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2010 International Conference on Electrical Machines and systems, ICEMS2010

作者： Yao, Siwang Wang, Weijian Luo, Ling Gui, Lin Qiu, Arui State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing China

Loss of excitation (LOE) is a common fault found in the generators. The most widely applied method for detecting a generator loss of excitation is the use of impedance relays to sense the variation of impedance as viewed from the generator terminals [1]. However, compared with China's approachs, in the setting of impedance circle, the IEEE's allow the circle to extend along the negative X axis, meanwhile, in the latest edition of the "IEEE Guide for AC Generator Protection", the circle is further extended, reaching to -1.25X_d.We think this is adverse, to prove our point, the paper ,basing on the IEEE 9 bus model and using computer digital simulation, have studied various loss-of-excitation conditions and some system disturbances that may lead to the relay false tripping. simulation results indicate that the IEEE's method not only can't accelerate the operation effectively, but also will increase the chances of maloperation.

关键词： Impedance Generators Relays Analytical models power system stability Reactive power

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High impedance fault detection on distribution systems with harmonic interference in wind farms 13

High impedance fault detection on distribution systems with ...

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13th International Conference on Development in power system Protection 2016, DPSP 2016

作者： Ni, Jiang Wang, Bin Dong, Xinzhou State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing100084 China

ISBN: (纸本)9781785618260

High impedance faults (HIFs) are easy to occur in collective feeders in wind farms and may cause the cascading of wind generators tripping. This kind of faults is difficult to be detected by traditional relay or fuse due to the limited fault current values and the situation is worse in wind farms. The mostly adopted HIF detection algorithms are based on the 3rd harmonic characteristic of the fault zero-sequence currents, whereas these 3rd harmonics are very easy to be polluted by wind power back-to-back converters. To solve this problem, the typical HIF arc flash based on Mayr's arc model is first built, and the typical fault waveforms of HIF in wind farm are presented. Then the characteristics of high impedance faults are analysed to distinguish the occurrence of HIF from other harmonic interference. After that, the performance of the traditional harmonic based HIF detection algorithm is discussed, and a novel detection algorithm is presented to prevent harmonic interference influence in wind farms.

关键词： Electric utilities

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Common-mode voltage reduction for three-phase-to-four-leg direct matrix converter with a novel control strategy

Common-mode voltage reduction for three-phase-to-four-leg di...

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2017 IEEE Transportation Electrification Conference and Expo, Asia-Pacific, ITEC Asia-Pacific 2017

作者： Huang, Songtao Guo, Yougui Xu, Lie Li, Yongdong School of Information and Engineering Xiangtan University Xiangtan China State Key Lab of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing China

ISBN: (纸本)9781538628942

Due to the three-phase-to-three-leg direct matrix converter (3 × 3 MC) cannot be achieved with unbalanced load, then the three-phase-to-four-leg direct matrix converter (3 × 4 MC) is introduced. A novel modulation strategy is proposed to ensure the capability of 3 × 4 MC with arbitrary loads, which is development by using fixed voltage vectors and one zero vector. Considering the harm of common-mode voltage (CMV), the switch configurations of the proposed modulation strategy are improved. Selecting the reasonable zero vectors by the subsection partition, which is capable of reducing the CMV to half of the input source voltage produced by the zero vectors, and the ability of 3 × 4 MC with arbitrary load is also realized. The feasibility of the proposed strategy is verified by the accompanying simulation results. © 2017 IEEE.

关键词： Matrix converters

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Design Optimization of Ferrite Rings for VFTO Mitigation

Design Optimization of Ferrite Rings for VFTO Mitigation

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作者： He, Jiaxi Guan, Yonggang Liu, Weidong Chen, Weijiang Li, Zhibing The 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 are made 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： Damping

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power Output Monitoring and Anomaly Identification of Photovoltaic systems Using Graphical Modeling 4

Power Output Monitoring and Anomaly Identification of Photov...

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4th International Conference on Sensing, Diagnostics, Prognostics, and control, SDPC 2020

作者： Chen, Yonghua Zhang, Xiaochen Liu, Gang Wu, Rui Liu, Chao Jiang, Dongxiang Nari Technology Co. Ltd Nanjing211106 China Tsinghua University Department of Energy and Power Engineering Beijing100084 China Tsinghua University State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Energy and Power Engineering Beijing100084 China

ISBN: (纸本)9781728170503

Photovoltaic cells are being increasingly installed worldwide as a type of important renewable resource for power generation. Among the installed photovoltaic systems, data are collected from the control and monitoring system, and the anomaly detection researches are mostly based on the individual photovoltaic cells and the systematic behavior in a group of photovoltaic systems is not well studied. Based on the assumption that the photovoltaic cells installed in the same location are with very close solar radiation, the power output of each subsystem is considered in this work for monitoring the operating status of the subsystem and identifying the anomalous subsystem, where spatiotemporal pattern network, a probabilistic graphical modeling approach, is applied. The results show that the presented framework is able to detect the anomaly and locate the anomalous subsystem. © 2020 IEEE.

关键词： Condition monitoring

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Virtual flux based direct power control for three-level PWM rectifier 17

Virtual flux based direct power control for three-level PWM ...

