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 220V or 380V. 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 Ill. 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 15kVA prototype are presented.