Dissertações em Engenharia Elétrica (Mestrado) - PPGEE/ITEC

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2316

O Mestrado Acadêmico inicou-se em 1986 e pertence ao Programa de Pós-Graduação em Engenharia Elétrica (PPGEE) do Instituto de Tecnologia (ITEC) da Universidade Federal do Pará (UFPA).

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Agora exibindo 1 - 17 de 17

Acesso aberto (Open Access)
Aplicação de uma metodologia de lógica fuzzy à gestão de estoques: um estudo de caso em uma instituição pública
(Universidade Federal do Pará, 2011-03-01) SANTOS, Gilbert Queiroz dos; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
This paper presents a proposal for implementing a fuzzy logic approach to inventory management on a public institution of the federal administration, located in Manaus-AM. Initially, a review of the literature on logistics and supply management, was made. After that were discussed issues relating to inventory management. Then, we discussed issues related to the fuzzy logic. The proposed methodology will allow a better control over inventory, since it will replace traditional quantitative methods of inventory management. The data were collected directly from the warehouse of the institution under study, and refer to the movement of stock of a particular item during the year 2009. The use of fuzzy logic has attracted increasingly more attention from researchers in different areas of knowledge, being, however, that the great challenge posed to them is the modeling of the data collected, due to its computational support needed application. The interaction with the observed values, operated by the rules of fuzzy logic allows a better control of stock in a warehouse, such as service, parts and tender, since it deals with uncertainty and subjectivity. The methodology appears to be able to indicate a better performance of the quoted shares, being able to operate on an automated tracking and inventory management.
Acesso aberto (Open Access)
Desenvolvimento de um sistema multiconversor para a realização de estudos experimentais em microrredes de corrente contínua
(Universidade Federal do Pará, 2015-08-10) COSTA JUNIOR, Fernando José da; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
This paper presents the design and development of a Multiconverter System based on a Microgrid comprised of a DC bus and static power converters DC-DC and DC-AC. This system is located at the Power Systems Control Laboratory (LACSPOT) at Federal University of Pará (UFPA). The Multiconverter System consists in three power converters, two in step-down Buck topology and the third a three-phase inverter. The first converter feeds a direct current voltage controlled bus that provides voltage to a second Buck converter. On the second Buck converter is also applied a voltage control strategy in order to maintain a constant power supply. The three-phase inverter is also powered by a DC bus can be connected to the local power grid, allowing studies with grid-tied systems and distributed generation. To test the buck converter studied in this work, were developed digital controllers, based on indirect digital control design method. Both controllers were developed using the output voltages as feedback signals in order to maintain the voltage and power as constant as possible, on the primary and secondary converters, respectively. Besides inner difficult in systems with parametric uncertainties and nonlinearities shown in power converters, the power converter with voltage control also feeds the second power converter. That introduces non-linear characteristics that may cause bar voltage instability. For that reason, it is necessary to develop a control strategy with the goal of keeping the voltage near to the voltage bus reference. To sum up, several tests were performed both in computer simulation, as in the real system in order to check the effectiveness of control techniques studied and applied. The obtained results shown that the Multiconverter System was able to provide a good performance under the designed control strategy.
Acesso aberto (Open Access)
Desenvolvimento e implementação de estratégias de controle digital para regulação de tensão e amortecimento de oscilações eletromecânicas em um gerador síncrono de 10kVA
(Universidade Federal do Pará, 2012-04-29) MORAES, Anderson Roberto Barbosa de; BARREIROS, José Augusto Lima; http://lattes.cnpq.br/1246564618922453; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
This paper presents the development and implementation of control strategies for digital automatic voltage regulation and damping of oscillations in a 10kVA synchronous generator 10kVA located at the Power Systems Control Laboratory (LACSPOT) at Federal University of Pará (UFPA). The design of both controllers is based on the pole placement technique. For the design of the Automatic Voltage Regulator (AVR), it was adopted a first order simplified model for the synchronous machine, whose parameters were obtained experimentally. For the damping controller, also called Power System Stabilizer (PSS), it was used an auto-regressive with exogenous input (ARX) discrete model. This model was estimated by means of parametric identification techniques considering, for this purpose, the motor-generator connected to a larger system. The control laws were embedded in a high-performance microcontroller and, for the measurement of signals used in the controllers, an electronic instrumentation was developed which is based on operational amplifiers for the sensors signal conditioning. The control signal is based on the technique of pulse width modulation (PWM) and controls the average voltage of a DC-DC converter, which is used as an excitation circuit which energizes the field winding of the generator. Moreover, the electric drive of the machines that make up the 10kVA group generator was designed and automated by adding security to operators and components of this generation system. The experimental results demonstrate the good performance achieved by the proposed strategy.
