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International Conference on Condition monitoring and Diagnosis

作者： Wei Wang Xu Cheng Chong Liu Zhifu Yang Heming Huang Qiang Xue Beijing Key Laboratory of High Voltage & EMC Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing 102206 P. R. China Beijing ElectricTest And Research Institute Beijing 100075 China

ISBN: (纸本)9781424416219

In this paper, four 110kV prefabricated cable joints models containing four kinds of known representative insulation defects were designed. The models can simulate some typical PD phenomena, such as sliding discharge, floating discharge, cavity discharge and protrusion discharge. Based on them, type frequency spectrums of AE PD signals in XLPE cable joints were studied. The investigation indicated that the main frequency component of AE PD signals for XLPE cable is less than 400kHz;the attenuation of higher frequency component is very fast;the energy is relatively centralized in 50～250kHz;the sensitivity in this band is very high;the characteristics of different PD models are apparently dissimilar from each other. The obtained results provided basis for future investigation on PD pattern identification.

关键词： AE Attenuation Frequency spectrums Insulation defects PD characters PD models

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Time series online prediction algorithm based on least squares support vector machine

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Journal of Central South University of Technology 2007年第3期14卷 442-446页

作者：吴琼刘文颖杨以涵 Key Laboratory of Power System Protection and Dynamic Security Monitory and Control of Ministry of Education North China Electric Power University

Deficiencies of applying the traditional least squares support vector machine （LS-SVM） to time series online prediction were specified. According to the kernel function matrix＇s property and using the recursive calculation of block matrix, a new time series online prediction algorithm based on improved LS-SVM was proposed. The historical training results were fully utilized and the computing speed of LS-SVM was enhanced. Then, the improved algorithm was applied to timc series online prediction. Based on the operational data provided by the Northwest power Grid of China, the method was used in the transient stability prediction of electric power system. The results show that, compared with the calculation time of the traditional LS-SVM（75 1 600 ms）, that of the proposed method in different time windows is 40-60 ms, proposed method is above 0.8. So the improved method is online prediction. and the prediction accuracy（normalized root mean squared error） of the better than the traditional LS-SVM and more suitable for time series online prediction.

关键词： time series prediction machine learning support vector machine statistical learning theory

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Research on temperature field of turbo-generators based on coupled physical field

Research on temperature field of turbo-generators based on c...

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International Conference on Electrical Machines and systems, ICEMS 2007

作者： Junqing, Li Shaoli, Ma Heming, Li Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Baoding 071003 China

ISBN: (纸本)8986510081

Temperature is one of the important physical variables in turbo-generators, so accurate prediction of temperature is very necessary in generators design and operation. This paper presents coupling mathematical model of electromagnetic and temperature field and calculates them by finite element method (FEM). First, magnetic field distribution of generators is accurately determined, so thermal source is known. Then, the mathematical model of temperature field is proposed, and temperature filed can be obtained. Couple Hield of electromagnetic and temperature in QFSN-200-2 turbo-generators is calculated by finite element analysis software (ANSYS), the proposed method is validated to be correct by comparing calculation and measurement values.

关键词： Electromagnetic fields

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Hybrid non-linear state estimation with voltage phasor measurements

Hybrid non-linear state estimation with voltage phasor measu...

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2007 IEEE power Engineering Society General Meeting, PES

作者： Qin, Xiaohui Bi, Tianshu Yang, Qixun IEEE Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing 102206 China

ISBN: (纸本)1424412986

In this paper, a new method of hybrid non-linear state estimation with PMU is proposed. Firstly, the voltage phasor measurements are transformed into indirect equivalent branch current measurements, with which the conventional state estimator takes the impact of PMU into consideration. Secondly, the indirect measurement errors caused by the measurement transforming are analyzed and calculated in detail. Thirdly, the accuracy of hybrid estimator is analyzed in the paper. The simulation results show that the proposed method improves the accuracy of estimator and the convergence speed also. © 2007 IEEE.

关键词： State estimation

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Multi-layer disturbance processing system based on multiple information sources

Multi-layer disturbance processing system based on multiple ...

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2007 IEEE power Engineering Society General Meeting, PES

作者： Bi, Tianshu Li, Qian IEEE Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing 102206 China

ISBN: (纸本)1424412986

More and more IEDs have been commissioned in power systems, such as digital relays, PMUs, metering and control devices, fault recorders and so on. Once there is a disturbance (for example, fault, low-frequency oscillation, etc.), large amount of information will pour into the control center. Therefore, how to identify the disturbance and then take corresponding countermeasures is crucial for power system security and reliability. A multi-layer disturbance processing system based on multiple information sources is proposed in this paper. Firstly, the characteristics of different kinds of information sources, including PMUs, RTUs, digital relays and fault recorders, are analyzed. Secondly, according to the arrival times of the information, the framework and functions of multi-layer fault diagnosis system is presented in detail. After a disturbance occurs, the suggested system could realize disturbance identification, fault element diagnosis and detailed post-fault analysis in succession at different time frames with the information coming, which fits the needs of operators well. © 2007 IEEE.

