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.

Estratégias de trabalho com blogs no ensino de geometria em turmas de 5° ano do ensino fundamental

This paper presents a survey conducted through collaborative work, which took place in a suburb school in the city of Uberlandia-MG. The research is characterized as case study and has a qualitative approach. Had the objective to look for different strategies of teaching and learning through the use of technology in pedagogical practice. Regarding the methodology in this research, we analyzed the work with the support of blogs, whose pages were used for student records and discussions directed to the geometry content. The students who were attending the fifth (5th) year of elementary school were invited to participate in this project. However, the research subjects were only those students who accepted the invitation to participate in the study through statement signed by parents. The project was developed with 30 students in the second half of 2014 and another 30 in the first half of 2015. The physical space at school, where most of the project activities were done was at the computer lab. In the process of compiling the data, at school, the following instruments were used: field notes produced by the entire project team, photographs and footage of the activities produced in the computer lab and in classroom (recorded by the research team) questionnaires, interviews, virtual space records: the blogs. The results of this research mainly focused on the analysis of the fifth year student‟s productions records in blogs. Regarding the conclusion, the research has shown that blogs, software and differentiated dynamic studies attracted the student‟s attention, leaving them mostly instigated by the unknown. Gradually, students built their own knowledge from their mistakes and successes. The entire work process enabled the computer lab to be an environment that is used not just to solving computerized and tedious drills. The blogs production work in groups, developed in students the reading and writing of both the mother language as symbols and mathematical nomenclature. The interaction between students became noticeable throughout the project, since it provided the student‟s personal growth, respect, tolerance and mutual cooperation. In this sense, we concluded that the project greatly contributed to the students' literacy process in the mother language, mathematics and computer literacy.