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2013 IEEE 25th Symposium on Fusion engineering, SOFE 2013

作者： Xia, L.L. Zhang, M. Ma, S.X. Yu, K.X. State Key Laboratory of Advanced Electromagnetic Engineering and Technology Wuhan China

ISBN: (纸本)9781479901715

The power supply based on pulse step modulation (PSM) technology has been widely used as the high voltage power supply for additional heating systems, such as RF H&CD and NBI in tokamaks. The topology contains numbers of converters and multi-secondary transformers. For the magnetic inrush of the transformer and the charge current of the converters connecting with the secondary windings of transformer, the power up of the power supply system is quite complex. PSM power supply starts up by two steps: the soft start of transformer and the pre-charge of the converters. Resistor branches series with the transformer and each converter are used to limit the inrush current. A lot of resister branches and parallel contactors in the converter modules are required, as a result the dissipation and electromagnetic interference (EMI) are serious. In this paper, the soft start circuit is simplified to only one step for decreasing the dissipation and EMI. The pre-charge circuits of the converters which are connected to the secondary at first are diverted to the primary winding of transformer can also limit the magnetic inrush current. Since the multi-secondary transformer powers up as the same time as converters, the capacitors in all converters will limit the ramp up rate of the transformer voltage, and the magnetic inrush current can be ignored. To analyze the characters of the precharge branches, all converters can be equaled as parallel during the soft start process. The equivalent circuit, a series RLC circuit, is proposed in this paper. A 1.2kV power supply, contains 12 converters, with soft-start has been built up in laboratory. Simulation and experiment results are shown to verify the theoretical analysis. A new soft start circuit of 100kV high voltage power supply system was designed. © 2013 IEEE.

关键词： Electric power systems

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Transient overvoltage control for a wind farm based on goal representation adaptive dynamic programming

Transient overvoltage control for a wind farm based on goal ...

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International Conference on Power System technology (POWERCON)

作者： Yu Su Ju Liu Shiwu Liao Yu-fei Tang Jiakmi Fang Jinyu Wen Haibo He State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China University of Rhode Island Kingston RI USA Aalborg University Aalborg Denmark Huazhong University of Science and Technology Wuhan Hubei CN

With increasing intermittent and fluctuant wind power integrated into the power system, the high penetration of wind generation has brought a series of challenges including voltage stability for the safe operation of power system. Static VAR Compensator (SVC) has been widely used to control the voltage on the point of common coupling (PCC) of wind farm. When severe fault occurs and leads to serious voltage drop in the system, SVC controlled by the conventional control method may cause voltage overshoot after the fault clearance due to its response time lag. And this voltage overshoot of PCC may lead to the failure of high voltage ride through. In order to solve such a problem and improve the system voltage stability under severe fault conditions, a goal representation adaptive dynamic programming (GrADP) based SVC controller is proposed in this paper. The proposed control method can precisely control reactive output of SVC through its self-learning function to approximate the optimal control policy. Thus the voltage on the PCC is effectively controlled. An IEEE four-machine two-area system is used to verify the effectiveness of the proposed approach. Detailed simulation analysis and comparative studies with particle swarm optimization (PSO) optimized SVC controller are carried out to demonstrate the performance of the new method. Simulation results indicate that the proposed control strategy is effective in mitigating the voltage overshoot with good adaptability under various operating conditions.

关键词： Static VAr compensators Voltage control Voltage measurement Power system stability Wind farms Wind turbines Reactive power

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Tensile testing and microstructure analysis on Sn-Pb-Cd and Sn-Pb eutectic solder

Tensile testing and microstructure analysis on Sn-Pb-Cd and ...

