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Improved delay-dependent stability criteria for power system with multiple time delays

Dianli Xitong Zidonghua/Automation of Electric power systems 2008年第19期32卷 15-19+24页

作者： Jia, Hongjie An, Haiyun Yu, Xiaodan Key Laboratory of Power System Simulation and Control Tianjin University Tianjin 300072 China

An improved delay-dependent stability criterion for power system with multiple time-delays is presented. In this method, a Lyapunov function is constructed based on Lyapunov-Krasovskii theory. To reduce the conservativeness of the method, some necessary slack variables are introduced to its derivative function. The derivative function is then expressed as a set of Linear Matrix Inequalities (LMI), which can be solved by the LMI toolboxes. A typical two-dimensional time-delayed system and the WSCC 3-generator-9-bus system are employed in the case study. The results reveal the validity and effectiveness of the presented method.

关键词： Linear matrix inequalities

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Dynamical characteristic of MicroGrid with peer to peer control

Dynamical characteristic of MicroGrid with peer to peer cont...

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2008 China International Conference on Electricity Distribution, CICED 2008

作者： Guo, Li Wang, Chengshan Guo, Lingxu Cao, Jing Key Laboratory of Power System Simulation and Control Ministry of Education Tianjin University Tianjin 300072 China Tianjin Electric Power Co. Tianjin 300010 China

ISBN: (纸本)9781424433735

Based on constructing different types of distributed generations and energy storage equipments, this paper simulated the dynamical characteristics of MicroGrid with several operating modes under peer to peer control strategy. Two cases were used to analyze the role of storage equipment in MicroGrid. If micro turbine generation with traditional synchronization generator was used in MicroGrid as the main power adjustment unit, the frequency and voltage of MicroGrid would fluctuate during MicroGrid changed from grid-connected mode to islanded mode. In case 2, where the battery was installed in MicroGrid, the oscillation of frequency and voltage could be damped efficiently, and the operating mode switch time was shorten.

关键词： Distributed power generation

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Luminescence in tracking test of polymer insulating materials

Luminescence in tracking test of polymer insulating material...

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2008 International Symposium on Electrical Insulating Materials, ISEIM 2008

作者： Du, B.X. Gu, L. Liu, Yong Key Laboratory of Power System Simulation and Control of Ministry of Education School of Electrical Engineering and Automation Tianjin University 92 Weijin Road Tianjin 300072 China

This paper presents a study on effects of flammation retardant in polycarbonate (PC) on the luminescence phenomena during the tracking tests. A photo multiplier tube was employed to measure the light intensity, which is found to be well in accordance with the development of tracking failure. The results obtained reveals that light is easily emitted when the phase angle of applied voltage is around 90 and 270. Weak initial light indicates the coming scintillation discharge;the continuously enhanced light is associated the scintillation discharge and the arc discharge. Each light pulse is composed of a main pulse and scores of small pulses. With the increasing flame retardant in PC, the luminescence intensity significantly decreases. The detecting technique of luminescence is sensitive to measure the light information from faint discharge pulses during the tracking tests.

关键词： Light

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New line-selection method for single phase grounding fault in distribution networks with two phase's current transformers

New line-selection method for single phase grounding fault i...

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3rd International Conference on Deregulation and Restructuring and power Technologies, DRPT 2008

作者： Zhang, Yanxia Jin, Zhiqiang Dai, Fengxian Fang, Ting Key Laboratory of Power System Simulation and Control Ministry of Education Tianjin University Tianjin 300072 China College of Electrical Engineering Tianjin University Tianjin 300072 China

ISBN: (纸本)9787900714138

In China, current transformers (TAs) are just installed at A-phase and C-phase in most distribution networks with neutral indirectly grounding. It is a very difficult problem to select single-phase grounding line using the currents of A phase and B phase. After analyzing the currents of A-phase and C-phase when B-phase grounding fault occurs, the fault line detection algorithm applying the transient characters of the sum of A-phase mutational current and C-phase mutational current is proposed. For A-phase to ground fault or C-phase to ground fault, the algorithm of constructing B-phase transient current and furthermore constructing the exact zero-sequence current is founded out through the analysis in frequency domain and time domain, and the fault line-detection method can be actualized according to zero-sequence current's transient characters. Based on them, a new method used to identify single phase to ground fault line using transient characteristics in two TAs distribution networks is formed. The proposed line-selection method is not affected by the mode whether the Petersen coil exists at neutral and the unbalanced current under normal operation condition. © 2008 DRPT.

