The present invention is a wind, a system for storing renewable energy, including solar, short period ESS (Energy Storage System) long and short period in the long-period ESS (Energy Storage System) energy storage comprising the system output according to the control method , the back surface of the long-period ESS current charge state of the current SOC (state of charge) is predetermined within the upper limit SOC with a lower limit SOC, the step of controlling the output of the long-period ESS based on the current SOC state of the short-period ESS, the long-cycle ESS If the current SOC is the upper limit SOC or more, when the predetermined said long-period ESS the step and the current SOC is lower SOC or less of the long-period ESS for controlling to discharge according to the discharge time, the control to advance the long-period ESS charged in a predetermined charging time It includes the step of. By, according to the present invention suppress the output fluctuation of the renewable energy from the renewable energy storage system, and provides a stable output, it is effective to avoid the rapid change in the system in advance.