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International Conference on Electric Utility Deregulation and Restructuring and power Technologies (DRPT)

作者： Qing Liu Zengping Wang Yan Xu Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding City Heibei Province China

Thyristor controlled series capacitor (TCSC) used in power transmission line can increase the transportability and the stability of system, and decrease the system loss significantly. At the same time, TCSC brings many serious problems to transmission lines fault location and protective relaying. This paper analyzes the influence of TCSC to EHV transmission line protection, especially to the high-frequency directional protection. It can be obtained from the analyzing that the addition of TCSC to EHV transmission line would make the high-frequency directional protection unwanted operation or failure to operate. In order to solute the problems TCSC caused, this paper presents a novel transient protection scheme based on wavelet transform (WT). The simulation tests have proved that the analyzing and solution of the appearance of TCSC in EHV transmission line are correct.

关键词： power capacitors Thyristors power system protection power transmission lines control systems Stability Propagation losses Fault location Protective relaying Failure analysis

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Transient Stability Analysis of Asynchronous Distribution Generation and its Impact on protection

Transient Stability Analysis of Asynchronous Distribution Ge...

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2008 IET 9th International Conference on Developments in power system protection (DPSP 2008)

作者： Tianshu Bi Hongwei Zhao Peng Dong Qixun Yang Key Laboratory of Power System Protection and Dynamic Security Monitoring & Control (MOE) North China Electric Power University Beijing China

It is of great importance to study the dynamic behavior of distributed generation (DG), which might affect the fault level and protection system of distribution network greatly. In this paper, the transient stability of asynchronous type of DG is comprehensively analyzed. The critical shedding time and corresponding slip of DG are calculated. It is pointed out that the fault clearing time of existing relays cannot guarantee DG operates stable when a fault occurs in distribution network. The countermeasures to low down the possibility of instability of DG are suggested. Finally, case studies are carried out using PSCAD to demonstrate the viewpoint of this paper.

关键词： Torque Rotors Stability analysis Impedance Transient analysis Electromagnetics Resistance

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A fault classification method based on spectrum of fault component for EHV lines

A fault classification method based on spectrum of fault com...

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IEEE General Meeting power& Energy Society

作者： X. G. Wang S. F. Huang Q. K. Liu Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing China

This paper proposes a fault classification scheme for transmission lines based on spectrum of fault component. First it analyses the spectrum of fault component, then the characters of power frequency and nature frequencies in two data windows are used to identify fault type and fault phase respectively. The scheme performance was proven using ATP/EMTP simulations in a 500-kV power system considering different fault types and fault locations. The results show that the scheme works quickly and is not impacted by harmonics and the DC offset. It is also not sensitive to sampling rate and fault inception angle.

关键词： power transmission lines Circuit faults Frequency domain analysis Fault diagnosis Relays power systems Fault location

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Study of transient spectrum in transmission lines

Study of transient spectrum in transmission lines

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IEEE General Meeting power& Energy Society

When faults occur in transmission lines, the high frequency signals are caused by fault generated traveling waves and the spectrum is a series of harmonic in frequency domain. This paper utilizes lumped and distributed parameter models to express transmission lines respectively, analyzes the character of nature frequencies. Different influencing factors including different fault conditions, source impedance, bus capacitance, series compensated capacitance and shunt reactor are discussed in this paper. The results have been proven by ATP procedure in a typical 500- Kv power transmission line.

关键词： power transmission lines Capacitance Circuit faults Relays Copper Shunt (electrical) Inductors

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A security mechanism of Web Services-based communication for wind power plants

A security mechanism of Web Services-based communication for...

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IEEE General Meeting power& Energy Society

作者： Nian Liu Jianhua Zhang Wenxia Liu Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing China

The IEC 61400-25 standard has defined mapping of power plant information model to Web services. How to ensure the security of Web services-based communication for wind power plants is a unsolved problem. WS-security is a standard used to deal with the security requirement in application of Web services, while username/password and X.509 certificates are security tokens most commonly used in electric power utility. We propose a security mechanism that deal with the requirements of authentication, integrity, non-reputation, and confidentiality across the communication process based on WS-security and the two security token. The security mechanism is implemented by extension of SOAP message, design of security agent, and the related security message processing algorithm. An instance is modeling based on IEC 61400-25 to demonstrate the security enhanced remote control of wind power plants. The result support the usefulness of the security mechanism for Web Services-based wind power plants communication.

关键词： security Cryptography Wind power generation Web services Simple object access protocol Authentication IEC

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Approach on pricing electricity for large consumers based on hedonic price model

Approach on pricing electricity for large consumers based on...

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

作者： Ming, Zhou Xiangxin, Li Gengyin, Li IEEE Department of Electrical Engineering NCEPU NCEPU Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education

ISBN: (纸本)9787900714138

With the start of trial operation of direct purchasing electricity for large consumers in China, the method on how to price electricity is of vital theoretical and practical significance. Hedonic electricity pricing method is proposed to calculate the implicit prices of different characteristics of electricity. Based on the proposed model, the prices of electricity production cost, power quality and reliability characteristics are obtained. Comparing with the two-part pricing method, the hedonic electricity price model uses multiple electricity characteristics to make the electricity purchase price, instead of using single electric energy. Numerical examples show that the proposed approach can make purchase price more reasonable and fair. © 2008 DRPT.

