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2009 2nd Conference on power Electronics and Intelligent Transportation system, PEITS 2009

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

ISBN: (纸本)9781424442461

A new IGBT (Insulated Gate Bipolar Transistor) model for simulation of eomplicated multi-IGBT cireuits is presented. Based on the gate chargc and discharge behaviors of IGBT, it piecewise models the turn-on and -off transient oflGBT, and simulates the static characteristics with curve fitting method . With the kcy features of high simulation spccd, easy parameters extraction and clear physical meaning, the model is available for various IGBTs and system level circuits. This paper describes the structure and equivalent circuit of the model in detail, implements it with the simulation tool of PSIM package, and determines the parameters of the model for an IGBT of FF300R12ME3 as an example. The accuracy of the model is verified by the comparison between the simulated and experimental results. ©2009 IEEE.

关键词： Equivalent circuits

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Dynamical simulation of laboratory Microgrid

Dynamical simulation of laboratory Microgrid

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

作者： Zhao, Yishu Guo, Li Department of Electrical Engineering Shandong Electric Power Research Institute Jinan China Key Laboratory of Power System Simulation and Control of Ministry of Education Tianjin University Tianjin China

ISBN: (纸本)9781424424870

A MicroGrid can increase the reliability of energy supplies by disconnecting from the grid in the case of network faults or reduced power quality. The techniques that have been investigated to control MicroGrids in both modes are summarized as well as those proposed to maintain stability during the transitions from one mode to the other. This paper first introduces the MicroGrid planning structure in Shandong Electric power Research Institute (SEPRI) and discusses the various feasible control approaches used and presents for MicroGrid. Then, based on modeling different types of distributed generations and energy storage equipment, the SEPRI MicroGrid model was simulated with several operating modes under peer to peer control strategy. The importance of an energy storage to assist stability during transition between the operating modes is emphasized. © 2009 IEEE.

关键词： Energy storage

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Assessment Method for the Reliability of power Transformer Based on Fault-tree Analysis

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高电压技术 2009年第3期35卷 514-520页

作者： WANG You-yuan ZHOU Jing-jing CHEN Wei-gen DU Lin CHEN Ren-gang State Key Laboratory of Power Transmission Equipment & System Security and New Technology Department of High Voltage and Insulation Engineering College of Electrical Engineering Chongqing University Chongqing 400030 China

Accurate assessment of system reliability with limited or insufficient statistical data is difficult. At present, to assess the reliability of the transformers primarily depend on the statistics data, and the result of the assessment does not accurately reflect the reliability of a transformer. Fault tree is a powerful tool for depicting the logical relationships between the faults system. However, for a sophisticated reliability system, like power transformer, fault analysis is hard or infeasible because of the complexities of the equipment configuration and its faults. This paper presents a method which overcomes the drawbacks of traditional fault-tree analysis (FTA) by using FTA based on fault probability and equivalent calculation of each failure mode. Based on the further analysis of typical failure modes and influences of power transformer, the fault-tree of transformer is set up by using FTA techniques and the assessment method for the reliability of transformer is put forward, combined with the index of the importance and the method of improved analytic hierarchy process(IAHP). The assessment examples show the method can deduct the failure modes of transformer clearly, meanwhile, find out the weaknesses in time during the operation and get better assessment results. The method is helpful for the reliability analysis of a sophisticated system.

关键词：电力变压器供电系统故障树分析失效模式

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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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A Novel control Strategy for DFIG Based on Magnitude and Frequency of Rotor Voltage for Wind power Generation

A Novel Control Strategy for DFIG Based on Magnitude and Fre...

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

作者： Zhong Wang Yuanzhang Sun Guojie Li Xiong Li State Key Laboratory of Power System Department of Electrical Engineering Tsinghua University Beijing China

A magnitude and frequency control (MFC) strategy has been proposed for a doubly fed induction generator (DFIG). The proposed MFC is to make the DFIG equivalent to a synchronous generator in power system. It is found that the stator active and reactive powers depend on the phase and magnitude of the internal transient electro-magnetic field (EMF). The relationship between the rotor voltage and the internal transient EMF is also described. Unlike traditional control strategies such as stator-flux-orientation vector control and FMAC, the proposed MFC method manipulates the magnitude and frequency of the rotor voltage which can simplify the control system design and improve system reliability. Thus, complex coordinate transforms, rotor position detection, and rotor currents are not required in the proposed MFC for the DFIG control system. Furthermore, the rotor speed signal is also not required in the proposed MFC, but it is needed for MPPT. Simulation results are provided to demonstrate the correctness of the control scheme.

关键词： Voltage control Rotors Wind power generation power system transients control systems Stators Frequency control Induction generators Synchronous generators Reactive power

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A Circuit Model in a Wide Frequency Range for power Transformer and Analysis of its Characteristics

A Circuit Model in a Wide Frequency Range for Power Transfor...

