Engenharia Elétrica

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http://repositorio.ufes.br/handle/10/17617

Programa de Pós-Graduação em Engenharia Elétrica

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URL do programa: https://engenhariaeletrica.ufes.br/pt-br/pos-graduacao/PPGEE

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A brain-computer interface architecture based on motor mental tasks and music imagery
(Universidade Federal do Espírito Santo, 2013-08-30) Benevides, Alessandro Botti; Bastos Filho, Teodiano Freire; Sarcinelli Filho, Mário; Ferreira, André; Frizera Neto, Anselmo; Conci, Aura; Tierra Criollo, Carlos Julio
This present research proposes a Brain-Computer Interface (BCI) architecture adapted to motor mental tasks and music imagery. For that purpose the statistical properties of the electroencephalographic signal (EEG) were studied, such as its probability distribution function, stationarity, correlation and signal-to-noise ratio (SNR), in order to obtain a minimal empirical and well-founded parameter system for online classification. Stationarity tests were used to estimate the length of the time windows and a minimum length of 1.28 s was obtained. Four algorithms for artifact reduction were tested: threshold analysis, EEG filtering and two Independent Component Analysis (ICA) algorithms. This analysis concluded that the algorithm fastICA is suitable for online artifact removal. The feature extraction used the Power Spectral Density (PSD) and three methods were tested for automatic selection of features in order to have a training step independent of the mental task paradigm, with the best performance obtained with the Kullback-Leibler symmetric divergence method. For the classification, the Linear Discriminant Analysis (LDA) was used and a step of reclassification is suggested. A study of four motor mental tasks and a non-motor related mental task is performed by comparing their periodograms, Event-Related desynchronization/synchronization (ERD/ERS) and SNR. The mental tasks are the imagination of either movement of right and left hands, both feet, rotation of a cube and sound imagery. The EEG SNR was estimated by a comparison with the correlation between the ongoing average and the final ERD/ERS curve, in which we concluded that the mental task of sound imagery would need approximately five times more epochs than the motor-related mental tasks. The ERD/ERS could be measured even for frequencies near 100 Hz, but in absolute amplitudes, the energy variation at 100 Hz was one thousand times smaller than for 10 Hz, which implies that there is a small probability of online detection for BCI applications in high frequency. Thus, most of the usable information for online processing and BCIs corresponds to the α/µ band (low frequency). Finally, the ERD/ERS scalp maps show that the main difference between the sound imagery task and the motor-related mentaltasks is the absence of ERD at the µ band, in the central electrodes, and the presence of ERD at the αband in the temporal and lateral-frontal electrodes, which correspond tothe auditory cortex, the Wernickes area and the Brocas area.
A fairness-focused spectrum assignment algorithm for elastic optical networks
(Universidade Federal do Espírito Santo, 2016-09-27) Tessinari, Rodrigo Stange; Garcia, Anilton Salles; Waldman, Hélio; Martins, Joberto Sérgio Barbosa; Resendo, Leandro Colombi; Segatto, Marcelo Eduardo Vieira; Paiva, Marcia Helena Moreira
In the past few years, Elastic Optical Networking (EON) emerged as the next generation core network technology, intended to surpass Wavelength-Division Multiplexing (WDM) weaknesses and limitations. WDM is the most successful and widely used technology in the backbone of the optical networks. However, in recent years Internet traffic in the core network has been doubling almost every two years, and predictions indicate that it will continue to exhibit exponential growth due to emerging applications such as high-definition and real-time video communications. To keep pace with the always greater demand for bandwidth, EON relies on Optical Orthogonal Frequency Division Multiplexing (OOFDM) and advanced modulation technologies which enhance spectral efficiency and flexibility. OOFDM allows the aggregation of multiple sub-carriers to form super-channels, thus changing the paradigm of the network from fixed-size WDM channels to variable-sized EON channels that can reduce spectrum waste up to 60%. EON presents several other benefits such as high spectral and energy efficiency and flexible bandwidth adaptation over time. Despite all benefits, no technology is perfect, and the added EON efficiency and flexibility comes at the price of increased complexity and new problems, such as spectrum fragmentation and service unfairness. A considerable amount of work has been done on both fragmentation and unfairness problems, introducing a broad range of solutions, which raises the following question: "how to compare existent solutions and how to identify which one is better suited for the required scenario?" In this context, it is presented the first contribution of this Doctoral Thesis, ElasticO++, an Elastic Optical Network Simulation Framework for OMNeT++. ElasticO++ is a framework created to enable testing a whole range of routing, modulation, spectrum assignment, defragmentation algorithms, parameters, and topologies. At present, the proposed framework is the first software available capable of working with fragmentation and defragmentation in dynamic network scenarios. The flexibility offered on the proposed tool allows both academia and industry to develop new algorithms and techniques for Elastic Optical Networks. The second contribution of this Doctoral Thesis is the Zone-Based Spectrum Assignment Algorithm. The proposed algorithm is an attempt to solve the unfairness and fragmentation problems, taking advantage of the spectrum management concept. In this Doctoral Thesis, it is presented two versions of the technique: the static version and the dynamic version. The static version is intended to be used in cases where the information regarding the nature of the network traffic is known beforehand, whereas the dynamic version was developed as a solution in cases in which absolutely no information is known.
