Analysis of circulating energy for iZVT system: ZVT case study applied to a double conversion ups operating with FB PWM three-level inverter

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 commutations circuits (ACC), both attached to the same double-conversion UPS. Two advantages are obtained in relation to 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. The experimental results of the system rated at 1.2kW@70kHz are presented.