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harmonics
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Analysis and control of temporary overvoltages for automated restoration planning
, Article IEEE Transactions on Power Delivery ; Volume 17, Issue 4 , 2002 , Pages 1121-1127 ; 08858977 (ISSN) ; Ranjbar, A. M ; Feuillet, R ; Sharif University of Technology
2002
Abstract
The paper presents a new approach that assists power system restoration planning with regards to control of temporary overvoltages (TOVs) due to transformer energization. The frequency-domain analysis in combination with analytical calculations is applied to find an optimum resonance condition. The analytical equations are based on sensitivity analysis for single frequencies and are extended to total sensitivity calculation. After an introduction of the phenomenon of overvoltages during power system restoration and harmonic resonance overvoltages, basic principles of their control are explained. Also, an algorithm is introduced for the results evaluation of harmonic resonance studies where...
Analysis and control of temporary overvoltages for automated restoration planning
, Article IEEE Power Engineering Review ; Volume 22, Issue 6 , 2002 , Pages 64- ; 02721724 (ISSN) ; Ranjbar, A. M ; Feuillet, R ; Sharif University of Technology
2002
Abstract
The paper presents a new approach that assists power system restoration planning with regard to control of temporary over-voltages (TOV) due to transformer energization. The frequency domain analysis in combination with analytical calculations is applied to find an optimum resonance condition. The analytical equations are based on sensitivity analysis for single frequencies and are extended to total sensitivity calculation. After an introduction to the phenomenon of overvoltages during power system restoration and harmonic resonance overvoltages, basic principles of their control are explained. An algorithm is introduced for the results evaluation of harmonic resonance studies where it is...
Residential loads modeling by norton equivalent model of household loads
, Article Asia-Pacific Power and Energy Engineering Conference, APPEEC ; 2011 ; 21574839 (ISSN) ; 9781424462551 (ISBN) ; Rad, M. S ; Mokhtari, H ; Honarmand, M. E ; Youhannaie, M ; Sharif University of Technology
Abstract
These days the number of nonlinear loads in power systems is increasing dramatically. These nonlinear loads inject harmonic currents and the voltages. Accordingly, the modeling of these loads and analysis of their effects on power quality has gained much attention. This paper presents harmonic models for residential appliances. The model is based on Norton equivalent technique. The parameters of appliances models are determined using measurements. These models are then verified by comparison with the measurements results for each load. Based on the developed individual loads, an estimate for a household/an office customer is found and the harmonic content for such customers is estimated. An...
Magnetic field harmonic analysis in brushless doubly fed machine
, Article Proceedings of the 2011 3rd International Youth Conference on Energetics, IYCE 2011, 7 July 2011 through 9 July 2011 ; July , 2011 , Page(s): 1 - 7 ; 9781457714948 (ISBN) ; Jandaghi, B ; Saket, M. A ; Oraee, A ; Oraee, H ; Sharif University of Technology
2011
Abstract
In this paper, harmonic sources in a BDFM are studied, and a method for specifying rotor and stator space harmonic components is established. A criterion for evaluating different rotor designs is introduced, based on space harmonics. Then the equivalent space and time harmonic circuits are obtained, using basic equivalent circuit. Finally, the effects of these harmonics on the torque-speed characteristic are studied
A method for determination of harmonics responsibilities at the point of common coupling using data correlation analysis
, Article IET Generation, Transmission and Distribution ; Volume 8, Issue 1 , 2014 , Pages 142-150 ; ISSN: 17518687 ; Mokhtari, H ; Sharif University of Technology
Abstract
In this study, a new method is proposed to evaluate the utility harmonic impedance and the harmonics responsibilities at the point of common coupling. The former task is accomplished by involving the harmonic phase angles in the data correlation method, and the latter one is done using an approach based on the fluctuation of the background harmonic voltage. An important advantage of the method is to take the load harmonic impedance into account in appropriate manner. The performance of the proposed method is verified using simulation studies for different cases and also field measurements. Long-term measurement data are used to determine the harmonic contribution of the industrial customers...