A Human-Machine Interface Based on Eye Tracking for Controlling and Monitoring a Smart Home Using the Internet of Things
(Universidade Federal do Espírito Santo, 2019-02-20) Bissoli, Alexandre Luís Cardoso; Encarnação, Lucas Frizera; Bastos Filho, Teodiano Freire; Adams, Kimberly; Krishnan, Sridhar; Villa Parra, Ana Cecilia; Ferreira, André
People with severe disabilities may have difficulties when interacting with their home devices, due to the limitations inherent to their disability. Simple home activities may be even impossible for this group of people. Although many works have been devoted to proposing new assistive technologies to improve the lives of people with disabilities, some studies have found that the abandonment of such technologies is quite high. In this sense, this work presents a new and useful assistive system based on eye tracking for controlling and monitoring a smart home based on internet of things, which was developed following concepts of user-centered design and usability. With this system, a person with severe disabilities was able to control everyday equipment of her residence, such as lamps, television, fan and radio. In addition, her caregiver was able to monitor remotely, by internet, her use of the system in real time. Additionally, the user interface developed here has some functionalities that allowed improving the usability of the system as a whole. The experiments were divided into two steps. In the first step, the assistive system was assembled in an actual home, where tests were conducted with 29 participants without disabilities (group of able-bodied participants). In the second step, the system was tested with online monitoring, for seven days, by a person with severe disability (end-user), in her own home, not only to increase convenience and comfort, but also so that the system could be tested where it would in fact be used. At the end of both steps, all the participants answered the SUS questionnaire, which showed that both the group of able-bodied participants and the person with severe disabilities evaluated the assistive system with a mean of 89.9 and 92.5, respectively.Keywords:Human-Machine Interface (HMI); Human-Computer Interaction (HCI); Smart Home; Eye Tracking; Assistive Technology; Usability Evaluation; User-Centered Design (UCD); Home Automation; Internet of Things (IoT).
A novel approach of independent brain-computer interface based on SSVEP
(Universidade Federal do Espírito Santo, 2016-09-01) Tello, Richard Junior Manuel Godinez; Ferreira, André; Müller, Sandra Mara Torres; Bastos Filho, Teodiano Freire; Ciarelli, Patrick Marques; Lima, Eduardo Roncon de; Sá, Antônio Maurício Miranda de
Over the past ten years, Brain Computer Interfaces (BCIs) based on Steady- State Visual Evoked Potentials (SSVEP) have attracted the attention of many researchers due to the promissory results and the high accuracy rates achieved. This type of BCI provides to people with severe neuromotor difficulties the possibility to communicate with the world around them using visual attention modulation to blinking lights at a given frequency. This thesis aiming at developing a new approach of Independent BCI, in which users are not required to perform neuromuscular tasks to select visual targets, a feature that distinguishes it from traditional SSVEP-BCIs. Thus, people with severe motor disabilities as Amyotrophic Lateral Sclerosis (ALS) have a new alternative channel to communicate with the world around them using brain signals. Several contributions were done in this thesis, such as: improvement of the feature extractor called Multivariate Synchronization Index (MSI) for detecting evoked potentials; development of a new method for detecting evoked potentials through correlating multidimensional models (tensors); a first study on the influence of colored stimuli in SSVEPs detection using LEDs; the development of the concept of Compressive sensing applied to SSVEPs; and, finally, the development of a novel independent BCI under an approach named Figure-Ground Perception (FGP)
A novel stimulation paradigm for a brain-computer interface based on SSVEP
(Universidade Federal do Espírito Santo, 2015-11-30) Atencio, Anibal Cotrina; Ferreira, André; Bastos Filho,Teodiano Freire; Frizera Neto, Anselmo; Sarcinelli Filho, Mario; Krohling, Renato Antônio; Sá, Antonio Mauricio Ferreira Leite Miranda de
