Carlos Tavares da Costa Junior

Controle Fuzzy aplicado à melhoria da estabilidade dinâmica em sistemas elétricos de potência

Este trabalho propoe uma estrategia fuzzy, do tipo Rede de Controladores Locais, aplicavel a melhoria da estabilidade dinâmica em sistemas eletricos de potencia, visando compensar possiveis perdas de sintonia devido a ocorrencia de variacoes nas condicoes operacionais da planta. A adaptacao dos ganhos do controlador fuzzy e efetuada on-line, interpolando-se os ganhos de um conjunto finito de controladores locais fixos. Ao ocorrer variacoes nas condicoes operacionais da planta, os ganhos da lei de controle sao ajustados automaticamente de modo a manter satisfatorio o desempenho do sistema de controle. O desempenho do controle foi avaliado atraves de estudos de simulacao, utilizando-se um modelo dinâmico nao-linear, do tipo maquina barra infinita. Os resultados mostram que o emprego da estrategia proposta permite obter melhorias no desempenho dinâmico do sistema.

Estabilizador de sistemas de potencia digital aplicado a uma unidade geradora da uhe de Tucurui

Este trabalho apresenta o desenvolvimento e resultados de testes de campo de um estabilizador de sistemas de potencia (ESP) digital, destinado ao amortecimento de oscilacoes eletromecânicas em sistemas interligados. Os testes experimentais foram efetuados em uma das unidades hidrogeradoras, de 350 MVA, da UHE de Tucurui. A lei de controle amortecedor do ESP digital foi embarcada em um sistema de hardware baseado em um controlador digital de sinais (DSPIC 30f5011). A estrutura da lei de controle e na forma canonica RST, de tempo discreto, sendo os parâmetros do controlador calculados atraves da tecnica de deslocamento radial de polos. Para fins de projeto, a dinâmica da planta, no ponto de operacao considerado, foi representada por um modelo parametrico, o qual foi estimado a partir de dados medidos em campo. Os resultados experimentais mostraram um excelente desempenho do ESP digital no amortecimento de um dos modos eletromecânicos observavel na UHE de Tucurui.

A Low-Cost, Stand-Alone Sensory Platform for Monitoring Extreme Solar Overirradiance Events

In this paper, we present a low-cost, stand-alone sensory platform developed for in situ monitoring of environmental parameters, for use in the Amazon region in the north of Brazil. The mission of the platform is to perform monitoring and identification of overirradiance (solar irradiance > 1000 W/m2) and extreme overirradiance events (solar irradiance > 1300 W/m2) using a photovoltaic based irradiance sensor. The sensory platform was built using the ESP8266 microcontroller, an open embedded computer capable of Wi-Fi communication using the IEEE 802.11 standard, and small photovoltaic modules, air temperature, atmospheric pressure, voltage, and current sensors, enabling the development of a low-cost system (€70/R

Estratégias de identificação paramétrica aplicadas à modelagem dinâmica de um servidor web Apache

350.00 BRL). Calibration and tests were conducted at the Federal University of Pará (UFPA), Belém campus, Pará, where the platform measured an extreme overirradiance of 1321 W/m2 at a low-latitude (1 °S) and low altitude (7 m above sea level).

Electromagnetic interference reduction by dynamic impedance balancing applied in biosensors

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 servers 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.

Expansion of isolated electrical systems in the Amazon: An approach using fuzzy multi-objective mathematical programming

Electromagnetic interference, caused by the electric power line, affects the signals of electronic instruments, specifically those with low levels of amplitude. This type of signal is known as Common Mode Interference. There are many methods and architectures used to minimize or eliminate the influence of these interferences in electronic instrumentation, the most common is the use of band reject filters to eliminate them. With this objective, we present the analysis, prototyping, developing and testing of a new architecture reconfigurable filter with application in biomedical instrumentation, applied to the reduction of interference in common mode and conservation of components of the useful signal in the same range of noise, by the principle of balancing impedance dynamic using the hardware description software and simulation electronics software. The methodology was tested using a sinusoidal signal in the same standard frequency of an electrocardiogram signal in the same frequency interference (50/60 Hz). Excellent results were obtained in simulation with noise reduction of approximately 97%, while the results of experimental tests showed around 50% reduction. In both cases, the useful signal was preserved, confirming the efficiency of the proposed architecture. The method can be applied to eliminate the interference, which are in the same band the of the useful signal components.