Transient performance of a single-stage UPS system for single-phase trapezoidal-shaped AC voltage supplies

A high performance single-stage UPS system for single-phase AC power supply systems is presented. The topology generates a trapezoidal-shaped load voltage that is synchronized with the AC supply; therefore, a small DC link capacitor is required. These features lead to a high input power factor (0.94 at nominal voltage) and due to the single-stage structure, high efficiency (93% at nominal voltage) and high reliability are achieved. In this paper, the dynamic performance of the UPS system is analyzed under different transient conditions, specifically: (a) supply to battery; (b) battery to supply transition; (c) load transient; and (d) supply/battery voltage transient. The input power factor and efficiency as a function of the load and supply voltage are also included. The dynamic and static evaluations are performed on a 1 kVA UPS system.