Brain-computer interfaces (BCIs) are systems that provide a direct connection between users’ brain signals and a computer, generating an alternative channel of communication that does not involve the traditional way as muscles and nerves. They help to restore or replace useful functions of people with paralysis. For instance, BCI systems based on SSVEP (SSVEP-BCI) present a set of stimuli flickering at different frequencies to the users, detect which stimulus is being gazed and associate this information to commands that can be used to control a robotic wheelchair, an exoskeleton, or a speller. Nowadays, SSVEP-BCIs are being widely used due to the high SNR of their response that is achieved when the target stimulus is brought to the center of the user’s field of view. Paradoxically, it is their main disadvantage because bringing a stimulus to the center of the field of view demands muscular activity making them not suitably for paralyzed people who cannot control their head, neck and/or eyeball movements for redirecting their gaze. In optical systems, the range of distance near the point of focus where objects are perceived sharp is referred as Depth-of-field; objects outside this region are defocused and blurred. The mechanism of the visual system that adjusts the eye focal length for focusing does not demand neck, head and/or eyeball movements. Furthermore, ophthalmology studies state that the amplitude and the latency of visual evoked potentials are affected by defocusing. In this context, this Thesis proposes a novel SSVEP-BCI paradigm, in which two stimuli are presented together in the center of the user’s field of view but at different distances from him, ensuring that if one stimulus is focused on, the other one is non-focused, and vice versa; with the aim of providing an alternative way of sending commands through a stimuli selection by a focusing mechanism. In this sense, first, a model of VEP generation for two stimuli is introduced and the hypothesis that distinguishable SSVEP can be elicited by the focused stimulus, regardless of the non-focused stimulus is also present, is tested by employing the SFT-based ORD. Next, a demodulation method based in LPF and HPF is proposed for the case in that two stimuli are present in the field of view; and spatial-temporal retinal response for flickering stimuli is described by using PSF and NPSF functions. Finally, CCA, PSDA, LASSO with EEG signals re-referenced at Pz and CAR are employed to detect the SSVEP pattern. Accuracy rate, Kappa coefficient, AUC, and ITR are used to evaluate the detection performance. As a result of the hypothesis test, the absence of evoked potentials due to a focused stimulus, when a non-focused stimulus is also present was rejected in most of the cases. In SSVEP detection experiments, an average accuracy rate of 0.93 was achieved for a time window of 7s and for eight healthy subjects who were asked to focus on just one stimulus at a time.
A rede de média tensão como meio de transporte de dados em redes smart grid
(Universidade Federal do Espírito Santo, 2015-12-11) Castor, Leonardo Ribas Martins; Silva, Jair Adriano Lima; Segatto, Marcelo Eduardo Vieira; Garcia, Anilton Salles; Souza, Flávio Rabello de
The main purpose of any company is to increase its production with reduced operating costs and in the Oil & Gas industry is not different. In this scenario industrial automation plays a key role, maximizing operational safety and production efficiency. The use of human resources in order to operating, monitoring and controlling productionś processes is intense on this field, which is, yet, a serious drawback for this kind of company. Systems communications as part of the productionś automation contribute for reducing the operative expenditure and at same time provide efficient and reliable data traffic. The Oil & Gas industry has used fibre optics and wireless communications systems as last mile network solutions. However, these networks are implemented with high costs and at long time. More recently, the technology of data transmission over power line grid, called PLC, has becomes economically and technically a more interesting solution related to others technologies. As the onshore oil wells are already covered by the medium voltage power line grid, the reduced installationś costs for a PLC data network makes the project mre attractive. Additionally, the new PLC system use modern techniques, such as, adaptative coding and modulation, multiple access protocols, QoS, etc, for ensuring robustness, better use of signal power and greater privacy of data transmitted. In contrast, its performance depends on the communication channel condition based on transmission multipath, frequency selectivity, impulsive noise, RF interference, and others. This work was developed under a real scenario of Smart Grid conception. Through a three-phase medium voltage grid, supervisory, control and video surveillance information in oil production process have been transported to the remote operation center located at SM-8, São Mateus. It was obtained upstream and downstream speeds of 60 Mbps approximately in the physical layer through a multipath PLC channel with 322 m long without repeater. In a multipath stretch of 2 km long, a 3 Mbps ethernet traffic composed by automation data and high-definition images, was transported in a real-time frame to their servers without errors.
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; Sarcinelli Filho, Mário; 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.
