Absiruci -A PWM voltage-source inverter is used in order toimprove the electrical characteristics of an isolated induction generator. The electronic converter allows to achieve a better system behavior in many aspects: voltage regulation, frequency stabilization and reactive power compensation. The PWM inverter dc voltage is the control variable of the generator speed govemor, therefore the system power balance and the generator voltage regulation is accomplished by the dc voltage control, which is exerted by the speed governor. Both simulation and experimental results demonstrated the system is stable, robust and an effective source of regulated three-phase voltages.0-7803-5160-6/99/$10.00 0 1999 IEEE.
This paper presents a methodology to calculate the value of Carter's factor for airgaps with polygonal slots. A numerical evaluation of the Schwarz-Christoffel transformation is performed using Genetic Algorithms. The methodology presented here extends Carter's method to airgaps with more complicated geometry. Some case studies compare the results of the developed methodology to Carter's results.
The forecasting of solar irradiance in photovoltaic power generation is an important tool for the integration of intermittent renewable energy sources (RES) in electrical utility grids. This study evaluates two machine learning (ML) algorithms for intraday solar irradiance forecasting: multigene genetic programming (MGGP) and the multilayer perceptron (MLP) artificial neural network (ANN). MGGP is an evolutionary algorithm white-box method and is a novel approach in the field. Persistence, MGGP and MLP were compared to forecast irradiance at six locations, within horizons from 15 to 120 min, in order to compare these methods based on a wide range of reliable results. The assessment of exogenous inputs indicates that the use of additional weather variables improves irradiance forecastability, resulting in improvements of 5.68% for mean absolute error (MAE) and 3.41% for root mean square error (RMSE). It was also verified that iterative predictions improve MGGP accuracy. The obtained results show that location, forecast horizon and error metric definition affect model accuracy dominance. Both Haurwitz and Ineichen clear sky models have been implemented, and the results denoted a low influence of these models in the prediction accuracy of multivariate ML forecasting. In a broad perspective, MGGP presented more accurate and robust results in single prediction cases, providing faster solutions, while ANN presented more accurate results for ensemble forecasting, although it presented higher complexity and requires additional computational effort.
The operating cost reduction of photovoltaic (PV) systems is an important way to increase its economic viability for stakeholders. In this study, an inverter sizing ratio (ISR) analysis is carried out in order to quantify its potential benefit in the context of building-integrated PV systems and PV distributed generation in the central region of Brazil. An algorithm was created to analyse the ISR considering 12 years of measured climate data and data provided by manufacturers of system components. Among three analytical methodologies discussed in this study, the power limitation analysis seems to be the best reference for design adjustments related to a specific location or energy market. By that, a potential reduction over 10% of levelised cost of energy can be achieved in case of varying ISR from the unity value (theoretical) to its new fitted value.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.