Browsing by Author "Leite, Vicente"
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- Abordagens para a ligação à rede de sistemas pico-hidroelétricosPublication . Leite, Vicente; Ferreira, Ângela P.; Couto, José; Batista, JoséOs aproveitamentos hidroelétricos de pequena escala apresentam um impacte ambiental reduzido. Existe um enorme potencial inexplorado, apresentando portanto uma capacidade significativa para satisfazer a crescente procura de energia elétrica com muitas vantagens. Os sistemas pico-hídricos ligados à rede são uma solução emergente para um grande número de aplicações, tais como em sistemas de fornecimento de água para uso doméstico, em estações de tratamento de águas residuais e melhoramento de sistemas de controlo e otimização da geração como parte de sistemas de gestão integrada da água. Também são muito promissores para a integração em microrredes em muitos países em desenvolvimento. Este artigo apresenta e discute três principais abordagens para a ligação à rede de sistemas pico-hidroelétricos: utilizando conversores de energia especificamente concebidos, utilizando inversores eólicos estandardizados e utilizando inversores fotovoltaicos estandardizados. Estas últimas abordagens, baseadas em inversores convencionais, são soluções práticas capazes de explorar uma grande quantidade de locais viáveis com pequena e muito pequena queda de água. Além disso, os micro inversores fotovoltaicos, recentemente lançados no mercado, são propostos para os geradores de potência reduzida (250-300 W). Estas abordagens melhoram a eficiência, reduzem os custos e os impactes ambientais e melhoram a fiabilidade dos sistemas de conversão. A avaliação experimental do desempenho em regime permanente e em condições dinâmicas comprova a viabilidade destas abordagens inovadoras.
- An improved electronic circuit for tracing the I-V characteristics of photovoltaic modules and stringsPublication . Leite, Vicente; Chenlo, FaustinoThis paper presents an improved electronic circuit for testing photovoltaic (PV) modules or strings by tracing their I-V and P-V characteristics. It consists of an electronic fast varying load based on a power MOSFET controlled by means of an innovative sweeping gate-source voltage in order to improve the tracing of the I-V characteristics on an oscilloscope. In order to prevent damage of data acquisition systems and mainly for use with high voltage PV strings, galvanic isolation is introduced for the sweeping signal as well as current and voltage measurements. In spite of this improved characteristics, the developed electronic circuit keeps the advantages of low cost and simplicity. Experimental results obtained with the electronic circuit are presented.
- An integrated test bench for research, study or demonstration of variable speed drives of induction motorsPublication . Teixeira, Henrique José Alves; Leite, Vicente; Batista, José; Araújo, Rui Esteves; Freitas, Diamantino SilvaThis paper presents an integrated and low cost test bench for teaching and R&D purposes in variable speed drives of induction motors. The test bench is composed by different integrated sub-systems and the resulting platform is suitable for control, parameter estimation and condition monitoring of induction machines controlled by electrical drives
- Analyses of MPPT algorithms in real test conditionsPublication . Guimarães, Thiago Fialho; Leite, VicenteMaximum Power Point Tracking (MPPT) algorithms are of major importance for optimized yield in gridconnected PV systems. Many algorithms have been investigated. However, most of the works compare these algorithms based on a literature review or on simulation. This paper presents an experimental analysis of MPPT techniques: two of the simplest (Perturb & Observe and Incremental Conductance) and two of the most complex (Fuzzy Logic Controller and Particle Swarm Optimization). The results are carried out in real test conditions, with and without shadow. The power converter is based on a boost converter and a voltage source inverter. The control is implemented using Simulink® and dSPACE 1103 real-time controller board. Moreover, the MPPT techniques of three commercial string inverters are also analysed.
- Analysis of the operation of a microgrid with renewable distributed generationPublication . Leite, Vicente; Ferreira, Ângela P.; Batista, José; Couto, JoséThis article reports the ongoing research on the performance assessment of an experimental microgrid which integrates various renewable energy sources. The microgrid is based on a modular commercial solution, up to a rated power of 5 kW, integrating storage devices, a backup diesel generator and various renewable energy sources and also distributed energy sources developed under ongoing R&D projects, such as the integration of a pico hydropower plant with an interface able to perform power factor compensation of the microgrid, which is introduced briefly. The performance assessment of this microgrid is conducted through a characterization of different operational states and also a preliminary energy balance of the microgrid during a time span of 4 days.
