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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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Optimal design of SVC-based subsynchronous damping control using genetic and simulated annealing algorithm

Optimal design of SVC-based subsynchronous damping control u...

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International Conference on Information and Automation (ICIA)

作者： Tingzhi Yang Xiaorong Xie Shiyu Liu Donghui Zhang State Key Laboratory of security control & simulation of power systems and large-scale generation equipments Department of Electrical Engineering Tsinghua University Beijing China

In this paper, an optimal approach based on genetic and simulated annealing algorithm (GASA) is prosposed to design more effective and robust subsynchronous damping control (SSDC) of Static Var Compensator (SVC) for multimodal SSR damping improvement. A practical multi-machine series compensated power system suffering multimodal SSR has been studied to demonstrate the effectiveness of the approach. The developed SSDC comprises independent modal control path, each with separate feedback gains and phase-shifts, to damp different torsional mode. The problem of simultaneously tuning all the control parameters for robust stabilization of multiple torsional modes over various system conditions is formulated into a standardized constrained optimization problem. With the proposed GASA, the problem is efficiently solved and the SVC SSDC is optimized. Both eigenvalue analyses and electromagnetic simulations have been conducted on the test system to validate the approach and the designed SVC-based SSDC.

关键词： Static VAr compensators Damping Generators Gallium power system dynamics Optimization power systems

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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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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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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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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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Risk-based study on under voltage load shedding schemes

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2006年第19期26卷 18-22页

作者： Dai, Jian-Feng Zhu, Ling-Zhi Zhou, Shuang-Xi Lu, Zong-Xiang State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

A risk based method is proposed to design under voltage load shedding (UVLS) scheme. Different with traditional methods, the proposed one employs a series of risk indices, which are obtained based on a full-scale contingencies analysis, to determine the operating parameters of load shedding. According to this method, the load bus, in which the UVLS can exert itself with the highest efficiency to prevent voltage collapse, is selected as the first candidate to execute load shedding. And the amount of loads to be shed is identified though a relationship between risk values and shedding amount. The selection of shedding time conforms to the principle that the compound risk brought by failed shedding and unexpected shedding must be the minimum. Experiments conducted for IEEE 39-bus system reveal that the proposed method redound to identify the location, amount and time of load shedding more accurately and reasonably due to taking into account a great deal of uncertain factors.

关键词： Electric load shedding

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Study on probability of voltage instability based on the stochastic characteristic of load margin index

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2006年第13期26卷 26-30页

作者： Dai, Jian-Feng Wang, Hai-Chao Zhou, Shuang-Xi Lu, Zong-Xiang Zhu, Ling-Zhi State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

In order to make up the deficiency of traditional analytical method used in the research of voltage stability problem, we need to know the probability information concerned with voltage instability. Therefore, this paper proposes a method to calculate the probability of voltage instability based on the stochastic characteristic of load margin index. This method firstly determines the stochastic characteristic of load margin index through an analysis about the randomicity of parameters which tie up with the tracing of critical point in continue power flow computation, and then figures out the probability of voltage instability by using moment and cumulate method. Owing to take into account more uncertain factors' influence on the voltage stability, the result acquired by this method is much more accurate and reasonable. A numerical simulation based on IEEE 39-bus system reveals that the proposed method works properly.

关键词： Electric power systems

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Progressively Converging Deadbeat control for UPS Inverter

Progressively Converging Deadbeat Control for UPS Inverter

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Annual IEEE Conference on Applied power Electronics Conference and Exposition (APEC)

作者： Y.D. Liu Y. Xing L.P. Huang M. Sakane State Key Laboratory of Security Control & Simulation of Power Systems and Large Scale Generation Equipments Department of Electrical Engineering Tsinghua University Beijing China College of Automation Engineering Nanjing University of Aeronautics and Astronautics Jiangsu China GS Yuasa Power Electronics Limited Osaka Japan

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Improved simultaneous extrapolation in sharp impulse signals in time and frequency domains

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2006年第18期26卷 133-137页

作者： Zou, Jun Guo, Jian He, Jin-Liang Zhang, Bo Teng, Wen-Rui State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing 100084 China Dept. of Electrical Engineering Henan University of Technology Zhengzhou 450042 China

The characteristic of the transient response of the grounding system takes on a fast rising and slow damping with the lightning excitation. An improved simultaneous time and frequency domain extrapolation method is presented based on Hermite function expansion, which takes the above mentioned characteristic of the transient signal into account, using early time response and low-frequency data, the complete electromagnetic response is generated. By using mutually complementary data, simultaneous extrapolation in time and frequency domains are carried out by using the Hermite polynomials as the basis function. However, the extrapolation method is not suitable to deal with the transient response with the fast pulse excitation. The improvement for the extrapolation method is to pre- and post-process the transient response data with the fast pulse excitation. As a pre-processed procedure, in order to reduce the condition number of the matrix used for determined the coefficient of basis function, the scale transformation is used in time and frequency domain respectively, and the data in time domain is smoothed and padded with zero. An adaptive algorithm to determine the order of Hermite function is also proposed. As a post-processed step, the transient data are smoothed by using GPOF to obtain a convergent result. The numerical example and the field measurement are presented to illustrate the application of this methodology. The method proposed enhances the ability of the simultaneous time and frequency extrapolation techniques.

关键词： Signal processing

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