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IEEE/PES Transmission and Distribution Conference and Exposition: Latin America

作者： K. L. S. Shenxing X. Dong Z. Bo State Key Lab of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China Tsinghua University Beijing Beijing CN State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing China AREVA T&D Automation슠and Information Systems Stafford UK

Non conventional instrument transformer (NCIT) and IEC 61850 are crucial technologies in digital substations. But they bring some new uncertainties to protection IEDs, especially the time synchronization issue in current differential protection. The paper analyzes the time delay of transferring sampled values from NCIT to current differential relay in NCIT and IEC61850 based digital substation, then finds out the delay-non-deterministic problem, at last presents a novel current differential protection scheme by using phase-locked loops (PLL ) technology.

关键词： Substations Delay effects Ethernet networks Phase locked loops IEC Synchronization Data communication

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Comprehensive method on evaluation of distribution network planning

Comprehensive method on evaluation of distribution network p...

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

作者： Jun Xiao Yanyan Cui Fengzhang Luo Mingzhi Liu Jianmin Wang Yinong Li Yubo Gao Saiyi Wang Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University TJU Tianjin China Tianjin Electric Power Corporation Tianjin China SMEPC Urban Power Supply Company Shanghai China Urban Power Supply Company SMEPC Shanghai 200122 China

Planning is vital for the development of power system; and the quality of planning has direct influence on security, reliability and economy of the power system in the future. Therefore, it is urgently needed to study quantitative evaluation method for distribution network planning. First, this paper proposes a practical comprehensive hierarchy and method on evaluation of distribution network planning. Second, the implementation steps for the evaluation of planning network are given, which include the determination of indices hierarchy and the evaluation of planning. In the end, this paper takes 10 kV network distribution planning of a district in China for example in order to illustrate the specific evaluation steps and methods based on the hierarchy, at the same time, the case shows that the evaluation method has strong feasibility and practicability. The planning evaluation hierarchy and method proposed in this paper can not only seize the key elements influencing the characteristics of network planning, but also describe the planning integrally and quantitatively, and possess significant engineering practicability.

关键词： power system planning power system reliability power system security Urban planning Meeting planning Laboratories power system simulation control system synthesis power system measurements control engineering education

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Current differential protection based on Non-Conventional Instrument Transformer and IEC61850

Current differential protection based on Non-Conventional In...

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International Universities power Engineering Conference (UPEC)

作者： Kun Liu Xinzhou Dong Zhiqian Bo State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing China AREVA T&D Automation슠and Information Systems Staffordshire UK

Non Conventional Instrument Transformer (NCIT) and IEC 61850 are crucial technologies in digital substations. But they bring some new uncertainties to protection IEDs, especially the time synchronization issue in current differential protection. The paper analyzes the time delay of transferring sampled values from NCIT to current differential relay in NCIT and IEC61850 based digital substation, then finds out the delay-non-deterministic problem, at last presents a novel current differential protection scheme by using Phase-Locked Loops (PLL ) technology.

关键词： Substations Delay effects Synchronization IEC Phase locked loops Data communication Ethernet networks

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Simple method to determine power system delay margin

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Dianli Xitong Zidonghua/Automation of Electric power systems 2008年第1期32卷 6-10页

作者： Dong, Cun Yu, Xiaodan Jia, Hongjie Jilin Electric Power Company Changchun 130021 China Key Laboratory of Power System Simulation and Control Tianjin University Tianjin 300072 China

Delay margin is defined as the maximum time delay that system can sustain without losing its small signal stability. An effective approach is given to calculate the system delay margin. It determines the system critical eigenvalue and the local delay margin by tracing eigenvalue locus of a complex matrix in a finite interval. The proposed method does not make any transformation to the original characteristic equation. It can be applied to the delay margin analysis in the complicated bulk power systems. SMIB system and WSCC 3-generator-9-bus system are employed to validate its effectiveness.

关键词： Electric power systems

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Protection scheme against chain over-load trip based on wide-area information

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Dianli Xitong Zidonghua/Automation of Electric power systems 2008年第10期32卷 37-41页

作者： Wang, Yan Zhang, Yanxia Xu, Songxiao Key Laboratory of Power System Simulation and Control Tianjin University Tianjin 300072 China Baoding Electric Power Company Baoding 071000 China

Chain over-load trip is an early stage phenomenon of great blackouts. Anti-chain over-load trip scheme is an important measure to prevent large-scale blackouts. A principle of preventing chain over-load trip based on wide-area information is proposed. Taking important buses as units, the over-load current coefficient of each branch is calculated using relevant elements of the node impedance matrix in the normal operation conditions stored in the wide-area scheduling centre. The possibility of chain over-load trip cause'd by over-load branches is then estimated based on these coefficients, to help control centers take timely measures to prevent chain over-load trip and large-scale blackouts. simulation results on the IEEE-39 system indicate the feasibility of the method.

关键词： Electric power systems

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Medium voltage distribution system reliability calculation with the consider of high voltage distribution system and substation

Medium voltage distribution system reliability calculation w...

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3rd International Conference on Electric Utility Deregulation and Restructuring and power Technologies (DRPT 2008), vol.1

作者： Chengshan Wang Yue Lv Jun Xiao Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University TJU Tianjin China

According to the operational features of distribution network, the paper presents a method to calculate the distribution system reliability that also considers multi-layers failure. Based on the regular reliability calculation, the results are promoted. Firstly, the distribution system is divided into different parts by different voltage level. Secondly, based on the characteristics of the distribution system, a comprehensive evaluation method, which combines the high and medium voltage distribution system and the substation's influence, is taken into account. Through integration of the boundary condition, using the series and parallel formula, the promoted results are calculated. An example demonstrates the effectiveness and the accuracy of the method. It is a method which can be utilized in the cases of general index, and also satisfies with the various needs of the reliability calculation.

