THREE-PHASE 15KVA UPS SYSTEM WITH POWER FACTOR CORRECTION AND HIGH FREQUENCY TRANSFORMER ISOLATION

This work proposes a double conversion three-phase uninterruptible power system (UPS) with power factor correction, and high frequency (HF) transformer isolation. Ifs 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 front-end converter is based on three single-phase chopper modules [1], and the dc/ac converter is composed by a three-phase inverter with an additional leg to mitigate the voltage unbalance inherent to the series connection of dc-link bus capacitors. 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 step-up stage. Principle of operation of the proposed system, implemented control strategy and experimental results obtained for a 15kVA prototype are presented.