Analysis of circulating energy into iZVT system: ZVT case study applied to a double conversion UPS

In this paper the circulating energy of an integrated auxiliary commutation circuit applied to a double-conversion uninterruptible power supply is analyzed. This analysis is based on a comparison between the circulating energy of Zero Voltage Transition (ZVT) and integrated Zero Voltage Transition (iZVT) in Auxiliary Commutation Circuits (ACC), both attached to the same double-conversion UPS. Two advantages are obtained in relation to the classic ACC by using the technique of integration of ACC: the minimization of the reactive circulating energy and the reduction in the number of additional components. Thus, in iZVT UPS, it is obtained ZVT commutation for all the main switches and Zero Current Switching (ZCS) or Zero Voltage Switching (ZVS) for the auxiliary switches, while for the classic ZVT all auxiliary switches do not operate with soft-switching. In this way, the efficiency is increased and the electromagnetic interference (EMI) is reduced. The experimental results of the system rated at 1.2 kW@70 kHz are presented.