Bidirectional Boost/Buck Quadratic Converter for Distributed Generation Systems with Electrochemical Storage Systems

Trabalho apresentado no 5th IEEE International Conference on Renewable Energy Research and Applications, 20-23 de novembro 2016, Birmingham, Reino UnidoThe increasing number of distributed generation systems using renewable and non-conventional energy sources show the trend of future generation systems. Most of these systems require power electronic converters as an interface between the DC voltage buses and electrochemical storage systems. Such storage systems, like batteries or supercapacitors, usually need bidirectional DC-DC converters to allow their charge or discharge according with necessary operation conditions. In this paper, a non-isolated bidirectional Buck-Boost converter with high voltage gain for electrochemical storage devices used in distributed generation systems is presented. To achieve high voltage gain ratios, the proposed topology presents quadratic characteristics in both step-down (Buck) and step-up (Boost) operation modes. In addition to the wide conversion range, it presents continuous input and output current, reduced charging/discharging ripple and simple control circuitry. All these features allow the energy exchange smoothly and continuously resulting in a longer durability of storage devices. The principle of the operation of the proposed converter in both operation modes, as well as their theoretical analysis will be discussed. The performance of this bidirectional power converter is confirmed through simulation and experimental results.N/

A Review of the Power Converter Interfaces for Switched Reluctance Machines

The use of power electronic converters is essential for the operation of Switched Reluctance Machines (SRMs). Many topologies and structures have been developed over the last years considering several specific applications for this kind of machine, improving the control strategies, performance range, fault-tolerant operation, among other aspects. Thus, due to the great importance of power electronic converters in such applications, this paper is focused on a detailed review of main structures and topologies for SRM drives. The proposed study is not limited to the classic two-level power converters topologies dedicated to the SRMs; it also presents a review about recent approaches, such as multilevel topologies and based on impedance source network. Moreover, this review is also focused on a new class of topologies associated to these machines, namely the ones with fault-tolerant capability. This new category of topologies has been a topic of research in recent years, being currently considered an area of great interest for future research work. An analysis, taking into consideration the main features of each structure and topology, was addressed in this review. A classification and comparison of the several structures and topologies for each kind of converter, considering modularity, boost capability, number of necessary switches and phases, integration in the machine design, control complexity, available voltage levels and fault-tolerant capability to different failure modes, is also presented. In this way, this review also includes a description of the presented solutions taking into consideration the reliability of the SRM drive.info:eu-repo/semantics/publishedVersio

Industrial Automation Self-Learning Through the Develoment of Didactic Industrial Processes

Trabalho apresentado no 20th International Conference on Interactive Collaborative Learning, 27-29 de setembro 2017, Budapeste, HungriaTeaching industrial automation is a complex mission. The classical approach is based on lectures and laboratories assisted by teachers. Nevertheless, teaching industrial automation using the classical approach is not easy because this multidisciplinary area requires knowledge in control, energy, electronics, robotics and computer engineering, among others. In this way, this paper presents an approach to teach Industrial Automation based on a self learning strategy. Instead of using the classical approach, students must develop a research work and a didactic automation prototype. The results of this methodology indicate that students increase the interest about industrial automation and clarify important aspects of assembly, commissioning, parameterization and programming of electric and electronic devices. Additionally this methodology seems to increase self-confidence of students and give them the necessary background to face the challenge of working in the real world.N/

Dual Output and High Voltage Gain DC-DC Converter for PV and Fuel Cell Generators Connected to DC Bipolar Microgrids

This paper introduces a new topology for a DC-DC converter with bipolar output and high voltage gain. The topology was designed with the aim to use only one active power switch. Besides the bipolar multiport output and high voltage gain this converter has another important feature, namely, it has a continuous input current. Due to the self-balancing bipolar outputs, the proposed topology is suitable for bipolar DC microgrids. Indeed, the topology balancing capability can achieve the two symmetrical voltage poles of bipolar DC microgrids. Furthermore, it is possible to create a midpoint in the output of the converter that can be directly connected to the ground of the DC power supply, avoiding common-mode leakage currents in critical applications such as transformerless grid-connect PV systems. The operating principle of the proposed topology will be supported by mathematical analysis. To validate and verify the characteristics of the presented topology, several experimental results are shown.info:eu-repo/semantics/publishedVersio

A Fault Diagnosis Scheme Based on the Normalized Indexes of the Images eccentricity for a Multilevel Converter of a Switched Reluctance Motor Drive

Trabalho apresentado em ICRERA 2022, 18-21 setembro 2022, Istambul, TurquiaThis paper addresses the fault detection and diagnosis of a fault in the switches of the Switched Reluctance Machine (SRM) power electronic converter. Due to the advantages of using multilevel converters with these machines, a fault detection and diagnosis algorithm is proposed for this converter. The topology under consideration is the asymmetric Neutral Point Clamped (ANPC), and the algorithm was developed to detect open and short circuit faults. The proposed algorithm is based on an approach that discriminates eccentricity of the images formed by the converter voltages. This discrimination is realized through the development of normalized indexes based on the entropy theory. Besides the different fault type the algorithm is also able to detect the transistor under fault. The possibility to implement the proposed approach will be verified through simulation tests.N/

Molecular simulations of the synthesis of periodic mesoporous silica phases at high surfactant concentrations

