DEELT - Departamento de Engenharia Elétrica

Permanent URI for this community

https://monog.ufop.br/handle/123456789/5266

Browse

Now showing 1 - 20 of 65

Virtual learning environments : proposals for authoring and visualization of educational content.
(2014) Cinto, Tiago; Leite, Harlei Miguel de Arruda; Peixoto, Cecilia Sosa Arias; Arantes, Dalton Soares
Heated debates involving reforms in the educational system are becoming more and more frequent in recent years. This is due to the increasingly evident shortcomings in the educational system and its difficulties to evolve at the same pace as technological development. The aim of this work is to present an analysis of the current engineering educational context and propose an interactive content authoring system as well as a virtual professor in an attempt to make learning experience richer and more motivating to students.
Filtros adaptativos aplicados em condicionadores de energia.
(2014) Ferreira, Silvia Costa; Pereira, Rondineli Rodrigues; Gonzatti, Robson Bauwelz; Silva, Carlos Henrique da; Silva, Luiz Eduardo Borges da; Torres, Germano Lambert
Este artigo apresenta uma comparação entre quatro algoritmos para a compensação do conteúdo harmônico e da potência reativa através de condicionadores de energia. Os quatro algoritmos testados são: o método da referência síncrona, o filtro adaptativo sintonizado utilizando PLL para gerar os sinais de referência, o filtro adaptativo sintonizado utilizando a Transformada de Clarke para gerar os sinais de referência e o filtro adaptativo sintonizado com estimador de frequência. O principal objetivo ´e demonstrar a habilidade dos filtros adaptativos em acompanhar as variações do sinal de entrada, sem a necessidade de um algoritmo de sincronismo, como o PLL. Os algoritmos foram simulados, implementados no DSP TMS320F2812 e testados diretamente em filtros ativos de potência. Diversos aspectos relativos ao tempo de execução, à velocidade de convergência e ao erro em regime permanente são apresentados.
Comparative analysis of strategies for feature extraction and classification in SSVEP BCIs.
(2015) Leite, Sarah Negreiros de Carvalho; Costa, Thiago Bulhões da Silva; Suarez Uribe, Luisa Fernanda; Soriano, Diogo Coutinho; Yared, Glauco Ferreira Gazel; Coradine, Luis Cláudius; Attux, Romis Ribeiro de Faissol
Brain–computer interface (BCI) systems based on electroencephalography have been increasingly usedin different contexts, engendering applications from entertainment to rehabilitation in a non-invasiveframework. In this study, we perform a comparative analysis of different signal processing techniquesfor each BCI system stage concerning steady state visually evoked potentials (SSVEP), which includes: (1)feature extraction performed by different spectral methods (bank of filters, Welch’s method and the mag-nitude of the short-time Fourier transform); (2) feature selection by means of an incremental wrapper,a filter using Pearson’s method and a cluster measure based on the Davies–Bouldin index, in additionto a scenario with no selection strategy; (3) classification schemes using linear discriminant analysis(LDA), support vector machines (SVM) and extreme learning machines (ELM). The combination of suchmethodologies leads to a representative and helpful comparative overview of robustness and efficiency ofclassical strategies, in addition to the characterization of a relatively new classification approach (definedby ELM) applied to the BCI-SSVEP systems.
Adaptive real-time power measurement based on IEEE standard 1459-2010.
(2015) Ferreira, Silvia Costa; Gonzatti, Robson Bauwelz; Silva, Carlos Henrique da; Silva, Luiz Eduardo Borges da; Pereira, Rondineli Rodrigues; Torres, Germano Lambert
This article presents the theoretical development and implementation of an adaptive algorithm for real-time measurement of electrical powers under sinusoidal, non-sinusoidal, balanced, and unbalanced conditions according to the definitions given by IEEE Standard 1459-2010. The algorithm is based on adaptive filter notch filter implementation, where the parameters are adjusted by tracking the amplitude and phase variations to improve the accuracy of the power measurement. The algorithm uses the filter coefficients to calculate powers, resulting in low computational burden. The results of computer simulation and practical implementation using a fixed-point digital signal controller are shown in detail, proving the accuracy and efficiency of the algorithm.
H1 and H2 control design for polytopic continuous-time Markov jump linear systems with uncertain transition rates.
(2015) Morais, Cecilia de Freitas; Braga, Marcio Feliciano; Oliveira, Ricardo Coração de Leão Fontoura de; Peres, Pedro Luis Dias
