A reconfigurable uninterruptible power supply system for multiple power quality applications

A novel topology of an uninterruptible power supply (UPS) system is presented in this paper. The proposed UPS system presents the advantages of high power conversion efficiency as well as active front-end filtering which ensures unity input power factor (reactive power compensation) and low input total harmonic distortion (harmonic power compensation) in the voltages and currents. In addition, this UPS possess dynamic voltage sag compensation capabilities, hence eliminates any series transformer or boost converter which is normally used in conjunction with traditional stand-alone UPS systems. Meanwhile, during the backup (battery) mode of operation, this UPS has the capability of providing grid isolation without any backward power feed into the faulted utility gird, thus eliminates the needs of circuit breaker or static switch. In addition, it has the desirable characteristics of making seamless transition from normal to backup mode during power failures and vice versa, as well as providing controlled voltage charging at the dc bus link. The proposed UPS is also impervious to load variations, which enables it to operate under nonlinear load condition. Lastly, the circuit structure is simple, light weight, and can be implemented at a low cost using the standard commercial available components. A complete set of simulation as well as experimental results based on a 1 kW test prototype of the proposed UPS are presented here to demonstrate its viability and efficacy.