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The gut microbiota is increasingly recognized as an important regulator of host immunity and brain health. The aging process yields dramatic alterations in the microbiota, which is linked to poorer health and frailty in elderly populations. However, there is limited evidence for a mechanistic role of the gut microbiota in brain health and neuroimmunity during aging processes. Therefore, we conducted fecal microbiota transplantation from either young (3–4 months) or old (19–20 months) donor mice into aged recipient mice (19–20 months). Transplant of a microbiota from young donors reversed aging-associated differences in peripheral and brain immunity, as well as the hippocampal metabolome and transcriptome of aging recipient mice. Finally, the young donor-derived microbiota attenuated selective age-associated impairments in cognitive behavior when transplanted into an aged host. Our results reveal that the microbiome may be a suitable therapeutic target to promote healthy aging. The gut microbiome can change with age and influence aging-related diseases systemically, including in the brain. The authors show that rejuvenation of the gut microbiome by fecal microbiota transplantation from young mice reverses aging-induced deficits in the hippocampal immune system, metabolome and transcriptome, and rescues selective cognitive deficits.

Background: Early life stress is a key predisposing factor for depression and anxiety disorders. Selective serotonin re-uptake inhibitors (SSRI) are frequently used as the first line of pharmacology treatment for depression but have several negative qualities, i.e. a delay or absence of effectiveness and negative side-effects. Therefore, there is a growing need for new nutraceutical-based strategies to blunt the effects of adverse-life events.Objectives: This study aimed to use the maternal separation model in rats to test the efficacy of fish oil dietary supplementation, on its own and in conjunction with the SSRI anti-depressant fluoxetine, as a treatment for depressive and anxiety-like symptoms associated with early life stress.Methods: Behavioural tests (open field test, elevated plus maze test and forced swim test) and biochemical markers (corticosterone, BDNF, brain fatty acids and short chain fatty acids) were used to analyse the effects of the dietary treatments. Gut microbial communities and relating metabolites (SCFA) were analysed to investigate possible changes in the microbiota-gut-brain axis.Results: Maternally separated rats showed depressive-like behaviours in the forced swim and open field tests. These behaviours were prevented significantly by fluoxetine administration and in part by fish oil supplementation. Associated biochemical changes reported include altered brain fatty acids, significantly lower plasma corticosterone levels (AUC) and reduced brain stem serotonin turnover, compared to untreated, maternally separated (MS) rats. Untreated MS animals had significantly lower ratios of SCFA producers such as Caldicoprobacteraceae, Streptococcaceae, Rothia, Lachnospiraceae_NC2004_group, and Ruminococcus_2, along with significantly reduced levels of total SCFA compared to non-separated animals. Compared to untreated MS animals, animals fed fish oil had significantly higher Bacteroidetes and Prevotellaceae and reduced levels of butyrate, while fluoxetine treatment resulted in significantly higher levels of Neochlamydia, Lachnoclostridium, Acetitomaculum and Stenotrophomonas and, acetate and propionate.Conclusion: Despite the limitations in extrapolating from animal behavioural data and the notable differences in pharmacokinetics between rodents and humans, the results of this study provide a further advancement into the understanding of some of the complex systems within which nutraceuticals and pharmaceuticals effect the microbiota-gut-brain axis.

Depression is considered a major public health concern, where existing pharmacological treatments are not equally effective across all patients. The pathogenesis of depression involves the interaction of complex biological components, such as the immune system and the microbiota-gut-brain axis. Adjunctive lifestyle-oriented approaches for depression, including physical exercise and special diets are promising therapeutic options when combined with traditional antidepressants. However, the mechanisms of action of these strategies are incompletely understood. Accumulating evidence suggests that physical exercise and specific dietary regimens can modulate both the immune system and gut microbiota composition. Here, we review the current information about the strategies to alleviate depression and their crosstalk with both inflammatory mechanisms and the gut microbiome. We further discuss the role of the microbiota-gut-brain axis as a possible mediator for the adjunctive therapies for depression through inflammatory mechanisms. Finally, we review existing and future adjunctive strategies to manipulate the gut microbiota with potential use for depression, including physical exercise, dietary interventions, prebiotics/probiotics, and fecal microbiota transplantation.

Background Polyphenols are phytochemicals that have been associated with therapeutic effects in stress-related disorders. Indeed, studies suggest that polyphenols exert significant neuroprotection against multiple neuronal injuries, including oxidative stress and neuroinflammation, but the mechanisms are unclear. Evidence indicates that polyphenol neuroprotection may be mediated by activation of Nrf2, a transcription factor associated with antioxidant and cell survival responses. On the other hand, in stress-linked disorders, Fkbp5 is a novel molecular target for treatment because of its capacity to regulate glucocorticoid receptor sensitivity. However, it is not clear the role Fkbp5 plays in polyphenol-mediated stress modulation. In this study, the neuroprotective effects and mechanisms of the naturally derived polyphenols xanthohumol and quercetin against cytotoxicity induced by corticosterone were investigated in primary cortical cells. Methods Primary cortical cells containing both neurons and astrocytes were pre-incubated with different concentrations of quercetin and xanthohumol to examine the neuroprotective effects of polyphenols on cell viability, morphology, and gene expression following corticosterone insult. Results Both polyphenols tested prevented the reduction of cell viability and alterations of neuronal/astrocytic numbers due to corticosterone exposure. Basal levels of Bdnf mRNA were also decreased after corticosterone insult; however, this was reversed by both polyphenol treatments. Interestingly, the Nrf2 inhibitor blocked xanthohumol but not quercetin-mediated neuroprotection. In contrast, we found that Fkbp5 expression is exclusively modulated by quercetin. Conclusions These results suggest that naturally derived polyphenols protect cortical cells against corticosterone-induced cytotoxicity and enhance cell survival via modulation of the Nrf2 pathway and expression of Fkbp5.

There is a growing emphasis on the role of the microbiota-gut-brain axis as modulator of host behaviour and as therapeutic target for neuropsychiatric disorders. In addition, accumulating evidence suggests that early-life stress can exert long-lasting changes on the brain and microbiota, and this early adversity is associated with increased risk for developing depression in later life. The maternal separation (MS) model in rats is a robust paradigm to study the effects of early-life stress on the microbiota-gut-brain axis. Recently, we have shown that polyphenols, naturally occurring compounds associated with several health benefits, have anti-stress effects in in vitro models. In this study, we assess the therapeutic potential of a variety of both flavonoid and non-flavonoid polyphenols in reversing the impact of MS on behaviour and the microbiota-gut-brain axis. Rats underwent a dietary intervention with the naturally-derived polyphenols xanthohumol and quercetin, as well as with a phlorotannin extract for 8 weeks. Treatment with polyphenols prevented the depressive- and anxiety-like behaviours induced by MS, where xanthohumol effects were correlated with rescue of BDNF plasma levels. In addition, MS resulted in altered brain levels of 5-hydroxyindoleacetic acid (5-HIAA) and dopamine, accompanied by abnormal elevation of plasma corticosterone. Although polyphenols did not reverse neurotransmitter imbalance, xanthohumol normalised corticosterone levels in MS rats. Finally, we explored the impact of MS and polyphenolic diets on the gut microbiota. We observed profound changes in microbial composition and diversity produced by MS condition and by xanthohumol treatment. Moreover, functional prediction analysis revealed that MS results in altered enrichment of pathways associated with microbiota-brain interactions that are significantly reversed by xanthohumol treatment. These results suggest that naturally-derived polyphenols exert antidepressant-like effects in MS rats, which mechanisms could be potentially mediated by HPA regulation, BDNF levels rescue and modulation of the microbiota-gut-brain axis.