关键词： power quality

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The negative-sequence distance protection for UHV long distance transmission line

The negative-sequence distance protection for UHV long dista...

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IET 9th International Conference on Developments in power systems Protection, DPSP 2008

作者： Li, Bin Ma, Chao He, Jiali Bo, Zhiqian Key Laboratory of Power System Simulation and Control Ministry of Education Tianjin University Tianjin 300072 China AREVA T and D Automation and Information Stafford United Kingdom

ISBN: (纸本)9780863419027

UHV transmission can transmit huge capacity energy over long distance. The paper proposes a new negative-sequence distance protection based on Bergeron model. Since Bergeron model has taken distribution parameters into account, the proposed principle is valid for providing protection in the case of remote or close faults, and it has high sensitivity for fault with fault-path resistance. Furthermore, this protection will not be influenced by load current, system oscillation, etc. The superior performance of the protection shows that it is especially competent to be the backup protection of UHV long distance transmission lines.

关键词： Electric lines

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A Novel Direct power control Strategy for Three-Level PWM Rectifier Based on Fized Synthesizing Vectors

A Novel Direct Power Control Strategy for Three-Level PWM Re...

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11th International Conference on Electrical Machines and systems(第11届国际电机与系统会议)

作者： Ting Lu Yongchang Zhang Yingchao Zhang Zhengming Zhao Liqiang Yuan State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department o State Key Laboratory of Control and Simulation of Power System and Generation EquipmentDepartment of

A novel direct power control (DPC) strategy for three-level neutral-point-clamped (NPC) pulse-width-modulation (PWM) rectifier, based on fixed synthesizing vectors, is proposed in this paper. The strategy breaks through the restrictions of vector switching with a simple switching table, improves the excellent dynamic performance of DPC, avoids the neutral-point voltage unbalance and the excessive voltage jumps in phase and line-to-line voltages of the rectifier, and guarantees the proper minimum pulse width and switching intervals between switches in different phases simultaneously. Experimental results verify the validity and feasibility of the proposed scheme.

关键词： Pulse width modulation power control Rectifiers Space vector pulse width modulation Switches Thyristors Topology Voltage control Snubbers control system synthesis

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DC/DC Converter Applied in the Photovoltaic- Inclined Thermal Collector Hybrid systems for Brackish Water Desalination

DC/DC Converter Applied in the Photovoltaic- Inclined Therma...

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11th International Conference on Electrical Machines and systems(第11届国际电机与系统会议)

作者： Liqiang Yuan Mohamed Eltawil Zhengming Zhao Yaodong Lu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department o State Key Laboratory of Control and Simulation of Power System and Generation EquipmentDepartment of

A chronic drinking water shortage is one of the most important issues in the developing countries, and drinking water from dirty water sources causes serious damage to inhabitants health in some remote areas. The solar distillation remains the most favorable process for the supplying of water to small communities. Base on the traditional solar still, an improved hybrid photovoltaic/thermal (PVT) desalination system is presented. The PV modules that are combined with thermal units, constitute the PVT systems which has longer operating time and higher average fresh water production. This paper introduces the DC/DC converter applied in this type of systems, including its structure and control strategy which is suitable for PV array and driving supportive heater. The experimental results for the converter and the whole system are showed and analyzed.