Admittance control of a robotic knee orthosis based on motion intention through sEMG of trunk muscles
(Universidade Federal do Espírito Santo, 2017-12-04) Parra, Ana Cecilia Villa; Frizera Neto, Anselmo; Bastos Filho, Teodiano Freire; Ferreira, Andre; Caldeira, Eliete Maria de Oliveira; Rocon, Eduardo; Bó, Antonio Padilha Lanari
The population that requires devices for motion improvement has increased considerably, due to aging and neurological impairments. Robotic devices, such as robotic orthosis, have greatly advanced with the objective of improving both the mobility and quality of life of people. Clinical researches remark that these devices, working in constant interaction with the neuromuscular and skeletal human system, improves functional compensation and rehabilitation. Hence, the users become an active part of the training/rehabilitation, facilitating their involvement and improving their neural plasticity. For this purpose, control approaches based on motion intention have been presented as a novel control framework for robotic devices. This work presents the development of a novel robotic knee exoskeleton controlled by motion intention based on sEMG, which uses admittance modulation to assist people with reduced mobility and improve their locomotion. For recognition of the lower-limb motion intention, sEMG signals from trunk are used, which implies a new approach to control robotic assistive devices. The control system developed here includes a stage for human-motion intention recognition (HMIR) system, which is based on techniques to classify motion classes related to knee joint. The motion classes that are taken into account are: stand-up, sit-down, knee flexionextension, walking, rest in stand-up position and rest sit-down position. For translation of the users intention to a desired state for the robotic knee exoskeleton, the system includes a finite state machine, in addition to admittance, velocity and trajectory controllers, which has also the function of stopping the movement according to the users intention. This work also proposes a method for on-line knee impedance modulation, which generates variable gains through the gait cycle for stance control during gait. The proposed HMIR system showed, in off-line analysis, an accuracy between 76% to 83% to recognize motion intention of lower-limb muscles, and 71% to 77% for trunk. Experimental on-line results of the controller showed that the admittance controller proposed here offers knee support in 50% of the gait cycle, and assists correctly the motion classes. A positive effect of the controller on users regarding safety during gait was also found, with a score of 4 in a scale of 5. Thus the robotic knee exoskeleton introduced here is an alternative method to empower knee movements using motion intention based on sEMG signals from lower limb and trunk muscles.
Algoritmo de calibração de magnetômetros triaxiais utilizando ajuste de quádrica por distância algébrica
(Universidade Federal do Espírito Santo, 2017-08-22) Mucciaccia, Sérgio Silva; Salles, Evandro Ottoni Teatini; Frizera Neto, Anselmo; Ciarelli, Patrick Marques; Nogueira, Samuel Lourenço
The measurements obtained from magnetometers are sensitive to disturbances and errors, requiring a calibration method that can considerably improve accuracy. The ellipsoid fitting is one of the most widely used methods for magnetometer calibration, but most algorithms use iterative methods, causing runtime and convergence problems. As an alternative, a direct algorithm based on the method of least squares using the algebraic distance metric is proposed. This present work presents an algorithm of calibration of magnetometers and its use in a system of calibration and fusion of data of magnetometers, accelerometers and gyroscopes based on a Kalman filter forming an inertial sensor able to obtain its orientation in the space. Computational simulations and tests with real data show that the calibration algorithm eliminates almost all the linear errors while performing much faster than traditional algorithms. Measurements of a magnetometer calibrated with the proposed algorithm are used in conjunction with measurements from accelerometers and gyroscopes to form an inertial measurement unit (IMU) using a simple Kalman filter. The complete system worked as expected and the test results indicate that the magnetometer calibration algorithm is suitable for use in an IMU being more than ten times faster than traditional algorithms and presenting similar accuracy
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.
Alocação resiliente de Equipamentos BPL para comunicação em redes elétricas de média tensão
(Universidade Federal do Espírito Santo, 2017-04-20) Oliveira, Alinne Pereira de; Silva, Jair Adriano Lima; Rocha, Helder Roberto de Oliveira; Salles, Jose Leandro Félix; Nunes, Reginaldo Barbosa
Power line communications (PLC) appears as a good alternative for data communication due to the already installed and pervasive power distribution infrastructure. It is based on this features that, a methodology for resilient allocation of PLC equipments for data communication in medium voltage (MV) networks is proposed in this work. However, because electrical networks were not customized for data transmission purposes, destructive interference exists in the medium to degrades high data rate communications. In the frequencies above 1 MHz, the PLC medium is characterized as a multipath channel caused by the derivations and impedance mismatches that exists along the main transmission segment. Normally called interfering branches, the ramification lengths around 10 % of the main segment have a destructive influence on the PLC signal. Therefore, a methodology to strategically allocate the lowest quantity of PLC equipments in the MV considering the presence or absence of interfering branches is proposed. Moreover, due to changes in the topology of the electrical MV access network during its operation and/or mantainence, the proposed method should allocate repeaters to fit all the topological scenarios in order to prevent interruptions in the data communications. Another problem contemplated is the loss of any repeater without the powerline communications being impaired or even interrupted. The methodology proposed in this work uses metaheuristics based on a Genetic Algorithm and on a new Binary Particle Swarm optimization (NBPSO) to generate good solutions to the particular allocation problem addressed in this work. The same amount of PLC equipments installed in a real network was achieved after the application of the proposed methodology. Using the proposed Genetic Algorithm, the method also successfully designated 14 PLC repeaters for the MV located in Rio Preto do Oeste in S˜ao Mateus-ES, which should be addressed with technology in the near future.
