The present disclosure relates to an energy storage system for managing power of a system and a DC power distribution network linked with the system. In one embodiment, the system comprises a first converter connected between the system and the DC power distribution network so as to control voltage of the DC power distribution network; a second converter connected to the DC power distribution network; a battery which is connected to the second converter and in which a charging/discharging operation is controlled by the second converter; a third converter connected to the DC power distribution network; an emergency generator which is connected to the third converter and in which a power is controlled by the third converter; a fourth converter connected to the DC power distribution network; and a first load which is connected to the fourth converter and in which a voltage is controlled by the fourth converter.