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An efficient algorithm for strongly focused optical beams propagating in Kerr media

OPTICS AND LASER TECHNOLOGY 2012年第7期44卷 2100-2105页

作者： Guo, Xing Fu, Xiquan Wu, Lianglong Hunan Univ Coll Informat Sci & Engn Minist Educ Key Lab Micro Nanooptoelect Devices Changsha 410082 Hunan Peoples R China

Due to the lens-induced quadratic phase factor from converging lens, the beam-propagation method (BPM) is computationally expensive in simulations by the sampling theorem for lens-induced strongly focused beams propagating in nonlinear media. In the paper, we present a modified approach (MA) based on the separate envelope and lens-induced phase to only compute the envelope in the whole focal region. Then we demonstrate the correctness of MA analytically by the propagation of focused Gaussian beam and numerically by that of focused Super-Gaussian beam in linear media. Numerical simulations of strongly focused beams based on MA are in good agreement with those of BPM when propagating in Kerr media. The sampling requirement of MA which is similar with no lens-induced phase beam is lower than that of BPM which increases with the lens-induced chirp parameter and the propagation distance. Thus the computational efficiency can be greatly improved. (c) 2012 Elsevier Ltd. All rights reserved.

关键词： fourier algorithm Focused beam Kerr media

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A novel technique for internal fault detection of power transformers based on moving windows

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INTERNATIONAL TRANSACTIONS ON ELECTRICAL ENERGY SYSTEMS 2014年第9期24卷 1263-1278页

作者： Abniki, Hassan Sanaye-Pasand, Majid Univ Tehran Coll Engn Control & Intelligent Proc Ctr Excellence Sch Elect & Comp Engn Tehran Iran

Power transformer differential relays may incorrectly operate due to inrush condition or transformer external faults lead to current transformer (CT) saturation. In this paper, a new technique is presented to distinguish internal fault current from magnetizing inrush current in power transformers. The proposed technique applies two moving windows which both of them estimate magnitude of transformer differential current using different methods. The first moving window method is based on full-cycle fourier algorithm (long window) which uses one cycle samples of the current and provides precise estimation. The second one is originated from least error square (LES) method that has five sample point input data (short window). LES method has fast response, but its estimation might not be quite accurate. The proposed technique (which is a combination of two mentioned methods) presents a new criterion for discrimination between internal fault currents and inrush currents using the differences between output values of these two estimators. Meanwhile, obtained results demonstrate precise operation of the proposed algorithm for different conditions such as CT saturation and over-flux condition;therefore, it can be a multi-objective technique for transformer protection. Also, a general scheme is presented in order to improve differential protection. In this paper, a real part of 400/230kV Iranian national grid is simulated using PSCAD software for evaluating the performance of the proposed algorithm. Also, additional validation of the proposed technique is tested offline using data collected from a three-phase, 5 kVA, 60Hz, laboratory prototype transformer. Copyright (c) 2013 John Wiley & Sons, Ltd.

关键词： power transformer protection inrush current internal fault least error square method fourier algorithm

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Grid impedance estimation for grid-tie inverters based on positive sequence estimator and morphological filter

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ELECTRICAL ENGINEERING 2020年第3期102卷 1195-1205页

作者： Suarez, Jose H. Gomes, Hugo M. T. C. Sguarezi Filho, Alfeu J. Fernandes, Darlan A. Costa, Fabiano F. Univ Fed Bahia Salvador BA Brazil Fed Univ ABC Santo Andre SP Brazil Univ Fed Paraiba Joao Pessoa Paraiba Brazil

This paper proposes a method for estimating the appropriate grid impedance for applications in which distributed generators are connected to the grid through three-phase inverters. The method is based on variations in active and reactive power injected by the inverters into the power system. These variations give rise to changes in the direct synchronous voltage vd and in the synchronous direct and quadrature currents id and iq at the point of common coupling between the inverter and the power grid. These changes serve to compute the grid resistance and inductance seen by the inverter. This paper suggests the usage of a previously proposed technique for estimating the positive sequence from the grid voltage, so the method is robust against harmonic distortions. The technique is improved, employing a fourier filter. To further enhance the method, a morphological filter is incorporated to filter out the synchronous currents. This filter is suitable to be applied in DC signals, like the ones related to synchronous reference frames. A complete evaluation of the proposed method is performed through simulations in MATLAB/Simulink environment. The results show that the positive sequence estimator and the morphological filter significantly increase the accuracy of the grid impedance estimation.