This paper investigates the problems of H1 and H2 state feedback control design for continuous-time Markov jump linear systems. The matrices of each operation mode are supposed to be uncertain, belonging to a polytope, and the transition rate matrix is considered partly known. By appropriately modeling all the uncertain parameters in terms of a multi-simplex domain, new design conditions are proposed, whose main advantage with respect to the existing ones is to allow the use of polynomially parameter-dependent Lyapunov matrices to certify the mean square closed-loop stability. Synthesis conditions are derived in terms of matrix inequalities with a scalar parameter. The conditions, which become LMIs for fixed values of the scalar, can cope with H1 and H2 state feedback control in both mode-independent and modedependent cases. Using polynomial Lyapunov matrices of larger degrees and performing a search for the scalar parameter, less conservative results in terms of guaranteed costs can be obtained through LMI relaxations. Numerical examples illustrate the advantages of the proposed conditions when compared with other techniques from the literature.
Olhares sobre a prevenção dos acidentes de trabalho.
(2015) Soares, Eva Bessa; Curi Filho, Wagner Ragi
Este artigo traz, a partir da revisão de abordagens de autores nacionais e internacionais, alguns pontos de vista sobre a questão do acidente de trabalho e sua prevenção. No espaço desse artigo, não se pretendeu esgotar esta complexa discussão, apenas apresentar pontos de vista sobre a temática. São relatadas as duas principais abordagens sobre o acidente: a tradicional e a contemporânea, além de dados relacionados aos processos educativos para prevenção de acidentes. Na conclusão, são apontados aspectos concernentes à prevenção do acidente de trabalho. Embora ela seja possível, ainda há muito a ser feito em questões teóricas e práticas para se afirmar que a atuação de uma empresa está pautada em prevenção de danos à saúde do trabalhador.
Model-hierarchical column generation and heuristic for the routing and wavelength assignment problem.
(2016) Duhamel, Christophe; Mahey, Philippe; Martins, Alexandre Xavier; Saldanha, Rodney Rezende; Souza, Maurício Cardoso de
The routing and wavelength assignment (RWA) problem typically occurs in wavelength division multiplexing optical networks. Given a number of available wavelengths, we consider here the problem of maximising the number of accepted connections with respect to the clash and continuity constraints. We first propose a new strategy which combines two existing models. This leads to an improved column generation scheme. We also present two heuristics to compute feasible solutions: a hybrid heuristic and the integer solution at the root node of the column generation. Our approaches are compared with the best existing results on a set of classic RWA instances.
A circuit for automatic measurement of bifurcation diagram in nonlinear electronic oscillators.
(2016) Ricco, Rodrigo Augusto; Verly, Anny; Amaral, Gleison Fransoares Vasconcelos
Experimental bifurcation diagram is very helpful to describe the global behaviour of nonlinear electronic oscillators. The diagram allows insight gain of the oscillators behaviour for a parameter variation. However, when the bifurcation parameter is a resistance, experimental bifurcation diagrams are hard to achieve. In this case, if the potentiometer resistance has been used to change the gain, it is possible to replace the potentiometer by an alternative circuit using operational transconductance amplifier. This kind of circuit is presented in this work and experimental results are provided to piecewise affine Rössler electronic oscillator. The results obtained show a very good matching with the theoretical diagram. Then, if the bifurcation parameter is a resistance, voltage or current, we have implemented a circuit to extract the experimental bifurcation diagram of all nonlinear electronic oscillators.
Voltage gain analysis of the interleaved boost with voltage multiplier converter used as electronic interface for fuel cells systems.
(2016) Fuzato, Guilherme Henrique Favaro; Aguiar, Cassius Rossi de; Ottoboni, Klebber de Araujo; Bastos, Renan Fernandes; Machado, Ricardo Quadros
The connection of low power renewable energy sources, such as fuel cells, to the distribution generation system requires power electronics structures with high voltage gain, high capability to power processing and consequently, high levels of current flowing through the dc/dc converter. In this context, this study analyses how the parasitic resistances of the passive components and the load power demand affect the dc/dc converter voltage gain. Taking into account the mathematical model, the boundaries of operation of the Interleaved Boost with Voltage Multiplier converter is determined through a set of equations and by means of a graphical analysis. The theoretical analysis, simulations and experimental results are used to validate the proposed approach presented in this study.
