A battery ZVT bi-directional charger for uninterruptible power supplies

This paper proposes a ZVT auxiliary commutation circuit applied to a universal input AC-DC system with a bi-directional converter for DC bus and battery bank interface. With the bi-directional converter it is possible to reduce the cost of the battery bank and virtually to eliminate both low and high frequency current ripple in the batteries. The proposed auxiliary commutation circuit controls the di/dt of the resonant process, allowing the utilization of slow diodes (intrinsic diodes of MOSFET's) in the bi-directional converter and, consequently, reducing the overall system cost. Moreover, a control system has developed and analyzed for the perfect operation of the proposed system. Experimental results based on a 580W prototype are presented to demonstrate the good performance of the proposed system.