Modelagem e análise dinâmica de um sistema de conversão de energia eólica dotado de gerador síncrono de imã permanente utilizando a plataforma ATP

Human development requires a broad balance between ecological, social and economic factors in order to ensure its own sustainability. In this sense, the search for new sources of energy generation, with low deployment and operation costs, which cause the least possible impact to the environment, has been the focus of attention of all society segments. To do so, the reduction in exploration of fossil fuels and the encouragement of using renewable energy resources for distributed generation have proved interesting alternatives to the expansion of the energy matrix of various countries in the world. In this sense, the wind energy has acquired an increasingly significant role, presenting increasing rates of power grid penetration and highlighting technological innovations such as the use of permanent magnet synchronous generators (PMSG). In Brazil, this fact has also been noted and, as a result, the impact of the inclusion of this source in the distribution and sub-transmission power grid has been a major concern of utilities and agents connected to Brazilian electrical sector. Thus, it is relevant the development of appropriate computational tools that allow detailed predictive studies about the dynamic behavior of wind farms, either operating with isolated load, either connected to the main grid, taking also into account the implementation of control strategies for active/reactive power generation and the keeping of adequate levels of voltage and frequency. This work fits in this context since it comprises mathematical and computational developments of a complete wind energy conversion system (WECS) endowed with PMSG using time domain techniques of Alternative Transients Program (ATP), which prides itself a recognized reputation by scientific and academic communities as well as by electricity professionals in Brazil and elsewhere. The modeling procedures performed allowed the elaboration of blocks representing each of the elements of a real WECS, comprising the primary source (the wind), the wind turbine, the PMSG, the frequency converter, the step up transformer, the load composition and the power grid equivalent. Special attention is also given to the implementation of wind turbine control techniques, mainly the pitch control responsible for keeping the generator under the maximum power operation point, and the vector theory that aims at adjusting the active/reactive power flow between the wind turbine and the power grid. Several simulations are performed to investigate the dynamic behavior of the wind farm when subjected to different operating conditions and/or on the occurrence of wind intensity variations. The results have shown the effectiveness of both mathematical and computational modeling developed for the wind turbine and the associated controls.

Restrição externa, dependência estrutural de commodities primárias e o investimento direto externo no Brasil

As the beginning of the discussion about the reprimarization process of the Brazilian exportations, or about a deindustrialization process of the country foreign sales, this study purpose that the discussion, actually, should be about the existence of the commodities structural dependence as a way to face the foreign restrictions. Therefore the intention is to show that, historically, the way that the Brazilian economy has crossed for its development depends of the foreign capital, mainly in its way of Foreign Direct Investment (FDI), and in the balance generated by the primary products, which make us try to understand the impact of this capital for the equilibrium of the Brazilian Payment Balance and also for the economy. These points were discussed not only based on the Brazilian classic writers as Francisco Oliveira, Caio Prado Jr. and Celso Furtado, but also using the newest studies which contributes to point the causes and consequences of the external capital dependence in the actual scenario. The conclusions acquired in the end of the study, indicates the fact that the Brazilian specialization in products of low aggregated value is not recent. Brazil is, historically, a competitive country in primary products. At the same time, the country importation always was a pressure factor of the National Payments Balance, being composed by products with more aggregated value. According to some authors, this characteristic of the Brazilian Economy will be surpassed with the economic opening process, which will attract external capital making possible the modernization of the Brazilian productive sector. Therefore, we can claim that the FDI, in the way it has been inserted in the country, does not offer the opportunity to get out of the commodities dependence, as generators of the payment balances, because the country international competitive standard didn t get any important changes, keeping itself out of the step related to the global standard which has been intensified in products with more aggregated value. The changes in the national insertion standard directed to more technological products is really important to surpass the historical scenario of commodities dependence, making the country less vulnerable to external crisis.

Avaliação da incerteza de medição no Setor Médico-hospitalar

This study aims to evaluate the uncertainty associated with measurements made by aneroid sphygmomanometer, neonatal electronic balance and electrocautery. Therefore, were performing repeatability tests on all devices for the subsequent execution of normality tests using Shapiro-Wilk; identification of influencing factors that affect the measurement result of each measurement; proposition of mathematical models to calculate the measurement uncertainty associated with measuring evaluated for all equipament and calibration for neonatal electronic balance; evaluation of the measurement uncertainty; and development of a computer program in Java language to systematize the calibration uncertainty of estimates and measurement uncertainty. It was proposed and carried out 23 factorial design for aneroid sphygmomanometer order to investigate the effect of temperature factors, patient and operator and another 32 planning for electrocautery, where it investigated the effects of temperature factors and output electrical power. The expanded uncertainty associated with the measurement of blood pressure significantly reduced the extent of the patient classification tracks. In turn, the expanded uncertainty associated with the mass measurement with neonatal balance indicated a variation of about 1% in the dosage of medication to neonates. Analysis of variance (ANOVA) and the Turkey test indicated significant and indirectly proportional effects of temperature factor in cutting power values and clotting indicated by electrocautery and no significant effect of factors investigated for aneroid sphygmomanometer.