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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Agora exibindo 1 - 3 de 3

Acesso aberto (Open Access)
Análise de desempenho de algoritmos para classificação de sequências representando faltas do tipo curto-circuito em linhas de transmissão de energia elétrica
(Universidade Federal do Pará, 2019-12-05) FREIRE, Jean Carlos Arouche; MORAIS, Jefferson Magalhães de; http://lattes.cnpq.br/5219735119295290; CASTRO, Adriana Rosa Garcez; http://lattes.cnpq.br/5273686389382860
Maintaining power quality in electrical power systems depends on addressing the major disturbances that may arise in their generation, transmission and distribution. Within this context, many studies have been developed aiming to detect and classify short circuit faults in electrical systems through the analysis of the electrical signal behavior. Transmission line fault classification systems can be divided into two types: online and post fault classification systems. In the post-missing scenario the signal sequences to be evaluated for classification have variable length (duration). In sequence classification it is possible to use conventional classifiers such as Artificial Neural Networks, Support Vector Machine, K-nearest neighboors and Random forest. In these cases, the classification process usually requires a sequence preprocessing or a front end stage that converts the raw data into sensitive parameters to feed the classifier, which may increase the computational cost of the classification system. An alternative to this problem is the FBSC-FrameBased-Sequence Classification (FBSC) architecture. The problem with FBSC architecture is that it has many degrees of freedom in designing the model (front end plus classifier) and it should be evaluated using a complete dataset and rigorous methodology to avoid biased conclusions. Considering the importance of using efficient short-circuit fault classification methodologies and mainly with low computational cost, this paper presents the results of the KNN-DTW (K-Nearest Neighbor) algorithm analysis study associated with Dynamic similarity measurement. Time Warping (DTW) and HMM (Hidden Markov Model) algorithm for fault classification task. These two techniques allow the direct use of data without the need for front ends for signal pre-processing, as well as being able to handle multivariate and variable time series, such as signal sequences for the post-miss case. To develop the two proposed systems for classification, simulated data of short-circuit faults from the UFPAFaults public database were used. To compare results with methodologies already presented in the literature for the problem, the FBSC architecture was also evaluated for the same database. In the case of FBSC architecture, different front ends and classifiers were used. The comparative assessment was performed from the measurement of error rate, computational cost and statistical tests. The results showed that the HMM-based classifier was more suitable for the problem of classification of short circuits on transmission lines.
Acesso aberto (Open Access)
Estrutura de redes neurais auto-associativas aplicadas ao processo de identificação de equipamentos elétricos em sistemas de monitoramento não intrusivo de cargas
(Universidade Federal do Pará, 2019-10-23) MORAIS, Lorena dos Reis; CASTRO, Adriana Rosa Garcez; http://lattes.cnpq.br/5273686389382860
The pursuit of reducing and rationalizing electricity consumption is increasingly becoming a priority for all consumers worldwide. Residential environments are responsible for a large part of electricity consumption. Non-intrusive load monitoring systems were created with the aim of helping consumers, providing the possibility of obtaining information about the individual consumption of equipment and thus allowing a monitored consumption and the consequent increase in energy efficiency. In a Non-Intrusive Load Monitoring System, four steps are critical: acquiring aggregate data through a single sensor, detecting equipment on / off events from the aggregate load, extracting disaggregated signal characteristics and the identification of equipment based on the characteristics extracted from the disaggregated signal. In this context, this work proposes a new methodology for identification of electrical equipment in a residential environment employing a competitive structure of Auto-Associative Neural Networks. The proposed system is based on power signal measurements obtained from equipment on / off events. To test the proposed methodology 3 scenarios were developed using 3 different public databases. Due to the good results achieved, analyzed using statistical metrics, it is evaluated that the proposed methodology is able to efficiently perform the task of identifying electrical equipment, thus contributing to the development of future non-intrusive monitoring systems. meet market demands.
Acesso aberto (Open Access)
Extração de conhecimento em forma de regras difusas a partir de mapas auto-organizáveis de Kohonen: aplicação em diagnóstico de faltas incipientes em transformadores
(Universidade Federal do Pará, 2013-03-11) SILVA, Ana Carla Macedo da; CASTRO, Adriana Rosa Garcez; http://lattes.cnpq.br/5273686389382860
Despite the many advantages offered by the artificial neural networks, some limitations still prevent their widespread use, especially in applications that require making decisions essential to ensure safety in environments such as in Power Systems. A major limitation of artificial neural networks with respect to the inability of these networks is to explain how to arrive at certain decisions. This explanation must be humanly understandable. Thus, this paper proposes a method for extracting fuzzy rules from Kohonen self-organizing map, designing a fuzzy inference system capable of explaining the decisions taken by the map. To verify its effectiveness, the method is applied to solve the problem of classification for the diagnosis of incipient faults in power transformers used.

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