• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 41
  • 10
  • 4
  • 3
  • 2
  • 2
  • 1
  • Tagged with
  • 72
  • 72
  • 36
  • 28
  • 26
  • 23
  • 17
  • 15
  • 14
  • 13
  • 13
  • 10
  • 8
  • 7
  • 7
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Design And Implementation Of A Voltage Source Converter Based Hybrid Active Power Filter

Ucak, Onur 01 September 2009 (has links) (PDF)
This research work is devoted to the analysis, design and implementation of a shunt connected Hybrid Active Power Filter by the use of a lower rated voltage source PWM converter, and a series connected LC passive filter. In recent years, voltage and current harmonics have become a serious problem both in transmission and distribution systems, due to the widespread usage of non-linear loads such as diode/thyristor rectifiers, electric arc furnaces and motor drives. In order to obtain a better performance than those of the conventional passive filter solutions, active power filters (APF) have been worked on and developed. Among various configurations listed in the literature, conventional shunt connected voltage source active power filter is widely used in industrial applications. Unfortunately, for large power applications, the losses and the rating of the APF increase considerably. As a result, various hybrid filter topologies have been developed which combine the advantages of both passive and active filters. In this thesis, a shunt connected hybrid active power filter is developed by combining a 4.7 kVA voltage source converter and a 30kVAR 7th harmonic passive filter. The developed system has been implemented to eliminate the most dominant 5th, 7th and 11th current harmonic components existing at 400V low voltage bus of TUBITAK SPACE Technologies Institute. The theoretical and experimental results have shown that the DC link voltage of the converter and the rating of APF are minimized while keeping the filtering performance satisfactory.
42

Modelling and optimised control of a wind-photovoltaic microgrid with storage.

Letting, Lawrence Kiprono. January 2013 (has links)
D. Tech. Electrical Engineering. / Discusses the objectives of thesis in terms of : 1. To formulate and integrate models for the wind-turbine, induction generator, PV array, battery, supercapacitor, and power electronic converters in a form suitable for studying the dynamic behaviour of the microgrid; 2. To develop an online optimisation algorithm and use it to optimise local control algorithms for PV array, energy storage system, and the doubly fed induction generator. 3. To formulate an efficient power sharing strategy between battery and supercapacitor. 4. To implement an overall control system which sets the power reference for the energy storage system and ensures that the requested power demand is supplied to the grid.
43

Modeling and Simulation of an Autonomous Hybrid Power System

Gkiala Fikari, Stamatia January 2015 (has links)
In this report, the modeling process and operation of an autonomous hybrid power system is studied. It is built based on a hypothetical case study of electrification of a remote village of 100 inhabitants in Kenya. The power demand is estimated and the costs of equipment components are specified after extensive research, so that the techno-economical design of the system can be carried out. The microgrid consists of photovoltaics, wind turbine, batteries, diesel genset, basic loads and water pumping and purification load. The system is modeled and simulated in terms of power management and its operation as well as the performance of the dispatch strategy is assessed. Problems like the management of extra power or tackling the deficit of power in the system are addressed. The model represents reliably the behavior of the microgrid and several improving actions are suggested.
44

