Mestrado em Engenharia Elétrica

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A control structure for a bidirectional dc-ac converter with power quality support functions
(Universidade Federal do Espírito Santo, 2022-12-02) Ribeiro, Laila Sindra; Simonetti, Domingos Savio Lyrio; https://orcid.org/0000000159202932; http://lattes.cnpq.br/1107005171102255; Encarnação, Lucas Frizera; Reis, Fernando Soares dos
The expansion of distributed generation, especially photovoltaic, provokes an increase in the number of DC-AC converters connected to the grid. These converters may offer power grid support functions such as power factor correction and compensation of the current harmonic components. Those functions raise the equipment relevance to the grid and contribute to the power system’s confiability and power quality. In this context, the objective of this work is to design a DC-AC converter with the grid support functions as power factor correction and harmonic compensation, besides electrical power interchange. The work focuses on the controller of the converter, with the algorithms embedded in a DSP and power converter in a Hardware In the Loop (HIL). This dissertation includes a theoretical background of the converter topology operation, filter design, and control loops used in the project. Experimental results demonstrate that the converter is capable of operating with grid support functions with a good performance, correcting power factor and compensating 3rd, 5th, and 7th harmonics. Furthermore, the converter can have multiple functions activated, distributing its power capacity to prioritize the chosen operation mode.
Adaptação dos modelos de Markov para um sistema de segmentação e classificação de sinais de eletrocardiograma
(Universidade Federal do Espírito Santo, 2006-04-03) Müller, Sandra Mara Torres; Andreão, Rodrigo Varejão; Bastos Filho, Teodiano Freire; Resende Junior, Fernando Gil Vianna; Salles, Evandro Ottoni Teatini
In this work three incremental adaptation methods for the hidden Markov models (HMM) are studied and implemented, which are based on the Expectation-Maximization (EM), Segmental k-Means and Maximum a Posteriori (MAP) algorithms. These methods, already used in the speech recognition field, are applied here in the electrocardiogram (ECG) segmentation problem. For that, it was used an ECG analysis system able to segment and classify cardiac diseases, like premature ventricular contraction (PVC) and ischemia. The use of these methods allow us to adjust the models to the signal fluctuations commonly met during ambulatory recording. The methods can also be implemented for other kinds of biomedical signals, like electroencephalogram (EEG).
Adequação ao requisito cintilação em sistemas de comunicação via luz visível mediante uso de sinais OFDM com envoltória constante
(Universidade Federal do Espírito Santo, 2018-09-21) Neves, José Luís Costa; Segatto, Marcelo Eduardo Vieira; Silva, Jair Adriano Lima; Nunes, Reginaldo Barbosa; Pereira, Esequiel da Veiga; Pontes, Maria José
The scarcity of electromagnetic spectrum has been a problem in the development of new wireless applications. To solve this problem, visible light communication has emerged as a promising and complementary technology to radiofrequency due to its advantages such as green technology, unlicensed spectrum, low power consumption, high privacy protection and resistance to electromagnetic interference . Allied to this, because it is a technology that uses light emitting diodes for data transmission, also guaranteeing the lighting function, it allows its use in di erent types of environments. Orthogonal frequency division multiplexing (OFDM) in visible light communication systems has been attractive because of its ability to combat intersymbol interference and ensuring high data rates. However, OFDM signals have large amplitude uctuations, resulting in high peak-to-average power ratio (PAPR) and therefore can degrade the quality of the illumination due to Flicker light. Flickering light is harmful to vision and causes eye fatigue, seizures, headache, malaise, and other problems. The present work presents a simulation and experimental study that evaluates the performance of the OFDM transmission technique that transmits signals with constant envelope (CE-OFDM) in a communication system via visible light, by means of the adequacy of the Flickering requirements. The CE-OFDM system is based on the phase modulation of an electric carrier and reduces the PAPR parameter to 3 dB. The results obtained in the line-of-sight channel using a bandwidth of 5 MHz showed that, by adapting the icker requirements and considering the mapping levels 4, 16 and 64-QAM, the CE-OFDM system presents a upper performance than those presented by the conventional OFDM and ACO-OFDM systems. The results also showed that, in the presence of non-linearities introduced by the LED, the CE-OFDM system presents greater robustness.
