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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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A Two-level Energy Storage system for Wind Energy systems

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Procedia Environmental Sciences 2012年 12卷 130-136页

作者： Xi Xiao Hu Yi Qing Kang Jinfeng Nie State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment singhua University Beijing China

Wind power outputs fluctuate with the changing of wind speed. The use of energy storage equipment is considered a reasonable solution to suppress wind power fluctuations. An energy storage mode may have its disadvantages over the others, for example, capacity limits, dynamic response, higher prices or shorter lifetime. Moreover, wind power fluctuations are present at different frequencies, to demand the energy storage to offer power support in different time ranges. To improve the performance, in this paper, a combined energy storage mode is discussed to meet the short-term and long-term energy storage requirement for wind power. Short-term energy storage is designed to meet the fast-changing power, using such as super capacitors. Long-term energy is designed to meet the large-scale capacity requirement using Li-ion battery or Vanadium Redox Battery (VRB). By analyzing the actual data of wind power outputs, the capacities of the two kinds of energy storage means are given as an example of the method.

关键词： Wind power energy storage capacity designing

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Concurrent structural and material optimization of turbine frame in turbo-fan engine

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Hangkong Dongli Xuebao/Journal of Aerospace power 2013年第10期28卷 1274-2180页

作者： Gao, Xi-Guang Liu, Xing-Guo Zhang, Hua-Jun Song, Ying-Dong Jiangsu Province Key Laboratory of Aerospace Power System College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Representative Office Stationed 420 Factory Chinese People's Liberation Army Chengdu 610503 China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

Based on the traditional structural optimization method, a structural/material optimization method for turbine frame was developed in consideration of the effects of structural parameters and properties of materials on the performance of turbine frame. The original optimization problem was decomposed into structure level and the material level. The first one was solved by feasible direction method while the second problem was solved by parallel genetic algorithms. A distributed computer system was designed by C language and employed to obtain the optimal material combination and structural parameters of one typical turbine frame. The result shows that the structure/material optimization may obtain better design than structure optimization. In the examples, compared with the worst material combination, the mass of the optimal material combination is reduced by 29.0%.

关键词： Turbines

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Flame Imaging in Meso-scale Porous Media Burner Using Electrical Capacitance Tomography

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Chinese Journal of Chemical Engineering 2012年第2期20卷 329-336页

作者：陈琪刘石 School of Mechanical Electronic and Control Engineering Beijing Jiaotong University State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University

This study was conducted to investigate the characteristics of meso-scale *** technique of electrical capacitance tomography(ECT) was used to locate flame position and monitor the effect corresponding to varied air/fuel ratio in a meso-scale *** phenomena including igniting,quenching and unsteady combustion have been visualized using *** method of metallization protecting ECT sensor from high temperature damage and the novel calibration method adapted to ECT monitoring of unknown permittivity flame have been shown to be *** the same time,electrical nature of combustion and dielectric characteristics of hy-drocarbon flame were *** relationship between flame permittivity and state parameters of combustion gas was demonstrated preliminarily.

关键词： electr：ical capacitance tomography meso-scale burner combustion flame permittivity

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Linear cryptanalysis and security tradeoff of block ciphering systems with channel errors

Linear cryptanalysis and security tradeoff of block cipherin...

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6th International Conference on Network and system Security, NSS 2012

作者： Guo, Jing Wang, Zhuxiao Beijing 100029 China School of Control and Computer Engineering State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China

ISBN: (纸本)9783642346002

Channel errors are usually treated as an obstacle in designing an encrypted wireless system. So we are supposed to reduce them as much as possible due to the potential error bursts contributed by an avalanche effect of block ciphers. In this paper, we propose that channel errors are to be explored for the benefit of security enhancement as they could be translated to additional efforts in cryptanalysis for an adversary node. To achieve this, a system with an outer block channel coder and an inner block cipher is presented. A framework for linear cryptanalysis is established under which an eavesdropper takes advantage of linear relationship among coded symbols, as well as linear approximation of ciphers. Also presented is an analysis on the tradeoff between security enhancement and performance degradation in the presence of channel errors. © 2012 Springer-Verlag.

关键词： Cryptography

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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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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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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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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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