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2009 Asia-Pacific power and Energy Engineering Conference, APPEEC 2009

作者： Jianhua, Zhang Guohua, Zhang Manyin, Duan Jingyan, Yang Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China State Intellectual Property Office of the PRC Beijing China

ISBN: (纸本)9781424424870

An integrated indices system for urban power grid security assessment is proposed, which includes five kinds of indices such as capability of supplying power safely, static voltage security, topological vulnerability, transient security and risk indices. The indices system can scientifically and fully reflect the security level of power grid and provide a quantitative base for the establishment of emergency management technology and measures. The traditional indices and methods for power system security assessment are improved and some indices are first proposed such as "number of lost components after N-K contingencies" and "the largest power supply region index". Based on utility theory and considering effects of external environment on failure probability of lines, risk indices are constructed including "overload risk index", "low voltage risk index", "voltage collapse risk index" and "angle instability risk index". power system Security Assessment Indices Calculation and Analysis Software is developed, which provides an accessorial and practical tool for power system plan and operation. At last, one urban power grid is used as a research example and the results show effectiveness of the indices system and practicability of the software. © 2009 IEEE.

关键词： Risk management

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Shaft crack analysis and diagnosis for the 600mw steam turbine generator

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key Engineering Materials 2009年 413-414卷 591-598页

作者： Dongxiang, Jiang Liangyou, Hong Qian, Huang State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Thermal Engineering Tsinghua University Beijing 100084 China

Abstract: In order to find the cause of the shaft crack appeared in a 600MW steam turbine generator, several measurements are taken. The shaft assembly consists of three parts: shrink-fitted coupling, shaft and key which are used to transfer torque between coupling and shaft. First, the natural frequency of the shaft system is calculated. The result shows that the vibration signal contains the frequency nears the second natural frequency of the steam turbine shaft system. Second, stress field near the damaged coupling and shaft is analyzed using finite element method. The torque under different operation condition is calculated before stress analysis and applied to the shaft assembly, then. And, local stress concentrations position calculated is proved to be coincident with the place crack initiation. Finally, the cause of the fault is analyzed: at least three causes have found to be having something to do with the crack fault.

关键词： Finite element method

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A Fuzzy Neural Network Based Fault Detection Scheme for Synchronous Generator with Internal Fault

A Fuzzy Neural Network Based Fault Detection Scheme for Sync...

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International Conference on Fuzzy systems and Knowledge Discovery (FSKD)

作者： Hongwei Fang Changliang Xia Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University TJU Tianjin China

A fuzzy neural network (FNN) based inter-turn short circuit fault detection scheme for generator is proposed. The second harmonic magnitude of field current and the negative sequence components of voltages and currents are used as inputs for the FNN fault detector. The negative sequence voltage and current are obtained from the phase voltages and currents using the symmetrical component analysis method. And the second harmonic magnitude of field current is achieved by the FFT technique. The FNN fault detector with Gauss membership functions is trained off-line using the training data which comes from the Multi-Loop simulation program. The proposed fault detection scheme can perform the inter-turn short circuit fault detection, the fault type classification, and the fault location identification. Experimental results corroborate the effectiveness of the proposed scheme, which is implemented on a TI's DSP.

关键词： Fuzzy neural networks Fault detection Synchronous generators Electrical fault detection Voltage Circuit faults Gaussian processes Training data Circuit simulation Fault location

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Modeling and analysis of PEMFC in distributed generation system

Modeling and analysis of PEMFC in distributed generation sys...

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International Conference on Sustainable power Generation and Supply, SUPERGEN

作者： Bibin Huang Peng Li Dan Wang Fei Ding Chengshan Wang Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University TJU Tianjin China

With the rising of distributed generation technology, fuel cell, as an important distributed generation source, has become increasingly attractive by virtue of their inherently clean, efficient and quiet service. The dynamic characteristics of distributed generation system lie largely on the property of DG sources in it. Firstly, the dynamic characteristics of the fuel cell in small, medium and large timescale are summarized in this paper. The impact of factors, such as temperature and pressure, are also discussed. Then, the paper describes the models of proton exchange membrane fuel cell (PEMFC) in small, medium and large timescale. Also an improved dynamic model of PEMFC in small timescale is proposed and validated by simulated results.

关键词： Distributed control Fuel cells power system modeling Temperature Mathematical model Equivalent circuits power system dynamics Delay Thermodynamics Voltage

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simulation of Three-Phase Four-Wire Shunt Active power Filter

Simulation of Three-Phase Four-Wire Shunt Active Power Filte...

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IEEE PES Asia-Pacific power and Energy Engineering Conference (APPEEC)

作者： Jidong Wang Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University TJU Tianjin China

With the proliferation of nonlinear loads as power electronics equipment, the disadvantage of harmonic is more and more, which influence quality of power grid. Active power filter (APF) is a new harmonic restraint method comparing with passive filter, which is a power electronics device. This paper inspects harmonic current based on three-phase circuit instantaneous reactive power theory and simulates a three-phase four-wire shunt active power filter. The simulation results validate parameter is reasonable. The outcome indicates that active power filter can suppress harmonic and neutral wire current and balance three-phase current effectively.

关键词： Active filters power harmonic filters power system harmonics Reactive power Circuit simulation power filters power electronics Impedance power system simulation power grids

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Object-oriented analysis and design of transient stability simulation for distributed power generation system

Object-oriented analysis and design of transient stability s...