SCOPE Increasing scientific evidence is validating the use of dietary strategies to support and improve brain health throughout the lifespan, with tailored nutritional interventions catering for specific life stages. Dietary phospholipid supplementations in early life and adulthood have been shown to alleviate some of the behavioural consequences associated with chronic stress. This study aims to explore the protective effects of a tailored phospholipid-enriched buttermilk on behavioural and endocrine responses induced by chronic psychosocial stress in adulthood, and to compare these effects according to the life stage at which the supplementation was started. METHODS AND RESULTS We developed a novel phospholipid-enriched dairy product and assessed social, anxiety- and depressive-like behaviours, as well as the stress response and cognitive performance following chronic psychosocial stress in C57 BL/6 J mice, with supplementation beginning in adulthood or early life. Milk phospholipid supplementation from birth protected adult mice against chronic stress-induced changes in endocrine response to a subsequent acute stressor and reduced innate anxiety-like behaviour in non-stressed animals. When starting in adulthood, the dietary intervention reversed the anxiety-like phenotype caused by chronic stress exposure. CONCLUSION Dairy-derived phospholipids exert differential protective effects against chronic psychosocial stress depending on the targeted life stage and duration of the dietary supplementation. This article is protected by copyright. All rights reserved.

Chronic stress and ageing are two of the most important factors that negatively affect cognitive processes such as learning and memory across the lifespan. To date, pharmacological agents have been insufficient in reducing the impact of both on brain health, and thus, novel therapeutic strategies are required. Recent research has focused on nutritional interventions to modify behaviour and reduce the deleterious consequences of both stress and ageing. In this context, emerging evidence indicate that phospholipids, a specific type of fat, are capable of improving a variety of cognitive processes in both animals and humans. The mechanisms underlying these positive effects are actively being investigated but as of yet are not fully elucidated. In this review, we summarise the preclinical and clinical studies available on phospholipid-based strategies for improved brain health across the lifespan. Moreover, we summarize the hypothesized direct and indirect mechanisms of action of these lipid-based interventions which may be used to promote resilience to stress and improve age-related cognitive decline in vulnerable populations.

Nutrition is a crucial component for maintenance of brain function and mental health. Accumulating evidence suggests that certain molecular compounds derived from diet can exert neuroprotective effects against chronic stress, and moreover improve important neuronal processes vulnerable to the stress response, such as plasticity and neurogenesis. Phospholipids are naturally occurring amphipathic molecules with promising potential to promote brain health. However, it is unclear whether phospholipids are able to modulate neuronal function directly under a stress-related context. In this study, we investigate the neuroprotective effects of phosphatidylcholine (PC), lysophosphatidylcholine (LPC), phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylglycerol (PG), phosphatidic acid (PA), sphingomyelin (SM) and cardiolipin (CL) against corticosterone (CORT)-induced cytotoxicity in primary cultured rat cortical neurons. In addition, we examine their capacity to modulate proliferation and differentiation of hippocampal neural progenitor cells (NPCs). We show that PS, PG and PE can reverse CORT-induced cytotoxicity and neuronal depletion in cortical cells. On the other hand, phospholipid exposure was unable to prevent the decrease of Bdnf expression produced by CORT. Interestingly, PS was able to increase hippocampal NPCs neurosphere size, and PE elicited a significant increase in astrocytic differentiation in hippocampal NPCs. Together, these results indicate that specific phospholipids protect cortical cells against CORT-induced cytotoxicity and improve proliferation and astrocytic differentiation in hippocampal NPCs, suggesting potential implications on neurodevelopmental and neuroprotective pathways relevant for stress-related disorders.

Hypertrophic protein-losing gastropathy. Menetrier disease. A clinical case Introduction: Menetrier disease is a rare disorder characterized by gastric foveolar hyperplasia associated with secondary protein loss. In children, this condition is presented as an edematous syndrome without renal or hepatic impairment and differs from the adult form by the constant presence of edema and spontaneous remission. It has been related to infections in most published cases, especially to Cytomegalovirus (CMV) and Helicobacter pylori (H. pylori). Objective: To present a pediatric case of Menetrier disease and endoscopic imaging obtained during the evolution of the patient. Case report: A five year old preschooler who presented a generalized edema, abdominal pain and malaise. After ruling out renal and hepatic pathologies, an upper en-doscopy revealed a severe compromise of the gastric mucosa. Urease test for H. pylori and IgG test for CMV resulted positive. Albumin and H2 receptor antagonists were administered. The evolution was favorable and the patient was discharged after 14 days; 8 month follow-up endoscopy showed no abnormalities. Conclu-sion: The medical profile and endoscopy are enough evidence to suggest the diagnosis of hypertrophic protein-losing gastropathy. Further studies need to be developed that include a considerable number of patients to assess their association with CMV or H. pylori infections, as these viruses are very common in our population.(Key words: Menetrier disease, Menetrier, hypertrophic gastropathy, endoscopy in children).Rev Chil Pediatr 2014; 85 (1): 80-85RESUMENIntroduccion: La enfermedad de Menetrier es una entidad clinica rara, de etiologia desconocida, que se ca-racteriza por hiperplasia foveolar gastrica asociada a perdida secundaria de proteinas. En ninos, se presenta

Este artigo descreve uma experiência no ensino de projeto de processadores e sistemas microprocessados em uma disciplina teórico-prática de Sistemas, Processadores e Periféricos, para os cursos de graduação em Engenharia Elétrica, Engenharia de Controle e Automação e Engenharia de Sistemas da Universidade Federal de Minas Gerais (UFMG). Pretende-se mostrar como tem sido desenvolvida essa disciplina por meio da utilização das metodologias ativas de ensino (Orientada para Projetos) e a construção de material didático, norteada por essa metodologia. Considera-se uma abordagem de proposta de trabalhos práticos, motivando os alunos a adquirir conhecimentos sólidos por meio do material didático desenvolvido e apresentando suas próprias soluções de projeto, em vez da simples repetição de experimentos predeterminados. Os resultados observados são maior motivação e participação nas aulas, pesquisa dos conteúdos dos trabalhos em diversas fontes além dos livros didáticos e interação dos alunos da disciplina na procura de soluções adequadas aos trabalhos propostos.

