Load compensation in four-wire electrical power systems

This work describes a methodology for power factor control and correction of the unbalanced currents in four-wire electric circuits. The methodology is based on the insertion of two compensation networks, one wye-grounded neutral and another in delta, in parallel to the load. The mathematical development has been proposed in previous work [3]. In this paper, however, the methodology was adapted to accept different power factors for the system to be compensated. on the other hand, the determination of the compensation susceptances is based on the instantaneous values of the load currents. The results are obtained using the MatLab - Simulink environment.

Design of fuzzy regulators with optimal initial conditions compensation

In almost all cases, the goal of the design of automatic control systems is to obtain the parameters of the controllers, which are described by differential equations. In general, the controller is artificially built and it is possible to update its initial conditions. In the design of optimal quadratic regulators, the initial conditions of the controller can be changed in an optimal way and they can improve the performance of the controlled system. Following this idea, a LNU-based design procedure to update the initial conditions of PI controllers, considering the nonlinear plant described by Takagi-Sugeno fuzzy models, is presented. The importance of the proposed method is that it also allows other specifications, such as, the decay rate and constraints on control input and output. The application in the control of an inverted pendulum illustrates the effectively of proposed method.

Real-time multi-sensors measurement system with temperature effects compensation for impedance-based structural health monitoring

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ventilatory compensation of the alkaline tide during digestion in the snake Boa constrictor

The increased metabolic rate during digestion is associated with changes in arterial acid-base parameters that are caused by gastric acid secretion (the 'alkaline tide'). Net transfer of HCl to the stomach lumen causes an increase in plasma HCO3- levels, but arterial pH does not change because of a ventilatory compensation that counters the metabolic alkalosis. It seems, therefore, that ventilation is controlled to preserve pH and not P-CO2, during the postprandial period. To investigate this possibility, we determined arterial acid-base parameters and the metabolic response to digestion in the snake Boa constrictor, where gastric acid secretion was inhibited pharmacologically by oral administration of omeprazole. The increase in oxygen consumption of omeprazole-treated snakes after ingestion of 30% of their own body mass was quantitatively similar to the response in untreated snakes, although the peak of the metabolic response occurred later (36 h versus 24 h). Untreated control animals exhibited a large increase in arterial plasma HCO3- concentration of approximately 12 mmol 1(-1), but arterial pH only increased by 0.12 pH units because of a simultaneous increase in arterial P-CO2 by about 10 mmHg. Omeprazole virtually abolished the changes in arterial pH and plasma HCO3- concentration during digestion and there was no increase in arterial P-CO2. The increased arterial P-CO2 during digestion is not caused, therefore, by the increased metabolism during digestion or a lower ventilatory responsiveness to ventilatory stimuli during a presumably relaxed state in digestion. Furthermore, the constant arterial P-CO2, in the absence of an alkaline tide, of omeprazole-treated snakes strongly suggests that pH rather than P-CO2 normally affects chemoreceptor activity and ventilatory drive.

The Influence of Solutes on the Enthalpy/Entropy Change of the Actinomycin D Binding to DNA: Hydration, Energy Compensation and Long-Range Deformation on DNA

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Respostas fisiológicas ao déficit hídrico em duas cultivares enxertadas de seringueira (RRIM 600 e GT 1) crescidas em campo

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Enthalpy-entropy compensation based on isotherms of mango

Dados de equilíbrio da umidade da polpa de manga foram determinados utilizando-se o método estático gravimétrico. As isotermas de adsorção e dessorção foram obtidas na faixa de 30-70 ºC e as atividades de água (a w) de 0,02 a 0,97. A utilização do modelo de GAB nos resultados experimentais, através da análise de regressão não linear, proporcionou um bom ajuste entre os dados experimentais e os valores calculados. O calor isostérico de sorção foi estimado a partir dos dados de equilíbrio de sorção, utilizando-se a equação de Clausius-Clayperon. Notou-se que os calores isostéricos de sorção crescem com o aumento da temperatura e pode ser bem ajustado através de uma relação exponencial. A teoria da compensação entalpia-entropia foi aplicada às isotermas de sorção e gráficos deltaH versus deltaS forneceram as temperaturas isocinéticas, indicando um processo de sorção entalpicamente controlado.

