Multiple feedback loop control strategy for UPS system having active filter ability

A simple uninterruptible power supply (UPS) configuration having active power filter ability (APF) is proposed in this paper. The proposed device can be operated in two modes, APF in normal operation and backup power modes in case of failure of the utility source. The proposed device has the advantages of only one power stage, compactness, high power factor and the total harmonic distortion performance is improved. Computer simulations and experimental results obtained from a low power model (50 VA) are carried out to verify the control strategy of system. Finally, the authors present the transient performance at the moment of the change of operation mode.