Este trabalho mostra a análise de estabilidade para pequenos sinais de um sistema CA composto de vários inversores de tensão conectados em paralelo sem a presença de uma barra infinita. O controle de cada unidade inversora é baseado nas curvas características frequência versus potência ativa e tensão versus potência reativa, o qual não depende da comunicação entre as respectivas unidades de controle. Os resultados de simulação e experimentais comprovam a eficácia do modelo para pequenos sinais, facilitando os estudos de estabilidade do sistema. This paper presents the small signal analysis for parallel connnected inverters in stand-alone AC supply systems. The control technique of the inverters is based on frequency and voltage droops, which depends on the local variable measurements and do not need control interconnections. Simulation and experimental results show that system is well represented by the small signal model, which becomes stability studies easier.

This paper presents a small-signal analysis for parallel-connected inverters in stand-alone AC supply systems. The control technique of the inverters is based on frequency and voltage droops, which depends on the local variable measurements and does not need control interconnections. Simulation and experimental results show that the system is well represented by the small-signal model. Some root locus plots for the system are provided, which make the stability studies and design easier.

Ménétrier disease is a rare disorder characterized by gastric foveolar hyperplasia associated with secondary protein loss. In children, this condition is presented as an edematous syndrome without renal or hepatic impairment and differs from the adult form by the constant presence of edema and spontaneous remission. It has been related to infections in most published cases, especially to Cytomegalovirus (CMV) and Helicobacter pylori (H. pylori).To present a pediatric case of Ménétrier disease and endoscopic imaging obtained during the evolution of the patient.A five year old preschooler who presented a generalized edema, abdominal pain and malaise. After ruling out renal and hepatic pathologies, an upper endoscopy revealed a severe compromise of the gastric mucosa. Urease test for H. pylori and IgG test for CMV resulted positive. Albumin and H2 receptor antagonists were administered. The evolution was favorable and the patient was discharged after 14 days; 8 month follow-up endoscopy showed no abnormalities.The medical profile and endoscopy are enough evidence to suggest the diagnosis of hypertrophic protein-losing gastropathy. Further studies need to be developed that include a considerable number of patients to assess their association with CMV or H. pylori infections, as these viruses are very common in our population.

Teleost fish gills represent a considerable exchange surface with the external environment. Our group has previously presented evidence regarding the expression and detection of regulatory and effector molecules of the immune response system in salmonid gills. This observation is supported by increased macrophage infiltration in this organ. However, it is probable that gill epithelial tissue also possesses immunomodulatory abilities. The RTgill-W1 cell line presents an epithelial morphology and forms tight monolayer sheets, thereby representing a key model for understanding how fish gills are able to identify the presence of microorganisms and trigger the immune response. The aim of this study was to determine if the epithelial cells of salmonid gills are able to detect pathogen associated molecular patterns (PAMPS) through intracellular receptors, using the activation of intracellular signaling intermediaries to secrete immunomodulatory cytokines. The RTgill-W1 line expressed TNFα, IL-1β, and type 1 IFN in response to stimulation with LPS and Poly I:C. Knockdown of the NOD-like receptor (NLRC5) with siRNA (siNLRC5) decreased the expression of IFN-α/β in RTgill-W1 cells treated with Poly I:C. In turn, knockdown of the TRIM protein (siTRIM3) in cells treated with LPS resulted in the downregulation of TNFα and IL-1β. Additionally, the cell line responded to rIFN-γ stimulation by upregulating TRIM8, a facilitator of the JAK/STAT pathway. These data provide interesting evidence regarding the immune function of the gill epithelium. This studied was financed through Proyecto FONDECYT N° 1140797

This article describes a teaching experience in processor design and microprocessor systems in a theoretical and pratical course called Systems, Processors and Peripherals for the Undergraduate courses in Electrical Engineering, Control and Automation and Systems Engineering at UFMG. It is intended to show how this course has been developed through the use of active teaching methodologies (project-oriented) and building materials, guided by this methodology. It is considered a proposed approach to practical work, motivating students to acquire their own knowledge through teaching materials developed and presented their own design solutions, rather than the simple repetition of predeter-mined tasks. The results observed are increased motivation and participation in class, search the contents of the work in a variety of sources beyond the textbooks and students' interaction in the course of finding adequate solutions to the proposed work. Este artigo descreve uma experiência no ensino de projeto de processadores e sistemas microprocessados em uma disciplina teórico-prática de Sistemas, Processadores e Periféricos, para os cursos de graduação em Engenharia Elétrica, Engenharia de Controle e Automação e Engenharia de Sistemas da Universidade Federal de Minas Gerais (UFMG). Pretende-se mostrar como tem sido desenvolvida essa disciplina por meio da utilização das metodologias ativas de ensino (Orientada para Projetos) e a construção de material didático, norteada por essa metodologia. Considera-se uma abordagem de proposta de trabalhos práticos, motivando os alunos a adquirir conhecimentos sólidos por meio do material didático desenvolvido e apresentando suas próprias soluções de projeto, em vez da simples repetição de experimentos predeterminados. Os resultados observados são maior motivação e participação nas aulas, pesquisa dos conteúdos dos trabalhos em diversas fontes além dos livros didáticos e interação dos alunos da disciplina na procura de soluções adequadas aos trabalhos propostos.

Este artigo descreve uma experiência no ensino de projeto de processadores e sistemas microprocessados em uma disciplina teórico-prática de Sistemas, Processadores e Periféricos, para os cursos de graduação em Engenharia Elétrica, Engenharia de Controle e Automação e Engenharia de Sistemas da Universidade Federal de Minas Gerais (UFMG). Pretende-se mostrar como tem sido desenvolvida essa disciplina por meio da utilização das metodologias ativas de ensino (Orientada para Projetos) e a construção de material didático, norteada por essa metodologia. Considera-se uma abordagem de proposta de trabalhos práticos, motivando os alunos a adquirir conhecimentos sólidos por meio do material didático desenvolvido e apresentando suas próprias soluções de projeto, em vez da simples repetição de experimentos predeterminados. Os resultados observados são maior motivação e participação nas aulas, pesquisa dos conteúdos dos trabalhos em diversas fontes além dos livros didáticos e interação dos alunos da disciplina na procura de soluções adequadas aos trabalhos propostos.

Değirmencioğlu, Serdar (Arel Author), Brief descriptions of cross-national problem events by 1349 organizational employees from many nations were content analyzed. Contrasts between individualistic and collectivistic behaviors were much more strongly predicted by variations in business context (e.g., language spoken and hierarchical relations between the parties involved) than by a measure of nation-level in-group collectivism practices. Respondents from individualist nations emphasized performance goals and task focus, whereas those from collectivist nations emphasized personal aspects of work relations more strongly. Task-focused behavioral esponses to problems were uniformly associated with positive outcome, whereas the outcome of emotional responses interacted significantly with individualism–collectivism practices. The results are interpreted in terms of collectivists’ greater attention to context.

