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Eigenvalue analysis of multi-mode sub-synchronous resonance for multimachine plant-to-grid transmission systems with fixed series compensation

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2008年第SUPPL.期28卷 13-18页

作者： Zhang, Shu-Qing Xie, Xiao-Rong Yang, Ting-Zhi Liu, Shi-Yu State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China

For some domestic large thermal power plants delivering electric energy over long distances, the sub-synchronous resonance (SSR), which is induced by the fixed series compensation (FSC), attracts much attention. Eigenvalue analysis is one of the primary methods to assess the risk and explore the countermeasure. However, for handling multi-machine and multi-mode SSR problems, no practical toolkit based on eigenvalue analysis is on hand for the moment. In this paper, a systematic modeling approach and analysis flows for the purpose of eigenvalue analysis of multimachine plant-to-grid transmission systems with FSC were proposed. The equating technique of machines and networks was presented, and the effect of the q-axis damping windings on the SSR was also explored. The applicability of the proposed method was verified with an actual multimachine system. Furthermore, its advantage over existing SMIB based eigenvalue analysis was clarified by a comparative study between the original multi-machine system and the simplified single-machine system.

关键词： Eigenvalues and eigenfunctions

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Impedance fault location algorithm for UHV long transmission lines with single-line-to-ground faults

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Dianli Xitong Zidonghua/Automation of Electric power systems 2008年第14期32卷 25-29页

作者： Wang, Bin Dong, Xinzhou Bo, Zhiqian Klimek, Andrew State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China AREVA T and D Automation Co. Stafford ST17 4LX United Kingdom

Ultra-high-voltage (UHV) transmission lines (over 750 kV) normally have larger shunt capacitance and longer transmission radius, which impose limitations of direct application of traditional impedance algorithm. A novel impedance fault location algorithm is proposed for UHV transmission lines with single-line-to-ground faults due to higher voltage level than 750 kV. It is based on the precondition that the negative sequence current phase at meter location can precisely describe the phase information of negative current in fault path or fault voltage. The algorithm is immune to the influence of shunt capacitance with distributed parameters modeling for transmission line, and is not disturbed by fault resistance with fault location calculation at zero-crossing point of voltage at fault point. Theoretical analysis and simulation prove that the proposed method can guarantee good fault location accuracy, and fulfill the requirements in the field.

关键词： Electric lines

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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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H∞ analysis method for the small signal stability of power system

H∞ analysis method for the small signal stability of power ...

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26th Chinese control Conference, CCC 2007

作者： Mei, Shengwei Che, Wenyan State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)7900719229

This work is concerned with the small signal stability problem in multi-machine systems. By means of H∞ theory, firstly the math model with disturbances is constructed;and secondly, the excitation control law for each generator is designed based on solving Riccati Equation. Finally, simulations performed on 4-machine system shows that the proposed H ∞ method has more advantages over LQR method in both damping ratio and H∞ norm of the corresponding closed-loop system and so can enhance the small signal stability of power system greatly.

关键词： Electric power systems

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Vector control for a twelve-phase synchronous motor

Vector control for a twelve-phase synchronous motor

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International Conference on Electrical Machines and systems (ICEMS)

作者： Dejia Zhou Zhengming Zhao Shanming Wang Jianyun Chai State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering and Applied Electronic Technology Tsinghua University Beijing 100084 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China

A twelve-phase synchronous motor with four Y-connected 3-phase symmetrical windings displaced in turn by 15deg is modeled by using flux linkages as state variables, and an optimized method for the vector control is proposed with the simulation results. The observing model for magnetizing flux linkage at the direct-axis is derived whereby a vector control scheme of a twelve-phase synchronous motor, and related simulation is constructed in this paper. Using switch blocks to model the functions of twelve-phase voltage-fed inverter is convenient for simulating the driving system. The results of the simulations show that the torque and magnetizing flux linkage can be controlled separately, and the dynamic characteristics of the motor are satisfied with the operating requirements.

关键词： Machine vector control Synchronous motors Couplings Magnetic separation Magnetic flux Switches Optimization methods Voltage Inverters Torque control

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Breakdown phenomena caused by electrical tree degradation in high density polyethylene under high frequency voltage

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Gaodianya Jishu/High Voltage Engineering 2007年第12期33卷 14-18页

作者： Zhou, Yuan-Xiang Xing, Xiao-Liang Nie, Qiong Wang, Yun-Shan Wang, Ning-Hua Liang, Xi-Dong Guan, Zhi-Cheng State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China