Algoritmos evolutivos aplicados em projetos de redes ópticas passivas
(Universidade Federal do Espírito Santo, 2019-08-23) Silva, David Moscon Inacio; Rocha, Helder Roberto de Oliveira; https://orcid.org/000000016215664X; http://lattes.cnpq.br/8801325729735529; ; http://lattes.cnpq.br/5946991206561502; Moraes, Renato Elias Nunes de; https://orcid.org/0000-0001-5538-0504; http://lattes.cnpq.br/8323084944042061; Nunes, Reginaldo Barbosa; https://orcid.org/0000-0001-8877-1480; http://lattes.cnpq.br/0301147577506989
Alocação de recursos de uma rede óptica passiva BS-OFDMA-PON usando otimização multiobjetivo
(Universidade Federal do Espírito Santo, 2020-12-18) Flores, Jardel Terci; Rocha, Helder Roberto de Oliveira; https://orcid.org/000000016215664X; http://lattes.cnpq.br/8801325729735529; http://lattes.cnpq.br/0293197276972341; Coura, Daniel Jose Custodio; https://orcid.org/0000-0002-2134-7981; https://orcid.org/0000-0001-8877-1480; http://lattes.cnpq.br/5570995348839001; http://lattes.cnpq.br/0301147577506989; Nunes, Reginaldo Barbosa
With the growing demand for Internet traffic by users and the increased need for transmission rate by applications, it is necessary to use bandwidth efficiently and economically in optical networks, which plays an important role in improving service delivery. Scalability is an important requirement necessary to meet this demand. To serve it, multiple access can be provided through the OFDMA multiplexing technique (Orthogonal Frequency Division Multiple Access), which allows for flexible bandwidth allocation, in addition to being an efficient solution for ISI (Inter Symbol Interference). Through the variation of the signalto-noise ratio OSNR (Optical Signal to Noise Ratio), the level of modulation by subcarrier and the width of the sub-bands of the ONUs (Optical Network Units), this paper approach this important requirement in the architecture BS (Bandwidth Scalable)-OFDMA-PON (Passive Optical Network) in the communication downlink, by means of the optimization of parameters with Multi-Objective Grey Wolf Optimizer algorithm. The results obtained by the numerical simulation demonstrated in optical links that would vary from 20 to 40 km demonstrated the optimization of the resources allocated to the network in order to attend 16 ONUs and 32 ONUs with individual transmission rates equal to 1Gbps, by adopting 4, 8, 16, 32 and 64-QAM e OSNR mappings ranging between 1 e 50 dB. In the first case, 43.17% of the useful subcarriers were allocated to enable a transmission rate of 1 Gbps for all users, for the highest OSNR found, while in the second situation 68.55 % were allocated.
