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Investigation of the effects of compact fluorescent lamps in power distribution systems
, Article 2011 10th International Conference on Environment and Electrical Engineering, EEEIC.EU 2011 - Conference Proceedings, 8 May 2011 through 11 May 2011 ; May , 2011 , Page(s): 1 - 4 ; 9781424487820 (ISBN) ; Kazemi, A. R ; Dehghanian, P ; Vakilian, M ; Sharif University of Technology
2011
Abstract
The desire to decrease electrical loading by using energy efficient lighting has resulted in a high level of attention to replacing conventional incandescent lamps with compact fluorescent lamps (CFL). In Iran from energy management point of view, people are encouraged by ministry of power to use CFLs. Also after elimination of subsidies, the substantial increase in electric energy price resulted in a high level of penetration of CFLs in electricity grid. CFL is a nonlinear load, therefore it injects harmonic to the network. In past, due to lower application of CFL, these harmonics were ignored, however today by the widespread application of CFLs; these small sources are combined and have...
Analysis of random capacitor mismatch errors in pipeline analog-to-digital converters
, Article Proceedings - IEEE International Symposium on Circuits and Systems ; 2011 , Pages 514-517 ; 02714310 (ISSN) ; 9781424494736 (ISBN) ; Medi, A ; Sharif University of Technology
Abstract
A new modeling and analysis of the nonlinearities caused by the capacitor mismatch errors in the pipeline analog-to-digital converters (ADCs) is presented. Error in each stage is modeled by an input-referred gain error and a nonlinear term. A method is proposed for calculation of the ADC integral nonlinearity (INL) from the total input referred error. Analytical expressions for estimation of the ADC INL in terms of standard deviation of random capacitor mismatch errors are derived. The proposed model is verified by system-level Monte Carlo simulations
Hierarchical Co3O4/Co(OH)2 nanoflakes as a supercapacitor electrode: experimental and semi-empirical model
, Article ACS Applied Materials and Interfaces ; Volume 7, Issue 21 , 2015 , Pages 11172-11179 ; 19448244 (ISSN) ; Naseri, N ; Moshfegh, A. Z ; Sharif University of Technology
American Chemical Society
2015
Abstract
In this research, facile and low cost synthesis methods, electrodeposition at constant current density and anodization at various applied voltages, were used to produce hierarchical cobalt oxide/hydroxide nanoflakes on top of porous anodized cobalt layer. The maximum electrochemical capacitance of 601 mF cm-2 at scan rate of 2 mV s-1 was achieved for 30 V optimized anodization applied voltage with high stability. Morphology and surface chemical composition were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. The size, thickness, and density of nanoflakes, as well as length of the porous anodized Co layer were measured about 460 ± 45 nm,...
General Characterization Method and a Fast Load-Charge-Preserving Switching Procedure for the Stepwise Adiabatic Circuits
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 63, Issue 1 , 2016 , Pages 80-90 ; 15498328 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
An analytical method is presented to characterize stepwise adiabatic circuits (SACs). In this method, the SACs are modeled as a discrete time system. Unlike previous methods, the stability is verified for arbitrary load capacitor ratios. Moreover, this method presents analytical derivations to offer an area/energy efficient design methodology. MATLAB simulations, post-layout simulations in the CMOS 0.18 μm technology, silicon measurements, and measurements based on discrete components confirm the precision of the analytical derivations. Using the proposed design methodology, a capacitive tank has been designed which reduces the energy consumption by 20% while the total size of the tank...
