Switched-mode PFC rectifier with high-frequency transformer link for high-power density single phase UPS

The general purpose of single-phase UPS topologies are indispensable for the considerable reduction of harmonic current components in AC mains as well as realization of unity power factor correction (PFC). In particular, the single phase PFC rectifier with a high-frequency isolation transformer link has some advantages as an electrically-isolated AC/DC conversion circuit for small scale UPS. This UPS is capable of eliminating harmonic currents, leak current components and realizing an isolation between AC input and DC output power stage as well as matching the DC voltage of the PWM inverter by means of incorporating a compact high frequency transformer into high-frequency intermediate state. Three types of isolated PFC rectifiers designed for 2 kVA, 3 kVA and 5 kVA-UPSs are put into practical use respectively, as new topology. This paper presents a high-frequency link PFC rectifier, its related operating principle and control strategy, together with the steady-state and dynamic state performances of these types of UPSs developed from a practical point of view