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IEEE PES Transmission and Distribution Conference and Exposition

作者： Song Bi Li Yang Liu Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing China North China Electric Power University Beijing Beijing CN Beijing Power Company in Beijing China

In this paper, a novel method for perturbed trajectory prediction of post-fault rotor angle is presented based on PMU (phasor measurement unit) measurements and trigonometric function curve fitting technique. A mathematical model about the relationship of post-fault rotor angle and time is derived from a speed-governing system model, which reveals that the perturbed trajectory of the post-fault rotor angle can be expressed by trigonometric functions. By curve fitting technique, a least square method to predict the perturbed trajectory using trigonometric function is proposed. Numerical simulations are conducted on IEEE 9-bus system to test the effectiveness of this method. The proposed method can give more reasonable and more promising prediction results as compared with polynomial curve fitting technique

关键词： Trajectory Prediction methods Wide area measurements Curve fitting Phasor measurement units Mathematical model Measurement units Least squares methods Numerical simulation system testing

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Study on Energy-saving Strategies for dynamic Voltage Restorer

Study on Energy-saving Strategies for Dynamic Voltage Restor...

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International Conference on power system Technology (powerCON)

作者： L.x. Zhi Z.d. Yin H. Ding J.b. Han 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 Power Dispatching and Communication Center China Southern Power Grid Company Limited GuangZhou China

Traditional voltage injection methods for DVR are in-phase strategy which injects voltage in phase with the sag voltage and missing voltage technique which compensates for the difference between the sag and pre-sag voltages. Since a certain component of injected voltage is in-phase with the load current, DVR has to provide some amount of energy to the grid. This paper use DQ analyzing method based on instantaneous reactive power theories to detect and obtain the parameters of source side voltage for balanced faults of three-phase three-wire system. Through circumgyrating the phasor and injecting voltage with an appropriate advance phase relative to source side voltage, the minimum energy injection can be achieved. For unbalanced faults, fictitious three-phase voltages which come from a single- phase source can be constructed mathematically, so unbalanced faults can be dealt with easily in a balanced way. Simulation results are presented to demonstrate the validity of the proposed method.

关键词： Voltage fluctuations Uninterruptible power systems Voltage control power system restoration power system dynamics control systems Reactive power Fault detection Costs Energy management

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Research of Multi-Farms Transmission of Distributed Generation Based on HVDC Light

Research of Multi-Farms Transmission of Distributed Generati...

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International Conference on power system Technology (powerCON)

作者： Z.r. Zhang Z.d. Yin 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 Power Dispatching and Communication Center China Southern Power Grid Company Limited GuangZhou China

Nowadays worldwide, distributed generation plays a more and more important role in world's energy supply system. But distributed resources' innate weaknesses cause some problems such as wavy output power and instability of power generation. These innate weaknesses are hard to overcome only through improving one single distributed generation plant or adding energy storage equipment etc. In this article, a new concept of connecting several AC distributed generation plants (such as wind farm) via VSC-converter, and DC distributed generation plants (such as solar cell) via DC/DC converter and forming a low voltage DC network is given. This low DC network will be integrated into AC grid in some proper way. Namely equalize these small distributed generation plants to a big power generation farm to improve stability of electricity generation. Some simulations based on PSCAD/EMTDC are also given.

关键词： Distributed control HVDC transmission Distributed power generation Solar power generation power generation Wind energy generation Wind power generation Energy storage Joining processes Wind farms

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Fast Prediction of Loadability Margins by Constructing a Small-Signal Stability Boundary Based on Neural Networks

Fast Prediction of Loadability Margins by Constructing a Sma...

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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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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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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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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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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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