检索结果-内蒙古大学图书馆

作者： Yu, Zhanqing Li, Qian Zeng, Rong He, Jinliang Zhang, Yong Li, Zhizhao Zhuang, Chijie Liao, Yongli State Key Lab of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China Department of Mathematical Sciences Tsinghua University Beijing 100084 China Electric Power Research Institute China Southern Power Grid Guangzhou China

Lightning is the major cause of interruptions in power transmission lines. Ultra-high voltage (UHV) AC transmission line has been put into operation in China. Due to the large tower height up to 90 m and the high operation voltage up to 1000 kV, the shielding failure probability increase obviously. Nowadays the leader progression model is an advanced method to evaluate the shielding failure probability of transmission lines. The surface electric field is the key issue for lightning failure analyzing, because the upward leader inception mainly depends on the surface electric field. In this paper, the lightning leader model is introduced. A charge simulation method based piecewise linear function is adopted to analyze the surface electric field on phase conductors and ground wires. The influence factors, such as operation voltage, lightning peak current, lightning down leader position, protection angle, on surface electric field were analyzed. © 2012 Elsevier B.V. All rights reserved.

关键词： Electric lines

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A non-iterative affine arithmetic methodology for interval power flow analysis of transmission network

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2013年第19期33卷 76-83页

作者： Ding, Tao Bo, Rui Guo, Qinglai 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 Beijing 100084 China Midwest ISO St. Paul 55108 United States

power flow exhibits uncertainty when power injections randomly fluctuate. The variables of power flow problem are correlated through the constraints set forth by power flow equations. Affine arithmetic can effectively overcome the correlation and therefore is adopted in this paper. In order to improve the computational efficiency, non-iterative method was proposed, which can transform the interval power flow problem into optimization problems. Linear programming, nonlinear programming and quadratic programming optimization models were established to obtain intervals of nodal voltage magnitude, phase angle, branch active power and reactive power, respectively. simulation results of 9-bus and 57-bus test system show that the power flow interval obtained by the proposed algorithm is nearly the same as that by iterative algorithms, whereas the branch power flow results are better. The interval power flow problem can be solved quickly and efficiently with time complexity approximately O(m3). As well, parallel computing can be implemented to achieve promising improvement in computation time. © 2013 Chinese Society for Electrical Engineering.

关键词： Quadratic programming

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Ordinal optimization theory based planning for clustered wind farms considering the capacity credit

Ordinal optimization theory based planning for clustered win...

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第13届全国博士生学术年会——新能源专题

作者： Yi Wang Chongqing Kang Ning Zhang Qianyao Xu Rui Shi Hui Li Jinyu Xiao Zhidong Wang Shuai Wang State Key Lab of Control and Simulation of Power Systems and Generation Equipment (Department of Ele State Power Economic Research Institute ChangpingDistrictBeijing 102209China

Wind power planning aims at optimally locating and sizing wind ***,it tends to choose the wind farms with the richest wind resource in order to maximize the energy ***, the capacity benefit of wind power should also be considered in the large-scale clustered wind farm planning since the correlation among the wind farms performs an obvious influence on the capacity benefit brought by the whole wind *** paper proposes a planning model considering both energy and capacity benefit of the wind ***, the capacity benefit is evaluated by wind power capacity *** Ordinal Optimization (OO) theory, capable of handling problems with non-analytical forms, is applied to address the *** verify its feasibility and advantages, the proposed model is compared with widely-used genetic algorithm (GA) via a modified IEEE RTS-79 system and a real world case of Ningxia, *** results show that the diversity of wind farm enhances the capacity credit of wind power.

关键词： Capacity credit Correlation Ordinal Optimization Planning Wind power

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Switching Current Imbalance Mitigation for Paralleled SiC MOSFETs Using Common-mode Choke in Gate Loop

Switching Current Imbalance Mitigation for Paralleled SiC MO...

