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Design optimization of ferrite rings for VFTO mitigation

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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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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Application of the complex algorithm in PMU-only state estimaiton

Application of the complex algorithm in PMU-only state estim...

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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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On Dispatching power systems with Significant Wind generation Using Disturbance Feedbacks

On Dispatching Power Systems with Significant Wind Generatio...

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第三十二届中国控制会议

作者： WEI Wei MEI Shengwei LIU Feng State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical EngineeringTsinghua University

ISBN: (纸本)9781479900305

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 *** 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 ***-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 *** ADF-RD methodology is applied to an hourly ahead dispatch(HAD) *** effectiveness and efficiency of the proposed ADF-RD methodology are demonstrated by numerical experiments carried on a five-bus system.

关键词： Adjustable robust optimization affine disturbance feedback power system dispatch uncertainty wind power

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Modeling and analysis of unit commitment considering RCAES system

Modeling and analysis of unit commitment considering RCAES s...

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Chinese control Conference (CCC)

作者： Bin Liu Laijun Chen Yu Zhang Chen Fang Shengwei Mei Yuan Zhou State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing Beijing CN Electric Power Research Institute State Grid Shanghai Municipal Electric Power Company China Key Laboratory of Cryogenics Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing CN

Regenerative compressed air energy storage (RCAES) system is a practical and efficient solution to large-scale integration of renewable energy problems faced by power systems currently. Appropriately modeling of RCAES system is critical to its practical application, whereas research in this area has been very limited. According to the energy storage and transformation process, a concise model of RCAES system applicable to power scheduling field is proposed. Then, a unit commitment model with RCAES system is formulated as a MILP problem which can be accurately solved with high computation efficiency by CPLEX. A modified IEEE 39 bus system is used to study the impacts of parameters of RCAES system on unit commitment and the effectiveness of the proposed model is then validated. Furthermore, the proposed model can also be employed to optimize key parameters of RCAES system, e.g. efficiency and capacity of each part in an integrated way.

关键词： Energy storage Heating Computational modeling Wind power generation power grids Schedules

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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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Analysis and simulation research on cascading trips of multiple wind farms

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Dianwang Jishu/power System Technology 2014年第6期38卷 1425-1431页

作者： Xu, Fengda Guo, Qinglai Sun, Hongbin Zhang, Boming Wang, Bin Li, Zhengshuo Ding, Tao Jia, Lin Xu, Xiaofei State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China North China Grid Company Limited Xuanwu District Beijing 100053 China

A simulation based analysis is proposed to find out the most relative factors during the cascading process, which is significant to support the future voltage control schemes for wind integration region. A hierarchical distributed simulation platform is built, which contains both the transmission and wind farms' distribution grid. In this way both the coupling among wind farms and the detailed characteristics of device level can be considered. By simulating shunt capacitors, wind turbine generators and static var compensators (SVCs) under different control mode, the different impact to cascading trips process are analyzed. With the simulation, it is found that centralized integrated wind farms are so closed-coupled that variations of active or reactive power in one wind farm would cause great changes of voltages in wind farms nearby. Researching results also indicate that coordination of various reactive power implements is essential to system voltage safety.

关键词： Wind farm

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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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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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