Concept proposal and test run results for a hybrid electric energy storage method of high power capacitor/large energy battery combination

Energy storage will be critically important for stabilizing grids with renewable energy power sources; therefore various kinds of high performance devices such as batteries and capacitors are being developed at present. In particular, Li-ion batteries exhibit high energy density, and Li-ion capacitors have high input/output power ability with almost zero self-discharge. The authors have proposed a BAttery/Capacitor Hybrid Energy Storage system (BACHES) which delivers wide-range charge/discharge power with a large capacity by Li-ion capacitors and batteries. In this paper, the authors show the conceptual details and the features of this system. Also, experimental equipment was manufactured as specifications of maximum power of 6kW for connection to a 380V bus. The fundamental performances of the system components of Li-ion capacitors, Li-ion batteries, and converters were evaluated in test runs. This study concluded that the system operates itself by sharing roles between the Li-ion capacitors and the Li-ion batteries according to the characteristics of each, and then can control the bus voltage within 1.2% and 4.4% drops under sudden 0.47kW and 1.8kW power losses, respectively.