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The 15th International Conference on Electronic Packaging technology (ICEPT 2014) ) (第十五届电子封装技术国际会议)

作者： X.L.Wang G.D.Wu G.S.Yan Y.Ding C.J.Hang Beijng Institute of Control Engineering BeijingChina State Key Lab of Advanced Welding and Joining Harbin Institute of TechnologyHarbinChina

Since the 50Sn32Pb18Cd eutectic solder was melted at 145℃ which is lower than the melting point of 63Sn37Pb solder(183 ℃),it was selected as the interconnection joint to create a temperature gradient to avoid the former nearby 63Sn37Pb joint re-melted during the components assembly *** tensile testing and the microstructure analysis were carried out on 50Sn32Pb18Cd eutectic solder to get the fundamental data support for the reliable applications and also on 63Sn37Pb solder for *** tensile test was performed by Instron 5569 and Instron 5500R mechanical machine under different temperatures with different strain *** microstructure observation was conducted with SEM and EDX *** show that the tensile strength of Sn-Pb-Cd solder was much higher than that of Sn-Pb solder under the high strain rate(10-3s-1)at room *** the value was decreased and lower than that of Sn-Pb solder when the temperature was increased to 85℃,or the strain rate was lowered to(10-5s-1)at the room *** yield strength of both solder materials dropped when the tensile temperature was increased or the strain rate was lowered,and the yield strength of Sn-Pb-Cd solder would decrease more than that of Sn-Pb *** solder materials have uniform phase distribution but having significant different microstructure *** Sn-Pb solder,the Pb-rich phases distribute as islands in Sn-rich phase *** in Sn-Pb-Cd solder,Pb-rich phases with many different shapes appear in Sn-rich matrix and Cd-rich phases mainly distribute in the form of stripes inside Pb-rich *** preliminary microstructure analysis of these two different solder materials indicates that the different mechanical properties is resulted from their different microstructures.

关键词： 50Sn32Pb18Cd 63Sn37Pb tensile testing microstructure analysis

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Participation of large-scale wind power generation in power system frequency regulation

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Chinese Science Bulletin 2013年第36期58卷 4557-4565页

作者： SUN HaiShun LIU Ju WEN JinYu CHENG ShiJie LUO Cheng YAO LiangZhong State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic EngineeringHuazhong University of Science and Technology Midwest Independent Transmission System Operator Inc. China Electric Power Research Institute

The initiative participation of wind power generators in power system frequency regulation is an inevitable demand to ensure power system safe operation with large-scale wind power ***,it is principally difficult for conventional wind turbines to participate in power system frequency *** this reason,solution to this problem is becoming a hot topic in the current *** paper systematically reviews the relevant research progresses in the control strategies and the capability assessment of using wind power generators in the power system frequency regulation,including the comparing among the emulating inertia control,the droop control,the rotor speed control,the pitch angle control and the coordinated ***,future research in this area is pointed out in the paper.

关键词：风力发电机电力系统频率调节控制策略风力涡轮机安全运行惯性控制转速控制

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Study on polarization and depolarization current detection device for XLPE cable

Study on polarization and depolarization current detection d...

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IEEE Symposium Power Modulator

作者： Gang Ye Hua Li Fuchang Lin Jin Tong Qin Zhang Xiaogang Wu Zeqi Huang State Key Laboratory of Advanced Electromagnetic Engineering and Technology Humzhong University of Science and Technology Wuhan P. R. China Electrooic and Information School Yangtze University Jingzhou P. R. China

The polarization/depolarization current (PDC) detection device was designed to measure the broad range current from μA to pA level, which was suitable for 10kV XLPE cables ageing test. To achieve wide range of measurement, the ultra-low bias current amplifier and feedback resistances which had different values were used in the I/V conversion circuits. Teflon material was taken to prevent leakage current in the circuit board. Some effective methods (e.g. ultra-high value resistance, electromagnetic shielding, multiple filters, and high precision A/D conversion) were used to improve the accuracy and resolution of the measurement. The verification indicates that the device has a current measuring range of ±20μA, and a resolution of 0.1pA. The device was used to measure the PDC of the aged cable sample.

关键词： Current measurement Electrical resistance measurement Aging Resistance Cable insulation Switches

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Application analysis of large hydro-generator loss of excitation protection and its improvement

Application analysis of large hydro-generator loss of excita...

