DEELT - Artigos publicados em periódicos
URI permanente para esta coleçãohttp://www.hml.repositorio.ufop.br/handle/123456789/5267
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40 resultados
Resultados da Pesquisa
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 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.Item A study of the impacts caused by unbalanced voltage (2%) in isolated synchronous generators.(2019) Vanço, Wagner Eduardo; Silva, Fernando Bento; Monteiro, José Roberto Boffino de AlmeidaThis paper presents an analysis of the oscillations caused by unbalanced loads in salient pole synchronous generators that operate in isolation under steady state. The oscillatory disturbances, arising from the second-order harmonics, may have or have the potential to cause electromechanical damage to the salient pole synchronous generator. In this paper, the goal is to identify and quantify the magnitude of the electromagnetic torque, which assumes an oscillatory form due to the current component from the negative sequence, caused by unbalanced currents. The self-same analysis was included for second-harmonic voltage oscillations in the qd0 domain, the currents induced on the damper windings together with the oscillation of the load angle and on the field current. These oscillations situated on the synchronous generator are analyzed for a degree of voltage unbalance close to 2% which is an acceptable value according to international regulations for power supply from distribution networks, and this same degree of tolerated voltage unbalance will be used herein for isolated synchronous generators.Item A proposal of expansion and implementation in isolated generation systems using self-excited induction generator with synchronous generator.(2019) Vanço, Wagner Eduardo; Silva, Fernando Bento; Oliveira, Carlos Matheus Rodrigues de; Monteiro, José Roberto Boffino de Almeida; Oliveira, José Mário Menescal deThis work presents a theoretical and experimental study of the self-excited three-phase induction generator in steady state, operating with a synchronous generator for use in isolated generation. Through the remoteness of many locations or because of the absence of an energy distribution network, difficulties exist in the supply of electric energy. The proposal contemplated herein can be applied in order to provide a well-adjusted voltage and reduce project costs in the expansion and implementation of isolated systems. That is, when taking into consideration acquisition costs of the asynchronous squirrel cage rotor machine in relation to the synchronous generator. The main contribution of this study is the making of the synchronous generator into a voltage regulator of the isolated system, in such a manner that the synchronous generator supplies the minimum of active power necessary, where a lower power generator is able to play the role of being the sole voltage regulator.Item A low-cost wireless system of inertial sensors to postural analysis during human movement.(2019) Santos, Talysson Manoel de Oliveira; Barroso, Márcio Falcão Santos; Ricco, Rodrigo Augusto; Nepomuceno, Erivelton Geraldo; Alvarenga, Érika Lorena Fonseca Costa de; Penoni, Álvaro C. O.; Santos, Ana F.The dynamics of the human body has generated considerable recent research interest among scientist devoted to reducing the number of injuries and for performance improvement. In these studies, the investigation is usually addressed by means of commercial devices based on video recordings. However, these systems based on video recordings are usually expensive and require suitable laboratories for their use, which makes it unfeasible to collect data for activities outside controlled environments. In this work, we have shown that it is possible to present similar results with a much lower sampling rate, focusing on the evaluation of minimum and maximum values of the gait. As a result, it has been possible to develop a wearable, compact, portable, low-cost, wireless and embedded system to simultaneously analyze the three-dimensional angular position in eight points. This technology can be used in many sorts of environments. It is also possible to access information in real time with reliable and accurate measurements by means of simple modelling for the use of fusion techniques implemented in the microcontroller. Tests were conducted to evaluate the metrological characteristics of the system using the Complementary Filter (CF) and the Kalman Filter (KF). An algorithm of evolutionary strategies tuned both filters, providing errors of less than 5% for static situations in the measurement of the angular position over the entire system utilization range. Our results have been compared with the commercial system Qualisys Motion-Capture. The statistical method elaborated by Bland and Altman has been used. We have found our method yields a motion analyses in good agreement with results using post-processed video.Item Model, design and implementation of LCC converter for power generation and distributed generation.(2019) Bastos, Renan Fernandes; Dias, André Lage Almeida; Machado, Ricardo QuadrosThis paper proposes to model, design and implement a LCC (Line Commuted Converter) for power generation purpose, using alternative sources such as photovoltaic panel (PV), fuel cell and permanent magnet synchronous machine as the main power source. The converter is built with a full bridge twelve-pulse thyristor topology and connected to the alternative source through a line reactor. In order to extract maximum power from the sources, a classical maximum power point tracking algorithm (MPPT P&O) is applied. To validate the theoretical and simulated analysis, a 600 W experimental setup was built and controlled in closed loop. For the experimental results, the alternative source was represented by a variable DC power source in series with a resistor, making it possible to create controlled power steps and power events. During the operation, the grid current is analyzed in terms of power quality and an islanding event was created to analyze the converter’s behavior under critical conditions. All the experimental results show perfect conformity with the theory and simulation, proving the effectiveness of this converter topology for this purpose.Item Model, design and implementation of a lowcost HIL for power converter and microgrid emulation using DSP.