A non-isolated UPS topology with 110 V/220 V input output voltage

A circuit configuration of a single phase non-isolated on-line uninterruptible power supply (UPS) with 110 V/220 V input output voltage rating is proposed, allowing the bypass operation even if the input voltage is different of the output voltage. The converter consists of an AC-DC/DC-DC three level boost converter combined with a double half bridge inverter. In this type of configuration, size, cost and efficiency are improved due to reduced number of switches and batteries, as well as no low frequency isolation transformer is required to realize bypass operation because of the common neutral connection. Both stages of the proposed circuit operate in high frequency, using a passive non-dissipative snubber circuit in the boost converter and IGBTs switches in the double half bridge inverter, with low conduction losses, low tail current and low switching losses. A simple and well-known control strategy is used and explained. Principle of operation and experimental results for a 2.6 kVA prototype are presented to demonstrate UPS performance