A recém-adquirida competitividade pela energia eólica frente a outras fontes alternativas e, até mesmo, convencionais tem sido comemorada pelo setor de energia elétrica. No entanto, a base para essa comparação leva em conta apenas os parâmetros dos investimentos do parque viabilizado, não sendo considerados outros fatores inerentes à inserção da fonte na matriz, como, por exemplo, o aumento do risco ao sistema, investimento necessário à ampliação da Rede Básica para escoamento da energia para o centro de carga e os custos com redespacho de geração, reserva girante e controles do sistema. O maior potencial está concentrado no Nordeste e o maior centro de carga no Sudeste, assim, em caso de exploração intensiva do potencial da fonte, será necessário passar por grandes investimentos em reforços e ampliações da rede básica. A partir desse panorama, busca-se realizar as primeiras análises de sensibilidade sobre a eficiência econômica dos parques eólicos instalados no Nordeste e, ao mesmo tempo, analisar as condições de atendimento da ponta. / The newfound competitiveness in wind power compared to other alternative and even conventional energy sources has been celebrated by the electric power sector. However, the basis for this comparison takes into account only the parameters of the Capex, not considering other factors inherent in the insertion of the source in the array, for example, increase the risk to the system, expansion of the investment necessary for Basic network for transport of energy to the load center and the cost of redispatch generation, spinning reserve, and system controls. The greatest potential is concentrated in the Northeast and the largest load hub in the Southeast, so, in case of intensive exploitation of the potential of the source, large investments in reinforcements and expansions of the grid will be necessary. From this overview, we attempt the firsts sensitivity analysis on the economic efficiency of wind farms in the Northeast and the load peak supply conditions.

O setor elétrico é um setor de natureza estratégica para qualquer nação, na medida em que na era moderna a eletricidade é um insumo fundamental para a qualidade de vida das pessoas e para o desenvolvimento e a produção da indústria, sendo mesmo considerado como uma mola mestra da economia do país. Em função dessa importância, crescente ao longo do tempo e aguçada em decorrência de restrições de disponibilidade e de cunho ambiental para a utilização massiva do petróleo, o setor elétrico deve ser planejado com extrema atenção e de forma muito criteriosa, posto que sua expansão necessite estar garantida e se trata de um setor intensivo em capital e com empreendimentos de longo prazo de maturação, particularmente no caso dos grandes aproveitamentos hidrelétricos e as plantas nucleares. Dentro desse contexto, o presente trabalho buscou endereçar a temática de planejamento de sistemas elétricos, aproveitando a experiência profissional pregressa da autora, especialmente no que tange às vertentes de estudos tarifários e de mercado, como também pelo fato de conhecer em algum detalhe os marcos regulatórios e o funcionamento dos setores elétricos no âmbito do Mercosul. Nesse sentido, o presente trabalho apresenta uma análise crítica comparativa de modelos tarifários, dos sistemas de transmissão, atualmente vigentes em alguns países da América do Sul. As recentes tendências políticas e energéticas dos países considerados constituem-se em importantes sinais para o estabelecimento de futuras negociações na área elétrica. Isso propicia a realização de um estudo referente às condições tarifarias e regulatórias destes mercados. Questões técnicas em projetos deste tipo poderiam ser superadas, porém, eventuais divergências regulatórias e tarifarias entre os mercados elétricos poderiam adiar ou até mesmo inviabilizar os referidos projetos. Por outro lado, levando em conta o nexo existente entre o estudo dos modelos tarifários, os sinais de possíveis negociações de energia e a expansão do sistema, apresentam-se também uma análise comparativa entre as metodologias de previsão utilizadas no cálculo da demanda de energia elétrica nos países considerados. As referidas metodologias de previsão, sobre as quais foram utilizados o histórico de consumo do Brasil (1996-2006) e as variáveis explicativas inerentes a cada modelo, correspondem às classes de consumo Residencial, Industrial, Comercial e Rural; responsáveis por aproximadamente 90% do consumo nacional. Foram encontradas certas semelhanças principalmente no relacionado às variáveis econométricas utilizadas por estes modelos, os quais se refletiram nos resultados obtidos. / The electric power sector is an area of strategic nature for any country as electricity is an essential product for both the quality of life and the development of the industry. This reason led to consider it as a sound foundation for the economy development and GNP growing. Because of its role, which grows along time even due to the restrictions of availability and environmental issues for the massive use of oil, the electric sector must be carefully planned as its expansion needs to be guaranteed. This sector embraces large capital and long-term investments, particularly those related to hydroelectric projects and nuclear plants. Within that framework, this work aims at to address the electric power planning subject using the author\'s past knowledge related to electric tariffs as well as on the regulatory framework and market operation of the Mercosul. A critical comparative analysis of transmission tariff models currently applied in some South American countries is particularly addressed. The recent political and energy policy trends of the considered countries appear as important signals for the establishment of future negotiations of electricity. This situation demands the realization of new studies related to both tariff and regulatory conditions in these markets. Technical issues in projects of this kind may well be overcome; however, some regulatory differences and even tariff model differences among marketers could delay or even turn unfeasible the referred projects. On the other hand, considering issues like the link existing among the transmission pricing models adopted and the likely electricity trading as well as the system expansion, a comparative analysis of the methodologies used to forecast the energy demand in the South American countries previously considered, is also presented. Such forecast methodologies, upon which were applied the annual electricity consumption in Brazil in the period 1996 through 2006 as well as the explanatory variables inherent to each model, correspond to the Residential, Industrial, Commercial and Rural consumptions, responsible for nearly 90% of the national consumption. From this analysis, some similarities mainly those related to the econometric variables used by each methodology were found. Such similarities and related findings are reflected in the results presented.

