Feasible single-phase UPS incorporating switched-mode PFC rectifier with high-frequency transformer link

Abstract

The general purpose high performance single phase UPS topologies are indispensable for the considerable reduction of harmonic current components in a.c. mains as well as the realization of unity power factor correction (PFC). In particular, the single phase PFC rectifier with a high-frequency isolation transformer link has some feasible advantages as an electrically isolated a.c./d.c. conversion circuit for small scale UPS. This UPS is capable of eliminating harmonic currents and realizing an isolation between a.c. input and d.c. output power stage as well as matching the d.c. side input voltage of the PWM inverter by means of incorporating a compact high-frequency transformer into high-frequency intermediate stage. Electrically isolated PFC rectifiers designed for 2 kVA, 3 kVA and 5 kVA UPSs are put into practical use as new topological versions. This paper presents a circuit configuration of high-frequency link PFC rectifier for small scale UPS, its operating principle and related control strategy. The steady state and dynamic state performances of three power classes of UPSs which incorporate this type of PFC converter are evaluated from a practical point of view.