En el presente estudio fue evaluada la actividad antimicrobiana in vitro de cuatro muestras de mieles producidas en nuestro pais, sobre los recuentos de estreptococos del grupo mutans, en escolares con alto riesgo de caries dental. Se obtuvieron muestras de saliva de 20 escolares, con edades entre 12 y 14 anos, pertenecientes a la ciudad de Temuco, Region de La Araucania (Chile). El recuento de estreptococos del grupo mutans en saliva fue estimado por el metodo microbiologico semi-cuantitativo Linoscreen®. La evaluacion de la accion antibacteriana de la miel se realizo en 9 escolares que presentaron los recuentos mas elevados de estreptococos del grupo mutans, utilizando concentraciones de miel entre 5% y 35%. Los datos mostraron que el 100% de los ninos analizados poseian colonias de estreptococos del grupo mutans en su saliva. Ademas, se verifico que el 45% (9/20) de los escolares se encontraba en la categoria de alta actividad cariogenica. Con este estudio, tambien se comprobo que la miel de abejas posee actividad antimicrobiana sobre las bacterias estreptococos del grupo mutans y que no existian diferencias significativas entre las 4 mieles utilizadas, con relacion a su capacidad antibacteriana (p>0.05). Por otra parte, este estudio tambien permitio demostrar que a mayor concentracion de miel utilizada mayor era la reduccion de las bacterias cariogenicas. En conclusion, en el presente estudio se demostro la accion antimicrobiana in vitro de la miel sobre los recuentos de bacterias cariogenicas estreptococos del grupo mutans. Sin embargo, seran necesarios futuros estudios para identificar y evaluar los componentes de la miel de abejas, responsables de esta propiedad.

El presente artículo aborda el tópico de la secularización como concepto, tesis, teoría, paradigma, proceso socioempírico y dogma/fe, intentando dar cuenta de los profusos debates registrados en el marco de las ciencias sociales de los últimos 20 años en torno a la vitalidad/ agonía y porvenir de sus postulados en cada una de dichas acepciones. Asumiendo la excepcionalidad de Europa occidental, se destaca y discute una serie de desconfirmaciones empíricas -con particular atención en América Latina- que parecen venir minando lo que fuera el "paradigma de la secularización", generando una interesante dinámica entre autores críticos y defensores, así como un conjunto de interrogantes en torno al futuro de la noción de secularización.This article examines the topic of secularization as concept, thesis, theory, paradigm, socio-empirical process and dogma/faith, thus attempting to revise the profusión of debates which have taken place within the framework of social sciences during the last 20 years about the vitality/agony and future of these many faces of secularization. Presuming that Western Europe is an exception, Unlike the exceptional case of Western Europe, a series of empirical disconfirmations is highlighted and discussed -with particular attention paid to Latin America-that seem to undermine what has been the "paradigm of secularization". This generated and interesting dynamic between the critics and defending authors of such a paradigm, as well as a set of questions about the future of the secularization.

A control technique based on frequency and voltage droop is used to control a single phase inverter connected to a stiff AC system. The small signal analysis of the system is presented, which allows the behavior of the system to be obtained for the functions of frequency and voltage droop. Simulation results and experimental results for the different frequency and voltage droop are presented.

que dan a conocer un caso deasociacion de sindrome de Laurence-Moon-Biedl con cavum septi pellucidi,hasta 1950 habrian sido publicados 10 ca-sos en la Republica Argentina. En Chile,la presente observacion clfnica es la pri-mera en publicarse.Los sintomas mas comunes de esta afec-cion son: la obesidad, la retinitis pigmen-taria, la polisindactilia, el retardo mentaly el hipogenitalismo. Tambien se ha des-crito una marcada incidencia familiar,que aparece en el 80% de los casos, Estossignos que pueden ser considerados comocardinalss, no estan siempre todos pre-sentes y frecuentemente falta uno o dosde ellos o son reemplazados por otras ano-malias. Asi Reilly y Lisser

Este artigo descreve uma experiência no ensino de projeto de processadores e sistemas microprocessados em uma disciplina teórico-prática de Sistemas, Processadores e Periféricos, para os cursos de graduação em Engenharia Elétrica, Engenharia de Controle e Automação e Engenharia de Sistemas da Universidade Federal de Minas Gerais (UFMG). Pretende-se mostrar como tem sido desenvolvida essa disciplina por meio da utilização das metodologias ativas de ensino (Orientada para Projetos) e a construção de material didático, norteada por essa metodologia. Considera-se uma abordagem de proposta de trabalhos práticos, motivando os alunos a adquirir conhecimentos sólidos por meio do material didático desenvolvido e apresentando suas próprias soluções de projeto, em vez da simples repetição de experimentos predeterminados. Os resultados observados são maior motivação e participação nas aulas, pesquisa dos conteúdos dos trabalhos em diversas fontes além dos livros didáticos e interação dos alunos da disciplina na procura de soluções adequadas aos trabalhos propostos.

