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Brazilian Power Electronics Conference, COBEP

作者： Cleiton M. Freitas Edson H. Watanabe Luís F. C. Monteiro Rio de Janeiro State University Rio de Janeiro Brazil Electrical Engineering Program - COPPE Federal University of Rio de Janeiro Rio de Janeiro Brazil Post-Graduate Prog. of Electronic Eng. Rio de Janeiro State University Rio de Janeiro Brazil

ISBN: (纸本)9781665421300

This work presents an analysis of the grid-forming Modular Multilevel Converter (MMC), in the frequency domain, when it is controlled through single or dual-loop implementation. The dual-loop approach presents an inner current-loop control gathered with the external voltage-loop control, whereas the single-loop only presents a voltage-loop control for the grid-forming capability. In both cases, the control algorithms were implanted in a natural reference frame, including resonant controllers. The paper follows an impedance-modeling approach for introducing the analytical representation of the MMC in the frequency domain. These representations are, in fact, the linearized Teéenin-equivalent models of the single- and dual-loop grid-forming MMC. The results showed that the inner current-loop control is a feasible approach for damping specific resonant peaks of the Thevenin-equivalent impedance. In other words, the current-control loop adds a resistive parcel in MMC impedance in the frequency range in which the resonant peaks appear. As a consequence, the LC resonance between this impedance and the capacitor bank in the main bus is damped. The article also contains some switching-level EMTDC/PSCAD simulations to validate the work.

关键词： Damping Analytical models Shape Frequency-domain analysis Capacitors Resonant frequency Switches

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Plenary Speech Ⅰ: Data-Selection in Machine Learning Algorithms

Plenary Speech Ⅰ: Data-Selection in Machine Learning Algori...

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作者： Paulo S.R.Diniz COPPE/Poli Federal University of Rio de Janeiro Program of Electrical Engineering and Department of Electrical and Computer Engineering

The current trend of acquiring data pervasively calls for some data-selection strategy, particularly in the case a subset of the data does not bring enough innovation. As a byproduct, in addition to reducing power consumption and some computation, the discarding of data results in more accurate parameter estimation. In many practical situations, it is possible to verify if the acquired set of data qualifies to improve the related statistical inference or if it consists of an outlier or a noninnovative entry. In this presentation, we discuss some adaptive filtering and machine learning algorithms enabling data selection which also address the censorship of outliers measured through unexpected high estimation errors. The resulting algorithms allow the prescription of how often the acquired data is expected to be incorporated in the learning process based on some a priori assumptions regarding the environment data or some simple estimation based on the available data. Test results show the effectiveness of the proposed algorithms for selecting the innovative data without sacrificing the estimation accuracy, while reducing the computational cost. In neural networks applications the strategy leads to reduced training errors and improved test results.

关键词： Data-Selection in Machine Learning Algorithms Plenary Speech

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FEM modeling and simulation of broadband ultrasonic transducers with randomized inhomogeneous backing material

arXiv

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arXiv 2022年

作者： Moreno, Eduardo Pereira, Wagner C.A. von Kruger, Marco Antonio Leija, Lorenzo Ramos, Antonio Ultrasonic Group ICIMAF Calle 15 No 551 Vedado La Habana Cuba Biomedical Engineering Program COPPE UFRJ 2030 Horacio Macedo Ave Rio de Janeiro21941-914 Brazil Department of Electrical Engineering Bioelectronics Section Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional Cinvestav México City Mexico R&D Group "Sistemas y Tecnologías Ultrasónicas" Instituto de Tecnologías Físicas y de la Información CSIC Madrid Spain

A FEM application for the accurate design of composite backing of ultrasonic transducers is presented. The idea is to obtain the dependence between the volume ratio of the tungsten powder in an epoxy matrix used as a backing and the final pulsed RF signal emitted by the backed transducer. An inhomogeneous material model for the backing was adopted instead of the classic complex geometrical FEM. The model was developed in Comsol 5.5 using two of its physics interfaces. The first based on classic FEM or continuous Galerkin for ultrasonic propagation in the backing and the second based on a discontinuous Galerkin option for fluid pulsed propagation. In this way it is possible to avoid the use of an impedance-based model. The calculations for the resulting bandwidth are good enough as predicted for Desilets for the 1D case by using the KLM circuital model. We worked in a 2D space, where the transducer face vibration is far away from the assumed piston-like considered by the unidimensional KLM model. © 2022, CC BY.