Demand side management using time of use and elasticity price.
(2016) Manso, Juan Carlos Galvis; Costa, Augostino
Demand Side Management (DSM) has been traditionally seen as a mean of reducing peak electricity demand so that utilities can delay building further capacity. In fact, by reducing the overall load on an electricity network, DSM has various beneficial effects, including mitigating electrical system emergencies, reducing the number of blackouts and increasing system reliability. In this paper we propose a methodology to evaluate DSM in electric distribution systems, based on elasticity and time of use pricing concepts. This evaluation is performed through an optimal power flow model considering linear constraints. The results of the proposed method depend, to a great extent, on two parameters: the maximum share of load which consumers are able to shift and the elasticities used to express the consumer's level of participation in the dynamic pricing mechanism. Simulation results confirm the benefits of Time of Use Demand Side Management reducing the peak-toaverage ratio of the total power demand, as well as each user’s individual daily electricity charges.
Robust stability analysis of grid-connected converters based on parameter-dependent Lyapunov functions.
(2017) Braga, Marcio Feliciano; Morais, Cecilia de Freitas; Maccari Júnior, Luiz Antonio; Tognetti, Eduardo Stockler; Montagner, Vinicius Foletto; Oliveira, Ricardo Coração de Leão Fontoura de; Peres, Pedro Luis Dias
This paper deals with the problem of robust stability analysis of grid-connected converters with LCL filters controlled through a digital signal processor and subject to uncertain grid inductance. To model the uncertain continuous-time plant and the digital control gain, a discretization procedure, described in terms of a Taylor series expansion, is employed to determine an accurate discrete-timemodel. Then, a linear matrix inequality-based condition is proposed to assess the robust stability of the polynomial discrete-time augmented system that includes the filter state variables, the states of resonant controllers and the delay from the digital control implementation. By means of a parameterdependent Lyapunov function, the proposed strategy has as main advantage to provide theoretical certification of stability of the uncertain continuous-time closed-loop system, circumventing the main disadvantages of previous approaches that employ approximate discretized models, neglecting the errors. Numerical simulations illustrate the benefits of the discretization technique and experimental results validate the proposed approach.
Modelo matemático para resolver o problema de alocação de turnos de funcionários : um caso real.
(2017) Barrel, Mayara Alves; Moreira, Rafael Correia; Martins, Alexandre Xavier
O desafio de se escalar pessoas em turnos flexíveis em uma empresa consiste na elaboração de um cronograma para alocação de recursos necessários para executar uma atividade em um determinado período de tempo. Este trabalho tem o objetivo de propor uma otimização na programação de horários de turnos das faxineiras de um supermercado, através de um modelo matemático baseado no método de Programação Linear Inteira Mista, atendendo às restrições do Departamento de Recursos Humanos e às leis trabalhistas (CLT). O modelo foi desenvolvido no Lingo em interface com o MS Excel 2013. Os dados de entrada foram iterados no Lingo até que uma solução ótima fosse encontrada. A solução obtida pelo modelo apresentou um resultado satisfatório para o supermercado, pois minimizou a variação de horas trabalhadas durante a semana e distribuiu as funcionárias de maneira uniforme nas escalas de horário.
Finite control set model predictive control for dynamic reactive power compensation with hybrid active power filters.
(2017) Ferreira, Silvia Costa; Gonzatti, Robson Bauwelz; Pereira, Rondineli Rodrigues; Silva, Carlos Henrique da; Silva, Luiz Eduardo Borges da; Torres, Germano Lambert
This work applies finite control set model predictive control (FCS-MPC) for dynamic reactive power compensation using a hybrid active power filter (HAPF). The FCS-MPC uses a model based on LCL-Filter equations to predict the system behavior and optimize the control action. In fact, the application of FCS-MPC in gridconnected converters with LCL-Filter is quite recent. This algorithm is a very promising control technique for power electronics converters and its use for reactive power control of hybrid filter has not been reported in the literature yet. This work uses the FCS-MPC in a multivariable structure along with an adaptive notch filter (ANF) to damp resonance. The main purpose is to improve the dynamic response of the HAPF. Simulation as well as practical results prove the feasibility of FCS-MPC application in HAPF reactive power control. The dynamic response of the equipment was significantly improved and represents the main contribution of this work. As a result, the FCS-MPC allows tracking fluctuations and abrupt changes in load reactive power.
