Novel topology of a line interactive UPS using PQR instantaneous power theory

Abstract

This work proposes a novel topology and control algorithm for a three-phase line-interactive UPS system with active power-line conditioning capability. This paper presents a simple and systematic control algorithm to regulate the source current and the load voltage of the proposed UPS system using PQR transformation. A parallel inverter operating as a controlled voltage source regulates the source current sinusoidal by controlling the applied voltage on an AC line inductor. The series inverter operating as a dynamic voltage restorer (DVR) compensates for the main source voltage and rides through the output load voltage to be balanced and harmonic-free. Both of the series and parallel inverters always act as controllable voltage sources independently, so that the three-phase output voltages can transfer seamlessly between normal mode and backup mode. The proposed UPS system has high operation efficiency and high usage of the converter capacity, and good endurance against voltage transients or EMI noise resulted from the mains. The feasibility of the proposed UPS system has been investigated and verified through computer simulations and experiments by a 60 kVA prototype UPS.