Spatial and temporal study of extreme precipitation over north of Iran
, Article Global Nest Journal ; Volume 15, Issue 3 , 2013 , Pages 305-314 ; 17907632 (ISSN) ; Mohammadi, H ; Azizi, G. H ; Taghavi, F ; Masomnia, A ; Roradeh, H ; Masoompour, J ; Sharif University of Technology
2013
Abstract
Two main focus of this study is the spatial and temporal analysis of annual 24-hour extreme precipitation amounts for different return periods, and the intra-annual variability of the frequency of month to month maximum rainfall using harmonic analysis. Data for analysis gathered from 51 stations that well-scattered at north of Iran (Caspian Sea's southern region). These data are analyzed using extreme values theory and harmonic analysis techniques. The results indicate that the Gen. Extreme Value (Jenkinson solution) is more appropriate than the linear Gumbel solution for the extreme value law. The maximum expected values of 200
Constructing an entangled state in the Heisenberg picture for inflationary cosmology
, Article Physical Review D ; Volume 97, Issue 6 , March , 2018 ; 24700010 (ISSN) ; Taghizadeh Firouzjaee, J ; Sharif University of Technology
American Physical Society
2018
Abstract
The effects of the entanglement of the inflaton field which initially entangled with those of another field on observables like power spectrum are known in the context of the Schrödinger field theory. To clarify this effect in the Heisenberg picture, there were some attempts to construct the initial entangled state by making use of an entangled transformation (like Bogoliubov transformation) between the Bunch-Davies vacuums and squeezed states. We study the role of the time-dependent entangled transformation in the Schrödinger field theory. We derive the relation between two vacuum states which their mode functions are transformed by the entangled transformation in Schrödinger picture. We...
Wide-range single-ended CMOS track-and-hold circuit
, Article IEICE Electronics Express ; Volume 4, Issue 12 , 2007 , Pages 400-405 ; 13492543 (ISSN) ; Sedighi, B ; Sharif Bakhtiar, M ; Sharif University of Technology
2007
Abstract
This paper investigates the performance of a MOS track-and-hold circuit as the front end of a wide input range and high-speed single-sided ADC. In order to reduce charge injection and clock feedthrough errors, a new technique for employing a dummy transistor in the bootstrapped switch of the track and hold circuit is introduced. Performance of the proposed circuit for the two cases of constant and non-linear hold capacitor is studied. It is also shown that how and when dummy switch and bulk switching method can improve the accuracy of theT/H. © IEICE 2007
Harmonic class loading for damage identification in beams using wavelet analysis
, Article Structural Health Monitoring ; Volume 6, Issue 1 , 2007 , Pages 67-80 ; 14759217 (ISSN) ; Golafshani, A. A ; Beheshti Aval, S. B ; Noori, M ; Sharif University of Technology
2007
Abstract
The harmonic displacement response of a beam is utilized as the input signal function in wavelet analysis. Sudden changes in the spatial variation of transformed response identify the location of damages and defects. The damage incurred causes a change in the stiffness or mass of the beam. This causes a localized singularity which can be identified by a wavelet analysis of the displacement response. In this article, it is shown that using harmonic response is superior to the static deflection response and this approach is more effective in the presence of noise and more sensitive to the versatility of the applied harmonic loads. © 2007 SAGE Publications
Current harmonic compensation using predictive controllers
, Article Journal of Circuits, Systems and Computers ; Volume 13, Issue 5 , 2004 , Pages 1065-1078 ; 02181266 (ISSN) ; Kordari, K ; Sharif University of Technology
2004
Abstract
The power quality has become a major concern since late 1980's. There has been increasing interest in studying power quality problems, one of which is the existence of the current/voltage harmonics. In order to eliminate these harmonics, different methods have so far been proposed and developed. In this paper, line current harmonics reduction is achieved by using an active filter. More specifically, our aim is to introduce a proper control design method for the current control part of the active filter. To achieve the goal, two different predictive controllers are examined. Due to the existing physical constraints (switching frequency and computational limits) in real applications, a new...
Dynamic model for brushless doubly-fed machine with stator winding faults
, Article International Review of Electrical Engineering ; Volume 4, Issue 6 , 2009 , Pages 1223-1230 ; 18276660 (ISSN) ; Sotoodeh, P ; Oraee, H ; Sharif University of Technology
Abstract
In this paper, a detailed analytical model for dynamic analysis of the Brushless Doubly-Fed Machine is presented. The model is capable to predict the machine behavior under different modes of operation including: simple induction mode, cascade mode and synchronous mode, both with and without winding faults and unbalanced excitations. The proposed approach employs the basic principles of the generalized harmonic theory for calculating self inductances and mutual inductances of circuits with any distribution of conductors. Dynamic equations of modified coupled-circuit method are then solved to compute the currents flowing in the stator windings and rotor loops. Copyright © 2009 Praise Worthy...
