CNPq; CAPES / A expansão contínua dos atuais sistemas elétricos de potência tem levado ao desenvolvimento de técnicas de monitoramento que visam subsidiar a análise, o controle e o planejamento dos sistemas. Dentre essas técnicas destacam-se os sistemas SCADA (do inglês, Supervisory Control and Data Acquisition), os sistemas de monitoramento de grandes áreas (do inglês, Wide Area Measurement System) e os sistemas de análise de oscilografias. Sistemas de análise oscilográfica se baseiam no estudo dos registros oscilográficos provenientes de dispositivos chamados de Registradores Digitais de Perturbação (RDP) que permitem a análise das grandezas elátricas (tensão, corrente), bem como dos sinais digitais dos equipamentos de proteção monitorados (atuação do dispositivo, por exemplo). O excesso de dados presente nos centros de operação e controle de usinas geradoras torna difícil a tarefa de análise dos especialistas em oscilografia, juntamente a esse fato, vê-se uma crescença na utilização de sistemas inteligentes aplicados no diagnóstico de distúrbios em sistemas elétricos de potência. Deste modo, visando auxiliar o trabalho dos especialistas, bem como reduzir o tempo em que as unidades geradoras ficam fora de operação devido a distúrbios, busca-se aqui a elaboração de um sistema de diagnóstico e classificação de distúrbios em plantas geradoras de energia elétrica baseado em lógica fuzzy capaz de diferenciar situações operacionais e de conhecimento dos operadores das situações de contingência bem como classificar a natureza dos distúrbios que causam o desligamento de uma unidade de geração de acordo com as informações obtidas dos registros oscilográficos de longa duração, além de integralizar os eventos em um aspecto multi-máquina. / The electric power systems are getting more complex and covering larger areas day by day. This fact has been contribuiting to the development of monitoring techniques that aim to help the analysis, control and planning of power systems. Supervisory Control and Data Acquisition (SCADA) systems, Wide Area Measurement Systems and disturbance record systems. Unlike SCADA and WAMS, disturbance record systems are mainly used for offilne analysis in occurrences where a fault resulted in tripping of and apparatus such as a transimission line, transformer, generator and so on. The device responsible for record the disturbances is called Digital Fault Recorder (DFR) and records, basically, electrical quantities as voltage and currents and also, records digital information from protection system devices. Generally, in power plants, all the DFRs data are centralized in the utility data centre and it results in an excess of data that difficults the task of analysis by the specialist engineers. This dissertation shows a new methodology for automated analysis of disturbances in power plants. A fuzzy reasoning system is proposed to deal with the data from the DFRs. The objective of the system is to help the engineer resposnible for the analysis of the DFRs’s information by means of a pre-classification of data. For that, the fuzzy system is responsible for generating unit operational state diagnosis and fault classification.

