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International Conference on power system Technology (powerCON)

作者： Xueping Gu Claudio A. Canizares Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding Hebei China Department of Electrical and Computer Engineering University of Waterloo Waterloo ONT Canada

Determining loadability margins to various security limits is of great importance for the secure operation of a power system. A novel approach is proposed in this paper for fast prediction of loadability margins with respect to small-signal stability based on neural networks. Small-signal stability boundaries are constructed by means of loading the power system until the stability limits are reached from a base operating point along various loading directions. Back-propagation neural networks (BPNN) for different contingencies are trained to approximate these stability boundaries. A search algorithm is then proposed to predict the loadability margins from any stable operating point along arbitrary loading directions through an iterative technique based on the trained BPNNs. The simulation results for the IEEE two-area benchmark system demonstrate the effectiveness of the proposed method for on-line prediction of loadability margins.

关键词： Neural networks power system stability power system security Voltage power system simulation monitoring National security control systems Operating systems Bifurcation

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Application of Wavelet Entropy and Adaptive Nerve-fuzzy Inference to Fault Classification

Application of Wavelet Entropy and Adaptive Nerve-fuzzy Infe...

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International Conference on power system Technology (powerCON)

作者： Bin Zhang Zhengyou He Qingquan Qian Lanzhou Jiaotong University Lanzhou Gansu China Southwest Jiaotong University Chengdu Sichuan China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University China

A new method of fault classification based on transient signals for high voltage power transmission line is presented. Based on the wavelet analysis and the idea of entropy, the concept and definition of wavelet energy entropy (WEE) for feature extraction are introduced. First, appropriate wavelet decomposition of acquired post-fault signal is conducted and the WEE is calculated. ; then the characteristic vectors for post-fault signal are built; the characteristic vectors containing fault information are used as the input of adaptive nerve-fuzzy inference system; finally, the fault classification is realized according to the output of adaptive nerve-fuzzy inference system. The simulation results of fault classification have been analyzed on a 500 kV transmission line PSCAD/EMTDC model. The result shows that the variation regularity of WEE with time can effectively reflect fault features. With the help of adaptive nerve- fuzzy inference system, it achieves good classification effect.

关键词： Entropy power transmission lines Wavelet analysis Adaptive systems power system transients Voltage Feature extraction Analytical models PSCAD EMTDC

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An Alternative Approach for Coordinating Dispatching Day-Ahead and Real-Time Energy Markets

An Alternative Approach for Coordinating Dispatching Day-Ahe...

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IEEE PES power systems Conference and Exposition, PSCE

作者： Gengyin Li Ming Zhou Bo Liu Guoli Zhang Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding Hebei China Department of Applied Mathematics North China Electric Power University Baoding Hebei China

The paper investigates the features of separately clearing the energy in the day-ahead market and then doing the same for the real-time market from the system operator's perspective. The analysis will show that this separate clearing mechanism is not always the most economical. An alternative approach based on co-optimization of both energy markets is presented. Considering stochastic electric demand, a novel integrated energy dispatching model (IEDM) is proposed for system operators that schedules day-ahead energy trading taking possible real-time demand and prices into account to find an optimal day-ahead dispatching scheme so as to achieve the total purchase cost minimum. Mathematical analysis is provided to illustrate the IEDM is more economical than the conventional separate dispatching approach. The IEDM solution integrates Monte Carlo simulation and linear programming with Hooke and Jeeves pattern search method. A 6-unit system example is applied to illustrate that the IEDM provides a more economical approach

关键词： Dispatching Economic forecasting Real time systems power generation economics Fluctuations Job shop scheduling power markets power system economics power system planning Frequency

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A Novel Adaptive Algorithm to Identify Inrush Using Mathematical Morphology

A Novel Adaptive Algorithm to Identify Inrush Using Mathemat...

