Teses em Engenharia Elétrica (Doutorado) - PPGEE/ITEC
URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2317
O Doutorado Acadêmico inicio-se em 1998 e pertence ao Programa de Pós-Graduação em Engenharia Elétrica (PPGEE) do Instituto de Tecnologia (ITEC) da Universidade Federal do Pará (UFPA).
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Item Acesso aberto (Open Access) Influência da microgeração fotovoltaica no perfil de demanda e seus impactos na geração de harmônicos na rede(Universidade Federal do Pará, 2024-02-29) PARIJÓS JÚNIOR, Ivan Ruy de; GALHARDO, Marcos André Barros; http://lattes.cnpq.br/6672470707462259; https://orcid.org/0000-0001-6248-5187; MACÊDO, Wilson Negrão; http://lattes.cnpq.br/3386249951714088; https://orcid.org/0000-0002-6097-8620This study addresses the integration of photovoltaic generation into the electrical grid, emphasizing the necessity to consider changes in the load profile of consumer units and the presence of harmonic components in the grid current, originating from loads with nonlinear characteristics and photovoltaic inverters. Various percentages of inverter loading were considered in the study to evaluate their impact on grid operation due to varying levels of harmonic components. The research comprises an experimental phase, a phase dedicated to developing models of inverter output currents, and a simulation phase. In the experimental phase, data on the output currents of three photovoltaic inverters were collected. These data were then utilized in the development of models of inverter output currents for theoretical analyses, evaluating factors influencing the power quality of the grid. Subsequently, these models were applied in the simulation phase. The grids evaluated in the simulation phase include a standard IEEE system and a real isolated grid, located in the Northern region of Brazil. Comparative assessments of network hosting capacity were conducted using two different strategies. The first strategy employed conventional power flow analysis, while the second strategy applied the developed models. It is observed that the operation of different inverters within the same grid may contribute to harmonic attenuation. Furthermore, it is highlighted that the presence of grid-connected photovoltaic systems, operating in conjunction with loads, results in an apparent increase in harmonic current content in the grid, whereas, in reality, there is a reduction in the circulating fundamental component. The obtained results indicate that conventional power flow studies may underestimate the intensity of circulating currents in the grid by neglecting the presence of harmonic components. This study innovates by assessing the circulation of harmonic components in the grid due to the combined operation of photovoltaic generation and load, considering various inverter loading scenarios and the effects of consumer electrical current, including the phase of harmonic components.Item Acesso aberto (Open Access) Investigação experimental de estratégias de controle robusto aplicadas à melhoria de desempenho de um conversor de potência CC/CC do tipo buck com estrutura Single Inductor Multiple Output(Universidade Federal do Pará, 2024-08-05) MONTAÑO SAAVEDRA, Alvaro Christian; MEDEIROS, Renan Landau Paiva de; http://lattes.cnpq.br/8081923559538095; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608Recently, DC/DC power converters have gained wide attention, especially in industry,telecommunications, and the control of renewable energy sources. The increase in the use of this technology can be explained by the growing demand for high-quality DC voltage regulation in various applications. Additionally, recent advances in power electronics along with control engineering have accelerated the development of DC/DC power converters. Therefore, they looked to optimize these converters in several ways, such as improving conversion efficiency and reducing their weight and cost. In the proposed work, control strategies for voltage regulation in a single-inductor, dualoutput Buck DC-DC converter system (SIDO) are investigated. Based on a nominal multiple-input, multiple-output plant model and performance requirements, both a Linear Quadratic Regulator (LQR) and a Decoupled PI control strategy are designed to control the power converter system under parametric uncertainties such as variation of the voltage source, variations of constant power loads (CPLs) and variations of load resistances. A prototype of a single inductor dual output DC-DC Buck converter was developed for experimental testing. The results indicate that the proposed LQR strategy approach is reasonable and provides adequate performance improvements in SIDO converter controllers under conditions of varying voltage source and varying load resistances, offering robust performance and system stability; however, more research is needed to address variations in constant power loads and in the design of a PI controller for its application in this kind of system.Item Acesso aberto (Open Access) Metodologia integrada utilizando sensoriamento remoto em redes neurais artificiais na quantificação do potencial de biomassa florestal na Amazônia(Universidade Federal do Pará, 2008-04-08) ALMEIDA, Arthur da Costa; ROCHA, Brigida Ramati Pereira da; http://lattes.cnpq.br/9943372249006341Pattern recognition and pattern classification in digital images is a very important skill, today. With them, it is possible to recognize and identify target objects in those images. This