CAPES / Este trabalho tem como objetivo a análise, projeto e implementação de estratégias de controle repetitivo para aplicação em sistemas de alimentação ininterrupta de energia (UPS - Uninterruptible Power Supply). Inicialmente, a revisão da literatura aborda os controladores mais aplicados neste propósito. Uma visão geral sobre sistemas UPS é realizada, com foco em diferentes topologias e o projeto de um filtro indutivo capacitivo (LC), para reduzir o conteúdo harmônico proveniente das comutações do inversor, é discutido. Na sequência, uma estratégia de controle é proposta. Nesta estratégia um termo feedforward é utilizado para gerar a forma de onda da tensão de saída e um controlador do tipo proporcional derivativo (PD) é inserido para compensar distúrbios não cíclicos. Para compensação de distúrbios cíclicos, algumas técnicas de controle repetitivo são analisadas e implementadas. A adição destes controladores apresenta bom desempenho, porém, quando o sistema sofre interferências, as características dinâmicas destes controladores são afetadas. Modificações são realizadas para tornar o sistema menos suscetível a ruídos de alta frequência e a distúrbios aperiódicos. Ainda, é proposto um controlador repetitivo com adaptação do ganho que apresenta robustez suficiente para boa regulação de tensão mesmo na presença de distúrbios aperiódicos e interferências eletromagnéticas. Por fim, é descrita a implementação de uma plataforma flexível, baseado em um inversor PWM controlado por um processador digital de sinais com periféricos para aquisição de dados e geração de PWM, DSC TMS320F28335. A partir desta plataforma, foram obtidos resultados experimentais para um protótipo de uma UPS monofásica, os quais comprovam o desempenho das técnicas de controle apresentadas e propostas. / This work presents an analysis, design and implementation of repetitive control strategies applied to uninterruptible power supplies (UPS) systems. At the beginning, a literature review of the main controllers concerning this purpose is shown. A global vision of UPS systems with focus on different topologies is made and the project of an inductive capacitive filter (LC) is presented where the goal is to reduce harmonic content due to the inverter switching. After that, a control strategy is presented. In this strategy a feed forward term is used to generate the wave form shape of the output voltage and a Proportional Derivative (PD) controller is introduced to compensate non cyclic disturbances. For the compensation of cyclic disturbs some repetitive control techniques are analyzed and implemented. The inclusion of these controllers provides a good performance for the output system, however, when the system is exposed to interferences, the dynamic characteristics of these controllers are affected. Modifications are presented to make the system less susceptible for high frequencies noise and aperiodic disturbs. In addition, a repetitive controller with gain adaptation is proposed with sufficient robustness to obtain a good voltage regulation even in the presence of aperiodic disturbances and electromagnetic interferences. Finally, the implementation of a flexible platform is presented, based on PWM inverter controlled by a digital signal processor with data acquisition and generation PWM peripherals, DSP TMS320F28335. From this platform, experimental results for a monophasic UPS prototype was obtained, which ones prove the performance of the control techniques presented and proposed.

CNPq; CAPES / A expansão contínua dos atuais sistemas elétricos de potência tem levado ao desenvolvimento de técnicas de monitoramento que visam subsidiar a análise, o controle e o planejamento dos sistemas. Dentre essas técnicas destacam-se os sistemas SCADA (do inglês, Supervisory Control and Data Acquisition), os sistemas de monitoramento de grandes áreas (do inglês, Wide Area Measurement System) e os sistemas de análise de oscilografias. Sistemas de análise oscilográfica se baseiam no estudo dos registros oscilográficos provenientes de dispositivos chamados de Registradores Digitais de Perturbação (RDP) que permitem a análise das grandezas elátricas (tensão, corrente), bem como dos sinais digitais dos equipamentos de proteção monitorados (atuação do dispositivo, por exemplo). O excesso de dados presente nos centros de operação e controle de usinas geradoras torna difícil a tarefa de análise dos especialistas em oscilografia, juntamente a esse fato, vê-se uma crescença na utilização de sistemas inteligentes aplicados no diagnóstico de distúrbios em sistemas elétricos de potência. Deste modo, visando auxiliar o trabalho dos especialistas, bem como reduzir o tempo em que as unidades geradoras ficam fora de operação devido a distúrbios, busca-se aqui a elaboração de um sistema de diagnóstico e classificação de distúrbios em plantas geradoras de energia elétrica baseado em lógica fuzzy capaz de diferenciar situações operacionais e de conhecimento dos operadores das situações de contingência bem como classificar a natureza dos distúrbios que causam o desligamento de uma unidade de geração de acordo com as informações obtidas dos registros oscilográficos de longa duração, além de integralizar os eventos em um aspecto multi-máquina. / The electric power systems are getting more complex and covering larger areas day by day. This fact has been contribuiting to the development of monitoring techniques that aim to help the analysis, control and planning of power systems. Supervisory Control and Data Acquisition (SCADA) systems, Wide Area Measurement Systems and disturbance record systems. Unlike SCADA and WAMS, disturbance record systems are mainly used for offilne analysis in occurrences where a fault resulted in tripping of and apparatus such as a transimission line, transformer, generator and so on. The device responsible for record the disturbances is called Digital Fault Recorder (DFR) and records, basically, electrical quantities as voltage and currents and also, records digital information from protection system devices. Generally, in power plants, all the DFRs data are centralized in the utility data centre and it results in an excess of data that difficults the task of analysis by the specialist engineers. This dissertation shows a new methodology for automated analysis of disturbances in power plants. A fuzzy reasoning system is proposed to deal with the data from the DFRs. The objective of the system is to help the engineer resposnible for the analysis of the DFRs’s information by means of a pre-classification of data. For that, the fuzzy system is responsible for generating unit operational state diagnosis and fault classification.