Acesso aberto (Open Access)
Uma estratégia ativa para detecção de ilhamento em geradores fotovoltaicos por meio de injeção de sinais de teste
(Universidade Federal do Pará, 2016-10-27) CARVALHO, Fransérgio Martins; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
In this paper, is made a study of a active technique for detection of islanding that is proper for application in Grid-Connected Photovoltaic System (GCPS). The technique is based on injection of testing signals which affect negative-sequence of voltage after islanding case. Definitions and explanations are presented about power distributing system and about the elements which belong to Distributed Generation (DG). Standards about inverter’s function and about model of photovoltaic cell are presented. Details of islanding concept and its Non-Detection Zone (NDZ) as well as main current techniques for its detection are exhibited. It is shown the sequence-negative technique. Some instrumental applications related to negative-sequence measurement, sinusoidal inverter and PLL are developed. Models are designed to accomplish the injection and measurement of negative-sequence through VSI: controller and filter. Simulations were made to detect islanding under ordinary conditions of GCPS: irradiance variation and shading of photovoltaic cell; and under ordinary conditions of a power distribution system: charging variation and unbalanced charge. At last, the applied method performance is validated and compared.
Acesso aberto (Open Access)
Estratégia de identificação paramétrica aplicada à modelagem fenomenológica de um sistema do tipo correia transportadora industrial para fins de detecção de faltas
(Universidade Federal do Pará, 2014-07) MEDEIROS, Renan Landau Paiva de; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
Belt conveyor systems are essential for large companies, even though this equipment has a great deal of importance that makes its non-planned stop can generate huge amounts of losses or even the stall of the whole production process. Having this importance in mind it becomes necessary to realize the adequate monitoring of the system and detect with a larger prior notice the occurrence of some fault in the system. In an effort to reduce the unforeseen stop, this dissertation investigates a modeling of a belt conveyor system. At first a phenomenological model of the process is discussed based on the mechanical laws and considering the diverse types of movement opposition force throughout the belt conveyor. The main parameters of a belt conveyor belt where estimated through the non-recursive mean square. In sequence a fault detection algorithm was elaborated using the interval analysis theory, in a way that its possible to detect inadequate operation conditions. With the intent to evaluate the performance of the proposed algorithm a prototype that emulates the tipical operation of a conveyor belt was designed. The results were obtained experimentally, that confirms the great performance of the proposed methodology.
Acesso aberto (Open Access)
Estratégias de controle de ordem fracionária aplicadas ao amortecimento de oscilações eletromecânicas em sistemas elétricos de potência
(Universidade Federal do Pará, 2014-08-11) AYRES JÚNIOR, Florindo Antonio de Carvalho; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
In this work, a new project methodology was proposed to tune power systems stabilizers (PSS) based on fractional order systems theory (FOPSS). The strategy is based in a generalization of Lead-Lag compensators type project to fractional order transfer function domain. A new project variable, which defines the controller fractional order, is tuned to obtain a good compromise between the damping fulfillment of dominant electromechanical mode and the FOPSS amplified robustness. FOPSS performance was experimental evaluated, in a small-scalled system, located at Power Systems Laboratory of Federal University of Para. This test plant present a typical structure of synchronous generator connected to infinite bus and exhibits a decreased damping electromechanical dominant mode, whose around 1,2 Hz natural frequency value. So FOPSS was designed to improve relative damp of mode target, for all admissible operation range. For practical intent , first experimental tests was made to identify a plant nominal model in the form of a pulse transfer function, used in FOPSS project. This obtained model was validated and then used both to FOPSS project and conventional PSS (applied to performance comparison). The damp control rules of FOPSS were calculated, and then converted to difference equations, and subsequently, embedded in digital systems based on DSPIC microcontrollers. A couple of impulse test were made under different operational conditions. Respective dynamical responses data of plant output signals (active power deviation) and control effort were saved to analysis purposes. The experimental results showed that FOPSS presented a greater robustness and a similar performance compared to dynamical performance of conventional PSS, for all investigated operation range.