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2014 17th International Conference on Electrical Machines and systems, ICEMS 2014

作者： Yingchao, Zhang Liping, Jin Yongchang, Zhang Ting, Lu Zhengming, Zhao Key Lab. of Special Power Supply of PLA Chongqing Communication Institute China North China University of Technology Power Electronics and Motor Drive Engineering Research Center China State Key Lab. of Control and Simulation of Power System and Generation Equipments Tsinghua University China

ISBN: (纸本)9781479951611

This paper presents a new control strategy for three-level neutral point clamped (NPC) pulse width modulated (PWM) rectifier without power source voltage sensors. The relationship between instantaneous power and voltage vectors is derived mathematically. Virtual flux is estimated and used to calculate the phase of the power source voltage and instantaneous power. On these bases, a direct power control (DPC) scheme for three-level PWM rectifier is presented. An optimal switching table is established, vector switching scheme and balance strategy for the neutral point potential are discussed. Variable switching frequency and dynamic process of the startup are also analyzed. Experimental results have verified the theoretical approach and the three-level PWM rectifier with proposed DPC based on virtual flux exhibits several advantages, such as simple algorithm, low costs and excellent dynamic performance. © 2014 IEEE.

关键词： Electric rectifiers

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Wide-area Monitoring and Analysis of Wide-band Oscillation in New-type power systems 10

Wide-area Monitoring and Analysis of Wide-band Oscillation i...

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10th China International Conference on Electricity Distribution, CICED 2022

作者： Ma, Ningning Xie, Xiaorong Sun, Yiqian Zhang, Yanjun Li, Yongguang Liu, Pengyin State Key Lab of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China State Grid Xinjiang Electric Power Company Xinjiang Uygur Autonomous Region Urumchi830063 China

ISBN: (数字)9781665452687

ISBN: (纸本)9781665452687

The wide-band oscillation resulting from the interaction between power electronics and the power grid is increasingly evident to the power system. It is necessary to monitor the dynamic behavior of the wide-band oscillation. However, the existing phasor measurement unit (PMU) and the corresponding wide-area measurement system (WAMS) can hardly capture wide-band phasors. To get a better view of wide-band oscillation, a measurement method to capture wide-band phasors is proposed in this paper, as well as a frame of a corresponding wide-area monitoring system for wide-band oscillation (WOMS) is constructed. The prototype of the wide-band phasor measurement unit (WPMU)-based on this measurement method is developed. The essential software and hardware of the WPMU are elaborated. The steady tests and dynamic tests are executed to verify the capability of the WPMU. The results indicate that WPMU and WOMS are highly effective in analyzing wide-band oscillation. © 2022 IEEE.

关键词： Phasor measurement units

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Fault location method for high-voltage direct current transmission line using incident current travelling waves

Fault location method for high-voltage direct current transm...

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作者： Wang, Bin Yang, Lin Dong, Xinzhou Department of Electrical Engineering State Key Lab of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing10084 China

The reflection coefficient of the travelling wave is different with different frequencies because of the inductance and capacitive elements on the boundary of the DC transmission line, which leads to the oscillation of the travelling wave. It is difficult to obtain the wave head's arrival time accurately using travelling wave method to locate fault because of the oscillation. The current travelling wave is the superposition of the incident current travelling wave and the reflected current travelling wave. There is no oscillation in the incident wave. Therefore, a method using incident current wave for fault location is proposed here. The initial current travelling wave and the transmission line boundary function are used to calculate the incident current travelling wave, and the incident wave is used to locate fault. The Prony decomposition algorithm is used to identify boundary function using the initial current travelling wave generated in specific fault condition. PSCAD simulation shows that the influence of oscillations of travelling wave can be eliminated by using incident current wave to locate faults, and the accuracy of fault location is improved. © Institution of Engineering and Technology. All rights reserved.

关键词： Electric lines

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Shaft crack analysis and diagnosis for the 600mw steam turbine generator

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key Engineering Materials 2009年 413-414卷 591-598页

作者： Dongxiang, Jiang Liangyou, Hong Qian, Huang State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Thermal Engineering Tsinghua University Beijing 100084 China

Abstract: In order to find the cause of the shaft crack appeared in a 600MW steam turbine generator, several measurements are taken. The shaft assembly consists of three parts: shrink-fitted coupling, shaft and key which are used to transfer torque between coupling and shaft. First, the natural frequency of the shaft system is calculated. The result shows that the vibration signal contains the frequency nears the second natural frequency of the steam turbine shaft system. Second, stress field near the damaged coupling and shaft is analyzed using finite element method. The torque under different operation condition is calculated before stress analysis and applied to the shaft assembly, then. And, local stress concentrations position calculated is proved to be coincident with the place crack initiation. Finally, the cause of the fault is analyzed: at least three causes have found to be having something to do with the crack fault.

关键词： Finite element method

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Fault classification rules extraction of wind turbine based on C4.5 algorithm

Fault classification rules extraction of wind turbine based ...

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Prognostics and Health Management Solutions Conference - PHM: Driving Efficient Operations and Maintenance, MFPT 2012

作者： Chen, Jie Jiang, Dongxiang Yang, Wenguang Deng, Xiaowen Feng, Yongxin State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing 100084 China Electric Power Institute Guangdong Grid Company Guangzhou 510080 China

Distinguishing fault types in early time can prevent wind turbines from breaking down. C4.5 algorithm, different from ID3 algorithm, which can deal with continuous parameters, should be a choice fault diagnosis method of wind turbine. This paper strives to extract fault classification rules of wind turbine based on data collected from a small wind turbine in laboratory using C4.5 decision tree and validate the rules extracted using another set of data. According to the solution, fault types such as mass imbalance of rotor, aero-dynamic asymmetry, yaw misalignment, gearbox and bearing fault and so on can be distinguished by the method presented in this paper.

关键词： Wind turbines

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