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

作者： Yang Yu Wang Zanji Shao Chong Department of Electrical Engineering State key Laboratory of Power System Tsinghua University Beijing China

In order to predict VFTO (very fast transient overvoltage) distributions in the windings during transformer design stage, it is important to acquire the frequency range of the surge wave that could enter the transformer winding, and then model the windings in that frequency range. In GIS (gas insulated station), transformer is connected to bus through bushing and lead wire. The bushing capacitance to ground will bypass the high frequency components, so there should be a upper limit of the frequency components of the surge wave at the entrance of the transformer. In this paper, the transformer windings are modeled using MTL (multitransmission-line) model firstly, then the lumped equivalent circuit is formulated with the -type circuits, and finally the driving-point impedance and voltage transfer functions of the equivalent circuit are calculated using nodal analysis. The driving-point impedance of a model winding is calculated and compared with the measured result, and the validation of the equivalent circuit of transformer winding in the frequency range below 20 MHz is verified. Then the driving-point impedances of two real transformer windings are calculated with the equivalent circuit. Taking the lead impedance into consideration, the impedance of the winding is compared with the one of the bushing capacitance. The results show that most of the energy of the frequency components above 10 MHz in the surge wave will pass through the bushing capacitance and will not cause damage to transformer insulations.

关键词： Frequency power transformers power transformer insulation Impedance Windings Insulators Equivalent circuits Surges Capacitance Voltage control

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Novel connection scheme of backup power supply adaptive to Distribution Line Non-Communication Protection and new criterion for high voltage and large capacity induction motor

Novel connection scheme of backup power supply adaptive to D...

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

作者： Liu, Kun Dong, Xinzhou Bo, Zhiqian State Key Lab of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China AREVA T and D Automation Stafford ST17 4LX United Kingdom

ISBN: (纸本)9781424424870

This paper presents a new practical backup power supply connection scheme for Distribution Line Non-Communication Protection (DNCP). Simulation tests have been conducted using the Alternate Transient Program (ATP) with respect to a typical single circuit breaker multi-section system. The results prove that the new scheme is able to not only recover the power supply of loads on healthy lines automatically, but also create disturbances in favor of Accelerated Over Current (AOC) criterion. Aiming at the failure of Directional Under Voltage (DUV) criterion derived from high voltage and large capacity induction motor load, a novel criterion using the increment of reactive power is proposed. © 2009 IEEE.

关键词： Induction motors

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Sensorless 3-level Inverter-Fed Induction Motor Drive Based on Indirect Torque control

Sensorless 3-level Inverter-Fed Induction Motor Drive Based ...

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第六届IEEE国际电力电子与运动控制会议 (2009 IEEE 6th International power Electronics and Motion control Conference-ECCE Asia

作者： Yongchang Zhang Zhengming Zhao Ting Lu Liqiang Yuan The State Key Laboratory of Power System Department of Electrical EngineeringTsinghua UniversityBeijing100084China

A sensorless induction motor drive fed by 3-level inverter is presented, which combines the principle of indirect torque control, space vector modulation (SVM), speed adaptive flux observer and fuzzy logic controller (FLC). By using SVM, the switching frequency is kept constant and it is easy to solve the problems such as neutral point balance, voltage jump, etc, and more accurate results are obtained. A novel speed adaptive flux observer is proposed in this paper, which can observe flux and rotor speed accurately over a wide speed range. FLC is employed in the outer speed loop to provide excellent dynamic performance and steady state accuracy, especially for variable load changes. Large starting current is one of the problems in application for indirect torque control. By using pre-excitation technique and a ramp function, the stator flux is firstly established smoothly before motor starts, thus starting current is decreased while maintaining enough starting torque. Both simulation and experimental results are presented to validate the effectiveness of the techniques proposed in this paper.

关键词： Induction motor drives Torque control Support vector machines Inverters Programmable control Adaptive control Fuzzy logic Sensorless control Switching frequency Voltage

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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 Novel Direct power control Strategy with Wide Input Voltage Range for Three-level PWM Rectifier

A Novel Direct Power Control Strategy with Wide Input Voltag...

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第六届IEEE国际电力电子与运动控制会议 (2009 IEEE 6th International power Electronics and Motion control Conference-ECCE Asia

作者： Ting Lu Liqiang Yuan Zhengming Zhao Yingchao Zhang The State Key Laboratory of Power System Department of Electrical EngineeringTsinghua UniversityBe Department of Electrical Engineering Chongqing Communication InstituteChongqing400035China

This paper focuses on a three-level pulse width modulation (PWM) rectifier using direct power control (DPC) strategy, analyzes the relationship between the input power source voltage, the output dc voltage and the switching table, and presents the key-point which limits the input voltage range of the rectifier. A novel DPC strategy with wide input voltage range for three-level PWM rectifier is proposed through optimizing the switching table and consummating the rules of vector switching. Employing the proposed strategy, the effective region of input voltage vector is enlarged, the rectifier achieves satisfying stead-state and dynamic performances with low input voltages while maintaining the constant dc output, the ride-through capability of the three-level PWM rectifier against the power source voltage sags is significantly improved, the excessive voltage jumps in phase and line-to-line voltages are avoided and the neutral-point voltage is balanced at the same time. Simulation and experimental results verify the validity and feasibility of the proposed scheme.

关键词： Pulse width modulation power control Rectifiers power quality Pulse power systems Space vector pulse width modulation power system stability power system reliability Voltage control Laboratories

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