关键词： Information systems

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power system dynamic simulation validation based on similarity theory and analytical hierarchy process

Power system dynamic simulation validation based on similari...

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2006 International Conference on power system Technology, powerCON2006

作者： Han, Dong He, Renmu Ma, Jin IEEE Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University 102206 Beijing China

ISBN: (纸本)1424401119

Simulation assessment of error and veracity is the precondition in power system dynamic simulation validation that is directly related to power system stability. Own to the applications of Wide Area Measurement system (WAMS) that could provide synchronous measured information of power grid, it is possible to assess dynamic simulation. Based on the principles of similarity theory and Analytical Hierarchy Process (AHP), this paper proposes general assessment method on amplitude similarity degree of simulation and its relative error criterion by analyzing the characteristics of power system dynamic stability and variables. This method could not only systematically reflect the similarity degree of whole system and every time period, but also provide objective quantitative information and reference for further model validation and parameter correction. A case study is presented to verify the proposed method on the basis of the measured data from WAMS of certain power grid. © 2006 IEEE.

关键词： Circuit simulation

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Novel modeling and control of doubly-fed variable-speed constant-frequency wind power generator

Novel modeling and control of doubly-fed variable-speed cons...

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33rd Annual Conference of the IEEE Industrial Electronics Society, IECON

作者： Qihui, Liu Fang, Yu Jianhua, Zhang Key Laboratory of Power System Protection Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing 102206 China

ISBN: (纸本)1424407834

Reasonable modeling and control is of significance for theory study and practical operation of doubly-fed variable speed constant frequency (DFVSCF) wind power generator. Two sorts of simulation models called no-load model and generation model were obtained through linearization and discretization of the state equations of doubly-fed induction generator (DFIG), which was derived from the DFIG model in synchronously rotating reference frame. Both models work in coordination one after another to achieve the whole simulation of DFIG before and after grid-connection. Based on the field-oriented vector control technique, the decoupling control of output power of DFIG, together with grid synchronization, was investigated. The maximum power point tracking (MPPT) was realized by control of DFIG active power. The simulation results, which are highly consistent with the experiment results, verify the validity and correctness of the theoretical analysis and control strategy proposed by this paper. ©2007 IEEE.

关键词： Equations of state

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Damping low-frequency oscillation in AC/DC power systems based on multi-operation modes

Damping low-frequency oscillation in AC/DC power systems bas...

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2006 International Conference on power system Technology, powerCON2006

作者： Yanfeng, Ma Zhao, Shuqiang Gu, Xueping Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Ministry of Education Baoding 071003 Hebei China

ISBN: (纸本)1424401119

PSS and DC modulation (DCM) controllers are effective in suppressing low frequency oscillations of AC/DC mixed power systems, but controllers designed by conventional method for a certain oscillation pattern of a given operation mode maybe have a negative effect on other patterns, moreover, when the operate mode is changed, the damping effect becomes bad, so the coordination of parameters which are fit for multi-operation modes is a pivotal problem. Locations of controllers are determined by participation matrix, and parameters are coordinated by improved GA combined with sensitivity matrix and features of AC/DC mixed power systems. The example shows that parameters of controllers chosen by participation matrix and improved GA can have a good effect on damping low-frequency oscillations and have strong applicability. © 2006 IEEE.

关键词： Electric power systems

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A new adaptive method to identify inrush using grille fractal

A new adaptive method to identify inrush using grille fracta...

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2007 IEEE power Engineering Society General Meeting, PES

作者： Wang, Zengping Ma, Jing IEEE Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Baoding 071003 Hebei Province China

ISBN: (纸本)1424412986

This paper presents a novel scheme based on grille fractal for distinguishing between inrush currents and internal fault currents in transformers, which is derived from the singularity detection in the waveforms. First, differential currents are analyzed on the basis of grille fractal (GF). Noises are then filtered by use of the adaptive generalized morphological filter (AGMF). In a total of 158 experimental cases, the inrush current is characterized by the drastic variation, but the faulty current is kept almost constant. The experimental results indicate that the proposed technique is stable and reliable during discrimination between internal faults and magnetizing inrush currents, and saturation of current transformers (CTs). © 2007 IEEE.

关键词： Electric fault currents

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A novel algorithm for discrimination between inrush currents and internal faults based on equivalent instantaneous leakage inductance

A novel algorithm for discrimination between inrush currents...

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2007 IEEE power Engineering Society General Meeting, PES

作者： Ma, Jing Wang, Zengping IEEE Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Baoding 071003 Hebei Province China

ISBN: (纸本)1424412986

A novel scheme based on equivalent instantaneous leakage inductance (EILI) to distinguish inrush currents from internal fault currents in power transformers is proposed, which is derived from the circuit differential equation. First, the EILI that represents different characteristics between the inrush current and an internal fault is defined, and its calculation methods and the criteria of two-winding and three-winding transformers are derived. This method does not require B-H curve data and the parameters of leakage inductances obtained from the transformer manufacturer. A total of 147 experimental cases verify that the EILI calculated in real time is able to clear internal fault even light fault rapidly and correctly. © 2007 IEEE.

关键词： Fault tolerance

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