SUBSTATION INCLUDING ENERGY STORAGE SYSTEM, METHOD FOR ASSESSMENT OF CAPACITY OF THE SAME AND APPARATUS THEREFOR

Provided are a substation system including an energy storage device, a method of calculating capacity of the energy storage device, and a control apparatus for the same. The control apparatus may include a charge and discharge determination unit configured to determine a charge or discharge operation of an energy storage device based on whether a measured output value is within an output operation range; a forecast error determination unit configured to determine a ratio of a period in which the measured output value is out of the output operation range with respect to a total period; and a capacity determination unit configured to determine capacity of the energy storage device based on the ratio.