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The largest output fluctuation is an index used to quantify disturbance against a power grid caused by wind power plants and photovoltaic power generation systems connected to it. To develop its estimation method, we investigate the relationship between the largest output fluctuation and the standard deviation of a newly proposed stochastic variable derived from the output variation of photovoltaic power generation systems. Output fluctuation coefficients are defined and estimated using the measured data of photovoltaic power generation systems located at 52 places. An approximation formula is presented to predict correlation factors between the stochastic variables corresponding to photovoltaic power generation systems using distances between their locations. Finally it is shown that the largest output fluctuation of many photovoltaic power generation systems dispersed in a wide area is predictable by using the output fluctuation coefficients and the formula to approximate the correlation factors.

This paper describes the method for forecasting the cloud albedo as a basis study to estimate the irradiation by using geostationary meteorological satellite (GMS) images. A new procedure is also proposed to remove the effect of ground albedo, which disturbs the cloud movement analysis. The validity of the method for forecasting the cloud albedo was examined. The forecast probability was estimated as yearly 66.8% for one hour ahead, 58.5% for two hours ahead and 52.7% for three hours ahead at 20 sites in Japan. Results over 80% for one hour ahead at Sapporo were obtained. It seems reasonable to suppose that this method can be used only for a specific site and season.