Direct torque control of four-switch three phase inverter fed induction motor using a modified SVM to compensate DC-link voltage imbalance
, Article 2009 International Conference on Electric Power and Energy Conversion Systems, EPECS 2009, 10 November 2009 through 12 November 2009, Sharjah ; 2009 ; 9789948427155 (ISBN) ; Zolghadri, M. R ; Sharif University of Technology
Abstract
In this paper the direct torque control (DTC) of the induction motor fed by four switch three phase inverter (FSTPI) is investigated. A modified space vector modulation (SVM) approach with optimal voltage vector sequence is proposed to compensate the effect of dc-link voltage variations caused by circulating phase current through the capacitor bank. SVMDTC scheme of FSTPI fed induction motor is based on stator flux oriented control. According to simulation results, this approach significantly reduces the effect of dc-link voltage variation on the output torque, flux and current waveforms
Role of nitrogen doping at the surface of titanium nitride thin films towards capacitive charge storage enhancement
, Article Journal of Power Sources ; Volume 359 , 2017 , Pages 349-354 ; 03787753 (ISSN) ; Chaker, M ; Achour, H ; Arman, A ; Islam, M ; Mardani, M ; Boujtita, M ; Le Brizoual, L ; Djouadi, M. A ; Brousse, T ; Sharif University of Technology
Abstract
We recently reported an impressive cycling stability (over 20,000 cycles) of titanium nitride (TiN) electrodes with high specific capacitance. It is anticipated that nitrogen (β−N) doping in the oxidized surface of TiN film plays a crucial role in charge storage mechanism and stability of this material. In this work, we offer an evidence on the effect of β−N doping on improvement in specific capacitance of vacuum annealed TiN thin films. The annealing of the TiN films leads to the diffusion of the excess β−N from sub-surface to oxidized TiN film surface without further oxidation of the electrode surface. We demonstrate an increase in the TiN areal capacitance upon an increase in the amount...
Decorative reduced graphene oxide/C3N4/Ag2O/conductive polymer as a high performance material for electrochemical capacitors
, Article Applied Surface Science ; Volume 447 , 2018 , Pages 374-380 ; 01694332 (ISSN) ; Salari, H ; Daliri, A ; Omidi, M ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Here in, reduced graphene oxide/g-C3N4/Ag2O nano structure (RGO/CAO) was decorated through a facile and simple chemical method. After that RGO/CAO nano structure combined with poly aniline electrochemically to form a composite electrode. Several physicochemical techniques were applied to characterize the composite electrode such as X-ray Diffraction (XRD), Fourier Transform Infra-Red spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Furthermore, several electrochemical techniques were used to study the performance of composite electrode as an electrochemical capacitor. Results show that RGO/CAO nano...
Mitigating ferroresonance in coupling capacitor voltage transformers with ferroresonance suppressing circuits
, Article IEEE EUROCON 2009, EUROCON 2009, St. Petersburg, 18 May 2009 through 23 May 2009 ; 2009 , Pages 817-822 ; 9781424438617 (ISBN) ; Babazadeh, D ; Esmaeilnia Shirvani, R ; Purrezagholi, M ; Sharif University of Technology
2009
Abstract
In order to restrain ferroresonance in coupling capacitor voltage transformers (CCVT), two kinds of ferroresonance suppression circuits (FSCs) , are proposed in this paper: the resonant type, the fastsaturation reactor type which are connected to secondary side of CCVTs. Frequency domain analyses, for voltage ratio magnitude, are carried out for CCVTs to obtain preferable FSC. Furthermore, using surge suppressors such as metal oxide varistors (MOV) to improve the performance of the FSCs is investigated. Time domain simulations demonstrate that ferroresonance can be cleared in few cycles in presence of FSCs. The Electromagnetic Transients Program (EMTP) is used for modeling and fine-tuning...
Evolution of quantum electronic features with the size of silicon nanoparticles embedded in a sio2 layer obtained by low energy ion implantation
, Article 11th International Autumn Meeting on Gettering and Defect Engineering in Semiconductor Technology, GADEST 2005, 25 September 2005 through 30 September 2005 ; Volume 108-109 , 2005 , Pages 71-76 ; 10120394 (ISSN); 9783908451136 (ISBN) ; Shalchian, M ; Benassayag, G ; Coffin, H ; Bonafos, C ; Dumas, C ; Atarodi, S. M ; Claverie, A ; Pichaud B ; Claverie A ; Alquier D ; Richter H ; Kittler M ; Richter H ; Kittler M ; Sharif University of Technology
Trans Tech Publications Ltd
2005
Abstract
In this paper, we have studied the evolution of quantum electronic features with the size of silicon nanoparticles embedded in an ultra-thin SiO2 layer. These nanoparticles were synthesized by ultralow energy (1 KeV) ion implantation and annealing. Their size was modified using the effect of annealing under slightly oxidizing ambient (N2+O2). Material characterization techniques including transmission electron microscopy (TEM) Fresnel imaging and spatially resolved electron energy loss spectroscopy (EELS) have been used to evaluate the effects of oxidation on structural characteristics of nanocrystal layer. Electrical transport characteristics have been measured on few (less than two...
