Contribuições ao método de rastreamento de máxima potência para sistemas fotovoltaicos

The scarcity of natural resources and the search for alternative energy sources promote a rapid change in the energy world. Among the renewable energy sources, solar energy is the most promising, presenting technology of greatest growth rate nowadays. Researchers around the world are seeking ways to facilitate their progress, developing technologies with higher efficiency and lower cost. As a contribution to global progress, this master thesis proposes the development of a strategy of maximum power tracking based on perturbation and observation method for photovoltaic systems. The proposed control strategy is based on active power balance of the system, with a reduced number of sensors. It also allows the PV system to act as a regulator of the power quality at the point of commom coupling (PCC), compensating the harmonic distortion and power factor of the current netw

Avaliação muscular respiratória: adaptação do mano vacuômetro nacional para a avaliação da pressão inspiratória nasal e nível de intensidade da ventilação voluntária máxima em sujeitos saudáveis

The clinical importance of evaluating the respiratory muscles with a variety of tests has been proposed by several studies, once that the combination of several tests would allow a better diagnosis and therefore, a better clinical follow of disorders of the respiratory muscles. This study aimed to evaluate the feasibility of adapting a national electronic manovacuometer to measure the nasal inspiratory pressure (study 1) and analyze the level of load intensity of maximum voluntary ventilation, as well as the variables that may influence this maneuver in healthy subjects (study 2). We studied 20 healthy subjects by a random evaluation of two measures of SNIP in different equipments: a national and an imported. In study 2 it was analyzed the intensity of the load of MVV test, change in pressure developed during the maneuver, the possible differences between genders, and the correlations between the flow developed in the test and the result of MVV. In study 1 it was found the average for both measures of nasal inspiratory pressures: 125 ± 42.4 cmH2O for the imported equipment and 131.7 ± 28.7 cmH2O for the national one. Pearson analysis showed a significant correlation between the average, with a coefficient r = 0.63. The average values showed no significant differences evaluated by paired t test (p> 0.05). In the Bland-Altman analysis it was found a BIAS = 7 cmH2O, SD 32.9 and a confidence interval of - 57.5 cmH2O up to 71.5 cmH2O. In the second study it was found significant differences between the genders in the air volume moved, being higher in males 150.9 ± 13.1 l / min vs 118.5 ± 15.7 L / min for (p = 0.0002, 95% CI 44.85 to 20:05). Regarding the inspiratory and expiratory loading, they were significantly higher in men than in women, peak inspiratory pressure (34.7 ± 5.3 cmH2O vs 19.5 ± 4.2 cmH2O, 95% CI - 18.0 to -12.3, p <0.0001), peak expiratory (33.8 vs. 23.1 ± 5.9 cmH2O ± 5.4 cmH2O, 95% CI -17.1 to - 4.6, p <0.0001), and the delta pressure (59.7 ± 10 cmH2O vs 36.8 ± 8.3 cmH2O, 95% CI 14.5 to 31.2, p <0.0002). The Pearson correlation showed that the flow generated by the maneuver is strongly correlated with the delta-expiratory pressure / inspiratory (r2= 0.83,R = 0.91, 95%IC 0.72 a 0.97 e p< 0.0001).Through these results we suggest that the national electronic manovacuometer is feasible and safe to perform the sniff test in healthy subjects. For the MVV, there are differences between the genders in the intensity of pressure developed during the maneuver. We found a load intensity considered low during the MVV, and found a strong correlation between the flow generated in the test and the delta pressure expiratory / inspiratory

Normalização de eletromiografia de superfície dos músculos respiratórios em sujeitos saudáveis: contração voluntária máxima máxima isométrica versus pressões respiratórias máximas

Aim : To evaluate and to standardize surface electromyography (sEMG) normalization procedures for respiratory muscles by comparing muscle activation during Maximal Voluntary Isometric Contraction (MVIC) and Maximal Respiratory Pressures (MIP, MEP and sniff test). Methods: Healthy subjects were evalua ted regarding demographics, spirometry and sEMG during the five maneuvers: sniff test, MIP , MEP and Maximal Voluntary Isometric C ontraction (MVIC) of RA, SCM and SC A . For electrode placement, skin was prepared with abrasion, followed by shaving in the foll owing regions for acquisition of el ectromyographic signals: (1) SC M: lower third of the distance between the mastoid process and t he sternoclavicular joint; (2) SC A : 5 cm to the right from the sternoclavicular joint and at this point, up to 2 cm; and (3 ) RA: the level of umbilicus, 4 cm to the right. In electromyographic variables analysis , the data normality was assessed by Shapiro - Wilk test. Comparisons among studied maneuvers were performed by Friedman Test and Dunn’s post - hoc for multiple comparisons a mong inspiratory maneuvers, and Mann Whitney test for expiratory maneuvers. Subgroups differences between genders were performed by Student's t test or Mann - Whitney test according to data normality. Results: 35 subjects participated in the study, b ut 5 we re excluded (BMI> 25 kg/ m²). Sample consisted of 30 subjects (1 5 women), mean age 27.3±7.43 years, BMI 22.2 ± 1.69 kg/m² and spirometric indices within normal limits. Specific MVIC for SCM, SCA and RA showed the highest RMS. When we grouped sample into gender we found no difference among RMS values for the studied SCM maneuvers, while for SCA, MVIC SCM / SCA was the one with the highest RMS and for RA, MVIC RA in men. Once considering women, MVIC SCM/SCA showed the highest RMS for SCM, SCA and MVIC RA showed t he highest value for RA. Conclusion: MVIC for SCM, SCA and RA muscles showed the highest RMS values. When comparing RMS between the studied groups, there was no significant difference between men and women.