Acesso aberto (Open Access)
Implementação e testes de campo de um ESP digital
(Universidade Federal do Pará, 2010-05-18) GOMES, Marcus Ciro Martins; BARREIROS, José Augusto Lima; http://lattes.cnpq.br/1246564618922453; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
This work presents the development and implementation as well as the results of field tests of a power system stabilizer (PSS) designed with digital control method for damping electromechanical modes of oscillation observed for signs of electrical power measured in a generating unit of 350 MVA of Tucuruí power plant. It is presented and applied the methodology of identifying linear parametric models such as auto regressive with exogenous inputs (ARX) for estimation of models with the ability to capture the relevant information (natural frequency and damping) of dominant electromechanical modes of the system. In possession of ARX parametric model is done then the synthesis of digital damper control law for the ESP, using the technique of pole displacement of the closed loop transfer function. For the synthesis of digital control law, we used a canonical structure type RST. For the field tests, the control law digital ESP buffer was coded in C language and embedded in a hardware prototype of which is based on model DSPIC 30F3014 microcontroller, which incorporates a large number of peripherals for data acquisition and communication. In order to evaluate the performance of the digital PSS developed, experimental tests were performed in a generating unit of 350 MVA power house number 1 from Tucuruí power plant. The stabilizer acts carried out by adjusting the reference voltage regulator automatic voltage of the respective generating unit in accordance with the oscillations observed by measuring the electrical power generator stator. The results of field tests showed an excellent performance of ESP digital damping of electromechanical mode of natural frequency of approximately 1.7 Hz, observed in the field trial.
Acesso aberto (Open Access)
Investigação de estratégias de controle digital para regulação de velocidade e emulação da dinâmica de turbinas hidráulicas, com implementação e testes experimentais em uma micromáquina de 10 KVA
(Universidade Federal do Pará, 2011-04-28) NASCIMENTO FILHO, Paulo Sergio; COSTA JÚNIOR, Carlos Tavares da; http://lattes.cnpq.br/6328549183075122; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
Due to the study of power systems in real plants as a hydroelectric power plant it’s not common because the risks and costs involving their operation, it is preferred to conduct computational mathematical models of this system solving problems and developing new technologies. However, computer-realized models do not provide the visible, audible and tactile experience that a real physical model can offer. Therefore, in this work, it is presented a description and modeling of a micro-generation system of 10kVA, which is a real physical system, composed of a DC motor, a synchronous generator and transformers, also called micromachine system, which makes part of the infrastructure of the Laboratory of Electrical Engineering at UFPA. For this system, through this work and the Moraes’ work (2011), were developed electronic subsystems and computer drives, automation and control to operate it safely and to support research in control of power systems, as well as the development of academic work. In this same context, it is proposed an emulation technique of the dynamic of a hydraulic turbine controlling by the power applied to DC motor micromachine system, which was developed mainly for the purpose of supporting the study and development of techniques of speed regulation for hydraulic turbines. It also will present a proposal for a digital speed governor for hydraulic turbines based on the canonical structure RST digital control, whose parameters are designed by two techniques studied in this work. And to prove the effectiveness of tools for hardware, software and theory developed in this work, results of experiments performed at the micromachine system will be presented and analyzed.