The shape change of electrical tree propagating in ice-water quenched high-density polyethylene (HDPE) film under AC voltage of different frequency ranging from 50 Hz to 90 kHz as well as the breakdown phenomena caused by the treeing degradation under high frequency condition were studied. The electrical treeing aging experiment is carried out at room temperature. The shape change of electrical tree and the arcing process during the experiment is observed via a digital micro-observing system. It is found that the arcing process can be obviously observed under a high frequency voltage compared with that under low frequency voltage. It is also found that under different frequency voltages the electrical tree initiation shape is different. Most of the electrical trees are branch-shape tree under lower frequency voltage. When the frequency is higher than 5 kHz, trunk-shape tree and bosk-like tree appears. Once the frequency is higher than 50 kHz, breakdown tree can be found out. It is shown that the tree shape conversion is influenced by the frequency. The electrical tree usually has a simple shape and rarely changes under low frequency voltage in one hour or more. However, under a high frequency voltage, the electrical tree shape changes more frequently and has a large probability to breakdown. The influence of frequency on material polarization process, fatigue and thermo effect is considered as the main causes of the experiment results. The more serious destruction caused by high frequency electrical treeing degradation can well explain the reason of insulation premature inactivation in mid-frequency or high-frequency electrical equipment.

关键词：聚乙烯树老化电树形态转换击穿频率

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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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Influence of frequency on electrical tree initiation in polyethylene

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Gaodianya Jishu/High Voltage Engineering 2007年第4期33卷 138-142页

作者： Zhou, Yuan-Xiang Wang, Yi-Nan Xing, Xiao-Liang Wang, Yun-Shan Wang, Ning-Hua Liang, Xi-Dong Guan, Zhi-Cheng State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

Treeing degradation in dielectric polymers often leads to insulation failures in electrical equipment. In order to make out the breakdown failures, the tree initiation characteristics of ice-water quenched HDPE under AC voltage in frequencies ranging from 50 Hz to 90 kHz are, studied. It is found that the tree initiation voltages (TIV) change a little when the frequency is from 50 Hz to 1 kHz. When the frequency is higher than 1 kHz, the TIV increases with the increase of frequency before reaching a maximum TIV. While the TIV decreases at first then increases at frequency >10 kHz. There are 7 categories of tree shapes, including branch-like, trunk-like, bosk-like, direct breakdown, bosk-trunk, bosk-breakdown and branch-trunk, appeared in the experiment. The categories of tree shapes manifold with the frequency increasing. The TIV of different categories are different apparently. The breakdown shape shows the highest TIV while the branch-like one shows the lowest TIV. The damage degrees to insulation material are different for different categories. It is also found that as the frequency increases, the dispersion of TIV increases remarkably. Though the polymer shows higher average TIV values as the frequency is larger than 1 kHz, the larger dispersion in higher frequency region indicates that the application of polymer insulators in medium or high frequency area would bring a higher breakdown risk as one can find from the frequent insulation failures in high frequency machines. The influence of frequency on electron accelerating process and fatigue effect aggravation in material under high frequency are considered as main causes of the experiment results.

关键词：聚乙烯电树老化电树起始电树形态频率

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Safe Operating Area of High power Three-level Neutral Point Clamped Voltage Source Inverters Equipped with IGCTs

Safe Operating Area of High Power Three-level Neutral Point ...

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International Conference on Electrical Machines and systems 2007(ICEMS2007)(第十届国际电机与系统会议)

作者： Liqiang YUAN Zhengming ZHAO Fanbo HE Mohd Eltawil State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University China

To design and analyze the behavior of high power inverter, the definition and application of the inverter's own safe operating area (SOA) are presented in this paper. The relation between the switch devices behaviors and the other components of the inverter is playing a key role in the description of the novel SOA. Based on the proposed idea, the optimization of a real 1.25MW/3.3kV inverter equipped with IGCTs is presented and analyzed. The corresponding experimental results are shown.

关键词： Voltage Pulse width modulation inverters Semiconductor optical amplifiers Switches Induction motors power harmonic filters power system simulation Variable speed drives Circuits Topology

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Analysis and Experimental Study of Slot Effect in Synchronous Reluctance Permanent Magnet Motors

Analysis and Experimental Study of Slot Effect in Synchronou...

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International Conference on power Electronics and Motion control (IPEMC)

作者： Wei Guo Zhengming Zhao Yingchao Zhang Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

Slot effect in synchronous reluctance motors with permanent magnet assisted (SR-PM) are deeply analyzed, reduced and verified by experiments in this paper. The three different type sample SR-PM motors are introduced firstly. Then how the rotor layer numbers affect the torque characteristics is deeply analyzed, including the torque-angle, steady operating torque and position-setting torque. Then the reduction method is presented with simulation results. The detail experiment results are given in the final. The results shows that both more layers and stator slot skewing can reduce the teeth harmonics. However for the rotor with sintered NdFeB magnet, stator slot skewed is the best way because it only has few layers due to manufacture reason

关键词： Magnetic analysis Permanent magnet motors Reluctance motors Rotors Synchronous motors Torque Stators power system simulation Manufacturing Servomotors

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