Topologias de filtros híbridos de potência com número reduzido de chaves

SILVA FILHO, Luís Rodrigues da 30 January 2015 (has links)
Submitted by Haroudo Xavier Filho (haroudo.xavierfo@ufpe.br) on 2016-03-01T13:09:14Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Silva Filho, Luis Rodrigues da.pdf: 5874183 bytes, checksum: 60b4246d84e077fb2131d50faca19bd3 (MD5) / Made available in DSpace on 2016-03-01T13:09:14Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Silva Filho, Luis Rodrigues da.pdf: 5874183 bytes, checksum: 60b4246d84e077fb2131d50faca19bd3 (MD5) Previous issue date: 2015-01-30 / CAPES / Atualmente, um grande número de computadores e outras cargas elétricas sensíveis ligadas à rede elétrica são diretamente afetados por problemas de qualidade de energia. Uma das questões mais importantes está relacionada com as correntes harmônicas geradas pelo aumento do número de cargas não-lineares conectadas ao sistema elétrico, tais como retificadores a diodo e tiristores. Como consequência, estes harmônicos podem causar distorções na tensão, perdas adicionais no sistema de energia e mau funcionamento de equipamentos eletrônicos sensíveis. A literatura apresenta diferentes topologias de filtros híbridos de potência visando a compensação harmônica de corrente. Este trabalho apresenta o estado da arte de algumas topologias, realizando uma análise comparativa entre elas. Em comum, todas as topologias possuem um reduzido número de chaves. Adicionalmente, é apresentada uma nova topologia chamada six-switch two-leg hybrid power filter, que além de apresentar um número reduzido de chaves quando comparada a outras topologias com dupla compensação, é capaz de fornecer compensação total, mesmo para cargas com um alto conteúdo harmônico. Os resultados experimentais são apresentados para um protótipo, a fim de demonstrar que o desempenho de compensação harmônica da proposta cumpre a norma IEEE 519. / Nowadays, a large number of computers and other sensitive electrical loads connected to the power grid are directly affected by power quality problems. One of the most important issues is related to current harmonics generated by the increasing number of nonlinear loads connected to the power grid, such as diode and thyristor front-end rectifiers. As consequence, these harmonics can cause voltage distortions, additional losses in the power system and malfunction of sensitive electronic equipment. The literature presents several hybrid power filters topologies, aiming current harmonic compensation. This work presents some state of - art topologies with reduced number of switches and performs a comparative analysis among them. Additionally, a six-switch two-leg hybrid power filter topology, that presents a reduced number of switches when compared with dual topologies, is proposed. The solution is capable of providing fully compensation even for loads with high harmonic content. Experimental results, obtaneid by a prototype, are presented in order to demonstrate that the harmonic compensation performance meets the IEEE 519 standard.
45

Feasibility Study of Solar-Wind Hybrid Power System for Rural Electrification at the Estatuene Locality in Mozambique

Silinto, Berino Francisco, Bila, Nelso Alberto January 2015 (has links)
This project work focuses on the feasibility study of a hybrid PV-Wind System for rural electrification at the Estatuene Locality in southern Mozambique. This is in line with electricity network expansion, which, in Mozambique shows high implementation cost and low operation cost. Through field research, an analysis was made of the actual electrical demand in the Estatuene rural community. The wind data was collected from the installed weather stations in the region while the solar data were extracted internally from the HOMER software by introducing the site coordinates. All the configurations, simulations and selection of hybrid systems were also made using HOMER. For the Estatuene rural community it was estimated a scaled annual average demand of 9.4 kWh/day with a peak load of 1.4 kW for DC charge; and a total scaled annual average of 133 kWh/day with a peak load of 15.3 kW for AC Charge. The annual mean solar potential is 5.205 kWh/m2/d, and the mean wind speed is 4.84 m/s for 12 meters above the ground. Thus the calculations and the selection of the best configuration of the hybrid system were crossed out with the technical specifications and costs of photovoltaic panels, wind turbines, power converter, batteries, and the electricity network, specifically for the comparison between an optimum hybrid system solution and two separate ones. The calculations presented an analysis of the technical and the financial viability of the selected hybrid system for local electric power production.
46

A behavioral model of solar/diesel/Li-ion hybrid power systems for off-grid applications : Simulation over a lifetime of 10 years in constant use

Gaudray, Gordon January 2015 (has links)
Remote hybrid power systems (RHPS) serve local off-grid loads or various island grids when no grid extension is possible. They combine renewable resources, conventional generators and energy storage systems in order to balance the load at any moment, while ensuring power quality and energy security similar to large centralized grids. Modelling such a complex system is crucial for carrying out proper simulations for predicting the system’s behavior and for optimal sizing of components. The model should include an estimation of the renewable resource availability over the period of the simulation, a prediction of the load consumption and time variation, the choice of technologies, a prior dimensioning approach, an energy dispatching strategy between the components and, finally, the behavioral model of all components. This study limits its scope to the simulation of a RHPS composed of solar PV panels, a diesel generator set, and a Li-ion battery bank supplying a dynamic isolated load with a daily demand variation between 10 kW and 80 kW. Methods for building load scenarii are explained first and then, rules of thumbs for selecting the technologies and pre-sizing the components are reviewed. Commonly used dispatching strategies are described before detailing the algorithm of a Matlab behavioral model for the system’s components with an emphasis on the proper prediction of performance and aging for the Li-ion battery model. Finally, a 10-year simulation is carried out over a case study and the results are analyzed.
47

Jak dlouho by musela jezdit stará škodovka, aby vyprodukovala tolik emisí, jako by vyprodukovala výroba jednoho nového ekologického auta? / How long would it have to an old Skoda car to drive, that produced as many emissions as produced the production of new environmental car