Alocação e dimensionamento de geração distribuída e coordenação otimizada de religador-fusível baseados em algoritmos genéticos
(Universidade Federal do Espírito Santo, 2020-09-18) Ferraz, Renato Santos Freire; Medina, Augusto Cesar Rueda; https://orcid.org/0000000242913153; http://lattes.cnpq.br/7397584412509839; https://orcid.org/0000-0001-7571-1972; http://lattes.cnpq.br/1832936459743268; Trujillo, Joel David Melo; https://orcid.org/0000-0001-5046-1890; http://lattes.cnpq.br/4396532007704107; Fardin, Jussara Farias; https://orcid.org/0000-0003-4785-556X; http://lattes.cnpq.br/1912113095988528
Nowadays, it is possible to notice a growth in the integration of Distributed Energy Resource (DER) in the distribution systems. Despite the many benefits caused by this integration, there are some changes in the load and short-circuit current, which may lead to some issues in the protection system, such as simpathetic tripping, mis-coordination between protective devices, reduction in reach of impedance relays, among others. Moreover, an improper DER integration can generate problems regarding the levels of current, voltage and power factor of the network. Therefore, in this work, the author aimed to conduct a specific study related to the DER optimal allocation and sizing in a distribution feeder, in order to reduce investment and operation costs, regarding the operational and physical limits of the system and generators. In addition, optimal recloser fuse coordination was performed to reduce the actuation time of these protective devices, taking into account the generation and load variation during the day, DER operating modes and all the fault types. In this study, the optimization method adopted was genetic algorithms, due to the adaptive optimization and parallel computing which, based on the selection, crossover and mutation operations, are capable of searching for the optimal solution in the solution space; and the IEEE 34-Node Test Feeder was used to evaluate the proposed methodology. Therefore, from the results, it was possible to notice a 39.420% reduction of the overall cost, from the DER allocation proposed in this analysis. Regarding the coordination between reclosers and fuses, it was possible to achieve a single protection scheme, which is able to coordinate the protective devices for all the analyzed cases simultaneously, avoiding the need for adaptive protection or fault current limiters
Alocação ótima de geração distribuída e de sistemas de baterias em um sistema de distribuição para redução das perdas e controle de tensão nas barras
(Universidade Federal do Espírito Santo, 2021-04-16) Menezes, Luíza Saleme de; Encarnação, Lucas Frizera; https://orcid.org/0000000261627697; http://lattes.cnpq.br/5578918284508758; https://orcid.org/0000-0002-4141-4600; http://lattes.cnpq.br/6971088590764497; Rocha, Helder Roberto de Oliveira; https://orcid.org/0000-0001-6215-664X; http://lattes.cnpq.br/8801325729735529; Donadel, Clainer Bravin; https://orcid.org/0000-0002-3310-2762; http://lattes.cnpq.br/8624415630257203; Medina, Augusto César Rueda; https://orcid.org/0000-0002-4291-3153; http://lattes.cnpq.br/7397584412509839
A proposal of a method to determine the optimal allocation of Battery Banks and photovolvaic painels in a Distribution System. The methodology makes use of the photovoltaic generation profile in the summer season and is based on the load curve of low volt
Alocação ótima de geração distribuída em sistemas de distribuição considerando incertezas no modelo probabilístico de geração
(Universidade Federal do Espírito Santo, 2018-06-08) Pereira, Luan Diego de Lima; Rocha, Helder Roberto de Oliveira; Fardin, Jussara Farias; Donadel, Clainer Bravin; Medina, Augusto César Rueda
This dissertation proposes a methodology to determine a probabilistic model of distributed generation of electrical energy from wind generators and photovoltaic panels and to determine the optimal location of these generators in a distribution network of electric energy, based on technical and economic parameters. The methodology correlates the historical wind speed and solar irradiance data of a particular study region and applies the Monte Carlo simulation to model the power of wind and solar generation, preserving its stochastic nature. The optimization of the location of the distributed generation units aims to minimize the annual losses of active power and the installation costs of the generators connected to the network. The optimization problem also provides for the allocation of capacitor banks in conjunction with the distributed generators, in order to manage the reactive power of the network and, consequently, to improve the voltage profile and minimize the electrical losses. The optimization algorithm used was the Genetic Algorithm, which receives as input the annual data of active power of the wind generators, solar and the demand of the load and search for better solutions to the problem. In order to validate the effectiveness of the proposed model, tests were performed on two real radial feeders, resulting in annual losses of active power, voltage profiles and total investment cost.
Amplificadores Raman em fibras microestruturadas
(Universidade Federal do Espírito Santo, 2009-09-11) Castellani, Carlos Eduardo Schmidt; Cani, Shirley Peroni Neves; Pontes, Maria José; Romero, Murilo Araújo; Segatto, Marcelo Eduardo Vieira
The development of microstructured fibers, also known as photonic crystal fibers (PCF), which has happened principally during the last decade, has raised new possibilities on the field of optics and telecommunications due to its capability of presenting some constructive parameters with non conventional values. In the context of optical communications, more precisely on the construction of optical amplifiers, these photonic crystal fibers also have brought some new interesting possibilities. Due to its capability of at the same time presents very high negative dispersion and high non linearity, it allows for example, the construction of Raman amplifiers with high gains that also compensate dispersion with reduced fiber lengths. The conventional silica-based fibers need tens of kilometers of fiber length to accomplish the same task. Taking advantage of that situation, the main purpose of this dissertation is exactly the project and the study of multi-pump Raman amplifiers operating as discrete devices providing gain and compensating dispersion over the entire C band, using a PCF. In order to project such amplifiers, an optimization technique made through an exhaustive search based on an analytical solution method for the signal propagation is proposed. The analysis of these amplifiers is made via computational simulations that are done with numerical and also analytical models, by means of the verification of the gain, ripple, optical signal to noise ratio (OSNR), and eye penalty parameters. Their performance is also evaluated by comparing the performance of a Raman amplifier operating with a conventional dispersion compensating fiber (DCF).