Study of the numerical artifacts in differential analysis of highly conducting gratings
, Article Optics Letters ; Volume 33, Issue 2 , 2008 , Pages 159-161 ; 01469592 (ISSN) ; Mehrany, K ; Jazayeri, A. H ; Sharif University of Technology
2008
Abstract
Li's Fourier factorization rule [J. Opt. Soc. Am. A 13, 1870 (1996)] was recently shown to be problematic to apply to highly conducting metallic gratings. We provide further information about the applicability of different differential methods and are concerned with the relation of observed numerical artifacts, the total number of retained space harmonics, the presence of both positive and negative permittivity inside the groove region, and the validity of Li's inverse rule. Two different cases corresponding to lossless and low-loss binary metallic gratings are considered, and it is shown that an increase in the number of retained space harmonics can relieve the presence of numerical...
Efficient high harmonic generation of bromine molecule by controlling the carrier-envelope phase and polarization of driving laser pulse
, Article Chemical Physics Letters ; Volume 719 , 2019 , Pages 27-33 ; 00092614 (ISSN) ; Monfared, M ; Sharif University of Technology
Elsevier B.V
2019
Abstract
The generation of ultrashort attosecond pulse requires both an enhanced high harmonic generation and the spectral-phase control. In the present work, an efficient method is theoretically investigated for extending HHG cutoff energy in Br2 molecule using TDDFT. The effects of molecular orientation and carrier-envelope phase of the laser on the high harmonic spectrum are analyzed. As a result, by the fine modulations of the laser field, the harmonic plateau is enlarged and the position of structure-induced interference minimum shifts. We also provide a physical picture on the intensity dependence of the spectral minima in the harmonic spectra
An optimal measurement placement method for power system harmonic state estimation
, Article EPE 2012 - Proceedings of the 2012 International Conference and Exposition on Electrical and Power Engineering ; 2012 , Pages 271-275 ; 9781467350013 (ISBN) ; Mokhtari, H ; Karimi, H ; Sharif University of Technology
2012
Abstract
Harmonic state estimation (HSE) method has been used to locate harmonic sources and estimate harmonic distribution in power systems with limited number of harmonic meters. This paper focuses on a new technique for optimal placement of measurement devices and observability analysis for power systems harmonic state estimation. The proposed method optimizes the number of measurements and minimizes the error of estimation at the same time. The method is tested on the IEEE 14-bus power system to show its precision
Harmonic Sharing Determination between a Load and Utility in Multi Input - Multi Output Feeders
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
Harmonic distortions are one of the most important power quality issues in power systems. Nowadays, vast peneteration of the power electronic devices and nonlinear loads, which are the harmonic-producing devices in a network, causes increase in harmonic distortion level in distribution systems, which has negative impacts. The high level of harmonic peneteration in power system can lead to increase in losses and reduction of network equipment’s life. So, system operators have to find and improve some solutions to control the harmonic level. In this way, investigation in harmonic contribution of major nonlinear loads and utilities is a criticl task, specially when a harmonic problem occures....
An analytical approach to obtain optimum load impedance using X-parameters®
, Article 2012 Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits, INMMIC 2012 ; 2012 ; 9781467329491 (ISBN) ; Banai, A ; Cai, J ; Brazil, T ; Sharif University of Technology
2012
Abstract
This paper introduces an analytical approach to obtain fundamental and harmonic load-pull contours using X-parameters. This method is proposed to obtain the optimum load impedance at different harmonics. This approach has been applied on a two port X-parameter model and its results are independently verified by ADS simulation
High-order harmonic generation of CO and N2 molecules under linearly- and bi circularly-polarized laser pulses by TD-DFT
, Article Laser Physics ; Volume 28, Issue 7 , 2018 ; 1054660X (ISSN) ; Sadighi Bonabi, R ; Mohsen Nia, M ; Irani, E ; Sharif University of Technology
Institute of Physics Publishing
2018
Abstract
We present a method for high-order harmonics generation of N2 and CO molecules under two-color circularly polarized counter-rotating laser pulses at frequencies of and 2. Pulse envelope in this investigation is sin-squared and the intensity of each laser beam is with ten-optical cycle (o.c.). We show that an isolated pulse with a pulse duration shorter than 20 attosecond from the superposition of several harmonics can be generated. Both two-color linearly- and bicircularly-polarized laser pulses are considered. Our results have also been compared with the outcomes of the previous theoretical works as well as experiment observations. It is found that for CO molecule, the...
