An iZVT auxiliary circuit commutation applied to a double conversion uninterruptible power supply

In this paper it is proposed an iZVT circuit using the concept of integrated ZVT auxiliary commutation circuits (iACC) applied to a double-conversion uninterruptible power supply, operating with a Three-Level PWM Full Bridge inverter. This study has two objectives: to reduce the number of additional components necessary to obtain soft-switching as well as to minimize the circulating reactive energy by means of reusing the reactive energy of one commutation to assist another one, so that the efficiency improves without penalizing the cost. Thus, it is obtained ZVT commutation for all the main switches and ZCS and ZVS for the auxiliary switches. To demonstrate the technique of iACC applied to a double-conversion UPS, experimental results of the system rated at 1.2 kW - 70 kHz are presented. The efficiency comparison between iZVT UPS and the ZVT UPS is shown, justifying the proposed iZVT.