A crescente participação da geração distribuída com o uso de tecnologias de informação no sistema elétrico de potência tem causado mudanças na forma como a energia é gerada e consumida. Neste contexto, as microrredes e nanorredes surgem com uma solução capaz de proporcionar uma maior integração da geração distribuída à rede elétrica. Como os sistemas de distribuição atuais são predominantemente em corrente alternada (c.a.), as microrredes c.a. são amplamente pesquisadas e sua implementação acarreta pequenas modificações nas redes atuais. Contundo, o aumento significativo de cargas em corrente contínua (c.c.) nas redes c.a. aliado ao fato de que algumas fontes de energia renováveis possuem tensão c.c. incentivam o desenvolvimento de sistemas de distribuição em c.c. Essa nova configuração necessita de modificações significativas no sistema de distribuição atual. Com isso, a microrrede híbrida c.a.-c.c. surge como solução que combina vantagens dos sistemas c.a e c.c. com poucas modificações nas redes atuais. Neste trabalho são apresentados os principais tipos de microrredes híbridas encontrados na literatura e as técnicas de controle usualmente empregadas para operação paralela dos conversores. A necessidade de regulação de tensão em ambos os barramentos da microrrede híbrida, o compartilhamento de carga e o controle do fluxo de potência levam à utilização de estrutura de controle hierárquico. Este trabalho foi realizado no laboratório do Grupo de Eletrônica de Potência da Universidade Federal de Minas Gerais (GEP/UFMG) e apresenta o estudo e o desenvolvimento de um protótipo de nanorrede híbrida com capacidade de operar tanto em modo conectado quanto ilhado da rede elétrica, além de realizar a transição entre esses modos. Serão discutidos temas acerca da arquitetura hierárquica de controle da microrrede. Em especial, o trabalho trata da coordenação de conversores formadores de rede, definida pelo nível secundário, propondo duas técnicas inéditas de controle distribuído para mitigar o desvio de tensão causado pelo controle droop e promover a correção no compartilhamento proporcional de potência. Neste trabalho, a operação da nanorrede e as técnicas de controle propostas são validades através de simulações e experimentalmente. The increasing participation of distributed generation using information technologies in the electrical power system has caused changes in the way energy is generated and consumed. In this context, microgrids and nanogrids come up as a solution capable of providing greater integration of distributed generation to the electrical grid. As the current distribution systems are predominantly in Alternating Current (ac), the ac microgrids are widely researched and their implementation entails minor modifications in the current power grids. However, the significant increase in Direct Current (dc) loads in the ac power systems added to the fact that some renewable energy sources have dc voltage cause the development of dc distribution systems. This new configuration requires major changes to the current distribution system. Thus, the hybrid ac-dc microgrids emerges as a solution that combines the ac and dc advantages with few changes to the current electrical grids. This work presents the main types of hybrid microgrids found in the literature and the control techniques usually employed for parallel operation of the converters. The need for voltage regulation on both buses of the hybrid microgrid, load sharing and power flow control lead to the use of a hierarchical control structure. This work was carried out in the laboratory of the Grupo de Eletrônica de Potência at Universidade Federal de Minas Gerais (GEP/UFMG) and presents the study and development of a hybrid nanogrid prototype capable of operating in both connected and isolated modes of the electrical grid, in addition to making the transition between these modes. Themes about the hierarchical control structure of the microgrid will be discussed. In particular, the work deals with the coordination of network-forming converters, defined by the secondary level, proposing two novel distributed control techniques based on consensus algorithm to mitigate the voltage deviation caused by the droop control and promote the correction in the proportional power sharing. In this work, the proposed nanogrid operation and control techniques are validated through simulations and experimentally.

As UPSs (Uninterruptible Power Supplies) são equipamentos que garantem a alimentação sustentada de energia elétrica, com elevados níveis de qualidade e confiabilidade. Esses equipamentos são comumente empregados no suprimento de sistemas com missão crítica, em que distúrbios ou a indisponibilidade de energia elétrica podem acarretar perdas financeiras e/ou humanas (e.g., hospitais, bancos, datacenters e entre outros). Na literatura, diversas topologias de UPSs monofásicas foram propostas em alternativa à configuração clássica com transformadores, como solução para o aumento de rendimento e de densidade de potência e para a redução de custo. Dentre essas alternativas, as variações de UPS sem transformadores (transformerless) se mostram mais viáveis por dispensarem a necessidade de transformadores de baixa frequência, que representam uma fração significativa da massa e do volume total da UPS convencional. Nesse contexto, a UPS de três braços é reportada como alternativa para o projeto de UPSs sem transformador de baixa e média potência, com elevado rendimento e densidade de potência. Esse trabalho pretendeu avaliar o desempenho da topologia de três braços, no tocante ao rendimento e densidade de potência mássica e volumétrica. Uma proposta alternativa de ligação do banco de baterias, na entrada dessa UPS, também foi analisada. Ademais, protótipos de calorímetro direto de caixa simples e de dupla caixa foram construídos para medição das perdas em conversores. A metodologia adotada se baseou na comparação de projetos de UPSs de três braços com dispositivos semicondutores de vários materiais (silício, carbeto de silício e nitreto de gálio), tecnologias (IGBTs, MOSFETs e arranjo cascode com MOSFET de silício e HFET de GaN) e encapsulamentos (TO-247-3, TO-247-4, SMT top e HSOF-8). Simulações da UPS completa em MATLAB/Simulink validaram as estratégias adotadas para controle, modulação, sincronismo e comutação entre os estados normal e energia armazenada, bem como a proposta de conexão do banco de baterias sugerida neste trabalho. Essas simulações também demonstraram a operação da UPS em modo assíncrono ou síncrono, i.e., com frequência de saída desacoplada ou não daquela da rede elétrica. Os detalhes da construção, dimensionamento e calibração dos calorímetros construídos foram apresentados. Os resultados experimentais preliminares dos protótipos desenvolvidos também foram discutidos. An UPS is an equipment that provides continuous power supply, with high levels of quality and reliability. This equipment is usually employed for supplying mission-critical systems, in which disturbances or power interruptions can cause financial losses or damages (e.g., hospitals, bank offices, datacenters, etc.). In the literature, several topologies have been proposed as an alternative to the classical configuration with low-frequency transformers, as a solution for enhancing efficiency and power density and decreasing overall costs. Among these alternatives, transformerless solutions (i.e., without transformers) become promising, as they do not require low-frequency transformers which comprise an expressive part of overall weight and volume of a conventional UPS. In this context, a three-arm UPS is often reported as a suitable transformerless topology for low- and medium-power single-phase UPS, with high efficiency and power density. This thesis aimed to assess the performance of the single-phase three-arm UPS, concerning efficiency and power density. An alternative connection for battery set was also evaluated. Furthermore, a prototype of a direct double-jacketed calorimeter was built in order to measure the losses of power converters. The adopted methodology was based on the comparison of several three-arm UPS designs with devices made by different materials (silicon, silicon carbide and gallium nitride) and of various technologies (IGBTs, MOSFETs and cascode configuration with silicon MOSFET and GaN HFET) and packages (TO-247-3, TO-247-4, SMT top and HSOF-8). The UPS was also simulated in MATLAB/Simulink, in order to validate the modulation strategies and the techniques adopted for controlling, synchronizing and commutating between the normal state and the stored energy mode, as well as the alternative connection of the battery set. These simulations demonstrated the operation in asynchronous and synchronous modes, i.e., with an output frequency that can be decoupled or not to the means frequency. All details related to construction, dimensioning and calibration of the double-jacketed calorimeter were also presented. Preliminary experimental results were also discussed in this thesis.