Análise arquitetural, ontológica e proposta de modelo de referência para a recomendação ITU-T G.805
(Universidade Federal do Espírito Santo, 2011-04-07) Barcelos, Pedro Paulo Favato; Monteiro, Maxwell Eduardo; Garcia, Anilton Salles; Rezende, Luiziana Silveira de; Soares, Rosane Bodart
The ITU-T Recommendation G.805 (ITU-T, 2000) is an important recommendation for transport networks. It describes a generic functional architecture that is independent of technology for this domain and it is used as the basis for recommendations that describe the functional architecture of networks, management, performance analysis and functional specification of equipment. Despite providing a flexible tool for the architecture description, the recommendation presents its concepts textually, leading to confusion because of recursive definitions and unclear examples that are often contradictory. These aspects of the recommendation make it difficult to understand and may confuse the reader. It is important that, due to its fundamental importance, this recommendation is free from these problems. For this purpose, this work proposes the use of ontology-based conceptual modeling techniques for the generation of a reference model for the transport network domain, based on the ITU-T Recommendation G.805. In addition to the recommendation main concepts, the advantages of creating an ontology-based reference model and the main technologies used for this purpose are also presented. An architectural analysis and a restructuring of the components defined by the recommendation are performed together with an ontological evaluation of it. Cases of incompleteness, ambiguities and other deficiencies are checked and solutions are pointed. Finally, the ontology-based reference model developed for the ITU-T Recommendation G.805 is presented, including the conceptual model and its derivation and restrictions rules.
Analise comparativa de algumas estruturas de filtros digitais de segunda ordem imunes a ciclos limite
(Universidade Federal do Espírito Santo, 1994-08-19) Simmer, Ana Cristina Staut; Orientador1; Sarcinelli Filho, Mário
This work is a comparative study of the relative output roundoff noise variance performance for some second-order state-space structures, as a function of the filter bandwidth. The addressed second-order structures are used as building blocks for realizing lowpass, highpass, bandpass and bandreject digital filters. In this sense, this study complements a recent one, which just investigated the lowpass filter case. In both studies only narrow-band digital filters are discussed, regarding the well known good performance of the state-space structures in those cases. In order to compare the output roundoff noise performance for all spectra, new firstorder spectral transformations, derived from the well known transformations due to Constantinides, are developed, for varying the filter bandwidth of a parallel-form prototype filter. All this effort is justified by the importance of knowing the performance of the structures which are suitable for a desired application, what represents a significative contribution to the problem of designing digital filters.