关键词： fourier algorithm Impedance estimation Positive sequence estimation Distributed generation Mathematical morphology

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A new method for decaying de offset removal for digital protective relays

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ELECTRIC POWER SYSTEMS RESEARCH 2006年第4期76卷 194-199页

作者： Argüelles, JFM Arrieta, MAZ Domínguez, JL Jaurrieta, BL Benito, MS Univ Basque Country Dept Elect Engn Bilbao 48013 Spain Univ Basque Country Dept Appl Math Bilbao 48013 Spain

Voltage and current signals used in protection devices may contain harmonics and decaying dc offset in transient states. Because of this, protection devices must contain filters to remove the part of the signal which is not of interest and estimate the value of the component or components which are to be used for protection functions. Traditionally, the discrete fourier transform (DFT) filter has been used in digital protection devices. This filter has the advantage of being easily applied, but the disadvantage that when an exponentially decaying component is present the results obtained are incorrect. Because of this, different algorithms based on the DFT have been developed in order to remove the decaying dc offset and reduce digital processing errors. This paper describes a new method for removing the exponential component associated with electrical signals in transient states. Its ease of application results in a low computational load as compared with other methods. This characteristic, together with the accuracy of results, makes this new method suitable for application in real time on protection devices. (C) 2005 Elsevier B.V. All rights reserved.

关键词： digital filtering suppression of decaying DC offset effects digital relaying fourier algorithm

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Study on a new cable guard alarm system based on fuzzy state estimation

Study on a new cable guard alarm system based on fuzzy state...

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4th International Conference on Computer Science and Education

作者： Yu, Zhen Xiamen Univ Dept Automat Xiamen Peoples R China

ISBN: (纸本)9781424435197

This paper analyzes the principles and advantages of the current cable guard alarm technology. Given the limitations and defects of the low-voltage power cable guard alarm mechanism at present, we adopt the impedance measurement of alternating sampling algorithm and a combination of power line carrier, and propose a new mechanism for an integrated cable guard alarm system. The mechanism use fuzzy logic to judge the quality of the current, and calculate the protected setting value. It gives out the reliable alarm signal through the electric current dynamic analyses when the cable is cut off and stolen.

关键词： Cable Guard Alarm System Alternating sampling fourier algorithm Power Line Carrier

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ADAPTIVE SUB-LINEAR TIME fourier algorithmS

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ADVANCES IN DATA SCIENCE AND ADAPTIVE ANALYSIS 2013年第1期5卷

作者： Lawlor, David Wang, Yang Christlieb, Andrew Michigan State Univ Dept Math 619 Red Cedar Rd E Lansing MI 48824 USA Duke Univ Math Dept Durham NC 27708 USA

We present a new deterministic algorithm for the sparse fourier transform problem, in which we seek to identify k << N significant fourier coefficients from a signal of bandwidth N. Previous deterministic algorithms exhibit quadratic runtime scaling, while our algorithm scales linearly with k in the average case. Underlying our algorithm are a few simple observations relating the fourier coefficients of time-shifted samples to unshifted samples of the input function. This allows us to detect when aliasing between two or more frequencies has occurred, as well as to determine the value of unaliased frequencies. We show that empirically our algorithm is orders of magnitude faster than competing algorithms.

关键词： fourier algorithm

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A New Method of Fault Phase Identification for High Voltage Transmission Lines Based on the Fault Component of Phase Voltage

A New Method of Fault Phase Identification for High Voltage ...

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2nd International Conference on Energy and Environmental Protection (ICEEP 2013)

作者： Chen Yang Hu Yan Tai Neng-ling Shanghai Jiao Tong Univ Sch Elect Informat & Elect Engn Shanghai 200240 Peoples R China

ISBN: (纸本)9783037857434

Since the existing fault phase identification methods can not identify all fault types quickly and accurately for high voltage transmission lines, this article proposed a new method of fault phase identification based on the fault component of phase voltage difference and the kalman filter algorithm. The method defined the fault component's ratio of one phase voltage to the difference of the other two phase voltages as a fault phase identification factor. By analyzing the characteristics of fault phase identification factors in each fault type, the fault phase can be identified. Simulation results show that using the kalman filter algorithm to extract fundamental component is faster and more accurate. Meanwhile, the method can identify fault phases within half a cycle and is scarcely influenced by fault resistances, fault locations and fault initial phase angles. It also has a high sensitivity when the fault is on the side of strong source.