关键词： Finite element method

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A hierarchical approach for discrete-event model identification incorporating expert knowledge

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IFAC-PapersOnLine 2020年第4期53卷 275-281页

作者： Ryan P.C. de Souza Marcos V. Moreira Jean-Jacques Lesage COPPE-Electrical Engineering Program Federal University of Rio de Janeiro Cidade Universitária Ilha do Fundão Rio de Janeiro 21.945-970 RJ Brazil LURPA ENS Paris-Saclay Université Paris-Saclay 94235 Cachan France

Recently, a new technique for identification of Discrete-Event Systems (DES) with the aim of fault detection has been proposed in the literature, where a model is obtained from the observation of the fault-free system behavior. In some cases, the system may execute different tasks in a sequential order to perform the complete operation of the system. In these cases, the number of observed paths representing the complete system operation may grow exponentially with the number of tasks. In addition, by using black-box identification methods, it is possible that the sequential order that the tasks must be performed is not represented in the model, reducing the fault detection capability or delaying the fault detection. In this paper, a two-level hierarchical approach for DES identification is proposed. In the higher level of the model hierarchy, the system is described by using some basic knowledge of its functioning provided by an expert, and in the lower level of the hierarchy, the behavior is described by black-box identified models for the system tasks. The modeling framework proposed in this paper reduces the number of observed paths needed for system identification and increases the fault detection capability. A practical example is used to illustrate the results of the paper.

关键词： Discrete-event systems System identification Fault detection Finite automata Black-box identification

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A timed model for discrete event system identification and fault detection ⁎

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IFAC-PapersOnLine 2020年第2期53卷 808-813页

We present in this paper a timed discrete event model for system identification with the aim of fault detection, called Timed Automaton with Outputs and Conditional Transitions (TAOCT). The TAOCT is an extension of a recent untimed model proposed in the literature, called Deterministic Automaton with Outputs and Conditional Transitions (DAOCT). Differently from the DAOCT, where only the logical behavior of the discrete event system is considered, the TAOCT takes into account information about the time that the events are observed, and, for this reason, it can be used for the detection of faults that cannot be detected by using untimed models, such as faults that lead the fault detector to deadlocks. The TAOCT represents the fault-free system behavior, and a fault is detected when the observed behavior is different from the behavior predicted by the model, considering both logical and timing information. A practical example is used to illustrate the results of the paper.

关键词： Discrete-event systems System identification Fault detection Finite-state automata

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K-Loss Robust Diagnosability of Discrete-Event Systems

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IFAC-PapersOnLine 2020年第4期53卷 250-255页

作者： Vinicius S.L. Oliveira Felipe G. Cabral Marcos V. Moreira COPPE-Electrical Engineering Program Federal University of Rio de Janeiro Cidade Universitária Ilha do Fundão Rio de Janeiro 21.945-970 RJ Brazil Department of Automation and Systems Federal University of Santa Catarina Campus Trindade Florianópolis 88.040-900 SC Brazil

Recently, the problem of robust diagnosis against intermittent loss of observations (RDILO) has been proposed in the literature, where a model for the plant subject to intermittent loss of event observations is presented, and fault diagnosability verification methods are proposed based on the new plant model. In this method it is assumed that some sensors of the system are reliable and are always capable of communicating their readings to the diagnoser, while the other sensors, or communication channels between sensors and diagnoser, are subject to intermittent failures. The case of unreliable communication of all observable events cannot be addressed using the RDILO since the model of the plant subject to intermittent loss of event observations also represents their permanent losses. In this paper, we formulate a different problem of robust diagnosis that considers only intermittent loss of observations, which allows considering the case that all communication channels between the plant and diagnoser are not reliable. The new formulation leads to a different notion of robust diagnosability, called K-loss robust diagnosability.

关键词： Fault diagnosis Robust diagnosability Discrete Event Systems Automata Verifiers

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An Electronic Drive for a Switched Reluctance Motor Using a DSC

An Electronic Drive for a Switched Reluctance Motor Using a ...