Jurečková, Šárka January 2010 (has links)
This thesis covers primarily the detection of operating emission of an old Škoda Felicia car and the emission produced during the manufacturing of a new Toyota Prius, as the selected representative of an ecological car. The thesis also touches on hybrid technology in itself, the question of the greenness of hybrid cars, sphere of emission, but also related problems so called "scrapping" and its influence on environment and also current situation in automobile industry. The target of this study is calculation of operation time of an old Škoda Felicia during which the CO2 emission will reach the same amount of emission produced during manufacturing of a Toyota Prius. The objective is to point out incompetent and therefore not always serious comparison of cars greenness when only the operating CO2 is being compared. Other energy consumption and therefore also the greenhouse gases production is related with the car manufacturing, raw material extraction, petroleum processing and other economic sectors affected by production. Emission laboratory measurement executed by TÜV SÜD Czech discovered that the old Škoda produces 260m/km CO2 during its real running time. For the emission calculation was used an American model EIO-LCA created by Green Design Institute at Carnegie Mellon University that records ecological influence of car production, in stated amount, on all economy sectors. The outputs are quoted in CO2 equivalent. According to this model during manufacturing of 1 hybrid car 13.5 t of CO2e (equivalent CO2). is produced. Recalculation found out that the old Škoda Felicia could run for more than 5 years in order to produce as much emission as the manufacturing of new Toyota Prius third generation.
48

Μελέτη δομής και λειτουργίας ενός υβριδικού ηλεκτρομηχανικού συστήματος μετατροπής της ενέργειας από ανανεώσιμες σε ηλεκτρική

Αρχοντίκη, Μαρία 16 June 2011 (has links)
Στις μέρες μας παρατηρείται μία εγκατάλειψη των συμβατικών μορφών ενέργειας και μια ταυτόχρονη στροφή προς τις ανανεώσιμες. Από την συνδυασμένη χρήση δύο ή και περισσότερων ανανεώσιμων, συνήθως, μορφών ενέργειας προκύπτουν τα υβριδικά συστήματα ηλεκτρικής ενέργειας. Στα πλαίσια της παρούσας διπλωματικής αναλύεται ένα υβριδικό σύστημα το οποίο χρησιμοποιεί δύο ανανεώσιμες πηγές ενέργειας, αυτές του νερού και του αέρα. Η ανάλυση αυτού του υβριδικού συστήματος στηρίζεται σε δεδομένα τα οποία προέρχονται από το υπό κατασκευή υβριδικό έργο της Ικαρίας. Τέτοια συστήματα νησιών χαρακτηρίζονται ως συστήματα Μη $ιασυνδεδεμένων Νήσων, καθώς είναι αυτόνομα, αξιοποιώντας πηγές ενέργειας με τις οποίες τα νησιά αυτά είναι «ευλογημένα»,σε σχέση με άλλες περιοχές της ενδοχώρας όπως π.χ ο άνεμος. Στο πρώτο κεφάλαιο γίνεται μια σύντομη περιγραφή των βασικών αρχών στις οποίες στηρίζεται η κατασκευή των υδροηλεκτρικών και των αιολικών σταθμών και δίνεται ο ορισμός των υβριδικών συστημάτων ηλεκτρικής ενέργειας . Στα κεφάλαια δύο και τρία περιγράφονται βασικά μεγέθη για το υβριδικό έργο της Ικαρίας, καθώς και κανονισμοί λειτουργίας για αυτό . Στο κεφάλαιο 4 παρατίθεται η λογική στην οποία στηρίχθηκαν οι προσομοιώσεις καθώς και αποτελέσματα, γραφήματα και συμπεράσματα τα οποία προέκυψαν από αυτές .Ακολουθούν το παράρτημα και η βιβλιογραφία . / Nowadays there is an abandonment of conventional energy and a simultaneous shift to renewable energy. From the combined use of two or more renewable, usually, the resulting energy hybrid power systems. In the present study analyzed a hybrid system which uses two sources of renewable energy, which water and air. The analysis of this hybrid system is based on data from the hybrid under construction project of Ikaria. Such systems are islands designated as Non systems $ iasyndedemenon Islands, are autonomous, drawing energy with which the islands they are "blessed" than other inland areas like the wind. The first chapter is a brief description of the principles underpinning the construction of hydroelectric and wind power stations and given the definition of hybrid power systems. Chapters two three a.m. described fundamentals for the hybrid project Ikaria and operating regulations for this. Chapter 4 sets out the rationale relied on simulations and the results, charts, and conclusions drawn from them. Here are the Annex and the literature.
49

