A power converting device, such as one used in an energy storage apparatus, comprises a first input terminal to receive a first DC voltage from a battery, a second input terminal to receive a second DC voltage from a power generation device, a switching module including a plurality of upper arm switching elements and a plurality of lower arm switching elements, and to output DC voltage to a DC link by switching the first DC voltage or the second DC voltage, and, a DC link capacitor disposed at the DC link, wherein at least some of the plurality of lower arm switching elements of the switching module operate in a power generation mode of the power generation device, and at least some of the plurality of upper arm switching elements of the switching module operate in a charging mode of the battery.