Non-isolated single phase UPS based on step-up converters

This paper presents a single uninterruptible power supply topology that overcomes some drawbacks of the previous reported ones. Among the desired features of the proposed UPS topology are: small number of semiconductors, low battery voltage, flexibility for the selection of the input and output voltages, common neutral between the incoming AC line and the load. The proposed UPS is composed of three bi-directional step-up converters, where both the incoming AC line and the load are connected in differential mode across the output terminals of these step-up converters. A current limiter is introduced to improve robustness and reliability of the proposed UPS. In this paper, analysis and experimental results for both the line operating mode and backup mode are presented. In addition, the current limiter operation is experimentally verified under several load transient conditions