Orientador: Ernesto Ruppert Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-14T03:57:12Z (GMT). No. of bitstreams: 1 Lazarini_MarcosVinicius_M.pdf: 4342557 bytes, checksum: cca354c6cf0938fd0151555654c04067 (MD5) Previous issue date: 2008 / Resumo: Este trabalho apresenta um estudo detalhado de uma configuração de controle direto de torque (DTC) de motores de indução trifásicos usando modulação em largura de pulsos por vetores espaciais, controlador de estrutura variável tipo modos deslizantes (sliding mode) e estimador de velocidade adaptativo do tipo MRAS (model reference adaptive system). Procurou-se apresentar um tutorial detalhado sobre o assunto onde, desde a modelagem matemática adequada do motor de indução trifásico e do controle direto de torque, da modelagem do controlador tipo modos deslizantes e do estimador MRAS até a programação do sistema em processador digital de sinais foram detalhadas. Construiu-se uma plataforma experimental no Laboratório de Eletrônica de Potência da FEEC/UNICAMP para comprovação dos resultados teóricos obtidos através de modelagens matemáticas e simulações digitais realizadas. Os resultados em geral se mostraram adequados e o trabalho certamente contribuiu bastante para a formação do autor para trabalhos de pesquisas científica e tecnológica. Espera-se que o resultado deste trabalho venha contribuir para o estudo de futuros pesquisadores e para o ensino de pós-graduação e, quem sabe de graduação também, nas áreas de controle, eletrônica de potência e controle de máquinas elétricas. / Abstract: This work presents a detailed study of a three-phase induction motor direct torque control (DTC) using space vector pulse width modulation, variable structure controller of sliding mode type and a MRAS rotor speed estimator (model reference adaptive system). It is shown here a detailed tutorial, covering the three-phase induction motor dynamic mathematical modeling and the direct torque control, the sliding mode controller and the MRAS estimator model, up to the digital signal processor programming structure. An experimental set-up was built in the Power Electronics Laboratory of the FEEC/UNICAMP in order to confirm the theoretical results obtained using dynamic simulation. The results obtained were considered adequate in various situations, and the development of this work became a fundamental contribution to the author in terms of his scientific and academic research skills improvement. It is expected that this work could contribute to the future researchers' learning process and also to the graduate and undergraduate control students, control of electrical machines students and power electronics learning process. / Mestrado / Automação / Mestre em Engenharia Elétrica

