DEELT - Departamento de Engenharia Elétrica
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/5266
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4 resultados
Resultados da Pesquisa
Item 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 DiasThis 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.Item 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 DiasThis 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.Item 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 DiasThis 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.Item 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 DiasThis 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.