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- Design of a smart microgrid with small-scale hydro generation: a practical case studyPublication . Leite, VicenteMicrogrids are local electric grids integrating distributed generation and consumption, energy storage and management and power control. They can be an alternative for the energy supply of a house, a building, a small village or a wider region. Small-scale hydropower, in the range of 5 kW, consists of distributed generation systems gaining increasing interest. These so-called pico-hydro systems are becoming popular since they can take advantage of the integration of low-power wind generators and photovoltaic (PV) inverters, which are widely available at competitive prices. Thus, pico-hydro systems are not only relevant for energy generation in off-grid systems in remote areas but also for new contexts where the utility grid is available. This paper presents the design of a smart microgrid with small-scale hydro generation. It is a practical case study with the integration of two grid-connected pico-hydro turbines: a low-head propeller turbine and a water wheel. The microgrid was designed and implemented in a small museum: Casa da Seda (House of Silk). The energy generation is based on the complementarity between hydro and PV. The microgrid can operate in both grid-connected and islanded modes and feeds the House of Silk loads. The connection of both pico-hydro turbines into the microgrid is based on the integration of wind generators and PV inverters.
- Full and reduced order extended Kalman filter for speed estimation in induction motor drives: a comparative studyPublication . Leite, V.; Araújo, Rui Esteves; Freitas, Diamantino SilvaThis paper presents a comparative study between a new approach for robust speed estimation in induction motor sensor less control, using a reduced order Extended Kalman Filter (EKF), and the one performed by the full order EKF. The new EKF algorithm uses a reduced order state-space model that is discretized in a particular and innovative way, proposed in this paper. In this case, only the rotor flux components are estimated, besides the rotor speed, while the full order EKF also estimates the stator current components. It is well known that the EKF algorithm has some drawbacks, like computational effort for real-time applications, complexity and hard tuning of noise covariance matrices. This new approach introduces new improvements and very important and practical aspects that strongly reduce the execution time and simplify the tuning of the covariance matrices. The reduced order EKF algorithm was implemented and validated in real-time operation using the dSPACE's DS1103 controller board. The experimental results have proved to be very good. The performance of speed estimation using both EKF techniques is compared with respect to computation effort, tuning of the algorithms, speed range including low speeds, load torque conditions, robustness relatively to motor parameter sensitivity and other important aspects.
- Patente Nacional nº 106074 - Traçador de curvas corrente-tensão de módulos e fileiras de módulos fotovoltaicosPublication . Leite, VicenteO presente invento consiste num traçador de curvas corrente- tensão e potência-tensão de módulos e de fileiras, ou matrizes, de módulos fotovoltaicos (1) para o tracejamento contínuo de módulos é utilizado um transístor mosfet (2) e um sinal de comando (3) adequado. Para o tracejamento de curvas de fileiras de módulos, é necessário comutar de A para E o comutador (4) e, neste caso, é utilizado um transístor TGBT (5) que carrega o condensador (6), através do díodo (7), ao receber um impulso (8) com durante suficiente para varrer a curva corrente-tensão, à medida que o condensador carrega. Para o descarregar é ligada uma resistência de potência (9) através de um segundo IGBT (10), comandado por um impulso (11) de duração suficiente para garantir a descarga completa. A tensão e corrente fotovoltaicas são medidas através de (12, 13, 14), com diferentes escalas de tensão (15), e posteriormente isoladas. Este invento pode ser utilizado em laboratório ou em trabalho de campo, utilizando um os ciloscópio ou um computador portátil para obtenção de curvas que podem ser utilizadas no diagnóstico de avarias de módulos fotovoltaicos.
