound method were used to obtain the global pessimistic solution. Therefore, the interval bound information can provide the operator with institutive bound information for the future security assessment. Finally, a test system with 15 generators and 300 nodes was studied at different time scales. The result, compared with interior point method and enumeration, shows the effectiveness of proposed method. © 2014 Chinese Society for Electrical Engineering.

关键词： Wind power

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Summary of Health Index Theory and Application of state Maintenance equipment

Summary of Health Index Theory and Application of State Main...

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The 5th International Conference on Reliability of Electrical Products and Electrical Contacts

作者： Lin CHENG Manjun LIU Feijin PENG Dept.of Elec.Eng. Tsinghua UniversityState Key Lab of Control and Simulation of Power Systems and Generation Equipments Guangdong Power Grid Company Foshan Power Supply Bureau

This paper describes several methods for condition-based maintenance,introduced CBM,RCM development process,the main theoretical logic,techniques and *** on the health index based on equipment maintenance strategies,namely *** on the development of narrative context,theoretical foundation,model healthy *** for its application in power transformers were introduced.

关键词： Health Index(HI) Condition-Based Maintenance(CBM) Reliability Centered Maintenance(RCM) Condition Based Risk Maintenance(CBRM)

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Study of a new grid-connected LCL filter for shunt active power filter

Study of a new grid-connected LCL filter for shunt active po...

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IEEE Conference and Expo Transportation Electrification Asia-Pacific (ITEC Asia-Pacific)

作者： Yi Wang Jian-zheng Liu Xing-Tao Xu State Key Lab of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing Beijing CN Jiangsu Electric Power Company Research Institute Nanjing China

LCL filter can improve the output current of the shunt active power filter. The paper proposes a resonant LCL filter structure with a LC high-frequency filter branches adding to LCL filter with damping resistor. By LC resonance effect, the switching frequency harmonics are filtered more efficiently and the loss of the system is reduced. The paper also builds the system modeling and analyzes the stability of the grid filter with the deadbeat control, then gives parameter selection methods and simulates with PSCAD/EMTDC. All these are verified through the experiments on a 70-KW shunt APF prototype using deadbeat controller.

关键词： power harmonic filters Damping Active filters Harmonic analysis power filters Switching frequency Resonant frequency

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