Molecular dynamics simulations of a coarse-grained model are used to study the formation mechanism of periodic mesoporous silica over a wide range of cationic surfactant concentrations. This follows up on an earlier study of systems with low surfactant concentrations. We started by studying the phase diagram of the surfactant-water system and found that our model shows good qualitative agreement with experiments with respect to the surfactant concentrations where various phases appear. We then considered the impact of silicate species upon the morphologies formed. We have found that even in concentrated surfactant systems --in the concentration range where pure surfactant solutions yield a liquid crystal phase -- the liquid-crystal templating mechanism is not viable because the preformed liquid crystal collapses as silica monomers are added into the solution. Upon the addition of silica dimers, a new phase-separated hexagonal array is formed. The preformed liquid crystals were found to be unstable in the presence of monomeric silicates. In addition, the silica dimer is found to be essential for mesoscale ordering at both low and high surfactant concentrations. Our results support the view that a cooperative interaction of anionic silica oligomers and cationic surfactants determines the mesostructure formation in the M41S family of materials.publishe

CONSIDERAÇÃO DAS CORRELAÇÕES ESPACIAIS ENTRE OS REGIMES DE VENTOS NA GERAÇÃO DE CENÁRIOS DE PRODUÇÃO DE ENERGIA EÓLICA – APLICAÇÃO AO FLUXO DE POTÊNCIA PROBABILÍSTICO

Segundo uma tendência mundial, verifica-se no Brasil uma participação já elevada e crescente da energia eólica, o que requer o aprimoramento das ferramentas computacionais que suportam os processos de tomada de decisão na operação e no planejamento de sistemas elétricos. O presente trabalho descreve uma metodologia para a modelagem das correlações espaciais entre os regimes de vento no problema de fluxo de potência probabilístico. A metodologia proposta se baseia na transformação de Nataf, na Simulação de Monte Carlo e na estimação não paramétrica de densidades de probabilidades condicionais entre a velocidade do vento e a potência eólica. A efetividade da metodologia é ilustrada por meio de estudos de caso com o Sistema Teste IEEE 118 barras e com uma configuração do sistema elétrico do Nordeste brasileiro com 965 barras

A buck-boost converter with extended duty-cycle range in the buck voltage region for renewable energy sources

Buck-boost DC-DC converters are useful as DC grid interfaces for renewable energy resources. In the classical buck-boost converter, output voltages smaller than the input voltage (the buck region) are observed for duty cycles between 0 and 0.5. Several recent buck-boost converters have been designed to present higher voltage gains. Nevertheless, those topologies show a reduced duty-cycle range, leading to output voltages in the buck region, and thus require the use of very low duty cycles to achieve the lower range of buck output voltages. In this work, we propose a new buck-boost DC-DC converter that privileges the buck region through the extension of the duty-cycle range, enabling buck operation. In fact, the converter proposed here allows output voltages below the input voltage even with duty cycles higher than 0.6. We present the analysis, design, and testing of the extended buck-boost DC-DC converter. Several tests were conducted to illustrate the characteristics of the extended buck-boost DC-DC converter. Test results were obtained using both simulation software and a laboratory prototype.info:eu-repo/semantics/publishedVersio

Epidemiologia e controle da esquistossomose mansônica em área onde o hospedeiro intermediário é Biomphalaria tenagophila

The epidemiology and control of schistosomiasis mansoni in the Municipality of Pedro de Toledo (State of S. Paulo, Brazil) since 1980, has been studied. In 1980 the prevalence evaluated by stool exams (Kato-Katz method) was 22.8% and no statistical difference at 5.0% level was observed between rural and urban zones. The intensity of infection was low (58.5 eggs/g of faeces); the highest prevalence and intensity of infection rates were observed within the group of from 5 to 29 years of age, respectively. The transmission of schistosomiasis usually occurred during leisure time. The majority of the carriers of the parasite were asymptomatic. Of the B. tenagophila examined only 0.4% were found to be infected. The control programme has been intensified from 1981 on resulting in a sharp decrease in the prevalence from 22.8% in 1980 to 6% at the present time. This result shows that, in spite of the control programme there is a residual human prevalence. A beginning has been made on the investigation into the possible causes of this residual prevalence (6.0% was maintained through out 1987).Desde 1980, está-se estudando a epidemiologia e o controle da esquistossomose mansônica no Município de Pedro de Toledo (Estado de São Paulo, Brasil). Em 1980 a prevalência avaliada por exame de fezes (método de Kato-Katz) foi de 22,8%. Estatisticamente, ao nível de 5%, não houve diferença nas prêvalencias observadas nas zonas rural e urbana. A intensidade de infecção foi baixa (média geométrica de 58,5 ovos por grama de fezes). As maiores prevalências e intensidades de infecção foram registradas na faixa etária de 5 a 29 anos. Geralmente a transmissão da endemia verificou-se durante o lazer. Apenas 0,4% de B. tenagophila mostraram-se positivos para cercárias de S. mansoni. A maioria dos portadores era assintomático. O programa de controle foi intensificado após avaliação dos dados de 1980, resultando em diminuição acentuada da prevalência de 22,8% em 1980 para 6%. Esta prevalência residual vem se mantendo até 1987. Agora iniciamos estudos para investigar as possíveis causas dessa prevalência residual