Apparatus for storing power and method of controlling the same

A power storage apparatus comprising:

• a bi-directional inverter connected between a first node and a second node connected to a power grid and a load, the bi-directional inverter converting a direct current (DC) voltage supplied from the first node to an alternating current (AC) voltage and outputting the AC voltage to the second node, the bi-directional inverter converting an AC voltage supplied from the power grid to a DC voltage and outputting the DC voltage to the first node;
• at least one battery cell;
• a battery management unit for detecting a remaining amount of power in the at least one battery cell and controlling charging/discharging of the at least one battery cell;
• a bi-directional converter connected between the battery management unit and the first node, the bi-directional converter converting a DC voltage supplied from the at least one battery cell to another DC voltage and outputting the another DC voltage to the bi-directional inverter via the first node, the bi-directional converter converting a DC voltage supplied from the bi-directional inverter to another DC voltage and outputting the another DC voltage to the at least one battery cell;
• and
• a central controller performing a control operation for charging the at least one battery cell with power supplied from the power grid, the central controller controlling the battery management unit, the bi-directional converter, and the bi-directional inverter so as to supply power stored in the at least one battery cell to the power grid, the central controller blocking power supply from the at least one battery cell to the power grid when the remaining amount of power of the at least one battery cell is lower than a reference level.