This paper presents an enhanced centralized voltage control method utilizing real-time satellite-observed solar radiation data for distribution networks with PVs. Conventional centralized voltage control methods cannot prevent voltage deviation between data acquisition periods when large voltage fluctuation occurs because of PV output fluctuation. This is because the tap positions are determined regardless of PV output although there is few risk of large voltage rise/drop when PV generates full/no power. The proposed method forecasts voltage fluctuation width by utilizing the real time solar radiation data, which are acquired every 30 minutes at grid points with a 1 km resolution, and determines tap positions of an on-load tap changer and step voltage regulators to maximize the minimum voltage margin between the forecasted voltage and the voltage limits. The numerical simulation utilizing actual measured PV output profile and solar radiation data will show that the proposed method enhanced the voltage control effectiveness.