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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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Investigation of bipolar block emergency in UHVDC convertor station caused by lightning stroke

Investigation of bipolar block emergency in UHVDC convertor ...

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2012 31st International Conference on Lightning Protection, ICLP 2012

作者： Zhang, Xiao Yu, Zhanqing He, Jinliang Luo, Bin Cai, Hansheng State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China Xipeng Chen Technology Research Centre China Southern Power Grid Co. Ltd Guangzhou Guangdong Province China

ISBN: (纸本)9781467318976

It is noteworthy that bipolar block emergencies of the ±800kV UHVDC system in china happened twice within two years caused by lightning strokes. To recur and investigate the mechanism of such emergencies, lightning transient performance and relative electromagnetic interference (EMI) in the UHVDC system are investigated. Wide-band circuit models of major UHVDC equipments are set for calculation, while the lightning stroke shielding failure process and transmission corona loss are also considered during the simulation. By combining the fault records in the converter station and simulation results , possible ways of EMI into the secondary system produced by primary circuit lightning transient are analyzed. The results would help explain the cause of such bipolar block emergency and provide reference for protection methods of lightning caused EMI in UHVDC system. © 2012 IEEE.

关键词： Lightning

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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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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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Substation switching electromagnetic transient analysis using the time domain integral equation with a high order implicit scheme

Substation switching electromagnetic transient analysis usin...

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2012 IEEE International Symposium on Electromagnetic Compatibility, EMC 2012

作者： Xiang, Hongjun Chang, Sughun Zou, Jun Heng Yuan, Jians Shenderey, Sergey V. State Key Lab of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China Electrical Environment Group Korea Electrotechnology Research Institute Changwon 641600 Korea Republic of

ISBN: (纸本)9781467320610

A fast electric field integral in time domain using the uneven discretization and the implicit scheme is proposed to calculate the switching electromagnetic transient at a substation. The switching transient currents and the resultant radiated electromagnetic field are calculated. The propose d approach has the strength to model the bus system at a substation with a more complicated and realistic configuration that is difficult to simulate using the circuit-based method, because all the electromagnetic couplings within the bus system are included globally. The proposed method might be one of good candidates to predicate the EMI level at a substation. © 2012 IEEE.

关键词： Electric fields

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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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Equivalent capacity of the lower voltage ride through for wind farm from overcurrent protection in power collection lines

Equivalent capacity of the lower voltage ride through for wi...

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11th IET International Conference on Developments in power systems Protection, DPSP 2012

作者： Wang, Bin Dong, Xinzhou Bo, Zhiqian State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China Alstom Grid Stafford ST17 4LX United Kingdom

ISBN: (纸本)9781849196208

Magnitude and duration of voltage sags are the most important two factors to the Lower Voltage Ride Through (LVRT) capacity of the wind generator. Since most voltage sags are caused by the system faults, and sag durations are controlled by the tripping time of overcurrent relay in power collection lines based on the sags' magnitude. The specification of the LVRT capacity of wind generator is introduced into the operation characteristics of the relay in power collection lines. The evaluation model of equivalent LVRT capacity to overcurrent protection is proposed in paper, and the equivalent LVRT capacities from zone I and zone II relay are quantified. Improvement measures are also proposed.

关键词： Overcurrent protection

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Application and benefit analysis of substation state estimation

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Dianli Xitong Baohu yu Kongzhi/power System Protection and control 2012年第12期40卷 56-61页

作者： Li, Qing-Xin Wang, De-Xing Sun, Hong-Bin Wu, Wen-Chuan Wang, Jing Guo, Qing-Lai Zhang, Bo-Ming State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China East China Electric Power Dispatch and Control Sub-Center East China Grid Company Limited Shanghai 200002 China

A substation three-phase nonlinear state estimation method based on zero impedance branches helps to identify topology and analogy errors at substation level and accordingly enhances the control center's state estimation reliability and accuracy. Some issues during the practical implementation process of the technology are reported, such as the hardware configuration, measurement integration, the communication between substation and control center, time setting and period selection. The benefits of the proposed technology have also been analyzed. It is shown that this technology has high reliability and low burden on communication, and improves the ability of monitoring of power grids and the reliability of the real-time power network model significantly. The proposed technology is verified effective by both simulation experiments and field-site applications in East china power Grid, and is well qualified for real-time online applications, which has broad popularization and application prospects.

关键词： state estimation

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A novel hybrid-clamped four-level converter

A novel hybrid-clamped four-level converter

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Annual IEEE Conference on Applied power Electronics Conference and Exposition (APEC)

作者： Kui Wang Yongdong Li Zedong Zheng Lie Xu State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing China

A novel hybrid-clamped four-level inverter topology is proposed in this paper. Only two active switches and a floating capacitor are required as clamping devices per phase leg. The DC-link of this topology is subdivided into three parts and the voltage balancing of DC-link capacitors and floating capacitors can be achieved by selecting proper redundant switching states. The operating principle and voltage balancing method of this converter are introduced in details. simulation and experimental results are presented to confirm the validity of this topology.

关键词： Capacitors Switches Voltage control Topology Clamps Integrated circuit modeling Electric potential

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