Alternativas de topologias retificadoras para aerogeradores síncronos a ímã permanente de baixa potência
(Universidade Federal do Espírito Santo, 2015-12-11) Freitas, Tiara Rodrigues Smarssaro de; Menegáz, Paulo José Mello; Simonetti, Domingos Sávio Lyrio; Antunes, Fernando Luiz Marcelo; Fardin, Jussara Farias; Encarnação, Lucas Frizera; Pinto Filho, Wilson Aragão Correia
Two controlled rectifier topologies applied to low power wind energy conversion system with permanent magnet synchronous generator are presented. For low power or stand-alone operation systems, where the energy from wind generation is a significant part of the total power system, generators and converters have the role of maintaining the grid’s voltage and frequency constant, despite the fluctuations of the wind turbine. In variable speed permanent magnet synchronous generator (PMSG), the preferred solution has been a conversion on two stages: AC-DC-AC. Several converter topologies have been explored, but kind of this conversion has many controlled elements, most of them with 6 controlled switches in AC-DC conversion, making it difficult and more expensive its control; each new topology introduces new aspects and always looking for a converter that best suits the system with minimally influence to the quality of power generation. The topologies presented in the literature are effective for the high power levels, but when it comes to systems with lower power levels, simpler converters (single or three controlled switches) can serve the purpose of rectification with a lower cost and without the conversion quality been reduced. The contribution of this thesis is the development of a new SEPIC rectifier topology using three controlled switches, and the analysis and new application of an existing resonant buck topology, with a single controlled switch, to wind energy system. They are simpler rectifying solutions, applied to low power wind generation based on permanent magnet synchronous generator, offering simplicity and control facility. The converter’s project, the equations that define them, the simulation and experimental results for each converter are presented. It was verified that both topologies could achieve high power-factor and low harmonic distortion employing only one single gate signal, on a wide range of wind speed with no current’s generator closed loop control.
Amplificadores óticos a fibra sob um ambiente dinâmico
(Universidade Federal do Espírito Santo, 2006-08-18) Freitas, Márcio; Calmon, Luiz de Calazans; Barbero, Andrés Pablo López; Ribeiro, Moisés Renato Nunes; Pontes,Maria José; Segatto, Marcelo Eduardo Vieira; Frasson, Antônio Manoel Ferreira
The recent advance in WDM technologies with the ability of add, drop and in effect construct wavelength-switched and wavelength-routed networks has brought a new dynamic-reconfigurable WDM network. This dynamic environment brings, besides the already well-known transmission impairments (such as chromatic dispersion, nonlinear effects, PMD, ASE, etc), a new set of impairments related to the add-drop possibilities that could severely degrade the system performance. Furthermore, the development of new optical amplifiers that could reach high output power values has also brought an increasing impact of nonlinear effects in the signal propagation at different applications. The optical fiber amplifiers presented in the study are the erbium-doped fiber, the ytterbiumdoped fiber amplifier, the erbium-ytterbium codoped fiber amplifier and the Raman fiber amplifiers. For this study, appropriate numeric models for each amplifier were implemented. This work investigates by numerical simulation how the optical fiber amplifiers and consequently the system performance are affected by the dynamic-reconfigurable traffic. Some contributions about the study of the power transient evolution generated by the optical amplifiers in different transmission bandwidths, under different amplifier configurations and in different applications are presented. It is also presented a contribution for the optimization of control methods to minimize the power transients generated by the optical amplifiers due the add-drop of channels in the system. Moreover, this work also analyzes the impact of high powers generated in the amplification process, and presents some contributions for the study of the nonlinear effects in the signals propagation through the amplifier.
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.

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