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A voltage control strategy for preventing cascading trips of large-scale wind power in centralized area

Dianli Xitong Zidonghua/Automation of Electric power systems 2014年第11期38卷 7-12页

作者： Ding, Tao Guo, Qinglai Sun, Hongbin Xu, Fengda Xu, Xiaofei Jia, Lin Department of Electrical Engineering Tsinghua University Beijing China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing China North China Power Grid Co. Ltd. Beijing China

Cascading wind farm trips have brought new challenge to the wind power integration. Traditional reactive power optimization can achieve a desirable control result, but voltage security violation usually happens after N-1 contingency because of the redistribution of power flow and slow response by the reactive power compensator. Therefore, a reactive power optimization model is set up with security constraints, aiming to maintain the voltage within the security region under both normal condition and N-1 contingency. Besides, Benders decomposition method is employed to solve the complex model, dividing into one master and some slave problems. Iterative method is used between master and slave problems to obtain the optimal solution. Practical power grid with nine wind farms is tested, and the comparison of security constrained optimal power flow (SCOPF) and traditional optimal power plow shows that the SCOPF has better effect, which can maintain the voltage security under both normal condition and N-1 contingency. So it is an effective method to prevent cascading faults of multiple wind farms integrated into power grid. Finally, the relationship of maximum wind power integration, wind farm capacity and reactive power capacity of wind units is fully studied to provide certain help for the operation of wind farm. ©2014 state Grid Electric power Research Institute Press

关键词： Wind farm

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Technology and application of online partial discharge monitoring for power equipments 5

Technology and application of online partial discharge monit...

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5th International Conference on Reliability of Electrical Products and Electrical Contacts, ICREPEC 2014

作者： Gao, Shengyou Gui, Junfeng Dept. of Elec. Eng. Tsinghua University State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Beijing100084 China School of Electrical Engineering Beijing Jiaotong University Beijing100044 China

ISBN: (纸本)9789881532329

Online partial discharge monitoring for power equipments is useful to improve the capacity of the power supply. Main technology for PD testing is introduced in this paper. Advantages and disadvantages of pulse current, UHF, ultrasonic and TEV method are present. The status quo of online PD monitoring is analyzed, and the detection effect of online PD monitoring is not good. Opinions to improve the effect are given. They include built-in sensors, increasing sensitivity and sample rate. Analysis of the state quo indicates that the relevant technical standards and specifications must be revised to improve the normalization and standardization.

关键词： Partial discharges

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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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RF energy harvesting with broadband antenna

RF energy harvesting with broadband antenna

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

作者： Xudong Wang Zhengming Zhao Guanhua Chen Fanbo He State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing P. R. China

A broadband RF energy harvesting system over a frequency range of 900MHz-3GHz has been designed and tested. Some detailed issues of RF design have been studied and tested to improve the efficiency of the rectifier. Test results show that as low as -20dBm RF power can be harvested by this system. The series and parallel connections of two RF energy harvesting systems have also been studied, compared with the single system.

关键词： Radio frequency Broadband antennas Rectifiers Energy harvesting Broadband communication Antenna measurements

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Impact of inertia control of DFIG wind turbines on system small-signal stability

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Dianli Xitong Zidonghua/Automation of Electric power systems 2014年第23期38卷 6-12页

作者： Chen, Runze Wu, Wenchuan Sun, Hongbin Lan, Haibo Liu, Haitao Liu, Xiaomin Department of Electrical Engineering Tsinghua University Beijing100084 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing100084 China State Grid Jibei Electric Power Company Limited Beijing100053 China

The impact of inertia control of doubly-fed induction generator (DFIG) wind turbines on the small-signal stability of systems is studied. Firstly, the principle of DFIG wind turbines offering inertia responses is discussed, followed by the introduction of two approaches of inertia control. Then, possible influences of two control schemes on system small-signal stability are analyzed. Finally, on the basis of simulation, the modal analysis method is adopted to analyze the influence characteristics of different control strategies and various control parameters on system small-signal stability. Analysis results show that inertia control may have an appreciable impact on the system small-signal stability. Therefore, security constraints of small-signal stability should be carefully considered when designing the control strategy and parameters. ©, 2014 state Grid Electric power Research Institute Press.

关键词： Wind turbines

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Research on HVIGBT transient mixture model and parameter extraction method

Research on HVIGBT transient mixture model and parameter ext...

