Bi-directional zero-current-switching approach applied for energy storage system using electric double layer capacitor

We have proposed the current-source energy capacitor system (CS-ECS) in our previous work, which consists of an electric double-layer capacitor (EDLC), current-source inverter, and bi-directional DC-DC converter (four-quadrant DC-DC converter). However, this system has low efficiency due to hard-switching losses. Improvements of efficiency and performance are indispensable to implement the proposed system. This paper proposes the soft-switched four-quadrant DC-DC converter with an simple L-C resonant circuit for CS-ECS. High efficiency of the proposed system is achieved based on zero-current switching (ZCS) since a insulated gate bipolar transistors (IGBTs) of that converter softly turns on and turns off by using current-mode resonance. In order to illustrate the operating principle of the proposed system, we analyze in detail through a theoretical approach and computer simulations with MATLAB/SIMULINK.