Study on smoothing effects of PV outputs — Method with autocorrelation function

Photovoltaic power generation systems (PVs) are significantly increasing in recent years. On the other hand, large-scale penetration of PVs causes concerns in keeping supply-and-demand balance of a power system because output power of PVs shows considerable fluctuations due to weather conditions. To assess the impacts on the balance, fluctuation characteristics of PVs should be examined for the case of large-scale penetration of PVs. Since the fluctuations of total output of many PVs dispersed across an area are dominated by smoothing effects, it is essential to figure out the factors that govern the smoothing effects. This paper proposes a method to analyze solar irradiance data with an autocorrelation function to examine their fluctuation characteristic. Applying the method to the solar irradiance data measured at an observation site within one kilometer for four seasons, the paper discusses the relationship between the fluctuations of solar irradiances and the smoothing effects. The results implicate that horizontal scale of clouds governs the smoothing effects.