DEELT - Artigos publicados em periódicos
URI permanente para esta coleçãohttp://www.hml.repositorio.ufop.br/handle/123456789/5267
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Resultados da Pesquisa
Item Distribution network reconfiguration using iterative branch exchange and clustering technique.(2023) Pereira, Ezequiel C.; Barbosa, Carlos Henrique Nogueira de Resende; Vasconcelos, João Antônio deThe distribution network reconfiguration problem (DNRP) refers to the challenge of searching for a given power distribution network configuration with better operating conditions, such as minimized energy losses and improved voltage levels. To accomplish that, this paper revisits the branch exchange heuristics and presents a method in which it is coupled with other techniques such as evolutionary metaheuristics and cluster analysis. The methodology is applied to four benchmark networks, the 33-, 70-, 84-, and 136-bus networks, and the results are compared with those available in the literature, using the criteria of the number of power flow executions. The methodology minimized the four systems starting from the initial configuration of the network. The main contributions of this work are the use of clustering techniques to reduce the search space of the DNRP; the consideration of voltage regulation banks and voltage-dependent loads in the feeder, requiring the addition of a constraint to the mono-objective model to guarantee the transferred load will be supplied at the best voltage magnitude level, and the application of the methodology in real distribution networks to solve a set of 81 real DNRPs from CEMIG-D (the distribution branch of the Energy Company of Minas Gerais). Four out of those are presented as case studies to demonstrate the applicability of the approach, which efficiently found configurations with lower power and energy losses with few PF runs.Item SHIL and DHIL simulations of nonlinear control methods applied for power converters using embedded systems.(2018) Rosa, Arthur Hermano Rezende; Silva, Matheus B. E.; Campos, Marcos Fidelis Costa; Santana, Renato A. S.; Rodrigues, Welbert Alves; Morais, Lenin Martins Ferreira; Seleme Junior, Seleme IsaacIn this work, a new real-time Simulation method is designed for nonlinear control techniques applied to power converters. We propose two different implementations: in the first one (Single Hardware in The Loop: SHIL), both model and control laws are inserted in the same Digital Signal Processor (DSP), and in the second approach (Double Hardware in The Loop: DHIL), the equations are loaded in different embedded systems. With this methodology, linear and nonlinear control techniques can be designed and compared in a quick and cheap real-time realization of the proposed systems, ideal for both students and engineers who are interested in learning and validating converters performance. The methodology can be applied to buck, boost, buck-boost, flyback, SEPIC and 3-phase AC-DC boost converters showing that the new and high performance embedded systems can evaluate distinct nonlinear controllers. The approach is done using matlab-simulink over commodity Texas Instruments Digital Signal Processors (TI-DSPs). The main purpose is to demonstrate the feasibility of proposed real-time implementations without using expensive HIL systems such as Opal-RT and Typhoon-HL.Item Analysis of the spatiotemporal MVDR filter applied to BCI-SSVEP and a filter bank extension.(2022) Vargas, Guilherme Vettorazzi; Leite, Sarah Negreiros de Carvalho; Boccato, LevyArtifacts inevitably permeate brain signal acquisition by electroencephalography (EEG). Hence, brain-computer interfaces based on steady-state visually evoked potentials (BCI-SSVEP) frequently require a filtering to increase signal-to-noise ratio (SNR) in an attempt to improve its ability to identify a command selected by the user. By combining the signals from different electrodes, the spatiotemporal filtering technique based on the minimum variance distortionless response (MVDR) attenuates undesired frequency components while preserving the spectral content at the visual stimuli frequencies. In this study, we revisit the MVDR filter, further evaluating its behavior with respect to critical factors in a BCI-SSVEP system: proximity amid stimulation frequencies, number of stimuli and stimulation window-length. Additionally, the main parameters of the filter were also varied, such as the order and the number of electrodes to be combined. The experimental analysis confirmed the effectiveness of the MVDR filter for the majority of the scenarios. However, it also revealed a significant difficulty that the MVDR filter has when dealing with short-length time windows, especially when compared with classical filtering techniques, such as CAR and CCA. So, in order to mitigate this limitation, we propose a filter bank MVDR (FBMVDR), where each element is a MVDR filter designed to preserve a single stimulation frequency or harmonic components. This new approach provided an increase of more than 5% in relation to the standard MVDR, reaching a performance of 92.6% in scenarios with 4 visual stimuli and 1s window-length and achieved competitive results with the state-of-the-art technique filter bank CCA (FBCCA).Item Comparative performance of three phasor-extraction algorithms for co-simulation of electrical power systems.(2021) Theodoro, Thainan Santos; Barbosa, Pedro Gomes; Tomim, Marcelo Aroca; Lima, Antonio Carlos Siqueira deThis work presents a comparison of the three phasor extraction algorithms proposed in the literature for the co-simulation of transient stability and electromagnetic transients programs. Initially, a brief mathematical review of two algorithms widely used in the literature is made: the discrete Fourier transform and the adjustment of the least-squares curve. In addition, a technique proposed by the authors based on the use of the generalized second-order integrator is presented. Then, these three techniques will be implemented and evaluated numerically through a comparative performance study extracting the fundamental phasor component of a test signal.Item Power-sharing for dc microgrid with composite storage devices and voltage restoration without communication.