- Estimação de estados, parâmetros e velocidade do motor de indução trifásico com metodologias de identificação em tempo realPublication . Leite, VicenteAs leis de controlo dos sistemas electrónicos de accionamento do motor de indução trifásico, em aplicações de velocidade variável, utilizando técnicas de controlo recentes e de elevado desempenho, designadamente, o controlo vectorial, requerem o conhecimento preciso dos parâmetros eléctricos do motor. A variação destes parâmetros, ao longo do tempo, afecta o desempenho das leis de controlo, sendo necessário proceder à sua estimação durante o funcionamento normal do motor. Neste contexto, são estudados procedimentos de modelação e identificação paramétricas, com o objectivo de obter modelos descritos directamente pelos parâmetros físicos do motor, ou por outros, a partir dos quais aqueles possam ser obtidos. Nesta dissertação, são desenvolvidos novos procedimentos de modelação, na representação de espaço de estados, que permitem estimar, conjuntamente, estados e parâmetros eléctricos do motor de indução. A estimação, em tempo real, é realizada utilizando o algoritmo do filtro de Kalman estendido (EKF – Extended Kalman Filter), dada a sua natureza recursiva e sua adequação a modelos não lineares e variantes no tempo, sob a forma de espaço de estados. Tendo em conta a elevada dimensão dos modelos e esforço computacional do EKF, para aplicações em tempo real, são introduzidos, nesta dissertação, procedimentos inovadores para a redução da ordem e uma nova forma de discretização dos modelos de espaço de estados no tempo contínuo. Aos modelos de ordem reduzida obtidos, é aplicado o EKF, para a estimação conjunta das componentes do fluxo do rotor e dos parâmetros eléctricos. Os mesmos modelos são também utilizados para a estimação conjunta do fluxo do rotor e da velocidade angular do motor de indução. Atendendo ao peso computacional do EKF e às dificuldades específicas da estimação de grandezas associadas ao motor de indução, é desenvolvido um conjunto de modelos lineares simples, para a estimação dos parâmetros do estator, utilizando métodos recursivos de erro de predição, nomeadamente, o algoritmo do gradiente, o método recursivo de mínimos quadrados e o filtro de Kalman. Estes algoritmos, são então interligados com o EKF, com base no princípio de estimadores de estado adaptativos, tendo em vista a estimação conjunta, mas autónoma, dos parâmetros do estator, por um lado, e das componentes do fluxo do rotor e parâmetros do rotor, por outro, depois de identificadas as potenciais vantagens da utilização desta metodologia de identificação. Deste modo, às estruturas de modelos desenvolvidas, são associados algoritmos recursivos, de modo a construir uma base de procedimentos de identificação suficientemente genérica, flexível e configurável, para estimação das diferentes variáveis associadas ao controlo do motor de indução. Com esta metodologia, é possível ter em conta o regime dinâmico do motor e o seu ponto de funcionamento, de modo a garantir a correcta estimação de todos os parâmetros eléctricos, com base na informação dos sinais da tensão e corrente do estator e da velocidade angular do motor. A estimação da velocidade, requer apenas as componentes da tensão e corrente do estator. As diferentes metodologias de identificação, adequadas à estimação de estados, parâmetros eléctricos e velocidade do motor de indução trifásico, foram validadas experimentalmente, em tempo diferido e em tempo real, utilizando o sistema de desenvolvimento da dSPACE, baseado na carta de controlo DS1103, no programa Simulink e outros programas específicos. The control of modern and high-performance electrical drives for induction motors, in variable speed applications, like vector control, requires the accurate knowledge of the induction motor electrical parameters. Since these parameters are time-varying and variations affect the performance of the control laws, their on-line estimation is needed during the normal operation of the motor. In this context, parametric modeling and identification procedures are investigated with the objective of obtaining models described by a set of either directly the physical parameters of the induction motor, or other parameters from which those could be obtained. In this thesis, new modeling procedures are developed, in the state-space representation, in order to enable the joint estimation of states and electrical parameters of the induction motor. Since the extended Kalman filter (EKF) is suitable for time-varying and non-linear state-space models and considering its recursive nature, this algorithm was used for the joint and on-line estimation of those variables. Taking into account the relatively high order of the models and the computational effort of the EKF for real time applications, new procedures are introduced in this thesis so as to reduce the order of the models and an innovative strategy is proposed for the discretization of the continuous time state-space models. The EKF is then applied to the reduced order models, obtained in this way, for joint estimation of the rotor flux components and the electrical parameters. The same models are also used for the joint estimation of the rotor flux and angular speed of the induction motor. Considering the computational effort of the EKF and the specific difficulties in the estimation of the variables related to the induction motor, a set of simple and linear models is developed for the state parameters estimation, using recursive prediction error methods, namely, the gradient algorithm, the recursive least squares method and the Kalman filter. These algorithms are connected with the EKF in a bootstrap manner based on the concept of adaptive state estimators in view of the joint, but autonomous, estimation of the stator parameters, on the one hand, and the rotor flux and rotor parameters, on the other hand, following the observation of the potentialities of using these identification methodologies. By this way, the recursive algorithms are associated to the developed model structures in order to build a sufficiently