Comportement des supercondensateurs en environnement sévère et conception optimale d’alimentations hybrides embarquées aérospatiales / Behavior of supercapacitors in severe environment and optimal design of hybrid power supplies for aerospace applications

Fleury, Benoît 14 May 2013 (has links)
L’objectif de cette étude est de développer une alimentation multisources exploitant la complémentarité batterie/supercondensateurs pour gagner en masse sur le stockage de l’énergie électrique embarquée à bord des aéronefs et des véhicules spatiaux. L’étude se déroule en trois parties :Dans la première partie, un outil d’aide à la décision permettant développer une alimentation hybride pour une application donnée est présenté. Cet outil a pour but d’estimer la masse optimale d’une alimentation hybride à partir des seules informations d’énergies spécifiques et puissances spécifiques des sources candidatesLa deuxième partie de l’étude s’appuie sur la complémentarité d’une étude bibliographique sur le comportement interne des supercondensateurs, couplée avec une campagne expérimentale de caractérisation et de vieillissement des supercondensateurs, pour construire et identifier les modèles multiphysiques de références commerciales de supercondensateurs nécessaires à l’optimisation fine du dimensionnement de l’alimentation hybride.À partir du modèle des sources, la troisième et dernière partie de cette étude a pour objectif de présenter la conception d’une architecture électrique répondant au besoin. En particulier, l’alimentation hybride proposée dans cette partie exploite dynamiquement et au maximum de leur capacité chacune des deux sources, tout en prenant soin de ne pas les contraindre excessivement. De par cette manière de faire, on se prémunit contre d’éventuelles défaillances des sources liées à leur utilisation abusive / The aim of this study is to develop an hybrid power supply using the complementarities between batteries and supercapacitors in order to improve the mass of electrical storage systems on aircrafts and spacecrafts.The study is divided into three parts: In the first part, a decision-making tool to develop a hybrid power supply given a mission profile is presented. Thanks to this tool, an estimation of the optimal mass of the hybrid power supply is done based only on the specific energy and the specific power of the sources.The second part is firstly composed of a synthesis of bibliography results on the internal behavior of supercapacitors; secondly an experimental test campaign is described. Its aim is characterizing, modeling and identifying the multiphysics behavior and ageing of supercapacitors on several commercial references. Those models are required for the fine sizing optimization of the hybrid power supply. Basing on the internal model of the sources, the aim of the third part of this study is to present the development of an hybrid architecture battery/supercapacitors which fulfills the electrical need for a specific application. This hybrid power supply takes dynamically advantage of the electrical sources at the maximum of their possibilities, but without overstressing them at the same time. Thanks to that, the aging rate of the sources and the failure rate of the system are limited
50

Hybrid Power System Intelligent Operation and Protection Involving Plug-in Electric Vehicles

Ma, Tan 02 April 2015 (has links)
Two key solutions to reduce the greenhouse gas emissions and increase the overall energy efficiency are to maximize the utilization of renewable energy resources (RERs) to generate energy for load consumption and to shift to low or zero emission plug-in electric vehicles (PEVs) for transportation. The present U.S. aging and overburdened power grid infrastructure is under a tremendous pressure to handle the issues involved in penetration of RERS and PEVs. The future power grid should be designed with for the effective utilization of distributed RERs and distributed generations to intelligently respond to varying customer demand including PEVs with high level of security, stability and reliability. This dissertation develops and verifies such a hybrid AC-DC power system. The system will operate in a distributed manner incorporating multiple components in both AC and DC styles and work in both grid-connected and islanding modes. The verification was performed on a laboratory-based hybrid AC-DC power system testbed as hardware/software platform. In this system, RERs emulators together with their maximum power point tracking technology and power electronics converters were designed to test different energy harvesting algorithms. The Energy storage devices including lithium-ion batteries and ultra-capacitors were used to optimize the performance of the hybrid power system. A lithium-ion battery smart energy management system with thermal and state of charge self-balancing was proposed to protect the energy storage system. A grid connected DC PEVs parking garage emulator, with five lithium-ion batteries was also designed with the smart charging functions that can emulate the future vehicle-to-grid (V2G), vehicle-to-vehicle (V2V) and vehicle-to-house (V2H) services. This includes grid voltage and frequency regulations, spinning reserves, micro grid islanding detection and energy resource support. The results show successful integration of the developed techniques for control and energy management of future hybrid AC-DC power systems with high penetration of RERs and PEVs.

Page generated in 0.0774 seconds