Acesso aberto (Open Access)
Metodologia baseada em sistema fuzzy intervalar do tipo-2 para detecção e identificação de faltas de incipientes em motores de indução
(Universidade Federal do Pará, 2013-02-27) ROCHA, Erick Melo; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
Since the incorporation of automation in the production processes, aiming at order to improve productivity and quality of products and services, researches on more efficient methodologies for fault diagnosis became more intensive. Such techniques allow the early detection of faults, before then lead to failures. This work investigates techniques for detection and diagnosis of faults and its application to induction motors, limiting their study to two situations, namely: system free of faults and system under incipient partial short-circuit in the coils the stator winding. For faults detection, parametric analysis of fist order ARX (autoregressive with exogenous input) were applied. The parameters of identified ARX modes, which bring information about the dynamics of the dominant system, are recursively obtained by the techniques of recursive least squares (RLS). In order to evaluate the capability for early fault detection, a type-2 interval fuzzy system was developed. This kind of fuzzy system has capability to capture a larger set of uncertainties than conventional (type-1) fuzzy systems. The footprint of uncertainty (FOU), characteristic of type-2 fuzzy system, is a way to accounts for uncertainties coming from noise and numerical errors from the process of parameter estimation. The ARX model parameters are the inputs to the supervisor system. Genetic algorithms (GA’s) were used for optimization of SIF interval type-2, aiming at to reduce the diagnostic error. The results obtained in tests of computer simulation show the effectiveness of the proposed methodology.
Acesso aberto (Open Access)
Modelagem e controle robusto paramétrico aplicados a sistemas driven-right-leg para rejeição de ruídos em amplificadores biopotenciais.
(Universidade Federal do Pará, 2022-03-30) GOMES, Alan Sovano; FONSECA, Maria da Conceição Pereira; http://lattes.cnpq.br/3496755183083633; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
The Driven-Right-Leg (DRL) system is widely applied to mitigate the effects of common mode voltage in biopotential amplifiers. It works as a closed-loop controller, whose objective is to reject disturbances caused by the capacitive coupling of the human body with the power line. In this work, the DRL system is evaluated from a robust parametric control point of view, with the intention of doing a more complete evaluation than the one found in the literature, measuring gain, phase and module extremal margins. The range of interval parametric variations, found in the literature, were used to describe the parametric uncertainties that disturb the studied system. Furthermore, a Lead-Lag controller was designed based on the model under parametric variation obtained, showing how both the analysis and synthesis of DRL controllers can be done with the presented theory. The results obtained were discussed in comparison with the DRL systems found in the specialized literature.
Acesso aberto (Open Access)
Performance evaluation of robust parametric control strategies applied on suppression of oscillations effects due to constant power loads in multi-converter buck-buck systems
(Universidade Federal do Pará, 2018-06-11) MARCILLO, Kevin Eduardo Lucas; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
Multi-converter electronic systems are becoming widely used in many industrial applications; therefore, the stability of the cascaded system is a big concern to real-world power supplies applications. Instability in cascaded systems may occur due to the constant power load (CPL), which is a behavior of the tightly regulated converters. CPLs exhibit incremental negative resistance behavior causing a high risk of instability in interconnected converters; therefore, the mitigation of this problem is an important issue in the multiple-stage switched mode power supply design. Thus, it is important to guarantee stability of the whole system. However, some difficulties remains besides the CPL, e.g., non-linearities due to the inductive element and uncertainties due to imprecision of mathematical models and/or variation of nominal values of the discrete elements that compose the DC/DC buck converter. Aiming to evaluate the performance of the proposed robust methodologies in this work to mitigate the instability problem caused by a CPL, several tests were developed by using an experimental plant and Matlab/Simulink, when the multi-converter buck-buck system is subjected a variation of power reference. The results show the improved performance of the proposed methodologies.
