Very short term forecasting of solar radiation

Variations of solar irradiance are known to have a significant influence on electric power generation by solar energy systems. With high connection densities of PV system in the low voltage (LV) network, this might cause to degrade electric power quality. The present study describes a multiplicative ARMA models to generate instantaneous series of global irradiation. The data set used in this work corresponding to five minutes global irradiance data were recorded in a radiometric station located in south Spain (Córdoba) during a four years period (1994-1997). The development of these models is based on removing the annual periodicity and seasonal variation of solar radiation. The method proposed considers fitting an AR model to the data. The selection of the order of the model has been made on the basis of seven different criteria. The predicted values of solar radiation are compared with the observed data series and it was found that this approach leads to optimal predictions.