Análise comparativa entre filtros híbridos aplicados a cicloconversores em uma siderúrgica
(Universidade Federal do Espírito Santo, 2009-07-20) Antunes, Hélio Marcos André; Sousa, Gilberto Costa Drumond; Simonetti, Domingos Sávio Lyrio; Aragão Filho, Wilson; Canesin, Carlos Alberto
In steel industry that uses the process of hot strip mill, cycloconverter-fed synchronous motors of megawatts nominal power are usually employed. The cycloconverters absorb a distorted current from the electric main, causing voltage distortion in its point of common coupling (PCC) and many problems with respects the electric power quality. A standard solution used for the harmonic mitigation in this application is obtained through the use of composite passive filter. However this is a solution that can cause harmonic resonance, increasing the harmonic distortion in the electrical system and causing overload in the filtering system. In this work a case in a huge steel industry, located at Grande Vitória is presented. Through measurements in the substation of the hot strip mill, the main currents and voltages waveforms are presented, along with the harmonic spectrum, that confirm the existence of harmonic resonance phenomenon. As an expansion of 30% is foreseen in the load of the rolling mill, it becomes necessary a study of the influence in the associated electrical system. This is due to the harmonic amplification phenomenon, that can increase the distortion levels affecting the passive filtering system behavior. A previously developed model of the system under study was used, which allows the representation of the real system with great correlation degree. Using the model, a comparative simulation analysis is done, by simulation, between two topologies of hybrid filters, the series and parallel, with the objective of harmonic filtering and resonance damping. The obtained results show that the series hybrid filter is the topology that allows better damping of harmonic resonance, and improving the characteristics of harmonic compensation in the passive filtering system, with an active filter of low nominal power, when compared to a parallel hybrid filter. However, this structure doesn't have good filtering characteristics in high frequency, function that the parallel hybrid filter can perform, however with an active filter of higher nominal power. Finally, it is shown that a series hybrid filter, consisting in an active filter and a capacitor bank applied in the electrical system of the rolling mill, can provide the same results of harmonic compensation and resonance damping, with an active filter of smaller nominal power, when compared to the traditional hybrid structure, formed by the series association of active and passive filters.
Análise da aplicação de conexão em paralelo de capacitores em circuitos secundários de baixa tensão
(Universidade Federal do Espírito Santo, 2005-05-13) Sarcinelli, Carlos Alberto; Sousa, Gilberto Costa Drumond; Simonetti, Domingos Sávio Lyrio; Aragão Filho, Wilson Correia Pinto de; Pomílio, José Antenor
The objective of this work is to analyze the behavior of a radial low voltage secondary distribution network subject to linear and non-linear loads, with and without magnitude voltage control by the automatic insertion of capacitor banks. The analysis is performed by considering the variations in the secondary distribution network elements. These elements are the loads connected to each pole of the network (power varying from no-load to full load, and displacement factor varying from 0.7 to 1.0), the changes in the ratings of the supply transformers (apparent power in kVA, primary and secondary impedances, and primary and secondary voltages), the number of poles and the distance among them. The harmonic behavior of the rms voltage of the distribution network is also analyzed, with and without the insertion of a capacitor bank at the last pole, since the distribution network might amplify harmonics as a result of resonances in the system, which have influence on the control of the voltage magnitude. Finally, a steady-state frequency domain analysis is performed by using a computer program (MATLAB), whose results are confirmed through time domain simulations performed using SIMULINK. The results concerning the time and frequency analyses are presented as a set of plots, from which some conclusions are highlighted, for a case study consisting in a network having five poles and a 13,800/220 V, 75kVA transformer.
Análise da Contribuição do Uso do Gerador Síncrono virtual Como Técnica de Controle em Sistemas elétricos de Potência
(Universidade Federal do Espírito Santo, 2017-12-20) Broedel, Dayane Corneau; Encarnação, Lucas Frizera; Medina, Augusto César Rueda; Donadel, Clainer Bravin
Electric power systems have to convey electricity at synchronized frequency and voltagein order to be reliable. Voltage control systems can use different strategies to achievevoltage regulation - reactive power compensation being one of them. On the other hand,frequency control is traditionally obtained by regulation of large scale synchronous machinesoperations. However, the increasing use of alternative energy sources and the operation ofthese generators in parallel with the traditional power systems emphasize the importanceof studying the integration of these generation units. An aspect to be analyzed is theimpact in the reduction of the system total inertia, that might increase frequency andvoltage variations, affecting the power system stability when facing different types ofdisturbance. In this context, this work is dedicated to discuss the use of the concept ofadditional virtual inertia, where each generation unit behaves as a virtual synchronousgenerator, in comparison with the traditional PQ technique for power control of interfaceinverters. Simulation results show the virtual generator contribution to the stability of aknown system, the IEEE-14 Bus.
