A single-phase resonant snubber inverter with fixed timing control for a UPS

In a UPS, the output voltage of a single-phase inverter is filtered with an LC filter to provide a sinusoidal output voltage. Since this inverter has an inductive load like an inverter for a motor drive, topologies for ZVS inverters utilized for motor drives can also be applied in the UPS application. A single-phase resonant snubber inverter (RSI) for application in a UPS has been developed. Analysis of the RSI in a normalized state plane provided insight into the operation of this ZVS inverter. Based on this analysis, fixed timing control based on the direction of the current flowing through the inductor in the output filter was implemented to control the auxiliary switches in a prototype RSI. The direction of the inductor current was sensed using a secondary winding on the output filter inductor. Experimental results are provided for a 1 kW prototype RSI in a UPS.