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IEEE Energy Conversion Congress and Exposition

作者： Jiye Liu Zedong Zheng State Key Lab of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing China

ISBN: (数字)9781728158266

ISBN: (纸本)9781728158273

Paralleling SiC MOSFETs is a popular way to increase the current capacity. However, due to asymmetric layout, device parameter mismatch and other factors, imbalanced switching or dynamic current is observed among the paralleled switches in multi-device paralleling application which results in unequal switching loss, challenging the security and reliability of the system. In this paper, a common-mode choke in the gate loop is proposed and analyzed to suppress the imbalanced switching current induced by asymmetric layout in a half-bridge configuration with a Kelvin-source connection. The mechanism of the proposed method is comprehensively investigated to show that though the common-mode choke is placed in the gate loop, it can also mitigate the imbalanced current caused by asymmetric power loop. And it also shows that only the leakage inductance of the choke is seen in the gate loop and thus the switching speed is not expected to be influenced. The proposed method can be easily extended to multi-device paralleling application and the switching transients is hardly influenced by the common-mode choke. simulation and experimental results are presented to verify the proposed method.

关键词： Inductance MOSFET Silicon carbide Switches Logic gates Inductors Transient analysis

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Implementation of non-communication protection of double circuit line systems based on integrated protection platform

Implementation of non-communication protection of double cir...

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

作者： Hu, Xi Dong, Xinzhou Wang, Bin Shi, Shenxing Liu, Kun Li, Youyi State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China Research Ltd. Chaoyang District Beijing 100016 China

ISBN: (纸本)9781424496198

The implementation of non-communication protection of double circuit line systems based on two independent relays has disadvantages like information shareless,complex connection and lack of economic. This paper researched the implementation of non-communication protection of double circuit line systems based on one relay - the integrated protection platform. Hardware structure of the integrated protection platform is described, and software flow of non-communication protection of double circuit line systems which implemented on the integrated protection platform is also described. Large number of RTDS experiments proved that, according to various asymmetrical fault and symmetrical fault, this protection scheme has reliable and sensitive action performance. It is proved that the implement non-communication protection of double circuit line systems based on the intergrated protection platform is feasible. © 2011 IEEE.

关键词： Timing circuits

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Study on new leading-out mode of neutral points of large-sized turbo-generator

Study on new leading-out mode of neutral points of large-siz...

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International Conference on Electrical Machines and systems (ICEMS)

作者： L. Gui X.H. Wang Y.G. Sun W.J. Wang Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China

To supply overall protection for large-sized turbo-generator, a new approach about leading-out mode of neutral points and disposition of protection schemes is firstly presented in this paper. To check up the sensitivity of the new protection scheme, two turbo-generators with 300 MW are simulated using the multi-loop method. simulation results indicate the performance of the new protection scheme is much better than that of the traditional protection. Without adding hardware investment, the new leading-out mode is agreed by electrical machine designers.

关键词： power system protection Stator windings Current transformers power system simulation power generation Sun laboratories power system control power systems Hardware

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Research on the prediction-model of the surface-temperature of large oil-immersed power transformer

Research on the prediction-model of the surface-temperature ...

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International Conference on Electrical Machines and systems (ICEMS)

作者： H.Y. Wang P.S. Su X.H. Wang Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China

In order to detect the abnormal temperature of large oil-immersed power transformer earlier, this paper presents a new prediction-model of surface-temperature for the transformer to predict the normal surface-temperature. And to compare the difference between the predicted value and the measured value can judge if the condition of the transformer is fit to operate. The model parameters are estimated from the field data by using the partial-least-square method, which overcomes the instability of results estimated by using the traditional least-square method. Furthermore, the appropriate amount of data for the parameter estimation was decided according to the principle of heat transfer and the characteristics of the predicted deviation, such as mean, variance and normal distribution. The prediction model is verified from the accuracy of results predicted with one year of field data.