No description available.

All digital communication channels are subject to inter-symbol interference (ISI). To achieve the desired system performance, at receiver end, the effect of ISI must be compensated and the task of the equalizer is to combat the degrading effects of ISI on the transmission. Due to the demand of high data transmission rate, the multicarrier modulation (MCM) technique implemented with the orthogonal frequency division multiplexing (OFDM) has been adopted in many modern communications systems for block transmission. In block transmission systems, transmitter-included redundancy using finite-impulse response (FIR) filterbanks can be utilized to suppress inter-block-interference (IBI). However, the length of redundancy will affect the system performance, which is highly dependent on the length of channel impulse response. To deal with the effect of ISI, many equalizing schemes have been proposed, among them the FIR zero-forcing (ZF) equalizer with the non-orthogonal projector provides a useful transceiver design structure for suppressing the IBI and ISI, simultaneously. In this thesis, we propose a new equalizing scheme; it combines the FIR-ZF equalizer with non-orthogonal projector as well as the Bayesian decision feedback equalizer (DFE) for IBI and ISI suppression. The Bayesian DFE is known to be one of the best schemes to achieve the desired performance for eliminating ISI. It can be employed to achieve the full potential of symbol-by-symbol equalizer. That is, after removing the effect of IBI with the non-orthogonal projector, the Bayesian DFE is employed for eliminating the ISI, simultaneously. For comparison, the system performance, in term of bit error rate (BER) is investigated, and compared with the minimum mean square error (MMSE)-IBI-DFE. The advantage of the new proposed equalizing scheme is verified via computer simulation under condition of insufficient redundancy.

In this study, the use of modified genetic algorithms (MGA) in the parameterization of the Transmission Mechanisms is facilitated. The new algorithm is proposed from the genetic algorithm with some additional strategies, and yields a faster convergence and a more accurate search. Firstly, this near-optimum search technique, MGA-based ID method, is used to identify the parameters of a system described by an ARMAX model in the presence of white noise and to compare with the LMS (Least mean-squares) method and GA method. Then, this proposed algorithm is applied to the identification of the Transmission Mechanisms of DC motor. The parameters of the friction force and DC motor are estimated in a single identification experiment. It is also shown that this technique is capable of identifying the whole transmission system. Finally, the Minimum Variance Controller (MVC) is taken to track the desired speed trajectory and then a comparison to the conventional digital PID controller is shown. Experiment results are included to demonstrate the excellent performance of the MVC.