Acesso aberto (Open Access)
Projeto de controlador baseado em inequações matriciais lineares aplicado a um sistema multiconversor sujeito à incertezas paramétricas
(Universidade Federal do Pará, 2024-08-23) SILVA JUNIOR, Carlos Roozenbergh Porto da; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
Conversion systems are critically important devices in electrical systems across various environments, especially in modern times, as multiple components with different voltage levels and sources are interconnected within a single system. Consequently, dynamic study methods of this network are examined using approaches that simplify the network based on speed modes and switching of other conversion systems, wherein fast systems are simplified to constant power loads (CPL). This method evaluates the network’s stability conditions. The study reveals that CPLs act as negative incremental resistances, and when analyzed through a linear model, it is observed that such loads reduce system damping, thereby decreasing stability margins and potentially rendering the system unstable. Additionally, uncertainties in the physical components of the circuit further affect the stability and performance of microgrids. Hence, designing regulators to mitigate oscillations caused by these effects becomes crucial to ensure the proper performance of these systems.In this work, a robust controller is designed to handle uncertainties and attenuate oscillations in the presence of constant power loads. This controller is implemented in a microgrid composed of two cascaded DC-DC buck converters, one of which is modeled as a CPL. The system model is utilized for both stability analysis and robust controller design in state space, where the compensator synthesis is structured in the form of a linear matrix inequality, solved using system optimization tools. The controller’s results are compared with another controller based on pole placement in both linear and nonlinear switched models, within the Matlab/Simulink simulation platform. Transient response and control signals are evaluated graphically and through performance indices under various operating conditions, including load disturbances and system parameter variations.
Acesso aberto (Open Access)
Projeto de um controlador amortecedor robusto aplicado a um sistema de potência sujeito a incertezas paramétricas
(Universidade Federal do Pará, 2016-03-16) CUNHA, Leiliane Borges; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
This work presents the design of a Stabilizer for the damping of the electromechanical oscillations in electric power systems using robust control technical based on affine parametric uncertainties. These systems are represented by models that have uncertainties in yours parameters, relating to changes in operating conditions. The project methodology is structured to provide a stabilizer that provides the maximum damping to the system, specified by a polytope of characteristic polynomials. For this, it is used poles robust allocation techniques and Chebyshev's theorem, integrated into the solution of linear programming techniques, for the controller design. This technique allows incorporating restrictions on system performance, corresponding to the uncertainties present in the system, making the controller design more robust. Comparisons of the robust controller with a classic controller are made in order to evaluate the results and validate the advantages of the use of controllers designed by the technique proposal. The results and comparisons are performed in simulation environments using MATLAB / SIMULINK software, which allows to model and simulate all kinds of dynamic systems.
Acesso aberto (Open Access)
Projeto e avaliação experimental de uma estratégia baseada em análise intervalar aplicada ao projeto de estabilizador de sistemas de potência robusto implementado em um sistema de geração de 10KVA
(Universidade Federal do Pará, 2013-12) COSTA, Cleyson Amorim; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
In this paper, are presented the design methodology and the experimental test results of a power system stabilizer (PSS), implemented in a small-scale generation system of 10 kVA, located in the Control and Power System Laboratory (LACSPOT) at the Para Federal University (UFPA). The PSS design is based on a robust control strategy with emphasis on the structured parametric uncertainties, which are treated with tools of the interval analysis theory. These uncertainties are arising from the system operation point, which cause variations in the parameters of a linearized mathematical model referent on the dynamic behavior of the power electric system in the operation point. For the interval robust PSS design, are performed experimental tests with the purpose of estimating the linearized plant models parameters, representing the low damped modes dynamic of the interconnected generation system. The identification method is based on parametric identification technique based on least squares. From a set of input and output data, for each operation point, a ARX linear model is estimated with the purposed of the PSS design. Finally, a set of experimental tests is performed in the interconnected generation system, with the purpose of analyze the effectiveness of the interval robust control technique proposed to the PSS design. From the analysis of the active power deviation signal cost function at the synchronous generator terminal and the PSS control signal cost function, proves experimentally the good performance achieved by robust control technique proposed in comparison with a classic control technique.