Effects of sire breed-grazing system and environmental parameters on the behaviour of beef calves just after birth

Effects of sire breed-grazing system and environmental factors on the first activities of high grade Nellore and crossbred Canchim x Nellore, Angus x Nellore, and Simmental x Nellore calves raised in intensive production systems and high grade Nellore calves raised in an extensive production system, after birth, were studied. During 2 years, 185 calves were observed from birth until the end of first suckling, and the following variables were estimated: duration of maternal attention (cow to calf) during the first 15 min after calving, latency to first attempt to stand up, latency to stand up, latency to first suckling, duration of first suckling and the interval from standing to suckling. Data were analyzed by least squares methods, with models that included fixed effects of year and time of the year of birth (March-April (early autumn) and May-June (late autumn)), sire breed-grazing system (Sy), sex of calf (Se), category of cow (primiparous and pluriparous), time of birth, Sy x Se, year x Sy and year x time of the year interactions and the covariates weight of calf, rainfall, air temperature and relative humidity in the day of birth. Calves born from 6:00 to 8:00 h presented the longest latencies to first stand up (40.3 +/- 5.1 min) and the shortest occur from 14:00 to 16:00 h (15.8 +/- 2.7 min) (P < 0.01). Primiparous cows provided longer attention toward the calf in the first 15 min after birth than pluriparous cows (13.0 +/- 0.7 min versus 11.1 +/- 0.5 min; P < 0.05). This attention was also shorter in earlier autumn (11.0 +/- 0.5 min) and longer in late autumn (13.1 +/- 0.8 min) (P < 0.05). Relative to sire breed-grazing system, Nellore calves raised intensively did take longer to stand and to suckle after birth as compared to crossbred calves also raised intensively (P < 0.01). However, grazing system did not affect (P > 0.05) any behaviour variable studied. As regard to sex differences, female calves did take less (P < 0.01) time to suckle after standing than male calves. Results showed that even purebred or crossbred Bos indicus calves in subtropical environmental need extra care when born on rainy days, especially during the first hours of the day. (C) 2006 Elsevier B.V. All rights reserved.

Water sorption enthalpy-entropy compensation based on isotherms of plum skin and pulp

The net isosteric heat and entropy of water sorption were calculated for plum, based on sorption isotherms obtained by the static gravimetric method at different temperatures (20 to 70 degrees C). The Guggenheim-Anderson-deBoer model was applied to the experimental data giving a good agreement between experimental and calculated values. The net isosteric heat of water sorption, estimated by applying Claussius-Clapeyron equation to sorption isotherms, was found to be different for plum skin and pulp, mainly at low moisture contents, and could be well adjusted by an empirical exponential relationship. Plots of enthalpy in contrast to entropy provided the isokinetic temperatures for skin and pulp, indicating an enthalpy-controlled sorption process. Thermodynamic data on water sorption for plums are not found in literature, as opposed to prunes for which the data are abundant.

Methodology for load compensation in four-wire electrical power systems based on instantaneous sampling

This work describes a methodology for power factor control and correction of the unbalanced currents in four-wire electric circuits. The methodology is based on the insertion of two compensation networks, one wye-grounded neutral and other in delta, in parallel to the load. The mathematical development has been proposed in previous work [3]. In this paper, however, the determination of the compensation susceptances is based on the instantaneous values of load currents. The results are obtained using the MatLab-Simulink enviroment

Possible shunt compensation strategies based on Conservative Power Theory

Considering the Conservative Power Theory (CPT), this paper proposes some novel compensation strategies for shunt passive or active devices. The CPT current decompositions result in several current terms (associated with specific physical phenomena), which were used for the definition of different selective current compensators, in terms of minimizing particular disturbing effects. Simulation results have been demonstrated in order to validate the possibilities and performance of the proposed strategies for single and three-phase four wired circuits.

Analysis and design of constant-frequency peak-current-controlled high-power-factor boost rectifier with slope compensation

This paper presents the analysis and the design of a peak-current-controlled high-power-factor boost rectifier, with slope compensation, operating at constant frequency. The input current shaping is achieved, with continuous inductor current mode, with no multiplier to generate a current reference. The resulting overall circuitry is very simple, in comparison with the average-current-controlled boost rectifier. Experimental results are presented, taken from a laboratory prototype rated at 370 W and operating at 67 kHz. The measured power factor was 0.99, with a input current THD equal to 5.6%, for an input voltage THD equal to 2.26%.