generic, flexible and configurable base of identification procedures for the estimation of the different variables related to the induction motor control. Using this methodology, it is possible to take into account the dynamics of the motor as well as its operating point, for the suitable estimation of all electrical parameters considering only the information provided by the stator voltage and current signals and the rotor speed. In the speed estimation algorithm only the stator voltage and current components are required. The different identification methodologies, as well as the speed estimation, were validated with experimental data, in off-line and real time operation, using the dSPACE development system, based on the DS1103 controller board, Simulink and other specific software. Les lois de contrôle des systèmes électroniques d’actionnement du moteur d’induction triphasé sur des applications de vitesse variable, utilisant des techniques de contrôle moderne de performance élevée, spécialement le contrôle vectoriel, exigent la connaissance assez précise des paramètres électriques du moteur. La variation temporelle de ces paramètres, affecte la performance des lois de contrôle. Il est donc nécessaire de procéder à son estimation pendant le fonctionnement du moteur. Dans ce contexte, des procédés de modélisation et d’identification paramétriques sont étudiés, avec l’objectif d’obtenir des modèles décrits directement par les paramètres physiques du moteur d’induction, ou d’ autres, qui peuvent être utilisés pour obtenir ces paramètres physiques. Dans cette dissertation de nouveaux procédés de modélisation sont développés, dans la représentation d’espace d’état, qui permettent d’estimer conjointement, états et paramètres électriques du moteur d’induction. L’estimation en-ligne, de ces paramètres, est réalisée à travers l’utilisation du filtre de Kalman étendu (Extended Kalman Filter), pour sa nature récursive et parce que cet algorithme est adapté aux modèles d’espace d’état variables dans le temps et non-linéaires. En considérant la dimension élevée des modèles et le temps de computation du EKF, pour les applications en temps réel, dans cette dissertation des procédés innovatrices pour la réduction de l’ordre des modèles et une nouvelle forme de discrétisation des modèles d’espace d’état dans le temps continu sont introduites. Aux modèles d’espace d’état d’ordre réduite qui sont obtenus est appliqué l’EKF pour estimer conjointement les composantes du flux du rotor et les paramètres électriques. Les mêmes modèles sont aussi utilisés pour estimer conjointement le flux du rotor et la vitesse angulaire du moteur d’induction Considérant l’effort de computation du EKF et les difficultés spécifiques de l’estimation des grandeurs associées au moteur d’induction, un ensemble de modèles linéaires simples, pour l’estimation des paramètres du stator, est développé, en utilisant des méthodes récursives d’erreur de prédiction, spécialement, l’algorithme du gradient, la méthode des moindres carrés récursifs et le filtre de Kalman. Ces algorithmes, sont interliés avec l’algorithme du EKF en considérant le principe des estimateurs d’état adaptatifs, pour effectuer l’estimation simultanée, mais autonome, des paramètres du stator en utilisant une méthode récursive d’erreur de prédiction, et des composantes du flux du rotor et des paramètres du rotor en utilisant l’EKF, après avoir identifiées les potentiels avantages de l’utilisation de cette méthodologie d’identification. Aux structures des modèles développées sont donc associés des algorithmes récursifs, avec l’objectif de construire une base de conduites d’identification suffisamment générique, flexible et configurable, pour l’estimation des différentes variables associées au pilotage du moteur d’induction, en considérant le régime dynamique et le point de fonctionnement, pour garantir une correct estimation des paramètres électriques du moteur. Dans l’estimation des paramètres, des composants de tension et courrant du stator et la vitesse angulaire du moteur sont utilisés. L’estimation de la vitesse utilise seulement des composants de tension et courrant du stator. Les différentes méthodologies d’identification des paramètres électriques, et d’estimation de la vitesse, ont été validées expérimentalement, hors-ligne et en-ligne, en utilisant le système de développement de dSPACE, qui est basé dans la carte de contrôle DS1103, Simulink et autres programmes spécifiques.
- Conservation voltage regulation at residential levelPublication . Silva, Rafael; Freitas, Tiago Joel Pimenta de; Ferreira, Ângela P.; Leite, VicenteThe continued growth of the world energy consumption requires the implementation of new and effective energy strategies, targeted to enhance the transition toward low-carbon technologies, where energy efficiency and renewable energies play a major role. In order to cope within this scenario, an intelligent integration in electrical energy infrastructure, called Smart Grids, allows the implementation of the Conservation Voltage Regulation (CVR) technique, which is based on the premise that reduction of the supplier voltage will lead to reduced energy consumption by final consumers without harming their appliances. This work aims to evaluate the power consumption reduction due to CVR implementation and its economic viability at residential level. Several experimental tests were carried out on residential appliances, including lighting systems, liquid-crystal-display televisions, washing machines, air-conditioning devices, fridges and laptop computers. To quantify the energy savings achieved by the CVR implementation for each of the mentioned equipment, it was used the CVR factor, fCVR, which measures the ratio between energy savings and voltage reduction. This quantitative indicator has typical values between 0,4 and 1,0, and may take values higher than 1,0 in the case of resistive loads, upon how long they are in operation. The obtained results validate the implementation of CVR technique at residential level, indicating a considerable energy and money savings for final consumers.