Desde o surgimento dos primeiros sistemas fotovoltaicos sua geração de energia é prejudicada por sombreamento parcial em conjunto com outras condições de incompatibilidade. Além disso, também criam mecanismos que degradam e aceleram o envelhecimento não uniforme do arranjo, fazendo com que dure bem menos do que o planejado. Muitas são as soluções propostas na literatura para este tipo de problema. Os conversores integrados são capazes de processar a potência de forma diferencial, aproveitando o máximo de potência disponível de cada módulo. Dentre estes conversores, existem os que processam apenas parte da potência, correspondente ao sombreamento parcial. Estes são conhecidos como desviadores de corrente e podem ser acionados apenas no momento da ocorrência do sombreamento parcial. Neste trabalho, é proposta uma nova arquitetura híbrida, aqui denominada PV-to-PV-to-Bus, que acumule vantagens de dimensionamento e operação de duas arquiteturas já consolidadas, PV-to-PV e PV-to-Bus. Esta arquitetura pode ser aplicada a diversos tipos de desviadores sejam capacitivos ou indutivos. Primeiramente, é feito um estudo dos desviadores PV-to-PV, e de seu dimensionamento. Sobre mesmas condições de irradiância solar, é mostrado que a arquitetura proposta, comparada a PV-toPV, possui menores níveis de corrente nos indutores e menor queda das tensões equalizadas. Ao final, são apresentados resultados comparativos de simulação e experimentos de um Desviador Buck-Boost Bidirecional para ambas as arquiteturas PV-to-PV e PV-to-PV-to-Bus. Também são mostrados resultados experimentais de forma a avaliar a metodologia de dimensionamento para uma string de dois módulos. A arquitetura proposta mostrou ter menores níveis de corrente e também tensões com menor diferença após a equalização, em relação à arquitetura PV-to-PV. Partial shading has always been an issue since the first photovoltaic systems operation. Since this is just one between many kinds of incompatibility conditions, partial shading not only affects the instantaneous generated power during its occurrence, but also the modules life-time, accelerating the degradation, even if only a part of one module is being shaded. Many are the solutions for this problem, like global maximum power point tracking techniques, modules reconfiguration and also differential power processing of each module. This last one is implemented using integrated converters of various types. Among the known converters, there is a type capable to process only the energy related to partial shading. They are known as current diverters and may be programmed to operate only in the occurrence of partial shading. The Current Diverters are divided in to architectures: PV-to-PV, that process power from module to module, and PV-to-Bus, that process power from each module to the string Bus. The PV-to-PV circuits present several advantages over PV-to-Bus circuits. However, they are affected by a phenomenon here called deviated current accumulation, which makes it difficult the operation and design of some of its elements. In this work, as a solution for this problem, a hybrid architecture, here called PV-to-PV-to-Bus, is proposed, and applicable for many types of circuits, rather capacitive or inductive. First, a study on PV-to-PV circuits and its design feature is made, and an approach to calculate its is proposed. Than, the effects of partial shading in voltages and currents are presented for both architectures, under the same conditions. The proposed circuit showed to be a better voltage equalizer, and with smaller current levels than the PV-to-PV circuits. At last, experimental results for a Buck-Boost Bidirectional are shown in to experiments, one to evaluate the proposed design approach, and the second to evaluate the proposed architecture. The proposed architecture shows results that proves smaller current and better voltage equalization than the PV-to-PV architecture.

A demanda por energia elétrica tem aumentado nos últimos anos, além da busca por novas fontes de energia para atender esse crescimento de forma não poluente e sustentável. Assim, as energias renováveis como a fotovoltaica e a eólica, tem ganhado posição de destaque no cenário energético mundial. O proposito deste trabalho é apresentar o projeto, construção e comissionamento de um conversor monofásico híbrido em ponte H multicelular entrelaçado para geração fotovoltaica e eólica de pequeno porte, com potência nominal de 11,7 kW. O sistema é composto por: i) dois arranjos fotovoltaicos de 5,1 kW cada que tem sua potência rastreada através de dois conversores Boost entrelaçados; ii) uma turbina eólica com gerador de imã permanente com potência de 1,5 kW, cuja potência é extraída através de um terceiro conversor Boost. A interface entre a geração e a rede elétrica é realizada por um inversor VSI entrelaçado de quatro braços via um ICT. O trabalho de dissertação apresenta os principais conceitos da geração fotovoltaica e eólica, modelagem dos principais elementos do sistema e as técnicas utilizadas para o controle e rastreamento da máxima potência do sistema. Por fim os resultados simulados e experimentais para o sistema desenvolvido são apresentados e discutidos. The demand for electricity has been increased in recent years, in addition to that, the search for new sources of energy to meet this growth in nonpolluting and sustainable way. Thus, renewable energies sources such photovoltaic and wind power has been gaining prominent position in the world energy scenario. The purpose of this work is to present the design, construction and commissioning of a single-phase hybrid H-bridge parallel multicell converter for photovoltaic and small wind generation, with nominal power of 11.7kW. The system consists of i) two photovoltaic arrays of 5.1kW each one, that have their maximum power point tracked by two interleaved Boost converters ii) a wind turbine with permanent magnet synchronous generator with nominal power of 1.5kW, whose the maximum power point is tracked by a third boost converter. The interface between the power generation system and the electrical grid is carried out by a four arms interleaved voltage source inverter, connected to ICT inductor. The present theses show the main concepts of photovoltaic and wind power generation, components modelling, used control techniques and systems maximum power point tracking. Finally, the simulated and experimental results for the developed system are present and discussed

As UPSs (Uninterruptible Power Supplies) de dupla conversão são equipamentos que proveem a alimentação segura e sustentada de subsistemas com missão crítica, em que os distúrbios oua interrupção no suprimento podem levar a perdas e danos. Esta dissertação objetiva comparar os rendimentos globais de UPSs trifásicas de dupla conversão nas topologias de dois níveis,com componentes de silício e de carbeto de silício (SiC) e de três níveis em arranjos NPC1 (Neutral-Point Clamped) e NPC2, com dispositivos de silício. A metodologia adotada se baseia na comparação de 80 projetos de UPSs de dupla conversão, com distintas especificações de tensão no barramento c.c., frequência de chaveamento e potência nominal. Para tanto, ferramentas de software com interface gráfica foram implementadas em MATLAB para estimar as perdas nos semicondutores e nos indutores dos filtros LCL de entrada e LC de saída da UPS. As simulações das UPSs foram conduzidas no ambiente MATLAB/Simulink e incluem o controle dos estágios inversor e retificador. Para fins de validação experimental das estimativas teóricas de perdas, um protótipo de um conversor buck de 5; 5 kW foi construído e a potência dissipada neste circuito foi medida via wattímetro digital. Em seguida, um protótipo simples e de baixo custo de um calorímetro indireto série foi desenvolvido, para que as incertezas associadas às leituras de perdas fossem reduzidas. Os resultados de simulação indicam que a topologia NPC1 exibe maior rendimento global dentre as UPSs com componentes de silício, para a maior parte dos projetos deUPS avaliados. Ademais, as UPSs com SiC superam o desempenho da maioria das variações de silício em análise, o que acena para a viabilidade dos componentes de SiC para estas aplicações.Os resultados experimentais apontam para a concordância entre as estimativas de perdas e as medições via wattímetro. A efetividade do protótipo de calorímetro indireto série para a medição de perdas é demonstrada em ensaios com resistores de potência. Por fim, as técnicas propostas para a avaliação teórica de perdas podem ser estendidas para qualquer conversor estático e podem orientar o projeto de equipamentos mais eficientes e com maior densidade de potência. Double-conversion UPSs (Uninterruptible Power Supplies) are devices that provide safe and continuous supply to mission-critical systems, in which disturbances or interruptions in power supply can lead to losses or damages. This thesis aims to compare the energy efficiency performance of three-phase double-conversion UPS in two-level topologies, with silicon and silicon carbide (SiC) devices, and in three-level topologies in NPC1 (Neutral-Point Clamped) andNPC2 configurations, with silicon power modules. The adopted methodology is based on the comparison of 80 designs of double-conversion UPS, with several values of d.c. bus voltages,switching frequencies and rated power. In order to accomplish this goal, software tools with graphical interface were implemented in MATLAB, for semiconductor losses estimation and for inductor losses calculation in input and output LC and LCL filters. UPS simulations were performed in MATLAB/Simulink and include the inverter and rectifier control. For experimental validation of the theoretical results, a circuit of a 5.5 kW buck converter was built and power losses measurements were conducted with a digital wattmeter. Then, a simple and low cost indirect series calorimeter prototype was developed, in order to reduce the uncertainties in power losses measurement. Simulation results show that NPC1 topology exhibits the highest global efficiency among the silicon based UPSs, in most UPS designs. Furthermore, the SiC based UPSsmostly overcome the performance of silicon based UPSs, which shows the competiveness of SiC devices for UPS applications. Experimental results prove the agreement between theoretical and measured results using digital wattmeter. Preliminary tests with power resistors demonstrate the effectiveness of the indirect series calorimeter prototype. Lastly, the proposed techniques for losses evaluation could be extended for any power converter and could enhance equipment design regarding energy efficiency and power density.