High harmonic generation in magnetic underdense plasma
, Article Progress in Electromagnetics Research Symposium 2009, PIERS 2009 Beijing, Beijing, 23 March 2009 through 27 March 2009 ; Volume 2 , 2009 , Pages 1030-1032 ; 15599450 (ISSN); 9781618390554 (ISBN) ; Abbasi, F ; Beijing Jiaotong University; MIT Cent. Electromagn. Theory Appl./Res. Lab. Electron.; National Natural Science Foundation of China; The Electromagnetics Academy; The Electromagnetics Academy at Zhejiang University; Zhejiang University ; Sharif University of Technology
Electromagnetics Academy
2009
Abstract
A high intensity laser normal incident (1020 W/cm2) on a vacuum-plasma interface produces high harmonics in reflected components. Efficiency of high harmonics increases with the intensity laser incident. So the non-relativistic velocities of the particles vary to the relativistic velocities. Consequently, electrons in such high fields are predicted to quiver nonlinearly, moving in figure eight patterns, rather than in straight lines, and thus to radiate photons at harmonics of the frequency of the incident laser light. To meet the challenge of high power, short wavelength coherent radiation generation, it is quite to investigate the conditions under which harmonics generation efficiency can...
A new definition for total harmonic distortion in inverter-fed induction motors including loss considerations
, Article 42nd International Conference on Large High Voltage Electric Systems 2008, CIGRE 2008, Paris, 24 August 2008 through 29 August 2008 ; 2008 ; Kaboli, S ; Oraee, H ; Sharif University of Technology
2008
Abstract
Harmonic information is necessary tools in the estimation of motors life and performance. The conventional expression of harmonic amount is carried out by total Harmonic distortion. This distortion factor is only related to amplitude of harmonics while the motor loss is affected by frequency domain of them. In this paper a new definition of this factor has been presented. This definition includes the frequency of harmonics as well as their amplitudes. Experimental results verify the validity of this new definition
Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at √sNN = 2.76 TeV
, Article Journal of High Energy Physics ; Vol. 2014, Issue. 2 , 2014 ; ISSN: 1029-8479 ; Khachatryan, V ; Sirunyan, A. M ; Tumasyan, A ; Adam, W ; Bergauer, T ; Dragicevic, M ; Ero, J ; Fabjan, C ; Friedl, M ; Fruhwirth, R ; Ghete, V. M ; Hartl, C ; Hormann, N ; Hrubec, J ; Jeitler, M ; Kiesenhofer, W ; Knunz, V ; Krammer, M ; Kratschmer, I ; Liko, D ; Mikulec, I ; Rabady, D ; Rahbaran, B ; Rohringer, H ; Schofbeck, R ; Strauss, J ; Taurok, A ; Treberer-Treberspurg, W ; Waltenberger, W ; Wulz, C. E ; Mossolov, V ; Shumeiko, N ; Suarez Gonzalez, J ; AlDerweireldt, S ; Bansal, M ; Bansal, S ; Cornelis, T ; DeWolf, E. A ; Janssen, X ; Knutsson, A ; Luyckx, S ; Mucibello, L ; Ochesanu, S ; Roland, B ; Rougny, R ; Van Haevermaet, H ; Van Mechelen, P ; Van Remortel, N ; Van Spilbeeck, A ; Sharif University of Technology
Abstract
Azimuthal dihadron correlations of charged particles have been measured in PbPb collisions at √s NN = 2.76TeV by the CMS collaboration, using data from the 2011 LHC heavy-ion run. The data set incluDes a sample of ultra-central (0-0.2% centrality) PbPb events collected using a trigger based on total transverse energy in the hadron forward calorimeters and the total multiplicity of pixel clusters in the silicon pixel tracker. A total of about 1.8 million ultra-central events were recorDed, corresponding to an integrated luminosity of 120 μb-1. The observed correlations in ultra-central PbPb events are expected to be particularly sensitive to initial-state fluctuations. The single-particle...