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IEEE PES power systems Conference and Exposition, PSCE

作者： Ma Jing Wang Zengping Xu Yan Wu Jie Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding Hebei China School of Electrical and Engineering North China Electric Power University Baoding Hebei China

A novel scheme based on mathematical morphology to distinguish the inrush current from the internal fault current in power transformers is proposed, which is derived from high non-linearity in exciting cores of transformers. Transient current signals are extracted by use of the novel morphological gradient and morphological opening and closing transform, meanwhile various kinds of additive white noises are effectively suppressed by adaptive filtering. Based on different characteristics of transients between the short circuit current and the inrush current, the transformer criterion is developed. The proposed technique is immune to CT saturation. A total of 120 Electrical power dynamic laboratory (EPDL) simulation cases are used to test the performance of the technique. This method has stability during the symmetrical inrush current and can be implemented in real time with very high accuracy. The results of different EPDL testing systems verify the feasibility and practicability of the proposed scheme

关键词： Adaptive algorithm Surges Morphology Fault currents power transformers Transformer cores Additive white noise Adaptive filters Short circuit currents Circuit faults

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Analysis of ionized field under /spl plusmn/800 kV HVDC transmission lines

Analysis of ionized field under /spl plusmn/800 kV HVDC tran...

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International Zurich Symposium on Electromagnetic Compatibility (EMC Zurich)

作者： Tiebing Lu Jie Zhao Xiang Cui Han Feng Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control underMinistry of Education North China Electric Power University Baoding Hebei China Technology research center China Southern Power Grid Company Limited Guangzhou Guangdong China

HVDC transmission lines system has some advantages, but it can generate an effect on the environment nearby due to the corona, especially the ionized field. Based on the electromagnetic field theory, a simple method to analyze the ionized field generated from the bundled conductors of bipolar lines is proposed. And then, after the validity of the method is testified, some examples are analyzed and some conclusions are drawn finally. The results have been used in the design of plusmn800 kV HVDC transmission lines system in China

关键词： HVDC transmission Space charge Corona Conductors Equations power transmission lines Electromagnetic field theory Testing power generation Voltage

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Effect on Earth Fault Detection Based on Energy Function Caused by Imbalance of Three-Phase Earth Capacitance in Resonant Grounded system

Effect on Earth Fault Detection Based on Energy Function Cau...

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International Conference on power system Technology (powerCON)

作者： Hongquan Ji Yihan Yang Hongbo Lian Shu'an Cong Key Laboratory of Power System Protection Dynamic Security Monitoring and Ministry of Education North China Electric Power University Beijing China School of Electrical Engineering North China Electric Power University Beijing China

In resonant grounded system when single-phase earth fault occurs, for arc suppression coil cannot compensate the active current of the zero-sequence grounding current passing through the fault point, the zero-sequence active current passing through the fault line is the sum of those passing through the non-faults. Therefore in theory the zero-sequence active current passing through the fault line is greater than others in absolute value. Energy function is the integrating of product of zero-sequence voltage with zero-sequence current. The fault line's energy function value is negative, while the non-fault's is positive. If three-phase earth capacitance is imbalanced, zero-sequence voltage produces, which will produce zero-sequence current passing through all the line. This zero-sequence current is the key variable that influences the phase-angle between non-fault zero-sequence current and the zero-sequence voltage. This paper analyzes the influences in different compensation conditions in theory. Simulation results are presented to demonstrate that the validity of earth fault line detection based on energy function will be worse and worse accompanied with the increasing of earth resistance when single-phase earth fault occurs on the imbalanced phase, and indicate that energy function has its validity scope.