Este trabalho desenvolve uma revisão bibliográfica sobre diferentes topologias de conversores estáticos cc-cc de energia com isolamento adequado a aplicação de máquinas de soldagem a arco elétrico. É explorada a possibilidade de operação em alta frequência de chaveamento tipo comutação dissipativa utilizando dispositivos de carbeto de silício associados com magnéticos de tecnologia planar. O objetivo é demonstrar novas possibilidades em aumento de densidade de potência, compactação, eficiência e redução de custo com foco nas máquinas de soldagem a arco elétrico. Nessa diretiva, foi feito o projeto de um conversor cc-cc aplicado a máquina de solda multi-processo com potência de 3,9kW e corrente de 150A/26V, operando em 200kHz de frequência de chaveamento. Resultados experimentais em potência nominal e sobre carga são demonstrados. This work developes a bibliography review over different isolated DC-DC static converter power topologies suitable to application of arc welding machines. Possibilities of high switching frequency of SiC in hard switching mode are explored linked by magnetics planar technology. The objective is demonstrate new possibilities of the main features desired in power electronics segment that are high power density, size reduction, efficiency, cost reduction with this technology. In this direction, was realized a project of multi-process arc welding machine of 3.9kW power and 150A/26V currente capacity in 200 kHz working switching frequency. Experimental results in rated power and over load are demonstrated.

O aumento da demanda de energia elétrica e a necessidade de diversificar a matriz elétrica nacional trazem desafios e oportunidades para novas tecnologias nos processos de geração, transmissão e distribuição de energia. Dessa forma, as redes inteligentes de energia ou Smart Grids introduzem novos conceitos para o sistema elétrico, como as microrredes e as nanorredes. A nanorrede do tipo c.c. apresenta inúmeras vantagens em relação a uma nanorrede c.a.. A interface da nanorrede com a rede elétrica é realizada via um conversor de potência bidirecional o qual pode operar com qualquer fator de potência do lado c.a., e também pode responder a solicitações de demanda para comercialização de potência ativa. No presente trabalho de dissertação é realizado o estudo, o projeto e a montagem de um conversor bidirecional c.c.-c.a. monofásico de dois estágios, o qual atua como interface entre o barramento c.c. de uma nanorrede e a rede elétrica. Um estudo introdutório sobre nanorredes é apresentado. Diferentes topologias de conversores bidirecionais c.c.-c.a. sem transformadores são discutidas, sendo proposto a utilização da topologia NPC (Neutral Point Clamped) para o primeiro estágio do conversor e da topologia retificador síncrono para o segundo estágio do conversor. São estudados os quatro blocos funcionais do conversor com o objetivo de otimizar a densidade de potência. É apresentada uma estratégia de controle a qual possibilita o conversor injetar na rede elétrica uma corrente com forma de onda senoidal, com baixa distorção harmônica e fator de potência quase unitário. Com essa estratégia de controle, o conversor também é capaz de regular a tensão no barramento c.c. da nanorrede, admitindose uma pequena ondulação. Um método para detecção de ilhamento é apresentado, o qual é baseado na instabilidade de um PLL (Phase Locked Loop) aprimorado. The increased demand for electricity and the need to diversify the national electric matrix pose challenges and opportunities for new technologies in the generation, transmission and distribution of energy. Thus, smart energy networks or Smart Grids introduces new concepts to the electrical system, as microgrids and nanogrids. The dc nanogrid presents several advantages compared to an ac nanogrid. The nanogrid interface with the power grid is performed via a bi-directional power converter which can operate with any power factor in the ac side, and can also respond to requests for demand for marketing active power. In this thesis, a study, a design and an assembly of a single phase ac-dc bi-directional converter with two stages is performed, which acts as an interface between the nanogrid dc bus and the power grid. An introductory study about the nanogrid is presented. Different transformerless bi-directional ac-dc converters topologies are presented and discussed. It is proposed the use of the NPC (Neutral Point Clamped) topology for the first stage of the converter and the synchronous rectifier topology for the second stage of the converter. The functional blocks of the converter are studied with the bias to optimize the power density. It is presented a control strategy which enables the converter to inject a sinusoidal waveform current in the power grid with low harmonic distortion and near unity power factor. With this control strategy, the converter is also able to regulate the nanogrid dc bus voltage, assuming a small ripple. A method for islanding detection is presented, which is based on the instability of an enhanced PLL (Phase Locked Loop).