(2019) Bastos, Renan Fernandes; Fuzato, Guilherme Henrique Favaro; Aguiar, Cassius Rossi de; Neves, Rodolpho Vilela Alves; Machado, Ricardo QuadrosIn this study, the authors propose a method to implement a low-cost hardware-in-the-loop (HIL) system for power converters and microgrids design, test and analysis. This approach uses a digital signal processor (DSP) Texas Instruments as the HIL core. All the differential equations of the power converters are solved in real-time by the DSP and displayed in the digital-to-analogue outputs. Three different converters are modelled in this study: boost converter, single-phase inverter connected to the grid and three-phase inverter connected to the grid. Experimental results are obtained and compared to the HIL response. These results were made triggering the real converter and the HIL with the same open-loop pulse width modulation signal, showing high fidelity between the digital models over the real systems. In a second moment, a microgrid is modelled in the proposed HIL and tested with a closed-loop controller. The experiments show that the proposed hardware supports time steps as low as 1 μs or 1 MHz update rate, depending on the model. The proposed technique has the potential to reduce testing time and cost, once commercial HIL devices such as Typhoon, dSPACE and RTDS have a significant cost, not affordable or available to all the research communityItem 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 Development and characterization of medical phantoms for ultrasound imaging based on customizable and mouldable polyvinyl alcohol cryogel–based materials and 3-D printing : application to high-frequency cranial ultrasonography in infants.(2019) Elvira, Luis; Durán, Carmen; Higuti, Ricardo Tokio; Tiago, Marcelo Moreira; Ibáñez, Alberto; Parrilla, Montserrat; Valverde, Eva; Jiménez, Javier; Bassat, QuiqueThis work presents an affordable and easily customizable methodology for phantom manufacturing, which can be used to mimic different anatomic organs and structures. This methodology is based on the use of polyvinyl alcohol–based cryogels as a physical substitute for biologic soft tissues and of 3-D printed polymers for hard tissues, moulding and supporting elements. Thin and durable soft-tissue mimicking layers and multilayer arrangements can be obtained using these materials. Special attention was paid to the acoustic properties (sound speed, attenuation coefficient and mechanical impedance) of the materials developed to simulate soft tissues. These properties were characterized as a function of the additives concentration (propylene-glycol and alumina particles). The polyvinyl alcohol formulation proposed in this work is stable over several freeze-thaw cycles, allowing the manufacturing of multilayer materials with controlled properties. The manufacturing methodology presented was applied to the development of a phantom for high-frequency cranial ultrasonography in infants. This phantom was able to reproduce the main characteristics of the ultrasound images obtained in neonates through the anterior fontanel, down to 8-mm depth.Item A simple dead-time compensation strategy for grid-connected voltagesourced converters semiconductor switches.(2019) Fogli, Gabriel Azevedo; Valle, Rodolfo Lacerda; Almeida, Pedro Machado de; Barbosa, Pedro GomesThis paper presents a simple strategy to compensate the distorted currents synthesized by a grid-connected voltage source converter due to dead-time, turn-on and turn-off time delays of the semiconductor switches. The algorithm consider only the polarity of the fundamental component of the currents flowing through the converter terminals and the values of the time delays and voltage drops supplied by the manufacturers to the semiconductors devices. The presented compensation belongs to the group classified as average value compensation technique methodology since it does not change the pulse pattern of the converter's semiconductor switches. A simplified mathematical description of the effects caused by these unwanted time delays is presented and used to derive a correction factor to be added, in real time, to the converter output controller in order to compensate for its terminal voltages. The asymptotic stability and robustness of the proposed methodology is investigated redrawing the converter current controllers, designed in dq-reference frame, as proportional-resonant ones, in the abc coordinates, and adding the effect of the compensating signal in the feedback loop using the concept of describing function. In addition, the minimum value of the DC bus voltage necessary is also evaluated to ensure the operation of the converter in the linear modulation region when the compensation algorithm is active. Experimental results are presented to validate the theoretical analysis and to demonstrate the effectiveness of the proposed strategy for three different operation conditions of a grid-connected converter: (i) active power injection; (ii) active power consumption and (iii) reactive power support.