Three-phase UPS with high power factor and high frequency transformer isolation

This work proposes an double conversion three-phase uninterruptible power system (UPS) with power factor correction, high frequency (HF) transformer isolation, and suitable for operation with line-to-line input voltages equal to 220 V or 380 V. For both input voltages, the proposed converter has almost the same efficiency processing the same output power. The structure is composed by single-phase chopper modules, single-phase boost modules, and one three-phase inverter . The relevant features are soft commutation of the controlled switches in the chopper stage, simple control strategy that can be implemented with well-known integrated circuits (IC), and the use of few batteries in series due to the same reference of the step-up stages. Principle of operation of the proposed system, implemented control strategy and experimental results obtained for a 15 kVA prototype are presented.