Orientadores: Jose Antenor Pomilio, Simone Buso / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T01:54:00Z (GMT). No. of bitstreams: 1 Machado_RicardoQuadros_D.pdf: 40226020 bytes, checksum: 3daf262738d5d4691a16184af4e741f1 (MD5) Previous issue date: 2004 / Resumo: Esta tese apresenta uma nova forma de conexão direta entre um gerador de indução trifásico e uma rede monofásica, situação típica de ambientes rurais, com possibilidade de geração local de energia. O funcionamento do sistema prevê que seja garantida ao usuário local energia elétrica de boa qualidade. Por energia de boa qualidade entende-se: tensões senoidais e equilibradas, freqüência fixa e boa regulação de tensão. Para a rede monofásica, controla-se o fluxo de potência de modo que o fator de potência resultante seja unitário. A obtenção destes comportamentos se dá com o uso de um conversor CC-CA PWM trifásico, conectado em derivação no ponto de acoplamento das cargas locais. Por este conversor flui uma parcela da potência da carga relacionada com desequilíbrios e distorções. A maior parte da potência ativa não precisa ser processada pelo conversor, o que dá a esta solução um rendimento maior do que se obtém com as alternativas de dupla conversão. O sistema completo de geração distribuída pode receber energia, da geração CA (gerador de indução), de uma fonte CC (células a combustível, painéis fotovoltáicos ou bancos de baterias) conectada ao barramento CC do conversor PWM ou da rede monofásica. No caso de alimentação apenas pela rede, tem-se uma estrutura de conversão mono-trifásica interativa com a linha / Abstract: This thesis proposes a novel solution to connect a three-phase induction generator directly to a single-phase feeder. Typical situations are found in rural areas in which is possible to obtain local power generation. High power quality at the customers such as sinusoidal and balanced voltages, constant frequency and regulated AC voltage, is provided. Additionally, unity power factor on the feeder is obtained. A three-phase shunt voltage source inverter VSI-PWM is connected at the point of common coupling. This converter processes a fraction of the load power that is associated with unbalances, reactive power and harmonics, as well. The efficiency of the partial power processing is higher when compared to double-conversion systems. On the other hand, the system is able to manage a DC source as a fuel cells, a solar panel and batteries. If only the single-phase source is available, the system operates as a single to three-phase line-interactive converter / Doutorado / Energia Eletrica / Doutor em Engenharia Elétrica

At many American colleges and universities, efforts to enhance the retention of a diverse group of students have become a priority. This study represents part of this effort at the University of Central Florida, a large public suburban state university in the South. Specifically, this investigation evaluated Pegasus '95 and the Academic Mentoring Program offered in the Summer and Fall Semesters of 1995 to specially-admitted students who fell short of regular admissions requirements. During the summer, Pegasus '95 provided testing, orientation, guided course work, study skills workshops, and mentoring, both individually and in the context of cohesive socialization groups of approximately 15 students each. In the Fall 1995 Semester, students were highly encouraged to participate in one-on-one mentoring in the Academic Mentoring Program (AMP) available through the Student Academic Resource Center (SARC), a university-based office which provides a variety of academic assistance services. A multiple regression analysis was conducted using the following independent predictor variables: gender, SAT/ACT scores, Pegasus participation, use of the AMP in the Fall 1995 semester, four summary scores from the College Student Inventory (CSI), and eight scaled scores from the Noncognitive Questionnaire (NCQ). Dependent variables were individual student GPA in the Summer and Fall 1995 semesters, cumulative GPA after two semesters, and enrolled credit hours into the Spring 1996 academic term. Overall, it was expected that a combination of predictor variables, including both traditional cognitive factors (SAT/ACT scores and high school GPA) and noncognitive factors (NCQ scores and CSI scores, Pegasus participation, and mentoring by the SARC) would significantly predict GP A and retention. The study found that a regression equation including gender, high school GPA, overall SAT scores and the eight NCQ scale scores significantly predicted Fall 1995 and cumulative GPA after two semesters but not Summer 1995 GPA or credit hours enrolled in Spring 1996. Attendance at Pegasus meetings was also shown to be significantly and positively associated with Fall 1995 GPA and cumulative GPA after two semesters but not of Summer 1995 GPA or credit hours enrolled in Spring 1996. Gender, high school GP A, the ACT score and the CSI Dropout Proneness scale significantly predicted credit hours enrolled in Spring 1996, as did use of the AMP program provided by the SARC. Of particular interest was the finding that including noncognitive factors in significant equations led to a greater explanation of the variance than could be obtained with any of the traditional cognitive measurements alone, suggesting that with academically disadvantaged students noncognitive measures must be considered in predicting who can succeed and persist in college.