work proposes an integrated methodology for pattern recognition related to biomass in the Amazon tropical rainforest to extract information about bioenergetics potential for electric energy production for use with isolated Amazonian communities. To achieve this aim, information gathered about forest inventory was mixed with pattern classification and recognition in medium resolution satellite imagery such as those from LANDSAT and CBERS. The approach used in this work comes from the computational intelligence area, using artificial neural networks equipped with radial basis functions and Kohonen´s self organizing maps. The results serve as input to a geographical information system application which creates and manages a geographical database for energetic planning with renewable energy resources applicable to isolated Amazonian communities.Item Acesso aberto (Open Access) Metodologia para o projeto preliminar de edifícios utilizando otimização multiobjetivo baseada na simulação de desempenho(Universidade Federal do Pará, 2019-12-11) ZEMERO, Bruno Ramos; TOSTES, Maria Emília de Lima; http://lattes.cnpq.br/4197618044519148Buildings energy consumption has a great energetic and environmental impact worldwide. The architectural design has great potential to solve this problem because the building envoltória exerts influence on the overall system performance, but this is a task that involves many objectives and constraints. In the last two decades, optimization studies applied to energy efficiency of buildings have helped specialists to choose the best design options. However, there is still a lack of optimization approaches applied to the early design stage, which is the most influential stage for the building energy efficiency over its entire life cycle. Therefore, this article presents a multiobjective optimization model to assist designers in the preliminary building design, by means of the PAES (Pareto Archived Evolutionary Strategies) algorithm with the EnergyPlus Simulator coupled, to evaluate the solutions. The search process is executed by a binary array where the array components evolve over the generations, together with the other building components. The methodology aims to find optimal solutions with the lowest constructive cost associated with greater energy efficiency. In the case study, it was possible to simulate the process of using the optimization model and analyse the results in relation to: bioclimatic principles, economic performance, environmental performance, energy performance, usability and accuracy, proving that the tool serves as support in building design. Optimal solutions achieved energy savings and operational CO₂ emissions over typical standards, as well as short-term return on investment in four different types of weather.Item Acesso aberto (Open Access) Metodologias de controle de tensão com justiça de corte da geração fotovoltaica em redes de distribuição de baixa tensão(Universidade Federal do Pará, 2024-01-31) LOPES, Andrey da Costa; VIEIRA, João Paulo Abreu; http://lattes.cnpq.br/8188999223769913The growing concern about climate change and global warming have motivated the current Energy Transition, which concerns the shift from fossil fuels to renewables energy sources (RES) in an effort to reduce CO2 emissions. This energy transition has driven the electrification of the economy, fostering significant growth in RES, particularly in photovoltaic solar energy. In this context, the decentralization of the electric sector has enabled the direct integration of these sources into Low Voltage Distribution Networks (LVDNs). However, the massive integration of Micro Photovoltaic Solar Generation (µPVSG) into these networks has caused reverse power flow, resulting in technical challenges such as overvoltage and thermal overload in their assets. Solutions, such as Volt-Watt Control (VWC) in Photovoltaic Inverters (PVIs), have proven effective in addressing voltagerelated issues. However, this control has led to an unfair distribution of active power among the PVIs during VWC operation, penalizing consumers located further from the distribution transformer. Additionally, stability issues related to the convergence in the dynamics of VWC, due to the slope of the Volt-Watt curve, have been considered in various studies. Therefore, this study presents a new methodology for adjusting Volt-Watt curves, ensuring the stability of VWC and simultaneously ensuring a fair power cut among PVIs. This approach is applied in two voltage control architectures, decentralized and centralized, respectively. In the first methodology, a linearized model of the network is used for Volt-Watt curve adjustment, employing local measurements at the connection points of the respective PVIs. In the second methodology, a voltage sensitivity matrix is used for the linearized model of the network when applying the Volt-Watt curve adjustment, where VWC parameters are coordinated in real-time, assisted by local measurements in the respective PVIs. The studies were conducted on a set of LVDNs and evaluated for effectiveness and fairness of power cuts quantitatively, using the Jain’s Fairness Index (JFI) as a metric. The results confirmed the effectiveness of the proposed control in mitigating voltage problems, acting fairly by equally exporting surplus energy to the grid, while ensuring controller stability. Additionally, penalties arising from the local dependence of PVIs in power cuts were eliminated compared to conventional VWC strategies.