关键词： power transformers Oil insulation Temperature sensors Predictive models Parameter estimation Heat transfer Temperature measurement Thermal resistance power system simulation Surface fitting

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Design and control of a Three-Phase Grid-Connected Photovoltaic System with Developed Maximum power Point Tracking

Design and Control of a Three-Phase Grid-Connected Photovolt...

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23rd Annual IEEE Applied power Electronics Conference and Exposition (APEC 2008), vol.2

作者： Zhou Dejia Zhao Zhengming Mohamed Eltawil Yuan Liqiang The State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

In this paper an optimum design and control of three-phase grid-connected PV system has been proposed and analyzed. Also, a developed maximum power point tracking (MPPT) controller that uses the PV array differential power to voltage (dP/dV) as an index to provide the reference voltage of maximum power point (MPP) quickly and accurately is presented. The control scheme of a three phase current-controlled space vector pulse-width modulation (SVPWM) inverter in rotating synchronous coordinate d-q with the proposed MPPT algorithm and feed-forward compensation is discussed. The PV grid-connected system controller employs multi-loop control with the filter inductor current of the inverter in the inner loop to achieve fast dynamic response and the outer loop to control dc bus voltage for MPPT. The design method provided in the paper for the controller parameters and filter proved to be very practical and effective. Both the power quality into the grid and power factor correction comply with standards IEEE 929-2000. Good agreement is obtained between simulation and experimental results which illustrated the high performance of the proposed approach.

关键词： Digital signal processor Grid-connected PWM inverter MPPT Photovoltaic (PV) system PI compensators Unity power factor

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Calculation on the thermal field of the water cooling stator of three-Gorge hydro-generator

Calculation on the thermal field of the water cooling stator...

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International Conference on Electrical Machines and systems (ICEMS)

作者： H.Y. Wang P.S. Su X.H. Wang Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China

To simplify the calculation of winding bar temperature for the condition monitoring of the water cooling stator of Three-Gorge hydro-generator, this paper calculates three of two-dimension thermal fields. Using the three fields simulates the different section along the axial direction of the generator. The total amount of heat taken away by water can be calculated by weighting the result of three fields on the total axial length of them. Four groups of thermal-fields with different outlet-water temperature are calculated by using ANSYS multi-physical software. The calculation results of temperature of measurement-point between up-layer and down-layer bars in stator are partly supported by the measurement data. And the relatively error between the heat taken by cooling-water and the heat generated by the stator bar is always less than 5%

关键词： Cooling Stator cores Stator windings Solids Bars Heat transfer power system simulation Temperature Thermal engineering Condition monitoring

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Ferro-resonance over-voltage and power frequency over-voltage on the neutrals of 220kV power transformer and corresponding protection strategy

Ferro-resonance over-voltage and power frequency over-voltag...

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作者： Yu, Hua-Peng Chen, Shui-Ming Yu, Hong-Qiao Yang, Peng-Cheng Yin, Hua Wu, Gaolin State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China Chongqing Electric Power Research Institute Chongqing 401123 China

ISBN: (纸本)9781457700668

In order to limit short-circuit current and satisfy the need of relay setting, only part of the 220kV power transformer is grounded, so on the neutrals of ungrounded transformers will appear the over-voltage. Currently the value of over-voltage on transformer neutral point and the corresponding protection strategy is based on theoretical formula, this article use the PSCAD/EMTDC software to calculate the over-voltage on the neutral point of 4 ungrounded power transformers in Chongqing 220kV power grid, the result shows that the power frequency transient over-voltage on the neutrals may reach 178kV, If the single-phase grounding fault occurs in ungrounded power system, the power frequency over-voltage on the neutrals will be more serious and rise to 138.6kV. Non-full phase operation may cause serious ferro-resonance over-voltage on the neutrals of no-load transformer, which may last for seconds and may rise to 723.7kV, causing serious threat to the transformer neutrals and line-side equipment. The article also studies the gap parameter which should be taken on the neutrals of 220kV transformers at the end. © 2010 Chinese Soc for Elec Eng.

关键词： power transformers

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