Analysis and Control Design for TCSC and PSS in a SMIB System Using Hopf Bifurcation
, M.Sc. Thesis Sharif University of Technology ; Karimi, Masoud (Supervisor)
Abstract
Analysis and design of power systems are challenging due to ever increasing dimension of the system and also the nonlinearities involved in the system. The conventional approach is to use linear analysis tools and then investigate the nonlinear impacts by the means of computer simulations. This requires great deal of trial and error and it is not always a timely approach. In this project, we initiate a comprehensive nonlinear analysis for a single-machine infinite-bus system by studying a Hopf bifurcation in its dynamics. We use results of our nonlinear analysis to study how a capacitive compensation such as TCSC works. Subsequently, we design a nonlinear controller for a PSS to have...
Designing an Automated and Smart Electric Power Distribution System
, M.Sc. Thesis Sharif University of Technology ; Vakilian, Mehdi (Supervisor)
Abstract
Feeder reconfiguration is one of the most prominent tasks for loss reduction, reliability improvement and also congestion alleviation in distribution networks. Besides improving abovementioned operational issues, during a long period of time, proper switching in appropriate times can causes a lot of economic savings. Furthermore, it can be intensified when capacitors are implemented and controlled in the network. To reach this purpose, most of the previous literature focuses merely on the power grid reconfiguration. Few of these researches have considered this problem as a dynamic one and studied that in a period of time, e.g. one day, considering fixed level of loads despite the others that...
Design And Simulation Of Fast Spectrum Sensing For Cognitive Radio Networks
, M.Sc. Thesis Sharif University of Technology ; Fotowat Ahmadi, Ali (Supervisor)
Abstract
Deployment of demands, increase in users and new services highlight the necessity of effective frequency allocation i.e. dynamic allocation instead of fixed allocation. Cognitive radio is a proper solution for dynamic frequency allocation. Cognitive radio can scan the spectrum and use the idle bands for transmitting and receiving data. The main part of this radio which is responsible for the most pivotal task is spectrum sensing. Recently, varied methods have been proposed to sense the spectrum. The scope of this research is on designing a very high-speed spectrum sensing system. In this thesis, in order to meet the required scan rate, a tunable complex filter with 40MHz pass-band has...
Design of Tunable, Multi-Mode, Multi-Path Filters
, Ph.D. Dissertation Sharif University of Technology ; Atarodi, Mojtaba (Supervisor)
Abstract
In this dissertation a special category of RF filters known as multi-path filters are introduced, chracterized and implemented. The center frequency of the multi-path filters can be tuned by changing the frequency of the clocks applied to the filter, which makes them attractive for use in multi-standard receivers. In this thesis, different types of multi-path filters are studied and by proposing different circuits, their various applications are covered. First, the concept of multi-path filters and their chracteristics are studied. Then a novel technique to analyze these filters based on Fourier analysis is proposed and then, based on this analysis, a new circuit architecture with reduced...
Design and Implementation of High P.F, Flicker Free, E-capless LED Driver
, M.Sc. Thesis Sharif University of Technology ; Zolghadri, Mohammad Reza (Supervisor)
Abstract
LED Drivers with near 1 power factor, Because of using electrolytic capacitors (to become flicker-free) have lifetime drawbacks. This research will focus on solutions to use magnetic energy storage instead of electrolytic capacitors (used for energy storage) to solve lifetime drawbacks and decrease output light flicker. Calculations show that magnetic energy density using iron powder cores are lower than electrolytic capacitors, also a little lower than ceramic capacitors, but obviously higher than film capacitors. After calculations, conventional isolated and non-isolated LED drivers will be reviewed and new non-isolated off-line 230v with 10w output power LED driver with magnetic energy...
Sensorless Estimation of Lifetime of High-Voltage Power Supplies
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
High voltage power supplies have a wide range of applications, and due to their high cost, it is essential to monitor their condition to predict potential failures and prevent significant losses. The most common cause of power supply failure is the wear and tear of its components. However, these components can be replaced before they wear out completely to prevent the failure of the power supply and, consequently, avoid damaging the load. Estimating the lifetime of power supplies is crucial because it allows for scheduled maintenance and helps prevent significant problems in power supplies. By estimating the lifespan of a power supply, one can anticipate when it may fail, allowing for the...
