Power net system of a fuel cell and a method for controlling same

A power net system of a fuel cell, the power net system comprising:

• a fuel cell configured to generate electric power through a reaction of a fuel gas and an oxidation gas;
• batteries configured to be charged by the electric power generated by the fuel cell or be discharged to supply electric power;
• main lines electrically connecting the fuel cell and the batteries;
• main relays provided in the main lines and configured to open or allow electrical connections between the fuel cell and the batteries;
• COD lines branched from the main lines between the fuel cell and the main relays and provided with a COD device configured to consume input electric power and be immersed in a coolant that cools the fuel cell;
• COD relays provided in the COD lines and configured to open or allow electrical connections to the COD device through the COD lines;
• and
• a controller configured to control the main relays or the COD relays to supply electric power charged in the batteries to the fuel cell.