关键词： power markets

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Hierarchical yardstick competition approach to assessing operation performance of distribution utilities

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Dianli Xitong Zidonghua/Automation of Electric power systems 2008年第4期32卷 20-24页

作者： Zhou, Ming Zhao, Wei Wang, Peng Li, Gengyin Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China North China Bureau State Electricity Regulatory Commission Beijing 100070 China

Assessing distribution utilities' operation performance is an important precondition for effective supervision and competition promotion. A hierarchical yardstick competition approach to assessing the operation performance of distribution utilities is proposed. Firstly, a hierarchical analysis of indices reflecting the operation situation of distribution utilities is incorporated in the overall objective, the criteria layer and the index layer, by employing the analytic hierarchy process (AHP). Secondly, the judgment matrix and data envelopment analysis (DEA) are used to gain the weights and performance index of assessment criteria in the criteria layer and index layer, respectively. Finally, the overall relative performance index is derived by using the analytic hierarchy process. A numerical example is given to prove its feasibility and validity. This project is expected to provide scientific and practical reference to supervisors as well as managers of electric power companies for decision-making.

关键词： Analytic hierarchy process

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Study on a Super Capacitor Energy Storage system for improving the operating stability of Distributed Generation system

Study on a Super Capacitor Energy Storage system for improvi...

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International Conference on Electric Utility Deregulation and Restructuring and power Technologies (DRPT)

作者： Juanhua Wang Jiancheng Zhang Yun Zhong Key Laboratory of Power System Protection and Dynamic Security Monitoringand Control under Ministry of Education North China Electric Power University Baoding Hebei China

A super capacitor energy storage (SCES) can be used as energy storage element of DG (distributed generation) system and provides necessary energy buffering. And it plays a very important role in improving operating stability of power system. Based on a wide voltage change scope of the SCES system, its main circuit has been designed in this paper, where bi-directional DC-AC-DC converter is regarded as transition circuit. The working situations of the SCES system under different loads have been analyzed in detail, and the corresponding system unified model is established when super capacitor is charged or discharged. According to the operating mechanics of SCES system, the relation between the stability of DG system and SCES system has been analyzed, and a better control scheme has also been designed. At last, the investigation of the SCES system and its control strategy are done with the use of exact simulation model. The simulation results verify the validity of designed scheme and the flexibility of control system.

关键词： Capacitors Energy storage Distributed control power system stability Circuit stability control system synthesis Buffer storage power system analysis computing Voltage Bidirectional control

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A novel coordinated control strategy for improving the stability of frequency and voltage based on VSC-HVDC

A novel coordinated control strategy for improving the stabi...

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International Conference on Electric Utility Deregulation and Restructuring and power Technologies (DRPT)

作者： Chengyong Zhao Lei Li Guangkai Li Chunyi Guo Key Laboratory of Power System Protection and Dynamic Security Monitoringand Control under Ministry of Education North China Electric Power University Baoding Hebei China

At the early stages of electric network restoration, the capacity of power system is relatively small, and adding large power load to such a power system will result in severe fluctuation of system frequency and voltage. Thus the stable operation and the restoration speed of power system will be affected seriously. VSC-HVDC (voltage source converter based HVDC) can control active and reactive power injected into network independently and rapidly. Based on the characteristics of VSC-HVDC, a coordinated control method between VSC-HVDC and conventional speed governing system is proposed to maintain the stability of frequency at the early stage of network restoration. Similarly, a coordinated control method between VSC-HVDC and automatic voltage regulator (AVR) is proposed to maintain the stability of bus voltage. The whole system model is established in RTDS environment. Simulation results show that the fluctuations of frequency and voltage are diminished remarkably, and the stability is improved by adopting the method proposed. It's conducive to expediting the restoration process of power system.

关键词： Voltage control Frequency power system stability power system restoration Converters power conversion Fluctuations power system modeling power system simulation HVDC transmission

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dynamic secondary arc analysis and simulation research under different line model

Dynamic secondary arc analysis and simulation research under...

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IEEE Asia-Pacific Conference on Circuits and systems

作者： Lixia Zhou Zhongdong Yin Xiangning Xiao Yueting Tan Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China Langfang Power Supply Corporation (North China Power Grid) Langfang China

In the extra high voltage (EHV) transmission system, the transient single-phase to ground faults are the most frequent to occur. Even after the opening of breakers in the two sides of the fault line, an induced current still exists in the arc because of the electrostatic and the electromagnetic coupling from the other two sound phases. Along with the enhancement of the voltage grade, the influence of the secondary arc becomes more and more, and may probably lead to the failure of the reclosing if the secondary arc is not extinguished promptly. In this paper, the dynamic secondary arc model (including recovery voltage and the secondary arc current) in single-phase asymmetric breaking is established based on the distribution parameters of EHV long-line. The method of twice-mode transformation is adopted to calculate the steady-state value of the secondary arc current and recovery voltage. Furthermore, the affects of different overhead line models on the secondary arc current are also analyzed through the real time digital simulation.

关键词： Analytical models Voltage power system transients Electromagnetic transients Electrostatics Electromagnetic coupling power system dynamics Steady-state Digital simulation Stability

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