In orthogonal frequency division multiplexing (OFDM) systems, when transmitted blocks of signal through the multipath channel, the present transmitted blocks of signal will be interfered by the previous one due to the effect of channel delay spread. In order to solve this problem, conventionally we introduce a guard interval in transmitted blocks of signal to avoid inter-block interference (IBI). The most popular methods of the guard interval insertion are zero-padding (ZP) and cyclic prefixing (CP). ZP insert the guard interval at the end of the transmitted blocks of signal, in which all elements are zeros. The length of this interval must be equal to or greater then the channel order. In this way we can avoid IBI, at the expense of lossing the orthogonality between subcarrier due to the multipath channel. However, we can use CP to cope whit this problem. In CP we copy the 25% length at the end of the transmitted blocks of signal, and put it in front of the transmitted block to suppress the inter-block interference and inter-carrier interference. In this thesis, we consider OFDM system without the guard interval, hence the received signal contains IBI and ICI. In our proposed scheme, we use an oblique projector (OB) to suppress IBI at first. Then we combine it with a generalized sidelobe canceller (GSC) based equalizer [1] for ICI supppression and demodulate the receiver signal. In computer simulations, we use the GSC-based equalizer with oblique projector to suppress IBI/ICI in the time-invariant channel and time-varying channel. As we will see, in the CP-free OFDM system, the oblique projector can suppress IBI exactly. Moreover we can get better performance in channel with larger order.

The power transfer capability of a transmission line is determined by the magnitude of the voltage at each end of the line, angle difference of these voltages and the impedance of the line. This impedance is mainly inductive. Traditionally, fixed series capacitor banks have been used for series compensation. However, due to instability problems associated with loading transmission line close to their thermal limits, researchers have looked at other alternatives to line compensation by static devices such as fixed series capacitors. Flexible AC Transmission Systems (FACTS) has allowed power utilities to use existing transmission line networks close to their thermal limits without compromising stability of the power system. A FACTS series compensator is capable of influencing the transmission of power in a transmission line by dynamic control of the series compensating reactance inserted in the line. There are several different devices under the FACTS family, however, in this thesis only the Thyristor-Controlled Series Capacitor (TCSC) was considered. A TCSC comprises a fixed capacitor in parallel with a thyristor-controlled reactor (TCR). By varying the firing angle ex:. of the thyristors, the TCSC can be made to act in variable inductive or capacitive reactance mode. The thesis' overall objective was to design a practical TCSC for use in a research laboratory for further research initiatives. This thesis looks at different issues that need to be considered when designing and rating a TCSC compensator. In particular, the thesis examines the effects of different sizes of TCSC components on the rating of the device, the effects of harmonics on the TCSC ratings, sizing of TCSC's variable reactance, and the response time of TCSC to a step change in the firing angle. A mathematical model of a TCSC in a single-machine infinite bus (SMIB) system was developed and subsequently used in the initial design of the TCSC. Studies that were done using mathematical model of the TCSC module confirmed the ability of the TCSC controller to dynamically control the capacitive compensating reactance in the transmission line. The thesis then describes the development of a laboratory-scale TCSC for research investigations. Measured results from the laboratory demonstrate the ability of the TCSC series compensator to provide rapid control of series reactance of a transmission line. A detailed mathematical model of the SMIB equipped with TCSC module was developed, using parameter values of the laboratory scale prototype, to investigate power oscillation damping. Time-domain simulation results are presented in this thesis to demonstrate its ability to damp power swings in an electrical network. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