关键词： DC-DC power converters Photovoltaic systems Solar power generation Desalination Temperature Water resources Hybrid power systems Solar energy Water heating power system simulation

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Effects of corona discharge on surface deterioration of silicone rubber insulator under reduced pressures

Effects of corona discharge on surface deterioration of sili...

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2008 International Symposium on Electrical Insulating Materials, ISEIM 2008

作者： Du, B.X. Liu, Yong Wang, R.L. Key Laboratory of Power System Simulation and Control School of Electrical Engineering and Automation Tianjin University 92 Weijin Road Tianjin 300072 China Tianjin High Voltage Power Supply Company Tianjin 300250 China

With the broad application of silicone rubber (SIR) insulator in high-altitude regions, corona degradation is one of the inevitable electrical degradation caused by electric stress due to the organic properties of SIR. Although this phenomenon is investigated at atmospheric pressure, there is little investigation at low pressures. It is urgent to systematically investigate effects of low pressure on the corona degradation for the reliable application. Experiments were carried out in a decompression chamber and the ambient pressure was reduced by a rotary pump from the atmospheric pressure to 40 kPa. The specimens were exposed to corona discharges at low pressures for different lapse time. The surface static contact angles on the insulator were measured to reveal the hydrophobicity changes. The currents during corona discharges at different low pressures were measured to confirm the corona degradation with variation of the pressures. The results obtained showed that the intensity of corona discharge increased with reducing the ambient pressure, which accelerated the process of corona degradation.

关键词： Atmospheric pressure

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Breakdown phenomenon identification of biodegradable polyethylene film under UV-irradiation environment

Breakdown phenomenon identification of biodegradable polyeth...

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2008 International Symposium on Electrical Insulating Materials, ISEIM 2008

作者： Du, B.X. Liu, Yong Xia, Y.S. Liu, B.C. Key Laboratory of Power System Simulation and Control of Ministry of Education School of Electrical Engineering and Automation Tianjin University 92 Weijin Road Tianjin 300072 China Tianjin Electric Power Research Institute Tianjin 300022 China

Biodegradable polymers are increasingly expected for substitute of present insulating materials in the electrical and electronic devices. However, their electrical properties are not systematically confirmed and need further investigation. In this paper, biodegradable polyethylene (BDPE) films are employed as the specimens and high density polyethylene (HDPE) films are as the reference. The breakdown endurance of BDPE film is examined using bias DC voltage under UV-irradiation environments. The images of breakdown craters are captured through applying a monocular-video-zoom microscope. Both breakdown area and box dimension of breakdown craters are obtained by an image-pattern- identification technique. The results reveal that for both BDPE and HDPE films, the breakdown voltage, breakdown area and box dimension all decrease with the increase of UV-irradiation level. Based on comparison of the results, it shows that under UV-irradiation environment, breakdown endurance of BDPE film is better than that of HDPE film.

关键词： Biodegradable polymers

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The scheme of single-phase adaptive reclosing on EHV/UHV transmission lines

The scheme of single-phase adaptive reclosing on EHV/UHV tra...

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IET 9th International Conference on Developments in power systems Protection, DPSP 2008

作者： Bin, Li Shuo, Zhang Crossley, P. Bo, Zhiqian Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University Tianjin 300072 China Manchester University United Kingdom AREVA T and D Automation and Information Stafford United Kingdom

ISBN: (纸本)9780863419027

Automatic reclosure (AR) is extremely effective in improving the reliability, stability and security of the overall power system. However, the present autoreclosure operates blindly and practices employing a fixed time. In the case of permanent fault, a second shock to the system can cause irreparable damage to expensive equipments. According to characters of transient faults and permanent faults, this paper introduces the method of Bergeron line model into the field of single-phase adaptive reclosing (SPAR). Therefore, the paper proposes a novel scheme based on the calculation of Bergeron model to realize SPAR. Theoretical analysis and simulation prove that the proposed scheme of single-phase adaptive reclosing is valid with high sensitivity and reliability.

关键词： Reliability analysis

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