Development of a single-phase half-bridge active power filter with the function of uninterruptible power supplies

Analysis and implementation or a single-phase half-bridgc active power filter with the function of uninterruptible power supplies is presented. The system provides the combined functions or battery bank energy storagc, power-factor compcnsation, harmonics elimination and unintcrruption of the power supply. When the utility is in normal operation, thc proposed system will not only supply DC power for battery charging, but also function as an active power filter for improving the power factor and reducing the current harmonics on the utility side. If the utility power fails. the proposed system will fLmction as an inverter immediately, to supply the battery power to the AC load. Analysis for the proposed system is given first, and a personal coinp~itcris then used to implement digitised control of the proposed system to facilitate experimental evaluations for a 1 kVA prototype. The feasibility and niulti-fLiiictional results obtained indicate that the proposed system can be realiscd by using a digital Yignal processor as the core controller for cost reduction and reliability enhancement.