A single-phase, buck-boost based, dual-output AC-DC converter is studied in this thesis. The converter has two DC outputs with opposite polarities, which share the same ground with the input power line. The power stage performance, including the input filter, is studied and procedure to select power components is given. The circuit model is analyzed to develop appropriate control. Zerocrossing distortion of the source input current is addressed and a solution is proposed. Experimental results are satisfactory in that a high power factor line current results for steady-state operation.

abstract: In sub transmission systems, many more raptor deaths have been recorded near metal poles rather than wood poles. The metal pole, which is reliable in structure but also grounded, may increase the risk of electrocution when raptors perch on the insulator. This thesis focuses on evaluating the effectiveness of the raptor guard to prevent both debilitating and lethal electrocutions to local wildlife in 69 kV sub transmission systems. First, the two-dimensional (2D) finite difference methods (FDM) were proposed to solve the Poisson and Laplace equations, which describe the electric field. Second, the verification of the FDM algorithm was made based on a parallel-plate capacitor model. Then, the potential and the electric field were simulated by the raptor-insulator model to evaluate the possibility of flashover and leakage current under various conceivable scenarios. Third, several dielectric performance experiments were implemented to gain insight into the physical property of the raptor guard developed by the Salt River Project (SRP) as an example. The proposed initial-tracking-voltage and time-to-track experiments tested the ability of the guard, which is designed to prevent the tracking phenomenon under a contaminated situation such as rain, fog, and snow. A data acquisition also collected the leakage current data for the comparison of maximum raptor tolerance. Furthermore, the puncture voltage of this guard material was performed by the dielectric breakdown voltage experiment in an oil-covered container. With the combination of the model simulation and the experiments in this research, the raptor guard was proven to be practical and beneficial in sub transmission system. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2016

Made available in DSpace on 2014-06-11T19:22:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-03-29Bitstream added on 2014-06-13T20:49:12Z : No. of bitstreams: 1 brandt_is_me_ilha.pdf: 996540 bytes, checksum: 97a4b2aa127103d8e81ea086dc41e70e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Entre tantas tecnologias alternativas desenvolvidas ao longo das últimas décadas, procurando aumentar a eficácia das técnicas convencionais ou propondo novas técnicas não convencionais na transmissão da energia elétrica a longas distâncias e lugares de difícil acesso, o estudo proposto apresenta alguns conceitos e características para sistemas de transmissão constituídos por quatro fases genéricas. O sistema de transmissão tetrafásico tem sido tema de diversos estudos e aplicações em alguns países da Europa e Ásia, apresentando algumas vantagens quando comparado ao sistema de transmissão trifásico convencional. Esse sistema pode ser facilmente integrado ao sistema trifásico por meio de transformadores, amplamente abordado por diversas referências bibliográficas. Nesse estudo foi realizado uma análise comparativa das possíveis sobretensões ocorridas nos domínios da frequência e do tempo entre os sistemas de transmissão trifásico e tetrafásico, avaliando as características elétricas e as respostas transitórias eletromagnética e impulsiva, mostrando novas vantagens sobre esta tecnologia, fornecendo uma avaliação completa sobre o tema / Among the many alternative technologies developed over the past decades, seeking to increase the effectiveness of conventional techniques or proposing new non-conventional techniques in the transmission of electricity over long distances and places of difficult access, the proposed study presents some concepts and features to transmission systems that are constituted of four generic phases. The four-phase transmission system has been subject of numerous studies and applications in some countries in Europe and Asia, presenting some advantages compared to the conventional three-phase transmission system. This system can be easily integrated into the three-phase system through transformers, thoroughly approached by several bibliographical references. In this study was made a comparative analysis of the possible overvoltages that occurred in the areas of frequency and time between the transmission systems of three-phase and four-phase, evaluating the electrical characteristics and the transient answers, electromagnetic and impulsive, showing new advantages over this technology, providing a complete evaluation of this issue