Frequency Relay
Mostrando 1-12 de 36 artigos, teses e dissertações.
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1. A Wideband and Wide Axial Ratio Bandwidth Circularly Polarized Antenna Loaded with Circular Ring Slot
Abstract The presented model for wideband circularly polarized microstrip antenna is an improved version of the previous models which is widely applicable to satellite, microwave relay and radar. The designed circularly polarized antenna having overall volume of 20× 20 × 1.6 mm3 actively works at the impedance bandwidth of 9000 MHz (4.0–12.9 GHz) having
Journal of Microwaves, Optoelectronics and Electromagnetic Applications. Publicado em: 2022
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2. Computation of multiple limit cycles in nonlinear control systems - a describing function approach
Abstract Limit cycles play an important role in nonlinear systems, provided that many control loops with common nonlinearities like relay, hysteresis, and saturation can present them. Thus, a proper description of this nonlinear phenomenon is highly desirable. A strategy for the linearized analysis is the describing function method, which is a frequency doma
J. Aerosp. Technol. Manag.. Publicado em: 2011-04
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3. Tuning of multivariable decentralized controllers through the ultimate-point method
A successful method for tuning single-loop PID controllers is the ultimate-point method. This method is based on the identification of the ultimate point of the process’ frequency response followed by its shifting, through appropriate choices of the controller’s parameters, to a specified location of the complex plane. This paper presents an extension of
Publicado em: 2011
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4. APPICATION OF FUZZY LOGIC IN CONTROL THE CRYSTALLIZATION OF AN ABSORPTION REFRIGERATION SYSTEM WITH PAIR WATER LITHIUM BROMIDE / Aplicação da lógica fuzzy no controle da cristalização de um sistema de refrigeração por absorção com par brometo de lítio
This work presents theoretical and experimental study of a system of control for a steam generator. This system was developed to control the crystallization of a cooling system for absorption. The control system maintains the pressure generator above the zone of crystallization of diagram temperature pressure-saturated solution concentration of LiBr-water. T
Publicado em: 2010
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5. Use of Wavelet Transforms to Detect Abnormal Frequency Variation in Distributed Generation Systems / Utilização da transformada de Wavelet para detectar variações anormais de freqüência em sistemas de geração distribuída
This dissertation focuses the importance of registering eventual frequency variations in Electric Power System which may cross the established limits for normal operation. These can cause serious problems in the operation of sensitive equipments connected to the electric grid, such as the turbo-generators employed in thermoelectric plants. For power system f
Publicado em: 2009
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6. Um método prático para a definição dos ajustes de relés baseados em medidas de freqüência usados para detecção de ilhamento de geração distribuída
Antes de se proceder com a instalação de geração distribuída em redes de distribuição de energia elétrica, engenheiros de proteção devem projetar e parametrizar sistemas de proteção de forma eficiente para desconectar os geradores distribuídos dentro de um tempo pré-determinado, no caso de ocorrência de situações de ilhamento. Tanto o projet
Sba: Controle & Automação Sociedade Brasileira de Automatica. Publicado em: 2008-06
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7. Algoritmos genéticos aplicados à proteção e estimação de harmônicos em sistemas elétricos de potência / Genetic algorithms applied to protection and harmonic estimation in electric power systems
The aim of electric power systems is to generate electricity and to deliver it continuously to the end-user in an acceptable standard. Therefore, different applications using genetic algorithms (GAs) to solve electric power system problems are presented in this work. Harmonic estimation, frequency relays and distance protection are the subjects investigated
Publicado em: 2008
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8. Frequency estimation in power system through adaptive filtering / Estimação da freqüência em sistemas elétricos de potência através de filtragem adaptativa
This work presents a method for frequency estimation in power systems using adaptive filters based in the algorithm of least mean square (LMS). The analysis of the power system is made through the conversion of the three-phase voltages in a complex signal with the application of alfabetatransform, whose complex form was directed to the algorithm of adaptive
Publicado em: 2007
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9. New proposals for optmization of digital TV receivers based on OFDM in regional single frequency network environments / Novas propostas para otimização de receptores de TV digital baseados em OFDM em ambientes de redes de frequencia unica regionais
This thesis deals with the optimization of Digital TV receivers based on OFDM, with performance evaluation in regional single frequency networks (SFN). Such environment facilitates the channel distribution, however its characteristics degrade the receiver operation. Initially, projects of loop canceller filters in relay stations are treated, and they are nec
Publicado em: 2007
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10. Utilização da rede SFN para expansão da rede de retransmissão regional da TV digital aberta terrestre
This work presents an approach to the network relay station for free broadcasting television that may constructed with the future digital television in Brazil based on COFDM modulation. Differently of the traditional system, the network relay in multi frequencies (MFN), the proposal here described considers the use of a net in only one frequency (SFN) for th
Publicado em: 2006
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11. A proposal of a digital frequency relay based on genetic algorithms / Uma proposta de relé digital de freqüência baseado em algoritmos genéticos
Este trabalho apresenta um método baseado em algoritmos genéticos AGs, o qual consiste na estimação dos parâmetros associados as formas de ondas, tais como amplitude, freqüência e ângulo de fase das mesmas, referentes a uma proposição de relé de freqüência. O método proposto é baseado em algoritmos genéticos com representação real, tendo
Publicado em: 2005
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12. EFFECTS OF ATMOSPHERIC MULTIPATH IN LINE-OF -SIGHT MICROWAVE SYSTEMS / EFEITOS DE MULTIPERCURSOS ATMOSFÉRICOS EM ENLACES DE MICROONDAS EM VISIBILIDADE
The variations which happen in the troposphere layers throughout the time in relation to the median condition of the signal cause various phenomena that change the received signal level at digital radio relay systems randomly. The random changes are named fading. Fading is normally classified as fast or slow. The former is normally associated with the atmosp
Publicado em: 2004