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International Conference on Sustainable power Generation and Supply, SUPERGEN

作者： Dan Wang Ke Peng Yan Li Menghua Fan Chengshan Wang Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University TJU Tianjin China

ISBN: (纸本)9781424449347

The designs of model abstraction and application abstraction of transient stability simulation for distributed power generation system are presented. The main classes are presented, which are called model classes, function classes and system integration classes. An AC/DC double layer bus-tree structure belongs to model classes for grouping elements of distributed generation system is presented, The DC bus tree structure includes subclasses of distributed sources and storages. The design scheme descries the double layer structure. In order to study the whole dynamic process of whole system, the digital simulation method capable of dealing with the stiff problem is integrated in function classes. With the efficiency and simpleness of calling mechanism for the functional functions of elements during computation, system integration classes are capable of considering the influence of typical microgrid operation modes which are grid-connected mode, island mode and grid-reconnected mode, etc, and capable of control the switchover from one mode to another mode.

关键词： Transient analysis Stability analysis Object oriented modeling Analytical models Distributed power generation power system modeling Distributed control Tree data structures Digital simulation Grid computing

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A novel control algorithm for inverter-based distributed generation in unbalanced three-phase power systems

A novel control algorithm for inverter-based distributed gen...

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International Conference on Sustainable power Generation and Supply, SUPERGEN

作者： Shengwei Li Yongli Li Jingliao Sun Qiang Jin Xuguang Li Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University TJU Tianjin China

ISBN: (纸本)9781424449347

In distribution power system, the unbalanced operating state, harmonics, negative sequence components, which are caused by the nonlinear or unbalanced loads, not only increase the power transmission losses, but also are harmful to the electric devices. In this situation, the Active power Filter (APF) and the Static Var Generator (SVG) would be required. However as proved in this paper, the existing compensation methods are usually affected by the unbalanced and harmonic voltages. So a compensation algorithm based on the amended Park Transformation which is suitable for the unbalanced power systems is proposed. In addition, referring to the inverter-based distributed generation (IBDG) developed rapidly in recent years, the presented compensation algorithm is integrated with the active power control scheme to build a hybrid control algorithm used in IBDG existing distribution system. Based on the stated control algorithm, IBDG not only can supply the electric power, but also compensate for the reactive power, harmonics and negative sequence currents of the distribution power system. The feasibility and accuracy of the algorithm are verified by the DIgSILENT powerfactory simulation.

关键词： control systems Distributed control power system control power systems power system harmonics power harmonic filters Hybrid power systems Active filters power system simulation power transmission

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Selection method of transformer interconnecting distributed generation and distribution networks

Selection method of transformer interconnecting distributed ...

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IEEE/PES Transmission and Distribution Conference and Exhibition: Asia and Pacific

作者： Shouzhen Zhu Lin Geng Jinghong Zheng Xiaoyu Wang DaeHee Choi Yang Li State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

Recently, DG (distributed generation) is rapidly developed around the world. But there are several problems in the grid-connected operation. The paper focuses on the selection of proper transformers to meet the grounding requirements in the distribution networks. Through theory analysis and simulation, optimal selection methods are proposed. Yg/¿-connection transformer is suitable for small resistance grounding distribution networks while ¿ /Yg and ¿ / ¿ connection transformers are fit for small current neutral grounding networks. The conclusions are useful for the DG-connected power system.

关键词： Distributed control Grounding power transformer insulation power system simulation Coils power system interconnection Distributed power generation Ferroresonance Voltage power generation

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Research on fault mechanism of icing of wind turbine blades

Research on fault mechanism of icing of wind turbine blades

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World Non-Grid-Connected Wind power and Energy Conference, WNWEC

作者： Minghao Zhao Dongxiang Jiang Shaohua Li State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Thermal Engineering Tsinghua University Beijing China

In this paper, fault mechanism of icing of wind turbine blades is studied theoretically and experimentally. First, the aerodynamic performance of a wind turbine's primary airfoil under normal and icing conditions are simulated using Fluent software separately to analyze the geometry effect of icing on wind turbine. Then the formation and characteristics of vibration signal on main shaft caused by mass unbalance of wind turbine's rotor are analyzed using rotor dynamics theory to evaluate mass effect of icing on wind turbine. Finally, corresponding experiments are carried out on a self-made small wind turbine under laboratory conditions to testify the former theoretical analysis.

关键词： Wind turbines Blades Aerodynamics Automotive components Solid modeling Analytical models Software performance Performance analysis Geometry Shafts

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Test system of a small wind turbine under laboratory conditions

Test system of a small wind turbine under laboratory conditi...

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World Non-Grid-Connected Wind power and Energy Conference, WNWEC

作者： Dongxiang Jiang Qian Huang Liangyou Hong State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Thermal Engineering Tsinghua University Beijing China

As a clean, renewable, widely distributed, non-polluting energy, wind power plays an important role in the world's renewable energy development. In order to ensure the stable operation of wind turbines using non-grid-connected wind power, as well as the efficient utilization of wind resources, a study of condition monitoring of wind turbines is necessary. A test system of wind turbines under laboratory conditions based on a LabView platform has been designed and the system has been applied on small wind turbine test bed to test the performance of output power and vibration characteristics. The result of simulation testing has verified the effectiveness of the test system.

关键词： system testing Wind turbines Laboratories power generation Vibration measurement Wind energy Wind energy generation power measurement Rotors Acceleration

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