METHOD FOR CONTROLLING ESS OUTPUT

A method of controlling output of an ESS depending on droop control according to frequency variation range of a power grid in the present invention may comprise steps of: monitoring the frequency variation range of the power grid; predicting frequency correction range resulting from regulation of an engine generator during a predetermined unit regulation time if the frequency variation range is determined to exceed a first reference value; controlling the output of the ESS with an output value determined by a frequency of the power grid according to a droop control algorithm set as a default if the predicted frequency correction range does not exceed a second reference value; and fixing the output of the ESS during the unit regulation time if the predicted frequency correction range exceeds the second reference value.