Cost-effective practical developments of high-performance and multi-functional UPS with new system configurations and their specific control implementations

The state-of-the art UPS which is composed of power conversion and inversion conditioning and processing configuration incorporating simple half-bridge active AC/DC converter and half-bridge PWM inverter circuits with no electrical isolation power stage has attracted special interest in computer and telecommunication systems. This UPS topology is highly cost-effective and suitable for power conversion efficiency improvement and volumetric size and weight reduction. However, this attractive UPS topology has a significant disadvantage that storage batteries have to be connected to the high DC link bus. In order to provide an acceptable DC voltage link with storage batteries, an improved type of application-specific UPS topologies have been proposed and investigated from a practical point of view. This paper presents a nonelectrical isolated prototype of UPS circuit topologies incorporating converter circuits for battery bank interface and their related specific multi-functional control strategies, which are composed of cost-effective IGBT modules. The operating principles of power conversion topologies and control strategies are described. The experimental results of a unique and high-performance UPS topology with battery bank interface circuit are illustrated for 3 kVA UPS application and compared with the latest conventional UPS with storage batteries connected to the high DC voltage bus