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

作者： Gaohui Feng Zhengming Zhao Liqiang Yuan Shiqi Ji Jincheng Zhao Mechanical Engineering College Shijiazhuang China State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

This paper presents a kind of HVIGBT transient mixture model and corresponding parameter extraction method. The HVIGBT model can divide into MOSFET and BJT two parts. The two models are formed respectively according to HVIGBT work principle, in addition, the carrier transport equations have been simplified for avoiding Kirk effect in BJT model. The transient model is realized in PSIM software in the paper. Extraction methods, which include estimation by empirical values, calculation by testing waveforms and comparison with same type models, are adopted in extracting model parameters. Through comparing testing and simulation waveforms, the model's simulation accuracy is proved.

关键词： Mathematical model Testing Semiconductor device modeling Transient analysis Insulated gate bipolar transistors Integrated circuit modeling Capacitance

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An adaptive wind power smoothing method with energy storage system

An adaptive wind power smoothing method with energy storage ...

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IEEE General Meeting power& Energy Society

作者： Hanchen Xu Can Wang Chao Lu Zhigang Lu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China Electric Power Research Institute of China Southern Power Grid Guangzhou China

The random and intermittent nature of wind power (WP) makes the integration of large-scale wind farms into power system problematic. The energy storage system (ESS) is an effective means to smooth the WP. This paper presents a novel Kalman filter (KF) based adaptive wind power smoothing method to determine the power output of an ESS. ESS capacity can be significantly reduced by adjusting the parameters of KF adaptively according to the WP fluctuation. Meanwhile, a fuzzy logic controller is introduced to manage the remained energy level (REL) of the ESS. By considering the current WP fluctuation, the REL and the power output of the ESS together in the controller, the REL can be successfully managed to a reasonable range without deteriorating the WP fluctuation. A test case based on data from an actual wind farm validated the effectiveness of the proposed method.

关键词： Fluctuations Wind power generation Energy storage Wind farms Kalman filters Fuzzy logic Smoothing methods

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Low-carbon power grid index system and evaluation method

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Dianli Xitong Zidonghua/Automation of Electric power systems 2014年第17期38卷 157-162页

作者： Sun, Yanlong Kang, Chongqing Chen, Songsong Meng, Junxia Lu, Chang Luo, Jinshan Department of Electrical Engineering Tsinghua University Beijing100084 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing100084 China China Electric Power Research Institute Beijing100192 China State Power Economic Research Institute Beijing102209 China

The importance of establishment of the low-carbon power grid index system and its comprehensive evaluation model for the development of the low-carbon power grid is firstly discussed. Based on the concept of life cycle analysis, a comprehensive low-carbon power grid index system and a more refined central index system are designed in consideration of different aspects of coverage, and the meaning of each index explicated in detail. Furthermore, a comprehensive evaluation method is designed for the quantization of the low-carbon developing condition of different power grids. Finally, an example analysis is conducted based on the statistical data of some domestic power grids to demonstrate the actual application of the evaluation model. © 2014 state Grid Electric power Research Institute Press

关键词： Electric power transmission networks

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Automatic discovery method of power system critical flowgates considering multiple security themes in power grid

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Dianwang Jishu/power System Technology 2014年第5期38卷 1169-1174页

作者： Zhao, Feng Sun, Hongbin Tan, Yan Guo, Qinglai Guo, Wenxin State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China Guangdong Electric Power Control Center Guangzhou 510600 Guangdong Province China

Based on summarizing the features of selecting critical flowgates in actual power grid, an automatic discovery method of power system critical flowgates considering multiple security themes in power grid is proposed. Based on topological structure of power grid and online power flow, the electric partitioning of power grid is performed and different types of critical flowgates are selected according to different security theme: according to the demand on transient security theme the long-distance transmission channel composed by tie line between electric partitionings is chosen as critical flowgate;according to the demand on thermal stability theme, the transmission channel composed of high voltage transmission lines with high transmission capacity, which interact each other obviously, is chosen as critical flowgate;according to the thermal stability at load side the transmission channel composed of low voltage transmission lines with higher transmission capacity, which interact each other obviously, is chosen as critical flowgate. Taking Guangdong power Grid in china as testing example, test results show that the proposed method considers common security themes in power grid accurately and different kinds of critical flowgates can be attained;the obtained critical flowgates not only conform to a posteriori critical flowgate given by experts in the field of power grid operation, and new critical flowgates can be discovered, besides, the discovery results are reasonable and creditable.

关键词： Thermodynamic stability

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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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