Análise da correção de tensão em circuitos secundários de BT em anel usando capacitores
(Universidade Federal do Espírito Santo, 2011-05-27) Luchini, Octávio Matos; Simonetti, Domingos Sávio Lyrio; Cunha, Carla César Martins; Reis, Fernando Soares dos
This work presents a study of the best allocation point for capacitor banks in distribution secondary networks in ring in order to achieve suitable supply voltage levels for consumption. At first, the main characteristics of a secondary distribution system are presented, with emphasis on the ring topology, and quality of energy involved. Then, the major methods of drop voltage calculation on the network are discussed. It is presented the development of an unsimplified method that allow to trace the voltage profile along the feeder before and after insertion of the banks to assess the optimum allocation. The implemented algorithm is also presented, as well as the mathematical modeling of system components and the considerations that were made according to the chosen capacitor connection point. The impact of the introduction of capacitor banks in the amplification of voltage harmonics is also discussed with the due consideration and mathematical modeling for acertain harmonic frequency. Computer simulation results of the implemented algorithm are presented for certain networks at different level loading. Such results demonstrate the feasibility of the method in the analysis of the insertion of capacitive reactive power in the network and assessing the amplification of voltage harmonics caused by the banks connection.
Análise de aplicações em ambientes reais de IoT utilizando tecnologias de radiofrequência Wi-SUN e LoRaWAN
(Universidade Federal do Espírito Santo, 2025-06-28) Cerri, Hudson Mereles; Segatto, Marcelo Eduardo Vieira; https://orcid.org/0000-0003-4083-992X; http://lattes.cnpq.br/2379169013108798; https://orcid.org/0009-0005-3713-594X; http://lattes.cnpq.br/7902825869094261; Munaro, Celso Jose; https://orcid.org/0000-0002-2297-7395; http://lattes.cnpq.br/5929530967371970; Santos, Jessé Gomes dos ; https://orcid.org/0000-0001-8984-0599; http://lattes.cnpq.br/6857610972823488
This dissertation describes some applications in practical cases using two RF technologies, combining available literature with real tests carried out with IoT devices from the company Zaruc, as well as evaluating the behavior of sub-GigaHertz frequency protocols applied to electronic energy meters telecommunications by Zaruc Tecnologia and, in some cases, comparing, when pertinent, to theoretical results obtained through Radio Mobile. Among the technologies currently present in the Internet of things market for utilities, it is intended to work with Wi-SUN and LoRaWAN, seeking a model of analysis of both data collection systems for energy measurement linked to observation in real experiments, with qualitative and quantitative reflections through relevant performance indexes described in this work. At the end of this research, the goal is to provide a critical view on the empirical applications of each of the technologies, serving as an aid to decision-making in determining the ideal protocol to meet specific objectives within the field of electric energy data telemetry
Análise de Desempenho da Técnica de Modulação DMT para Comunicação via Luz Visı́vel
(Universidade Federal do Espírito Santo, 2017-12-20) Guimarães,Roziane Schneider; Segatto, Marcelo Eduardo Vieira; Silva, Jair Adriano Lima; Rocha, Helder Roberto de Oliveira; Nunes, Reginaldo Barbosa
abstract
Análise de desempenho de diferentes estratégias de modulação PWM para conversores de três níveis com diodo de grampeamento
(Universidade Federal do Espírito Santo, 2016-12-01) Delai, Antonio Marcos; Simonetti, Domingos Sávio Lyrio; Vieira, José Luiz de Freitas; Có, Marcio de Almeida; Encarnação, Lucas Frizera
Multilevel converters are finding greater increased attention in industry and academic research as one of the preferred choices of electronic power conversion for high-power applications that need to operate at medium voltage levels, mainly due to high demand of power ratings. Several researches are contributing to further improve the performance of multilevel converters, so that energy efficiency attached to good quality of energy with reduced power losses is desired. Thus, new or improved pulse width modulation (PWM) techniques are assisting to improve these requirements. Among of multilevel converters topologies available, the NPC converter (Neutral Point Clamped) is becoming an attractive option in the market and expanding its use in several applications, even as in medium and high voltage systems as well as in the industrial sector and renewable energy systems. The significance of modulation techniques in the performance of multilevel converters has been demonstrated. Due this, several carriers based PWM techniques and space vector PWM techniques suitable for the NPC converter are described, analyzed and evaluated. Detailed simulation studies, applying such modulation techniques, are performed on the PSCAD/EMTDC (Power Systems Computer Aided Design / Electromagnetic Transients including DC) platform. In addition, an algorithm was implemented to simulate the techniques: the conventional space vector scheme and space vector scheme without even order harmonics, developed for a three level NPC converter. With results of this research, it performs an analysis and comparison of the performance between space vector PWM and carrier based PWM schemes, suitable for a three-level NPC converter. The performance comparison is presented and evaluated in relation to the total harmonic distortion (THD), common mode voltage and rms voltage in the converter output.