Reduced order dynamic output feedback control of uncertain discrete-time markov jump linear systems.
(2017) Morais, Cecilia de Freitas; Braga, Marcio Feliciano; Oliveira, Ricardo Coração de Leão Fontoura de; Peres, Pedro Luis Dias
This paper deals with the problem of designing reduced order robust dynamic output feedback controllers for discretetime Markov jump linear systems (MJLS) with polytopic state space matrices and uncertain transition probabilities. Starting from a full order, mode-dependent and polynomially parameter-dependent dynamic output feedback controller, sufficient linear matrix inequality based conditions are provided for the existence of a robust reduced order dynamic output feedback stabilizing controller assuring an upper bound to the H∞ or the H2 norm of the closedloop system. The main advantage of the proposed method when compared to the existing approaches is the fact that the the decision variables of the problem. In other words, the matrices that define the controller realization do not depend explicitly on the state space matrices associated to the modes of the MJLS. As a consequence, the method is specially suitable to handle order reduction or cluster availability constraints in the context ofH∞ orH2 dynamic output feedback control of discrete-time MJLS. Additionally, as illustrated by means of numerical examples, the proposed approach can provide less conservative results than other conditions in the literature.
LMI-based stability analysis for piecewise multi-affine systems.
(2017) Nguyen, Anh Tu; Sugeno, Michio; Campos, Victor; Dambrine, Michel
This paper provides a computational method to study the asymptotic stability of piecewise multi-affine systems. Such systems stem from a class of fuzzy systems with singleton consequents and can be used to approximate any smooth nonlinear system with arbitrary accuracy. Based on the choice of piecewise Lyapunov functions, stability conditions are expressed as a feasibility test of a convex optimization with linear matrix inequality constraints. The basic idea behind these conditions is to exploit the parametric expressions of piecewise multi-affine systems by means of Finsler’s lemma. Numerical examples are given to point out the effectiveness of the proposed method.
Metodologia ativa na engenharia : verificação da abp em uma disciplina de engenharia de produção e um modelo passo a passo.
(2017) Ponciano, Thales Martins; Gomes, Frederico César de Vasconcelos; Morais, Isabela Carvalho de
Este artigo verifica a aplicação da metodologia Aprendizagem Baseada em Problema (ABP) na disciplina de Sistemas de Desenvolvimento de Produto do curso de Engenharia de Produção de uma universidade pública brasileira. Por meio da caracterização da metodologia foi possível observar a aplicabilidade dessa ferramenta em um curso de Engenharia que envolve diversas áreas do conhecimento e concilia atividades teóricas e práticas. De modo geral, as metodologias ativas, como a ABP, podem estimular os alunos a desenvolverem habilidades, como organização, liderança e pensamento crítico, que ultrapassam o conteúdo programático das disciplinas. Sendo assim, foi proposto um modelo passo a passo para a aplicação da ABP.
Using smart impedance to transform high impedance microgrid in a Quasi-infinite Busbar.
(2017) Gonzatti, Robson Bauwelz; Ferreira, Silvia Cristina; Silva, Carlos Henrique da; Pereira, Rondineli Rodrigues; Silva, Luiz Eduardo Borges da; Torres, Germano Lambert
Isolated microgrids, due to the high values of the output converter impedances, suffer power quality problems, such as harmonic distortion and resonances. These impedances are normally the LCL output filter needed to suppress the switching ripple of the converters. As complex impedances, they are dependent of the frequency, therefore very sensitive to harmonic content of load current. This leads to a significant microgrid voltage distortion which results in undesirable power quality levels. Hybrid active power filters are a reasonable choice for harmonic compensation allowing good filtering performance at reduced cost. This paper describes the use of Smart Impedance, which is a new application of a hybrid active power filter, to change the microgrid bus impedance forcing it to behave as a quasi-infinite bus, without increasing active power capacity of the microgrid. The implementation can improve microgrid power quality by mitigating harmonic currents and harmonic voltage resonance. It allows connecting more nonlinear load in the bus keeping the microgrid voltage quality. Experimental results are presented to demonstrate the effectiveness of the proposed approach.
