Patent ID: 8482155

Claim:
A power converting device for a renewable energy storage system, the power converting device comprising: a plurality of rechargeable batteries; a plurality of bidirectional converters respectively connected in parallel to the plurality of batteries; a plurality of direct current (DC) links connected in parallel to the plurality of bidirectional converters; a plurality of bidirectional inverters respectively connected in parallel to the plurality of DC links; an electric power system connected to the plurality of bidirectional inverters, the plurality of bidirectional inverters being selectably connected in series to the electric power system and configured to provide power to the electric power system; and a switch unit between the plurality of bidirectional inverters and the electric power system, the switch unit selectively connecting the plurality of bidirectional inverters in series to each other in a first state and in parallel to each other in a second state, wherein during discharging of the plurality of rechargeable batteries, the switch unit is in the first state which connects the plurality of bidirectional inverters in series to each other, and wherein during charging of the plurality of rechargeable batteries, the switch unit is in the second state which connects the plurality of bidirectional inverters in parallel to each other.