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International Conference on Power System technology (POWERCON)

作者： G. Q. Lu M. Long J. H. Li X. F. Tang J. Zou X. G. Yin Z. Zhang State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China Three Gorges Project Cascade Dispatching Communication Centre of China Yangtze Power Co. Ltd Yichang China

Concerned with loss of excitation (LOE) protection for large hydro-generators, several engineering issues with their improvement approaches are investigated. Based on the analysis of the variable excitation voltage criterion on its principle, performance and application, it's indicated that the expected function advantages of the criterion are actually not available, bringing about more potential failure in the rotor circuit instead. As a result, it's recommended LOE protection scheme for large hydro-generators should mainly consists of criteria on the stator side. The setting values of LOE protection and under excitation limit (UEL) control are calculated separately, resulting in the mismatch of each other easily, which impairs the generator's power supply support. Considering the steady state stability impedance criterion commonly used for large hydro-generator LOE protection as principal criterion, the paper presents an algorithm of comparing the operation zone of LOE protection and UEL control, followed by several schemes on their better cooperation.

关键词： Generators Stability criteria Power system stability Impedance Steady-state Stators

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Multilayer silicon and silicon oxide subwavelength grating as a reflective polarizer in visible region

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Digest of Technical Papers - SID International Symposium 2014年第1期45卷 1248-1250页

作者： Pan, Su Kwok, Hoi-Sing State Key Lab on Advanced Displays and Optoelectronics Department of Electronic and Computer Engineering Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong

We proposed a novel visible polarizer based on multilayer silicon and silicon oxide alternative subwavelength grating and its optical characteristic is numerically investigated by finite difference time domain method. The reflectance of TE mode and transmission of TM mode are above 90% with extinction ratio up to 103. Moreover, the proposed polarizer also has wide angular field and large fabrication tolerance. © 2014 Society for Information Display.

关键词： Silicon oxides

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Nucleation-control bistable twist nematic display

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Digest of Technical Papers - SID International Symposium 2014年第1期45卷 1435-1438页

作者： Tseng, Man-Chun Lee, Chung-Yung Ho, Tsz-Kin Kwok, Hoi-Sing State Key Lab on Advanced Displays and Optoelectronics Department of Electrical and Electronic Engineering Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong

A fast π bistable twist nematic (π-BTN) liquid crystal display controlled by nucleation process is developed. The nucleation induced by the patterned spacer inside the cell. The response time is fast and it depends ... 详细信息

关键词： Nematic liquid crystals

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Transient stability risk assessment of power systems incorporating wind farms

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Journal of Modern Power Systems and Clean Energy 2013年第2期1卷 134-141页

作者： Lu MIAO Jiakun FANG Jinyu WEN Weihua LUO State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and TechnologyWuhan 430074China Liaoning Electric Power Company Limited Shenyang 110006China

Large-scale wind farm integration has brought several aspects of challenges to the transient stability of power *** paper focuses on the research of the transient stability of power systems incorporating with wind farms by utilizing risk assessment *** detailed model of double fed induction generator has been *** penetration variation and multiple stochastic factors of power systems have been *** process of transient stability risk assessment based on the Monte Carlo method has been described and a comprehensive risk indicator has been *** investigation has been conducted into an improved 10-generator 39-bus system with a wind farm incorporated to verify the validity and feasibility of the risk assessment method proposed.

关键词： Wind farm integration Transient stability DFIG Risk indicator Wind farm location

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Novel Zero-Voltage Transition Semi Bridgeless Boost PFC Converter with Soft Switching Auxiliary Switch

Novel Zero-Voltage Transition Semi Bridgeless Boost PFC Conv...

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IEEE Energy Conversion Congress and Exposition

作者： Wei Hu Yong Kang Xuehua Wang Xiaoning Zhou State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan P. R. China Department of engineering Research Wuhan Quanhua Optoelectronics Co. Ltd Wuhan P. R. China

ISBN: (纸本)9781479957774

By using an active snubber, a novel implementation of the zero-voltage transition (ZVT) semi bridgeless boost power factor correction (PFC) converter is proposed. The active snubber reduces the reverse-recovery-related losses of the boost diodes and also provides zero-voltage switching (ZVS) for the main switches in the proposed converter. Furthermore, the auxiliary switch is operated at soft switching, the rest of the diodes are also realized to turn on and turn off naturally. Operating modes and optimal control strategy of the proposed converter are discussed in detail, and design of the proposed active snubber is given. On the basis of it, a prototype of 100 kHz, 600W, universal ac-line proposed circuit has been built to verify the proposed scheme. The efficiency curves show that the circuit improves efficiency significantly in the wide input voltage range and full power output.

关键词： Switches Inductors Capacitors Soft switching Snubbers Video recording Zero voltage switching

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