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Brazilian Power Electronics Conference, COBEP

作者： Brayan Sobral da Fonseca José Andrés Santisteban Graduate Program in Electrical Engineering COPPE - Universidade Federal do Rio de Janeiro Rio de Janeiro Brazil Graduate Program in Electrical and Telecommunications Engineering - PPGEET Universidade Federal Fluminense Niterói Brazil

ISBN: (数字)9781728141800

ISBN: (纸本)9781728141817

With the technological advances using electronic circuits based on microprocessors, the drive and control of electrical machines in electromechanical systems have become increasingly efficient. In this paper, for an axial magnetic flux reluctance motor, for which it is not possible to supply its energy directly from the utility, the developing of an electronic drive and its control is described. Unlike other alternatives, a development module, named DSC (Digital Signal Controller), which is based on a modern microcontroller, allows the reduction of discrete components, like operational amplifiers, and wires. The workbench comprises a three-phase power converter that is equipped with high-speed semiconductor switches, current sensors, voltage sensors and an USB interface to allow communication with a computer. The effectiveness of this approach is verified through open loop and closed loop experimental tests, where the waveforms of the trigger pulses generated by the DSC, the motor currents and their speed were monitored.

关键词： Rotors Reluctance motors Sensors Windings Stator windings Stator cores

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Distributed Synchronous Diagnosability of Discrete-Event Systems

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IFAC-PapersOnLine 2018年第7期51卷 88-93页

作者： Veras, Maria Z.M. Cabral, Felipe G. Moreira, Marcos V. COPPE-Electrical Engineering Program Federal University of Rio de Janeiro Cidade Universitária Ilha do Fundão Rio de Janeiro 21.945-970 RJ Brazil

Recently, the centralized and decentralized synchronous diagnosis of discrete-event systems have been proposed in the literature. In this paper, we propose a different synchronous diagnosis strategy called the distributed synchronous diagnosis, composed of local diagnosers that are capable of communicating the occurrence of events and their current state estimate to other local diagnosers. The diagnosers are implemented considering a specific communication protocol that refines the state estimate of the fault-free behavior of the system modules, reducing, therefore, the augmented fault-free language considered for diagnosis. © 2018

关键词： Fault detection Discrete event simulation Failure analysis State estimation Automata Diagnosability of discrete event systems Diagnosers Diagnosis strategies Distributed diagnosis Free languages State estimates System modules

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Unbalanced Voltage Mitigation using D2VC with Proportional Resonant Controller in αβ-Frame

Unbalanced Voltage Mitigation using D2VC with Proportional R...

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Brazilian Power Electronics Conference, COBEP

作者： Elienai O. Macedo Robson F. S. Dias Silvangela L. S. L. Barcelos Edson H. Watanabe COPPE Federal University of Rio de Janeiro - Electrical Engineering Program RJ Brazil Electrical Engineering Dept. Federal University of Maranhão São Luís MA Brazil

ISBN: (数字)9781728141800

ISBN: (纸本)9781728141817

This paper proposes a control algorithm for unbalanced voltage compensation using the Dynamic Direct Voltage Controller (D 2 VC). An advantage of this device is the possibility of a online direct voltage control in distribution systems, rather than on-load tap changers or other indirect control schemes. The proposed algorithm is based on the instantaneous positive and negative sequence components in αβ-frame, dismissing the use of a Unified Three-Phase Processor (UTSP), consequently avoiding its complexity and excessive computational efforts, and the compensation reference signals are obtained using proportional plus resonant (PR) controllers. There is no need of using any synchronism algorithm, e.g. PLL, which means that the D 2 VC's performance is independent of the dynamics of this type of synchronization circuit. Simulation results carried out in time domain using PSCAD/EMTDC are presented to show the effectiveness of the proposed solution.

关键词： Voltage control Heuristic algorithms Phase locked loops Time-domain analysis Synchronization Resonant frequency Power system dynamics

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Decision support system for a portfolio of a hydroelectric company in the Brazilian market

Decision support system for a portfolio of a hydroelectric c...

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International Conference on European Electricity Market, EEM

作者： Eduardo Raguenet Oumar Diene Senior Member IEEE COPPE-Electrical Engineering Program Federal University of Rio de Janeiro Cidade Universitria Rio de Janeiro RJ

In this paper, we propose a decision support system to solve the portfolio optimization problem of a hydroelectric company, considering simultaneously the energy allocation in the spot market, the bilateral contracts, and the seasonalization of physical guarantee. The objective is to maximize the expected revenue under a risk constraint, made by hedging the Condition Value at Risk (CVaR). Finally, a sensibility study of the Generation Scaling Factor is made, since it also depends on the decisions (seasonalization) of other agents. The problem is formulated as a linear optimization program, and the final algorithm is implemented using the software MatLab.

关键词： Companies Optimization Portfolios Transmission line measurements Forward contracts Reactive power

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