Effect of power on PPT discharge current
, Article Aircraft Engineering and Aerospace Technology ; Volume 85, Issue 3 , 2013 , Pages 207-214 ; 00022667 (ISSN) ; Sharif University of Technology
2013
Abstract
Purpose - The purpose of this paper is to investigate the effect of power on pulsed plasma thruster (PPT) discharge current with respect to its peak, duration, and behavior while the power elevates in a low power range. Design/methodology/approach - A rectangular parallel-plate breech-fed PPT has been developed with a self-inductor coupling element connecting the PPT cathode to the ignitor plug cathode. The PPT has been operated in vacuum chamber at 10-6mbar and its discharge current has been recorded using a Rogowski coil while input power has been changed by means of varying the capacitor voltage at given capacitance and frequency. Findings - The analysis leads to elucidate the effects of...
Integrating hybrid power source into an Islanded MV microgrid using CHB multilevel inverter under unbalanced and nonlinear load conditions
, Article IEEE Transactions on Energy Conversion ; Volume 28, Issue 3 , 2013 , Pages 643-651 ; 08858969 (ISSN) ; Ghazanfari, A ; Mokhtari, H ; Karimi, H ; Sharif University of Technology
2013
Abstract
This paper presents a control strategy for an islanded medium voltage microgrid to coordinate hybrid power source (HPS) units and to control interfaced multilevel inverters under unbalanced and nonlinear load conditions. The proposed HPS systems are connected to the loads through a cascaded H-bridge (CHB) multilevel inverter. The CHB multilevel inverters increase the output voltage level and enhance power quality. The HPS employs fuel cell (FC) and photovoltaic sources as the main and supercapacitors as the complementary power sources. Fast transient response, high performance, high power density, and low FC fuel consumption are the main advantages of the proposed HPS system. The proposed...
Reactive compensation investigation of TSC systems based on different power factor definitions
, Article IECON Proceedings (Industrial Electronics Conference) ; 2012 , Pages 1393-1398 ; 9781467324212 (ISBN) ; Najmi, V ; Mokhtari, H ; Sharif University of Technology
2012
Abstract
Accurate power factor definitions are of great importance for industries due to the fact that they affect the billing strategy. They also considerably affect the generation and distribution losses of the power system. At the moment, there are some ambiguities in power definitions to be used for this purpose. In recent years, because of a rapid growth in industry and the use of variable loads such as electrical furnaces and variable speed motors, there is a need for fast compensators that are capable of tracking load changes. One of these facilities is TSC, a capacitor bank that is controlled by static switches (thyristors). In this paper, the performance of these compensators in power factor...
A new t-type direct AC/AC converter
, Article 6th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2015, 3 February 2015 through 4 February 2015 ; February , 2015 , Pages 247-252 ; 9781479976539 (ISBN) ; Zolghadri, M. R ; Noroozi, N ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
In this paper a novel T type scheme for 1-phase direct ac/ac converters is proposed. In this topology, frequency changing takes place directly (without common DC voltage bus) through three converters that are connected in a T structure. Unity power factor and precise output voltage regulation is achieved through appropriate control of these three converters. H-bridge converters are implemented, as the basic unit, in each branches of T to make the proposed converter. The converter is controlled such that the average active power of each H-bridges remains zero. So capacitors are implemented in DC links of H-bridges. In comparison to conventional back-to-back converters, life time of each...
One-step fabrication of electrochemically reduced graphene oxide/nickel oxide composite for binder-free supercapacitors
, Article International Journal of Hydrogen Energy ; Volume 41, Issue 39 , 2016 , Pages 17496-17505 ; 03603199 (ISSN) ; Mohammadi, R ; Asadian, E ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
A three-dimensional (3D) graphene/Nickel oxide (ERGO/NiO) composite electrode have been fabricated directly on a Nickel foam substrate via a one-step electrochemical co-deposition in an aqueous solution containing Nickel nitrate and GO. By using this simple and one-step electrochemical deposition, it is possible to produce binder-free composite electrodes with improved electrochemical properties using a low-cost, facile and scalable technique. It is observed from FE-SEM images that graphene oxide sheets affect the electrodeposition of nickel oxide. The optimized ErGO/NiO electrode developed in this work exhibits high charge storage capacity with a specific capacitance of 1715.5 F g−1 at...