Faculdade de Engenharia Elétrica - FEE/ITEC

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2515

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Agora exibindo 1 - 3 de 3

Acesso aberto (Open Access)
Controladores fuzzy aplicados ao conversor de geradores de indução duplamente excitados em sistemas eólicos integrados a sistemas de potência
(2007-03) VIEIRA, João Paulo Abreu; BEZERRA, Ubiratan Holanda; BARRA JUNIOR, Walter; NUNES, Marcus Vinícius Alves; NASCIMENTO, André Cavalcante do
This paper presents new fuzzy control strategies for application on the control of the static converter that connects the doubly fed induction generator into the electrical grid in variable speed wind generation systems. The proposed control strategies are of the type "look-up- table" with supervision. The performance of these intelligent regulators is compared with those obtained with constant gain PI's controllers, when the electrical power systems is submitted to faults. The fuzzy controllers are intended to ensure the continous operation of the static converter, even during the fault period, and at the same time to improve the transient performance of the electrical system as compared with the case of using PI conventional controllers. The results presented confirm the efficiency of the proposed control strategies. The mathematical models that represent the dynamics of the wind turbines and generators were implemented using computacional programs developed in MATLABTM.
Acesso aberto (Open Access)
Estabilizador neural não-linear para sistemas de potência treinado por rede de controladores lineares
(2006-06) BARREIROS, José Augusto Lima; FERREIRA, André Maurício Damasceno; BARRA JUNIOR, Walter; COSTA JÚNIOR, Carlos Tavares da; BAYMA, Rafael Suzuki
Power System Stabilizers (PSS) have been applied as the most common solution to damp small magnitude and low frequency oscillations in modern electric power systems. Conventional Stabilizers, with fixed structure and parameters, have been used with this objective for several decades, but there are some system operation conditions where the performance of these linear stabilizers may deteriorate, especially when compared with that of stabilizers designed using modern control techniques. A Neural PSS, trained with a set of local linear controllers, is applied to establish the regions where a Conventional PSS shows low performance. Using non-linear digital simulations of a synchronous machine connected to an infinite-bus system and a multi-machine power system the Neural PSS is assessed showing superiority in those regions.
Acesso aberto (Open Access)
Estratégias de identificação paramétrica aplicadas à modelagem dinâmica de um servidor web Apache
(2012-02) ABREU, Thiago Wanderley Matos de; BARRA JUNIOR, Walter; BARREIROS, José Augusto Lima; COSTA JÚNIOR, Carlos Tavares da
This article presents an experimental study about parametric identification techniques applied to the modeling of an Apache webserver. In order to simulate load variations at the server, an experimental arrangement was developed, which is composed of two personal computers, one used to run the Apache server and the other to generate workload by requesting services to the Apache. Auto-regressive (AR) parametric models were estimated at different operating points and workload conditions. The mean values of the MaxClients input (a parameter which is used to set the maximum number of the server's active processes) were used to define the operating points, in order to obtain the Apache server CPU utilization (in %) as output. 600 samples were collected at each operating point every 5 seconds. To proceed with the system identification, half of the data set was used for parameter estimation while the other half was used for model validation, at each operating point. A study of the most adequate system order showed that a 7th order model could be satisfactorily used for MaxClients low values operating points. However, the results showed that higher order models are needed for MaxClients higher values, due to system inherent non-linearities.

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