- Aplicação de técnicas de identificação paramétrica ao motor de indução trifásicoPublication . Leite, VicenteCom o desenvolvimento das teorias de controlo e das tecnologias de aquisição e processamento de dados, nomeadamente, processadores digitais de sinal (DSP), o motor de indução trifísico tem vindo a substituir o tradicional motor de corrente contínua, como principal meio de accionamento nas aplicações de controlo industriais. Se associarmos a este desenvolvimento, as características mais importantes do motor de indução trifásico, como a robustez, a ausência de manutenção e o preço, compreendemos as razões pelas quais é hoje, o motor mais utilizado na indústria.
- Assessment of energy use and energy efficiency in two portuguese slaughterhousesPublication . Feliciano, Manuel; Rodrigues, Filipe; Gonçalves, Artur; Santos, José M.R.C.A.; Leite, VicenteWith the objective of characterizing the profile and performance of energy use by slaughterhouses, surveys and audits were performed in two different facilities located in the northeastern region of Portugal. Energy consumption from multiple energy sources was assessed monthly, along with production and costs, for the same reference year. Gathered data was analyzed to identify and quantify the main consuming processes and to estimate energy efficiency indicators for benchmarking purposes. Main results show differences between the two slaughterhouses concerning energy sources, consumption by source and sector, and global energy efficiency. Electricity is the most used source in both slaughterhouses with a contribution of around 50%, being essentially used for meat processing and refrigeration. Natural gas, in slaughterhouse A, and pellets, in slaughterhouse B, used for heating water take the second place, with a mean contribution of about 45%. On average, a 62 kgoe/t specific energy consumption (SEC) was found, although with differences between slaughterhouses. A prominent negative correlation between SEC and carcass production was found specially in slaughterhouse A. Estimated Specific Energy Cost and Greenhouse Gases Intensity (GHGI) show mean values of about 50 €/t and 1.8 tCO2e/toe, respectively. Main results show that there is a significant margin for improving energy efficiency and therefore lowering costs in this type of non-energy intensive industries.
- Bidirectional vehicle-to-grid interface under a microgrid projectPublication . Leite, Vicente; Ferreira, Ângela P.; Batista, JoséIn the emergent deployment of smart grids, storage systems play an important role into assets utilization optimization, providing backup power and peak-shaving. This concept becomes more critical in the context of microgrids with a high penetration of renewable energy resources. Plug-in electric vehicles provide an enormous distributed storage capability, which favours the technical and economical exploitation of such systems. This paper presents a comprehensive implementation and control of a bidirectional power converter for vehicle-to-grid integration, based on a bidirectional DC/DC converter followed by a full bridge DC/AC converter.
- Bidirectional vehicle-to-grid interface under a microgrid projectPublication . Leite, Vicente; Ferreira, Ângela P.; Batista, JoséIn the emergent deployment of the smart grids, storage systems play an important role into assets utilization optimization, providing backup power and peak-shaving. This concept becomes more critical in the context of microgrids with a high penetration of renewable energy resources. Plug-in electric vehicles provide an enormous distributed storage capability, which favours the technical and economical exploitation of such systems. This paper presents a comprehensive implementation and control of a bidirectional power converter for vehicle-to-grid integration, based on a bidirectional DC/DC converter followed by a full bridge DC/AC converter. The evaluation of the adopted topology and its control is performed through simulation and experimental validation. © 2014 IEEE.
- A boot-strap estimator for joint flux and parameters online identification for vector controlled induction motor drivesPublication . Leite, Vicente; Araújo, Rui Esteves; Freitas, Diamantino SilvaThis paper presents a new approach for joint rotor flux and electrical parameters on-line identification in vector controlled high-performance induction motor drives based on a boot-strap estimator that uses a reduced order extended Kalman filter for rotor flux components and rotor parameters estimation and a recursive prediction error method for stator parameters estimation. Within the prediction error method some approaches are used and compared that affect both the adaptation gain and the direction in which the updates of stator parameters are made. The induction motor model structures are described in the rotor reference frame in order to reduce the computational effort by using a higher sampling time interval.