Line-Interactive UPS as Shunt Active Power Filter

This paper describes a newly proposed solution for using the line-interactive uninterruptible power supply (UPS) system as a shunt active power filter. An overview of active power filters topologies and control strategies for active power filters are presented. The proposed solution is compared to similar solutions. Supercapacitors are proposed as a replacement for capacitors, that are used in all similar solutions at DC side of bidirectional inverter/rectifier. Bidirectional half-bridge DC/DC converter with transformer is proposed for energy transfer between supercapacitors and batteries. Two operation modes of the proposed solution are given. First, while there is a mains supply and the device is working as a shunt active power filter. Second, when the mains supply fails and the device is working as a uninterruptible power supply. Simplified Widrow-Hoff algorithm based on Artificial Neural Network is used in first operation mode and sinusoidal PWM modulation is used in second operation mode as a control strategy for bidirectional inverter/converter. The simulation experiments are done with multiple nonlinear loads, i.e., inductive and capacitive loads, connected to the point of common coupling. Experimental results confirm the presumed functionality of the suggested line-interactive UPS system for both operation modes.