关键词： Comprehensive Reliability Assessment Distribution system

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Hierarchical performance assessment method on the distribution network planning

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Dianli Xitong Zidonghua/Automation of Electric power systems 2008年第15期32卷 36-40页

作者： Xiao, Jun Cui, Yanyan Wang, Jianmin Luo, Fengzhang Li, Yinong Wang, Saiyi Wang, Hong Key Laboratory of Power System Simulation and Control Tianjin University Tianjin 300072 China Shanghai Municipal Electric Power Corporation Shanghai 200080 China

Given the lack of a quantitative evaluation method, the paper presents a hierarchically structured method on the evaluation of distribution network planning according to the network characteristics. The evaluation method and implementation steps are proposed, including the performance indices and the planning evaluation. The current network and two planning alternatives of a district in Shanghai, China are evaluated using this method. The method includes a few new performance indices such as capabilities of against large area blackouts, matching degrees of high and medium voltage network power supply, margins of network expansion, etc, which reflect the adaptability and coordination of planning alternatives. The method can not only be used to compare a planned network against existing one, but also to evaluate various planning schemes. Case studies indicate that the method can take into account of the key elements quantitatively, and provide guidelines in the distribution network planning.

关键词： Zoning

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Prediction of Instability Separation Modes and Its Application in Practical Dynamic Security Region

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Transactions of Tianjin University 2007年第3期13卷 157-162页

作者：曾沅余贻鑫王红梅闵亮张沛 LEES T Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University Electrical Power Research Institute

The transient critical boundary of dynamic security region (DSR) can be approximated by a few hyper planes correlated with instability separation modes. A method to fast predict instability separation modes is proposed for DSR calculation in power injection space. The method identifies coherent generation groups by the developed K-medoids algorithm, taking a similarity matrix derived from the reachability Grammian as the index. As an experimental result, reachability Grammian matrices under local injections are approximately invariant. It indicates that the generator coherency identifications are nearly consistent for different injections. Then instability separation modes can be predicted at the normal operating point, while average initial acceleration is considered as the measure of the critical generator group to amend the error. Moreover, based on these predicted instability separation modes, a critical point search strategy for DSR calculation is illustrated in the reduced injection space of the critical generators. The proposed method was evaluated using New England Test system, and the computation accuracy and speed in determining the practical DSR were improved.

关键词： instability separation mode dynamic security region K-medoids algorithm reachability Grammian

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PSIM and SIMULINK Co-simulation for three-level adjustable speed drive systems

PSIM and SIMULINK Co-simulation for three-level adjustable s...

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IPEMC 2006: CES/IEEE 5th International power Electronics and Motion control Conference

作者： Yongchang, Zhang Zhengming, Zhao Baihua Liqiang, Yuan Haitao, Zhang State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)1424404487

Applying co-simulation technology is a very important trend in power electronics simulation, which can make full use of the merits of different software to improve the efficiency of building up a system. In this paper, a simulation platform for three-level adjustable speed drive (ASD) based on co-simulation of PSIM and SIMULINK is presented, which includes the interface between PSIM and SIMULINK, main circuit in PSIM, space vector pulse width modulation (SVPWM), dead time and minimum pulse width, view of output voltage and its Fourier analysis in SIMULINK Based on this platform, the cause of large current when motor starts is studied. simulation and experimental results show that the minimum pulse width contributes a lot for the large starting current of the ASD. In conclusion, applying the simulation platform introduced in this paper, the dynamic behavior of the three-level ASD can be easily studied, which reduces the cost and improves efficiency at the same time compared to hardware investments, and may help to realize the optimal design of the ASD in practice. © 2006 IEEE.

关键词： Efficiency

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Dynamic Equivalent Circuit Design In Three-level High Voltage Inverters Based On Functional Model of IGCT

Dynamic Equivalent Circuit Design In Three-level High Voltag...

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Twenty-Second Annual IEEE Applied power Electronics Conference and Exposition (APEC 07), vol.2

作者： Hua BAI Zhengming Zhao Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

The integrated gate commutated thyristors (IGCTs) are commonly used for construction of high voltage three-level PWM controlled voltage source converter/inverters. When the output voltage is greater than the maximum rated voltage, IGCTs are connected in series. To ensure the safe and reliable operation of the converter/inverters, special measures are required to equalize the voltages across the IGCTs connected in series. An effective method for balancing voltages is to use resistors for static voltage balancing and RC snubber circuits for dynamic voltage balancing. However, most of the previous research work reported in the literature focused on the dynamic circuit design for converters of the BUCK topology. Trade off is made only between the performance of dynamic voltage balancing and the turn-on loss without any consideration of di/dt endurance and any procedural steps, which makes the design procedure not suitable for converters of the three-level topology. Based on a functional model of IGCTs, this paper presents a procedure for optimum design of the dynamic voltage balancing circuit for a 6 kV/1250 kW inverter. The specific transient processes in the three-level topology with dynamic snubber circuit are simulated and the mechanisms are analyzed, which is absent in the previous work.

关键词： IGCT Dynamic equivalent circuit Three-level inverter Dead band

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