Modelling and control of an interface power converter for the operation of small diesel gen-sets in grid-connected and stand-alone modes.
(2017) Fogli, Gabriel Azevedo; Almeida, Pedro Machado de; Barbosa, Pedro Gomes
This paper presents the modelling and control design steps of a two-stage static conversion structure used as interface to integrate a diesel generator setinto a secondary distribution network. In order to guarantee that the inverter works within the PWM linear range, a boost converter is used to increase the DC voltage level. The proposed structure allows two operation modes, connected to the AC mains or isolated. In the isolated mode the interface converter may be controlled as grid-forming or grid-conditioning (active power filter). The inverter current controllers are designed in the synchronous reference frame together with multiple integrators in order to effectively track non-sinusoidal currents. The stability analysis is performed through the Nyquist plot. Experimental results obtained with a 5.5 kW diesel generator set are presented to validate the proposed system operation and control strategies.
Digital redesign of analogue dynamic output-feedback controllers for polytopic systems.
(2017) Morais, Cecilia de Freitas; Braga, Marcio Feliciano; Tognetti, Eduardo Stockler; Oliveira, Ricardo Coração de Leão Fontoura de; Peres, Pedro Luis Dias
This paper is devoted to the problem known as digital redesign, i.e. given a previously designed stabilising continuous-time controller for a continuous-time plant, synthesise a digital controller that provides the hybrid closed-loop system with output trajectories as similar as possible to the continuous-time ones. To accomplish this goal, two distinct optimisation criteria are investigated: (i) the Euclidean norm of the difference between the dynamic matrix of the discretised closed-loop continuous-time system and the dynamic matrix that represents the discretised open-loop system fed back by the designed digital controller; (ii) the H∞ norm of the transfer function from the noise input to the error between the outputs of the two systems. As main novelties with respect to the existing results on digital redesign, the proposed conditions can deal with polytopic systems, and can synthesise reduced-order dynamic output-feedback digital controllers as well.
Voltage and power balance strategy without communication for a modular solid state transformer based on adaptive droop control.
(2018) Rodrigues, Welbert Alves; Oliveira, Thiago Ribeiro de; Morais, Lenin Martins Ferreira; Rosa, Arthur Hermano Rezende
Solid State Transformers (SST) are attracting considerable attention due to their great application potential in future smart grids. It is an essential technology capable of promoting the modernization of the electric power distribution system and it is considered a key element for interfacing future microgrid systems to medium voltage utility grids, allowing plug-and-play integration with multiple renewable energy sources, storage devices and DC power systems. Its main advantages in relation to conventional transformers are substantial reduction of volume and weight, fault isolation capability, voltage regulation, harmonic filtering, reactive power compensation and power factor correction. A three-stage modular cascaded topology has been considered as an adequate candidate for the SST implementation, consisting of multiple power modules with input series and output parallel connection. The modular structure presents many advantages, e.g., redundancy, flexibility, lower current harmonic content and voltage stress on the power switches, however component tolerances and mismatches between modules can lead to DC link voltage imbalance and unequal power sharing that can damage the solid state transformer. This paper proposes a decentralized strategy based on adaptive droop control capable of promoting voltage and power balance among modules of a modular cascaded SST, without relying on a communication network. The behavior of the proposed strategy is assessed through a MATLAB/Simulink simulation model of an 100 kVA SST and shows that power and voltage balance are attained through inner power distribution of the SST modules, being transparent to elements connected to the transformer input and output ports. Besides that, real-time simulation results are presented to validate the proposed control strategies. The performance of embedded algorithms is evaluated by the implementation of the SST in a real-time simulation hardware, using a Digital Signal Processor (DSP) and high level programming.

Browse

Browsing DEELT - Departamento de Engenharia Elétrica by Issue Date

Results Per Page

Sort Options