Análise de desempenho de um sistema COFDM para comunicação via rede elétrica
(Universidade Federal do Espírito Santo, 2006-05-22) Silva, Jair Adriano Lima; Salles, Evandro Ottoni Teatini; Segatto, Marcelo Eduardo Vieira; Andreão, Rodrigo Varejão; Montalvão Filho, Jugurta Rosa
The Internet popularization demands for inexpensive installation and provision of the access technologies and services. Power Line Communication (PLC) technology is a promising alternative since it uses the existing infrastructure of the distribution power network as a high-speed data channel. In order to implement advanced communication systems over hostile PLC channels, complete knowledge of its transfer function and its intrinsic noises are required. This thesis analyzes multicarrier Orthogonal Frequency Division Multiplexing (OFDM) communication systems for Internet access and home networking over both outdoor and indoor power line channel models. A trellis coded modulation OFDM (COFDM) system is proposed an its performance is compared with the classic OFDM system in terms of Bit Error Rate (BER) versus Signal-to-Noise Rate (SNR). A particular indoor power distribution system was built in order to obtain the transfer function and noise used in the simulations. Simulation results had shown coding gains up to 8 dB at 10−6 BER in COFDM with one tap equalizer.
Análise de dispersão em fibras PCF com o método de elementos finitos
(Universidade Federal do Espírito Santo, 2005-06-29) Ramos, Breno Guimarães; Frasson, Antonio Manoel Ferreira; Calmon, Luiz de Calazans; Figueroa, Hugo Enrique Hernandez
In the present work, the full vectorial, total anisotropic, Finite Element Method was implemented, using second order nodal base functions for the electric field longitudinal component discretization, and Nedelec base functions, quadratic normal and linear tangencial (QNLT), for the discretization of the magnetic field transversal component, applying triangular elements in the domain of solution. Through this implementation, it was studied several configurations of Photonic Cristal Fibers (PCF), making changes in the diameter of the holes and in the distance between then, also called pitch. The intention was to show how feasible and practical is the control of the ultraflattened dispersion profile for this new model of optical fiber, as was reported in recent works. The calculated dispersion results shown that is possible to get dispersion profile completely flat in a range of wavelength of 200 nm, and with the possibility to add offsets in this profiles, making it negative (for applications related to dispersion compensation), or yet, making it flat in a region as close as possible to zero, what is very useful for WDM multiplexing systems. In addition to the dispersion evaluation, the method developed also allows to calculate the effective modal area and also features a graphical presentation of the electric field distribution, or the magnetic field distribution, of the guided modes in the fiber. Concerning the tailoring of the dispersion curve, applying finite element simulation, it was validated the use of empiric equations for dispersion computations from scaling operations in the structure of PCF fibers. These equations can simplify even more the procedure of dispersion tailoring, because the number o simulations by finite element method is reduced considerably. It was also important to analyze the behavior of the propagating wave in the fiber’s interior. For this, it was implemented the Beam Propagation Method (BPM) using two different approaches. Initially, it was applied Crank-Nicholson method, which didn’t show good results because it was not possible to stabilize the propagation process. As a second option, the Newmark method was used, but it was only possible to make the propagation process stable with a simulation step which had the same order of magnitude of the wavelength applied. Thus, unfortunately it was not possible to observe any phenomena of interest during the guiding process.

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