Devido ao aumento da demanda de energia elétrica para atender as necessidades cres-centes da sociedade e suprir as deficiências na geração, existe a demanda de se aumentar a participação das fontes renováveis de energia na matriz de eletricidade dada as restrições am-bientais. Dessa forma, as redes inteligentes de energia introduzem novos conceitos para o sis-tema elétrico, tal como as microrredes e nanorredes, as quais possuem sua geração baseada em fontes renováveis como eólica e solar. A produção de energia por essas fontes depende de fatores naturais, como o sol e o vento, o que leva à necessidade de sistemas de armazenamen-to de energia em bancos de baterias para garantir o fornecimento ininterrupto à nanorrede. Nesse trabalho, um estudo acerca de um conversor bidirecional c.c.-c.c. para interface entre sistemas de armazenamento de energia e barramento c.c. da nanorrede é realizado com a finalidade de que se possa manter a tensão no barramento c.c. regulada através do controle do fluxo de potência entre o sistema de armazenamento e barramento. A estrutura da nanorrede é apresentada, o estudo das topologias de conversores bidirecionais c.c.-c.c. é realizado possibi-litando a utilização do conversor Dual-Active-Bridge como mecanismo de interface entre o barramento c.c. e o sistema de baterias. Os métodos de modulação para controle de potência são estudados para a seleção do método de modulação mais adequado para a implementação experimental do conversor. Uma técnica de controle é proposta para que se possa atender ao fluxo bidirecional de potência e o processo de carregamento de baterias. Due to the increase of electricity demand to attend the growing needs of society and to compensate deficiencies of the energy generation, there is a need to enhance the participation of renewable energy resources into the energy matrix, since conventional fossil energy sources will not be able to supply this increasing energy demand owing to environmental con-strains. The smart grids introduce new concepts for the electrical power system, such as mi-cro and nanogris, in which the power generation is based on renewable resources like wind and solar power. The energy production in such systems depends on natural factors as solar irradiation and wind speed, what requires the employment of local energy storage systems, based normally on batteries, in order to ensure uninterrupted power supply to the local power system, or nanogrid. In this thesis, a study is conducted over a bidirectional dc-dc converter, which inter-faces the energy storage system and the main dc bus of a dc nanogrid. This power converter will control the power flow between the nanogrid and the battery banks, hence providing a regulated dc voltage on the nanogrid side. The dc nanogrid architecture is presented and the bidirectional dc-dc converter topologies revised, thus enabling the selection of the Dual Ac-tive Bridge structure as the interface converter. A set of modulation techniques were studied in order to decide which one is more suitable for employment on an experimental converter. A control method is proposed which provides means for ensuring a regulated voltage on the nanogrid main dc bus and concomitantly respects the battery bank charging restrictions.

Lâmpadas de vapor de sódio de alta pressão são um tipo de lâmpada de alta intensidade de descarga. Suas características as tornam adequadas para uso em sistemas de iluminação de ambientes externos e industriais. No entanto, essas lâmpadas são dispositivos complexos, principalmente devido a seu comportamento de impedância incremental negativa. Sendo assim, modelos altamente fidedignos desses dispositivos possuem uma grande quantidade devariáveis e parâmetros a serem determinados. Neste trabalho é apresentado um estudo comparativo de modelos no domínio do tempopara uma lâmpada de vapor sódio de alta pressão de 70W. Quatro circuitos equivalentes de diferentes complexidades de obtenção e construção têm suas performances comparadas para operação com injeção de terceira harmônica para evitar o fenômeno da ressonância acústica. Esses modelos são a lâmpada como uma resistência linear pura, um modelo empírico que é se constituí em uma equação derivada de um conjunto de medições de correntes e tensões eficazespara diversas potências de saída (Ferrero), um fundamentado na ideia de que uma descarga no gás se comporta aproximadamente como um resistor de coeficiente negativo de temperatura (Mader-Horn) e um que se baseia nas equações de balanço de energia do sistema e incluia queda de tensão dinâmica sobre o eletrodo e os efeitos de histerese das características V-I da lâmpada (Yan). Para validação e qualificação desses modelos, são utilizados dados experimentais da lâmpada operando em regime permanente com e sem a injeção de harmônicas.O reator eletrônico utilizado para levantar dados experimentais de corrente e tensão na lâmpada é composto por vários elementos. O filtro de entrada atua para corrigir a distorção da corrente na rede, suprimir interferência de rádio frequência e remover picos na alimentação. Oretificador, combinado com o filtro capacitivo, converte a tensão de alimentação alternada em uma tensão contínua. O inversor ressonante converte a tensão contínua em uma tensão de alta frequência e proporciona a ignição da lâmpada, além de eliminar o efeito estroboscópio de baixa frequência e o flicker. Um conversor tipo Boost é colocado como estágio intermediário entre o retificador e o inversor ressonante para correção do fator de potência. O controle do índice de modulação, realizado com o auxílio de um microprocessador, permite o uso de um pequeno indutor elevador (o equipamento fica com menores dimensões e peso). Após devidamente escrutinados, o modelo considerado de melhor performance considerando o comportamento da lâmpada tanto em baixas quanto em altas frequências foi o modeloYan. A partir desse circuito equivalente é levantado um modelo da lâmpada no domínio da frequência. Por sua vez, a partir dessa função de transferência final, é proposta uma estratégia de controle de corrente circulante em regime permanente na lâmpada composta por uma malha de potência para fornecimento da referência de corrente e uma malha de controle de corrente. O sistema em malha fechada é, então, simulado em diferentes pontos de operação para averiguação de seu desempenho e verificação do efetivo controle de corrente desejado. Uma estratégia de controle de tensão durante a fase de aquecimento da lâmpada também é proposta. High pressure sodium lamps are a type of high intensity discharge lamp. Its qualities make them adequate to be used in external and industrial lighting systems. However, such lamps are complex devices, mostly due to their negative incremental impedance behavior. Thus, highly faithful models of these devices have a large number of variables and parameters to be determined. In this work, a comparative study of a 70W high pressure sodium lamp time domain models is presented. Four equivalent circuits of different obtainability and building complexitieshave their performance compared for operation with third harmonic injection in order to avoid the acoustic resonance phenomenon. This models are the lamp as a pure linear resistance, an empiric model constituted by an equation derived of a set of RMS current and voltage measurements for several output power values (Ferrero), one based on the idea that a discharge column in the gas behaves approximately as a negative temperature coefficient resistor (Mader-Horn) and one based in the system energy balance equations while including in its formulation the dynamic electrode voltage drop and the hysteresis effects of the V-I characteristics of the lamp (Yan). To validate and characterize these models, experimental data of the lamp operating in steady state with and without harmonic injection is used. The electronic ballast used to gather experimental lamp current and voltage data consists of numerous elements. The input filter act to correct the network current distortion, suppress radio frequency interference and remove feeding spikes. The rectifier, combined with the capacitive filter, converts the alternated feeding voltage into a continuous voltage. The resonant inverter converts the continuous voltage into a high frequency voltage and enables the lamp ignition, also eliminating the low frequency strobe effect and flicker. A boost converter is inserted as an intermediate stage between the rectifier and the resonant inverter to allow power factor correction. The modulation index control, performed with the help of a microprocessor,allows the use of a small step-up inductor (the equipment ends up smaller and lighter). After being duly scrutinized, the model considered to have shown best performance considering the lamp behavior in both low and high frequencies was the Yan model. From this equivalent circuit, a frequency domain lamp model is found. In turn, from this final transferfunction, a lamp circulating steady state current control strategy is proposed composed by a power control loop to provide current reference and a current control loop. The closed loop system is, therefore, simulated with different operation points to ascertain its performance andverify the effective desired current control. A voltage control strategy during the lamp warmup phase is also proposed.