(2022) Bastos, Renan Fernandes; Aguiar, Cassius Rossi de; Balogh, Attila; Sütő, Zoltán; Machado, Ricardo QuadrosIn this paper, we propose a new decentralized control and power-sharing strategy to manage the power flow among energy sources (ESs), energy storage systems (ESSs) and the common dc-link. In the proposed technique, we eliminate all communication among the ESSs, to reduce the complexity and increase reliability, maintaining dc-link voltage restoration. In this context, batteries and ultracapacitors (UCs) are the ESSs, while ESs can be any power source such as photovoltaic, wind, fuel-cell and etc. This technique shares the microgrid power imbalance between batteries, proportionally to their state-of-charge (SoC) and energy capacity, achieving SoC equalization. The technique also promotes voltage restoration for the UCs, keeping their average voltage constant after supplying the power peaks during power transients. For all ESSs only local variables are measured, such as local current and dc-link voltage, with no shared data between ESSs. Small signal and stability analysis are performed, along with experimental results in a lab bench show the feasibility and performance of the technique.Item An auxiliary system discretization approach to Takagi-Sugeno fuzzy models.(2022) Campos, Víctor Costa da Silva; Braga, Marcio Feliciano; Santos, Luciano Antonio FrezzattoThis paper proposes a new procedure for discretizing nonlinear systems described by Takagi-Sugeno fuzzy models. The discretization procedure consists of obtaining a linear auxiliary system that approximates the Takagi-Sugeno model over a sampling instant. By discretizing this auxiliary system, a norm bounded uncertain linear discrete-time system is found, which is capable of representing the fuzzy model. This auxiliary system, as well as the norm bounded uncertainty, is found by solving an optimization problem with Linear Matrix Inequality (LMI) constraints. To illustrate the discretization procedure, a constant state observer is synthesized based on simple LMI conditions and then applied to a real nonlinear Chua’s circuit. Additionally, a state-feedback controller based on our discretization approach is synthesized and we obtain larger maximum sampling periods than other tested strategies from the literature.Item Control of event-triggered quasi-LPV systems based on an exact discretization approach - a linear matrix inequality approach.(2022) Campos, Víctor Costa da Silva; Santos, Luciano Antonio Frezzatto; Oliveira, Tiago Gaiba de; Manzoc, Víctor Estrada; Braga, Marcio FelicianoThis paper presents an H∞ event-triggered state-feedback controller design for continuous-time non-linear systems via convex optimization techniques. The proposal is based on an exact discretization and its quasi-linear parameter varying representation. Thus, two sets of design conditions in terms of linear matrix inequalities by means of both parameter-dependent and quadratic Lyapunov functions are proposed. The proposed conditions also provide an estimate to system’s domain of attraction and an extra set of conditions is presented for a guaranteed minimum time between events. Well-known examples are employed to illustrate the effectiveness of the proposal.Item Theoretical-experimental analysis of the induction generator in the use of distributed generation.(2021) Vanço, Wagner Eduardo; Silva, Fernando Bento; Monteiro, José Roberto Boffino de Almeida; Oliveira, Carlos Matheus Rodrigues de; Gomes, Luciano CoutinhoThis work presents a theoretical-experimental study in permanent regime of the three-phase induction generator of squirrel cage connected directly to the distribution network at fixed speed. The study is based on the operation of the induction generator that operates with the capacitor bank and without the presence of the capacitor bank to show the improvement of the power factor of the induction generator when in connection with the electric distribution network.Item Effects of harmonic pollution on salient pole synchronous generators and on induction generators operating in parallel in isolated systems.(2020) Vanço, Wagner Eduardo; Silva, Fernando Bento; Oliveira, José Mário Menescal de; Monteiro, José Roberto Boffino de AlmeidaThis work presents a study of the disturbances caused by harmonic pollution in salient pole synchronous generators (SPSG) and induction generators, when operating in parallel in isolated systems. SPSG are known to operate with induction generators, since the excitation system of the synchronous generator is responsible for the voltage control on the island system. Due to the increase in the employment of power electronics, the loads take on a nonlinear behavior, where these become responsible for the generation of harmonics, due to the switching of electrical devices. Therefore, the analysis of the disturbances that these loads cause in generators, in this proposed and studied architecture, becomes essential. For the synchronous generator, there is also presented the analyses of the oscillations for voltages and currents on the dq0 model, the currents induced on the damper winding, the disturbances on the load angle and on the field current. In terms of the induction generator, the voltage and current oscillations are also analyzed from the dq0 model on the slip frequency. All the identified and quantified disturbances are oscillations on the electric variables, which possess a pulsating nature of frequencies 6ω, 12ω, and 18ω for the synchronous and induction generators, the oscillations of the sixth order and its multiples, will be given in the harmonic slip frequency of their respective harmonic orders in positive and negative sequence. In this way, verification is made as to the appearance of high slippage on the rotor of the induction generator.Item A study of the effects of magnetic saturation and spatial harmonics on isolated salient-pole synchronous generators.(2019) Vanço, Wagner Eduardo; Silva, Fernando Bento; Monteiro, José Roberto Boffino de AlmeidaThis article presents a study of the effects caused in isolated salient-pole synchronous generator due to magnetic saturation and spatial harmonics, these effects cause harmonic distortion in the generated voltage and current. An experimental analysis is necessary to verify the magnitude of the distortion of the generated voltage and current, focusing on which are the components generated by the non-linear constructive aspects of the salient-pole synchronous generator. The quality of generated energy depends on which harmonic components prevail in the total distortion, whether zero, positive or negative. In this way the study is based on the negative effects caused by these harmonious components of a constructive nature of the salient-pole synchronous generator.