This thesis describes two quadrant bidirectional soft switching converter for ultracapacitor interface circuits. The total efficiency of energy storage system in terms of size and cost can be increased by a combination of batteries and ultracapacitors. The required system energy is provided by battery, while ultracapacitor is used at high load power pulses. Ultracapacitor voltage changes during charge and discharge modes, therefore an interface circuit is required between ultracapacitor and battery. This interface circuit must have good efficiency, while providing bidirectional power conversion and protecting ultracapacitor from immediate discharge. In this thesis, ZVT and ZCT techniques are applied to increase efficiency. The proposed converter acts as a buck ZCT to charge ultracapacitor. On the other hand, it acts as a boost ZVT to discharge ultracapacitor. A laboratory prototype converter is designed and realized for hybrid vehicle applications. Experimental results presented, confirm theoretical and simulation results.