关键词： Fault detection Capacitance Resonance Voltage Earth power system security Coils Electrical fault detection Laboratories power system protection

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Novel scheme to fast discriminate inrush current from internal fault of power transformer

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2006年第2期26卷 47-51页

作者： Lu, Zhi-Juan Liu, Wan-Shun Xiao, Shi-Wu Zheng, Tao Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

A new algorithm based on waveform characteristics is presented for fast discrimination between inrush current and fault current of power transformers. The method is based on that the waveform of inrush current (concave) distorts seriously, while the fault current nearly keeps sinusoid (convexity). Utilizing the sample data within 5 ms after fault initiation and extending the data windows from 5 ms to 10 ms, the approximate current formula can be extracted from fault current or inrush current using least square fitting method. According to the curvature and convex-concave characteristic of the fitting curve, inrush current and fault current of power transformers can be distinguished. Experimental results indicate that this algorithm is not only effective under various fault conditions but also can be realized easily and hardly to be affected by current transformer saturation and decaying DC components. Moreover, fault clearance time can be limited within 5 ms.

关键词： Electric transformers

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New acquiring path of power system dynamic parameter based on RBFNN recognition

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2006年第10期26卷 104-108页

作者： Zhao, Shu-Tao Li, Bao-Shu Yuan, Jin-Sha Zhao, Dong-Sheng Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Baoding 071003 China

Acquiring the dynamic parameters based on computer vision instead of manual patrol, and via comparing power meter reading with its preliminary definition threshold, which is a new automatic monitoring scheme of power system running. In the process of power meter automatic recognition, three particle feature invariants, include length ratio, compactness and simplicity factor have been extracted. The RBFNN is utilized in the dial plate elements recognition. The meter identifying experiments proved that the RBFNN input invariants are stable and proper, and it is insensitive to the background noise. It can optimize the power system monitoring with the image-analyzing introducing.

关键词： Electric power systems

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Application of controllable Reactor in Suppressing the Voltage Fluctuation and Flicker under Hα control Strategy

Application of Controllable Reactor in Suppressing the Volta...

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International Conference on power system Technology (powerCON)

作者： L.x. Zhou Z.d. Yin J.r. Lin F.x. Hu Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China postgraduate student School of Electrical Engineering North China Electric Power University Power Dispatching and Communication Center China Southern Grid.

Voltage fluctuation and flicker are mainly caused by surge load with large capacity, which may lead to the unstable operation of the motor, the poor characteristics of electrical equipments and the mis-operation of the electronic device even damage etc. Traditional SVC can adjust the reactive power ideally to maintain the system voltage of the connection point and play an excellent role in suppressing the voltage fluctuation and flicker. The minor defect is that it can not be directly applied to the ultrahigh or extra-high voltage system. This paper puts forward a topology of SVC based on the controllable reactor. It can be made into voltage at any level to connect to the ultra-high or extra-high voltage network directly, and can dynamically adjust the saturation degree of the controllable reactor according to the fluctuation of the reactive power of the system, smoothly change the reactive power it sends out, effectively suppress the voltage fluctuation and flicker. Meanwhile, H alpha control is taker as the main control strategy. The validity of proposed approach is verified by calculation and simulation.

关键词： Voltage fluctuations Voltage control Inductors control systems Lamps Automatic voltage control Static VAr compensators Reactive power control power system control power systems

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The Study of Detailed Fossil Fuel Steam Unit Model for Long-term power system dynamic Simulation

The Study of Detailed Fossil Fuel Steam Unit Model for Long-...

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International Conference on power system Technology (powerCON)

作者： Xianrong Chang Zhenjian Guan Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education(North China Electric Power University) Baoding Hebei P.R.China School of Electrical Engineering North China Electric Power University Baoding Hebei P.R.China

Long-term power system dynamic simulation needs to reflect the dynamic process of the fossil fuel steam unit when occurring severely disturbances in the power system. A physically based detailed model of the fossil fuel steam unit for power system long-term dynamic simulation has been described in this paper. The model can reflect the dynamic variation of the internal parameters accurately. In particular, the detailed model considers the dynamic impact on the turbine output from the extraction system. The simulation is much closer to the reality in the power system long-term dynamic process. This detailed model of the fossil fuel steam unit can be used for the power system long-term dynamic simulation.

关键词： Fossil fuels power system modeling power system dynamics power system simulation Turbines power generation power system stability power system transients power system analysis computing Furnaces

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