Today, the information (signal timings, detector extension, phase sequence, etc.) to install traffic lights on the street are obtained from traffic software simulations platforms, meaning that information from simulation is not tested on the field (intersection where it will be installed) before the installation. Many installed controllers on the street use time of day (TOD) patterns due to cheaper cost than adaptive traffic control systems, but that is not the best solution for traffic volume changes that can occur during the day or even a month. To improve traffic signal operation most of the traffic signal controllers in the same corridor or zone operate in coordination mode. Furthermore, phases need to be in coordination to achieve “green wave”. Green wave is term used when in corridor traffic lights allow continues flow of traffic through intersections that are coordinated. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

University of Macau / Faculty of Science and Technology / Department of Electrical and Electronics Engineering

[Truncated abstract] This thesis studies current sensing techniques that are designed to meet the requirements for the next generation of power converters. Power converters are often standardised, so that they can be replaced with a model from another manufacturer without an expensive system redesign. For this reason, the power converter market is highly competitive and relies on cutting-edge technology, which increases power conversion efficiency and power density. High power density and conversion efficiency reduce the system cost, and thus make the power converter more attractive to the customer. Current sensing is a vital task in power converters, where the current information is required for monitoring and control purposes. In order to achieve the above-mentioned goals, existing current sensing techniques have to be improved in terms of cost, power loss and size. Simultaneously, current information needs to be increasingly available in digital form to enable digital control, and to allow the digital transmission of the current information to a centralised monitoring and control unit. All this requires the output signal of a particular current sensing technique to be acquired by an analogue-to-digital converter, and thus the output voltage of the current sensor has to be sufficiently large. This thesis thoroughly reviews contemporary current sensing techniques and identifies suitable techniques that have the potential to meet the performance requirements of the next-generation of power converters. After the review chapter, three novel current sensing techniques are proposed and investigated: 1) The usefulness of the resistive voltage drop across a copper trace, which carries the current to be measured, to detect electrical current is evaluated. Simulations and experiments confirm that this inherently lossless technique can measure high currents at reasonable measurement bandwidth, good accuracy and low cost if the sense wires are connected properly. 2) Based on the mutual inductance theory found during the investigation of the copper trace current sense method, a modification of the well-known lossless inductor current sense method is proposed and analysed. This modification involves the use of a coupled sense winding that significantly improves the frequency response. Hence, it becomes possible to accurately monitor the output current of a power converter with the benefits of being lossless, exhibiting good sensitivity and having small size. 3) A transformer based DC current sense method is developed especially for digitally controlled power converters. This method provides high accuracy, large bandwidth, electrical isolation and very low thermal drift. Overall, it achieves better performance than many contemporary available Hall Effect sensors. At the same time, the cost of this current sensor is significantly lower than that of Hall Effect current sensors. A patent application has been submitted. .... The current sensing techniques have been studied by theory, hardware experiments and simulations. In addition, the suitability of the detection techniques for mass production has been considered in order to access the ability to provide systems at low-cost.

This Thesis is concerned with the approximation of high order controllers or the controller reduction problem. We firstly consider approximating high-order controllers by low order controllers based on the closed-loop system approximation. By approximating the closed-loop system transfer function, we derive a new parametrized double-sided frequency weighted model reduction problem. The formulas for the input and output weights are derived using three closed-loop system configurations: (i) by placing a controller in cascade with the plant, (ii) by placing a controller in the feedback path, and (iii) by using the linear fractional transformation (LFT) representation. One of the weights will be a function of a free parameter which can be varied in the resultant frequency weighted model reduction problem. We show that by using standard frequency weighted model reduction techniques, the approximation error can be easily reduced by varying the free parameter to give more accurate low order controllers. A method for choosing the free parameter to get optimal results is being suggested. A number of practical examples are used to show the effectiveness of the proposed controller reduction method. We have then considered the relationships between the closed-loop system con gurations which can be expressed using a classical control block diagram or a modern control block diagram (LFT). Formulas are derived to convert a closed-loop system represented by a classical control block diagram to a closed-loop system represented by a modern control block diagram and vice versa.