- IV Congresso Ibero-Americano de Empreendedorismo, Energia, Ambiente e Tecnologia: livro de atasPublication . Boloy, Ronney Arismel Mancebo (Ed.); Val Springer, Marcus (Ed.); Guimarães, Vanessa de Almeida (Ed.); Oliveira, Elizabeth Mendes de (Ed.); Silva Junior, Amilton Ferreira da (Ed.); Leite, Vicente; Soares, Orlando (Ed.); Calvo-Rolle, Jose Luis (Ed.); Madeira, Jonni Guiller Ferreira (Ed.)Contém todas os artigos resultantes do IV Congresso Ibero-Americano de Empreendedorismo, Energia, Ambiente e Tecnologia, realizado em Angra dos Reis, Rio de Janeiro de 27 a 29 de novembro de 2018.
- Dealing with the very small: first steps of a picohydro demonstration project in an university campusPublication . Leite, Vicente; Figueiredo, Tomás de; Pinheiro, Tiago; Ferreira, Ângela P.; Batista, JoséThis paper presents the implementation, project and design of a small run-of-river hydropower plant, designed for demonstration purposes, under a Project aimed to be a framework of wide spread dissemination of renewable energies and energy efficiency in an University Campus. The details of the hydroelectric power plant, from the project design until the final use of the produced electric energy, are described. The main requirements of the implementation are presented, with regards to the environmental footprint and topography of the site and the adopted solutions are also described. Considering the demonstration purposes, two different electrical systems were installed in the power house: stand-alone and grid-connected. The latter establishes a case study in the development and application of picohydro power plants as microgeneration units in the context of distributed generation systems. The evaluation of both systems is also presented, based on the experimental results obtained from tests experiments and from monitoring the first months of operation at the site.
- Projeto de uma picocentral hidrelétrica em um campus universitárioPublication . Leite, V.; Figueiredo, Tomás de; Pinheiro, Tiago; Ferreira, Ângela P.; Batista, JoséEste artigo descreve os detalhes de implementação de uma central hidrelétrica de pequeno porte a fio de água, desde a concepção até à utilização da energia produzida, incluindo os requisitos relacionados à topografia do local, além da avaliação dos dois sistemas instalados (isolado e conectado à rede pública), com base em resultados de testes e ensaios e no monitoramento dos primeiros meses de operação.
- III Congresso Ibero-Americano de Empreendedorismo, Energia, Ambiente e Tecnologia: livro de atasPublication . Leite, Vicente (Ed.); Pereira, Ana I. (Ed.); Ferreira, Ângela P. (Ed.); Gonçalves, Artur (Ed.); Almeida, João P. (Ed.); Calvo-Rolle, Jose Luis (Ed.); Feliciano, Manuel (Ed.); Soares, Orlando (Ed.); Boloy, Ronney Arismel Mancebo (Ed.)O III Congresso Ibero-Americano de Empreendedorismo, Energia, Ambiente e Tecnologia (CIEEMAT), dá continuidade ao trabalho desenvolvido no Brasil pelo Centro Federal de Educação Tecnológica Celso Suckow da Fonseca – Rio de Janeiro, atravessando o oceano Atlântico para a sua primeira edição no contexto da Península Ibérica. Concebido para englobar um conjunto abrangente de áreas temáticas, este evento serve de ponto de encontro entre profissionais, investigadores, professores e estudantes dos países Ibero-Americanos, num fórum que reforça o perfil internacional do Instituto Politécnico de Bragança, assim como das demais Instituições Organizadoras e Parceiras, designadamente, no âmbito de Programas de Dupla Diplomação. Nos três dias do evento, esperamos que encontrem oportunidades para a partilha de ideias e resultados de investigação, reforçando ou estabelecendo novos contactos e parcerias no espaço Latino-Americano. Por fim, espero que a Vossa estadia em Bragança seja agradável e que levem de volta gratas recordações do CIEEMAT 2017.
- Effective grid connection approach for an overshot waterwheelPublication . Leite, VicenteInterest in very small-scale hydropower generation has increased over the past few years. These pico-hydro systems range from a few watts to several kW. The exploitation of low head sites does not require expensive civil works and is environmentally sustainable. Pico-hydro systems are attractive not only for remote areas where the grid is not available, but also for grid connection. This is especially relevant in existing infrastructures, used for other activities but which can also be used for energy generation. Waterwheels are emerging with enormous potential in this context. Low speeds and variations in head and water flow are a constraint to their connection to the grid. This study shows that they can be effectively connected to the grid using competitive and widely available technology for other renewable sources, such as photovoltaics. This paper presents an innovative approach for an effective grid connection of a pico-hydro system based on an overshot waterwheel. For this purpose, a permanent magnet synchronous generator and a photovoltaic inverter are used. The compatibility between them is analysed in detail and the analysis is valid for other hydro turbines. The 2 m diameter waterwheel has been installed on an existing infrastructure of an aquaculture centre. With a flow rate of about 13 l/s, it injects an average power of 126 W into a microgrid with a global efficiency of 50%.