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International Conference on Electrical Machines and systems (ICEMS)

作者： Liqiang Yuan Hualong Yu Xuesong Wang Zhengming Zhao Ting Lu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

The large-size planar DC bus bar is widely used in high power converters, whose stray parameters are significantly affected the converter reliability and performance. Taking the example of an actual 315kW/400V inverter, the design, simulation and analysis for its bus bar stray parameters is described in detailed. Being different from the conventional method that considers the bus bar conductor as an entirety, an improved method is proposed in this paper, which separates the bus bar into several segments and evaluates the influence of stray parameters in each segment to the power semiconductor devices respectively. Therefore, this improved method can provide support for the more accurate and effective design and optimization of bus bar. In addition, two different structure of bus bar are implemented in the actual inverter, the comparison and analysis of experiment results for both structures proves the validity of the proposed method.

关键词： Inverters Insulated gate bipolar transistors Equivalent circuits Integrated circuit modeling Inductance Conductors Snubbers

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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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Influence of the Structure Dimension of GIS on the Partial Discharge

Influence of the Structure Dimension of GIS on the Partial D...

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IEEE International Conference on Condition Monitoring and Diagnosis

作者： Dengwei Ding Wensheng Gao Weidong Liu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University

ISBN: (纸本)9781467310192

Partial discharge (PD) monitoring plays an important role in the online maintenance of the gas insulated switchgear (GIS). In recent years, the ultra high frequency (UHF) method for PD detection arouses great interest of many researchers because of the high sensitivity and anti-interference capability. The coupling of UHF signal is the key to the detection of partial discharge in GIS. The structure size of GIS has great impacts on the PD signal, because the cutoff frequency of the high order mode of the electromagnetic (EM) wave depends on the diameters of the inner conductor and enclosure. In this paper, the influence of the inner conductor diameter is investigated by varying the center conductor size. The inner coupler is adopted to receive the partial discharge signal, and two types of PD sources are tested in the experiment. Firstly, the amplitude and the duration of the time domain signal and the frequency spectrum are focused, and their variations with the size of inner conductor are analyzed. Besides that, In order to research the changes of the TEM mode component and the high order mode component, low pass (LP), band pass (BP) and high pass (HP) filters are applied to process the PD signals, and the cumulative energy rates are calculated to indicate the energy distribution. In addition, a simulation using the FDTD method is conducted for comparison with the experimental results, and it indicates that the results of experiment and simulation are almost consistent.

关键词： Partial discharge Ultra high frequency Structure size of GIS Frequency spectrum The cumulative energy rate FDTD

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power Losses in Two- and Three-Level Three Phase Photovoltaic Inverters Equipped with IGBTs

Power Losses in Two- and Three-Level Three Phase Photovoltai...

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International Conference on Electrical Machines and systems

作者： Zhiping Chen Liqiang Yuan Zhengming Zhao Xiaoying Sun State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University

ISBN: (纸本)9781467323277

To increase efficiency is an essential target in photovoltaic (PV) power generation system. The losses of the whole system consist of several parts. This paper focuses on the losses of the hard-switching devices. An improved method to calculate the device losses is proposed. And influences of different factors like DC link voltage, input power, switching frequency and power factor on the losses are considered. Then this paper compares the losses of conventional two-level inverter and of diode-clamped three-level inverter to provide the evaluation of power losses under different working conditions. This is helpful to design and optimize a certain PV inverter. Calculating results based on an actual three phase 10kW PV inverter are presented.

关键词： Loss-calculation IGBT Three-level Photovoltaic

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Research on shielding failure of UHVDC based on leader progression model

Research on shielding failure of UHVDC based on leader progr...

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2012 31st International Conference on Lightning Protection, ICLP 2012

作者： Geng, Yinan Zhuang, Chijie Institute of Nuclear and New Energy Technology Tsinghua University Beijing China State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China

ISBN: (纸本)9781467318976

Shielding failure is one of key problems of UHV transmission lines. Considering the high operating voltage and high tower of UHV transmission lines, the inception criterion of upward leader is proposed in this paper. The process of shielding failure is simulated by the method based on leader progression model and shielding failure rate is calculated. This method is verified by comparing the calculation results with the operated data of UHV transmission lines in Japan. The shielding failure characteristics of UHVDC transmission lines in China under different terrain conditions are researched. © 2012 IEEE.

关键词： Electric lines

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A cooperative game theory based multi-objective reactive voltage optimization model and its solution

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Dianli Xitong Zidonghua/Automation of Electric power systems 2012年第18期36卷 116-121+133页

作者： Zhang, Mingye Guo, Qinglai Sun, Hongbin Zhang, Boming Wu, Wenchuan Wang, Bin State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing 100084 China

To coordinately consider the economy and security of the system during reactive voltage control, a multi-objective reactive power optimization model is proposed. Apart from the conventional economic objective, the new model has the system static security added to the multi-objective to seek their optimization simultaneously. And the solution for the model is proposed based on the cooperative game theory. As two players of the game, the economy side and the security side decide on their game strategies alternately until equilibrium is attained. Tests on a 2-bus system and IEEE 9-bus system demonstrate the feasibility and advantages of the model along with the proposed method. © 2012 state Grid Electric power Research Institute Press.

