Active Power Line Compensation Applied to a Three-Phase Line Interactive UPS System Using SRF Method

This paper presents an application of an active compensation method, applied to a three-phase line-interactive uninterruptible power supply (UPS) system with series and parallel active power line conditioning capabilities. The control strategy, employed to achieve the reference currents for the UPS system, is based on the synchronous reference frame (SRF) method. The reference currents, obtained from the SRF algorithm, are used to compensate the reactive power and to eliminate harmonic currents generated from non-linear loads. The current SRF-based controller does not have the task of compensating fundamental zero sequence component of the neutral current, due to unbalanced loads or unbalance source voltages conditions. Thus, the efficiency of the three-phase UPS system is increased when it is feeding unbalanced single-phase non-linear loads. Besides, a mode to control the active power flow through the series and parallel active power filters of the UPS system is presented