Acesso aberto (Open Access)
Sistema de controle baseado em lógica fuzzy para regulagem de temperatura em aquecedor de óleo térmico da planta de anodo verde da Albrás
(Universidade Federal do Pará, 2011-12-23) ALMEIDA, José Guilherme Castro de; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
This work presents the results of a fuzzy control strategy to regulate the temperature of the heater thermal oil, in the Anode Green process at Albrás Aluminum Brasileiro S/A factory. The use of this methodology has resulted in the system being able to react adequately against of the variations on the point of operation of the heater, because the Fuzzy control displays some characteristics of human learning. The heater thermal oil equipment is fundamental in the process of manufacture of blocks butts, used as positive pole in the process of electrolysis in the acquisition of primary aluminum. The system of thermal oil warms the mixers and pre-heating of coke, keeping the temperature of the equipment within the limits established by process engineering. The variable temperature impacts directly in the energy mix of the pulp and the quality of the final product, which is block anode. The methodology presented allowed to reach a temperature control that satisfactorily achieved the process parameters. The program was developed in language scada is executed in programmable logic controllers (PLC'S) of Rockwell Automation. The methodology presented allowed to reach a temperature control that satisfactorily achieved the process parameters. The control is already in full operation at the plants of anodes and the results obtained demonstrate the effectiveness and viability of the system, which in future will be implemented in the control of other equipment of Albras.
Acesso aberto (Open Access)
Técnica de projeto de controlador fuzzy aplicada ao acionamento vetorial de motor de indução
(Universidade Federal do Pará, 2010-05-11) DIAS, Tainara da Costa; BARREIROS, José Augusto Lima; http://lattes.cnpq.br/1246564618922453; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
This paper investigates a strategy for Takagi-Sugeno fuzzy control applied to speed control of induction motor. The strategy implements a weighted interpolation between a set of local controllers previously designed. When changes occur in the operational conditions of the induction motor, the gains of the control law are adjusted automatically to maintain satisfactory performance of the control system. For controller design the fuzzy state space representation of the plant was considered in the form of an augmented system, including a new state variable which in this case, was selected as the integral of speed error. This formulation allowed the design of local controllers with the structure PI, through state feedback with pole placement. As variables of operation for the switching fuzzy controllers local variables were selected angular velocity and stator current component responsible for torque electric, expressed in a frame rotating synchronously with the rotor flux. Then, the stability of Takagi-Sugeno fuzzy controller designed was assured by the Lyapunov criterion, in the form of LMIs. The performance of the Takagi-Sugeno fuzzy controller was assessed through simulation studies and their results compared to the performance of a conventional PI controller, for regulating the rotor speed. The results obtained in simulation tests show that employing the proposed strategy makes the system more robust to parametric variations in the drive system.
Acesso aberto (Open Access)
Técnicas de controle robusto baseadas em resposta em frequência e via alocação de polos intervalar para sistemas com incertezas paramétricas aplicadas ao problema de regulação de tensão em conversores de potência.
(Universidade Federal do Pará, 2022-05-12) CARDOZO, Luise Ferreira; BARRA JUNIOR, Walter; http://lattes.cnpq.br/0492699174212608
Microgrids are a form of distribution system, which belong to the broad concept of smart grids. Multiconverter or multilevel systems are nothing more than DC microgrids composed of several power converters connected in cascade and/or in parallel. In this way, the multiconverter system described in this thesis has a DC - DC converter in the Buck topology, which is used as a source of direct voltage for the main bus of the microgrid, being an element of fundamental importance and whose voltage control is essential, because electronic loads are sensitive to voltage deviations. In order to control the voltage on the DC bus, the system is first modeled using the recursive least squares method, at which time the parametric variations are obtained forming a more comprehensive model called the interval transfer function, which is represented graphically by the extreme set. In a second moment, two robust controllers are developed, one through the extreme stability margins of the model culminating in a PI controller based on frequency response, and the other through an interval pole allocation control project in PID format. The robust performance of the controllers is evaluated through computational simulation, experimentally in the multiconverter system and, finally, using a quantitative analysis through performance indices.

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