关键词： high voltage transmission line fault phase identification fault component of phase voltage kalman filter algorithm fourier algorithm

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Anti-interference Measurement Method of Zero Sequence Capacitance of Transmission Lines Based on Harmonic Component 4

Anti-interference Measurement Method of Zero Sequence Capaci...

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4th Asia Energy and Electrical Engineering Symposium (AEEES)

作者： Yan, Tao Tan, Yi Li, Hongjiang Gao, Mingxin Hu, Zhijian Yunnan Power Grid Co Ltd Capital Construct Dept Kunming Yunnan Peoples R China Wuhan Univ Sch Elect Engn & Automat Wuhan Peoples R China

ISBN: (纸本)9781665479141

Aiming at the problem of how to improve the measurement accuracy of line zero sequence capacitance under strong electromagnetic interference environment, this paper proposes to use harmonic method to measure line zero sequence capacitance, so as to effectively avoid the influence of power frequency interference from other coupled lines. In the application of this method, the end of the tested line is opened first, and then the head end of the tested line is pressurized by the step-up transformer. The step-up transformer produces a large number of harmonics because the step-up transformer is saturated under no-load. Finally, the third harmonic components of voltage and current at the head and end of the line are extracted by fourier algorithm, and the zero sequence capacitance is calculated by transmission matrix. In this paper, the proposed method is applied to single-circuit line based on lumped parameter model, single-circuit and double-circuit lines based on distributed parameter model. The accuracy of the measurement method proposed in this paper is verified by PSCAD simulation software under strong electromagnetic interference environment, and this method has good robustness to the change of line length and different initial values of zero sequence capacitance.

关键词： transmission line zero sequence capacitance strong electromagnetic interference environment third harmonic fourier algorithm transfer matrix

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An Impedance Circle algorithm for Faulty Line Selection in Distribution Networks 4

An Impedance Circle Algorithm for Faulty Line Selection in D...

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4th International Symposium on Computer, Consumer and Control (IS3C)

作者： Lei, Li Mei, Wang Ji, Hejing Pan Hongguang Xian Univ Sci & Technol Sch Elect & Control Engn Xian 710000 Shaanxi Peoples R China

ISBN: (纸本)9781538670361

A fourier-impedance circle algorithm is proposed in this paper to handle timeliness and applicability problems in the literature. First, obtain the three-phase voltage and three-phase current near the fundamental frequency of the signal by fourier algorithm in order to solve the higher harmonic problem in the signal acquisition process. Then, calculate components of positive sequence and zero sequence using phase-sequence filter. Finally, the impedance of single phase to ground and the one between phases of the tested line are calculated to compare with the impedance circle, and the fault of the cable line can be detected if the impedances are fall into the circle. Performance of the proposed approach is evaluated in several scenarios, included the fault of single line to ground and two-phase line to ground. The results demonstrate the detection efficiency of the proposed approach.

关键词： Distance protection fourier algorithm impedance circle

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A Modified Adaptive algorithm of Dealing with the High Chirp When Chirped Pulses Propagating in Optical Fiber

A Modified Adaptive Algorithm of Dealing with the High Chirp...

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4th International Conference on Graphic and Image Processing (ICGIP)

作者： Wu, Lianglong Fu, Xiquan Guo, Xing Hunan Univ Coll Informat Sci & Engn Minist Educ Key Lab Micronanooptoelect Devices Changsha 410082 Hunan Peoples R China

ISBN: (纸本)9780819495662

In this paper, we propose a modified adaptive algorithm (MAA) of dealing with the high chirp to efficiently simulate the propagation of chirped pulses along an optical fiber for the propagation distance shorter than the "temporal focal length". The basis of the MAA is that the chirp term of initial pulse is treated as the rapidly varying part by means of the idea of the slowly varying envelope approximation (SVEA). Numerical simulations show that the performance of the MAA is validated, and that the proposed method can decrease the number of sampling points by orders of magnitude. In addition, the computational efficiency of the MAA compared with the time-domain beam propagation method (BPM) can be enhanced with the increase of the chirp of initial pulse.

关键词： fourier algorithm chirped pulse the sampling theorem beams propagation method

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