关键词： Multiobjective optimization

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X-ray backlighting of wire expansion and plasma merging of z-pinch load with 10-40kA/wire

X-ray backlighting of wire expansion and plasma merging of z...

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IEEE International Conference on Plasma Science (ICOPS)

作者： Xinlei Zhu Xiaobing Zou Ran Zhang Shen Zhao Haiyun Luo Xinxin Wang Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

It is well known that the evolution of wire array z-pinch load can be divided into several phases: wire explosion, inter-wire plasma merging, implosion and stagnation. In this paper, experiments with x-pinch backlighter to study the initial wire explosion and inter-wire plasma merging were performed on the pulsed power generator PPG-I at Tsinghua University. An x-pinch (13-25μm Mo and 5-18μm Wu wires) used as soft x-ray source was installed in the centre between the output main electrodes of PPG-I generator, and the object z-pinch load was installed in one of the return current posts. The object z-pinch load consists of 2-4 tungsten wires of 5-18 μm diameter, 12 mm long, and 2 mm spacing between wires. The evolution images of wire explosion and inter-wire plasma merging were recorded with high resolution x-ray film, which was covered with a mass step-wedge filter to calibrate the mass density distribution of wire explosion and inter-wire merging plasma. Based on extensive discharge tests, the time sequence of backlighting images of z-pinches was obtained. In the paper, we also discussed how to determine the interface between high-density wire core and low-density surrounding plasma, and then presented the expansion rates of high density wire core and the mass density distribution of inter-wire plasma under different z-pinch current.

关键词： Wires Plasmas Merging Explosions Educational institutions Generators Radio access networks

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Application of Fuzzy-Rough Set theory and improved SMO algorithm in aircraft engine vibration fault diagnosis

Application of Fuzzy-Rough Set theory and improved SMO algor...

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Prognostics and system Health Management Conference (PHM)

作者： Hongzhi Xu Dongxiang Jiang Lei Liang State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Thermal Engineering Tsinghua University Beijing China

ISBN: (纸本)9781457719097

Aircraft engine is an important component of the airplane, which lifespan and reliability have directly influence to flight safety. Vibration analysis is an effective fault diagnosis method for airplane's mechanical construction fault. Several typical vibration faults have drawn from the vibration analysis on the basis of fault mechanism in aircraft engine, and the standard vibration fault-symptom (Fuzzy Membership) relationship table have constructed based on Fuzzy Mathematic theory in this paper. Sample data are simulated on the basis of this table. Sequential Minimal Optimization (SMO) is a fast algorithm for training Support Vector Machines (SVM). The simulated result showed a great improvement on computation efficiency by selecting double threshold parameter for SMO algorithm than single threshold. In order to examine the algorithm's effect applying in the aircraft engine fault diagnosis, Radial Basis Function (RBF) Neural Network, C4.5 Decision Tree, SVM (chunking), Platt's SMO and Improved SMO algorithm are applied to the training data and test data. It is shown that the Improved SMO algorithm displayed superior comprehensive performance. Finally, the vibration fault feature is reduced based on Fuzzy-Rough Sets theory. The research shows that the Improved SMO algorithm is quicker than other algorithm in aircraft engine fault diagnosis with the reduced feature attributes, and its accuracy is high.

关键词： Vibrations Accuracy Safety Aircraft Classification algorithms Support vector machines

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Design and implementation of photovoltaic lighting system with high luminous efficacy LEDs

Design and implementation of photovoltaic lighting system wi...

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International Conference on power Electronics and Motion control (IPEMC)

作者： Liqiang Yuan Zhiping Chen Xianlai Hu Junjie Ge Zhengming Zhao State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9781457720857

With the background park lighting application, and based on the characteristics of advanced devices in the system, this paper studies the photovoltaic (PV) light emitted diode (LED) lighting system in three main aspects, which are the design of the whole system, hybrid control strategy combining the maximum power point tracing (MPPT, for PV panels) with the energy management(for battery), and LED driving and dimming. Taking the example of an actual 50W high luminous efficacy LED system, the design, implantation and experiments are described in detail. In addition, the long-term measurement results in real environment are illustrated in this paper.

关键词： Batteries LED lamps Switches Pulse width modulation Discharges (electric)

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Study on coordinated voltage control strategy of DFIG wind farm

Study on coordinated voltage control strategy of DFIG wind f...

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IEEE General Meeting power& Energy Society

作者： Hui-fen Chen Ying Qiao Zong-xiang Lu State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing China

ISBN: (纸本)9781467327275

This paper studies a combined voltage control strategy that coordinates a variety of reactive compensative devices such as fixed capacitors, SVC/Statcom, DFIGs (Double-fed Induction Generators) to improve voltage control performance in multi-time scale. Based on the control restraints and response performance, three modes - planning mode, online mode and emergency mode - are optimized for lower cost and higher security margin, respectively. The paper introduces wind power forecast into wind farm voltage planning for slow, discrete devices such as fixed capacitor, while engages devices that are capable of instantaneous response to smooth quick, small voltage fluctuation and track online voltage reference from dispatching centre. The feasibility, effectiveness and superiority of the proposed control strategy are verified with simulation.

关键词： Wind farms Reactive power Automatic voltage control Security Capacitors Static VAr compensators

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