Three-phase cross-phase voltage sag compensator to compensate balanced/unbalanced voltage sags and phase outages in distribution systems

Voltage sags are one of the most important and frequent problems in distribution systems. Voltage sags lead to huge financial losses all over the world which makes it more important for sensitive load centers. In this paper a three-phase voltage sag compensator is proposed. The proposed voltage sag compensator is based on the ac-ac conversion eliminating the energy storage elements and dc link capacitor in the conventional voltage sag compensators such as dynamic voltage restorers (DVRs). The proposed topology in this paper energizes the compensator of each phase from the other two phases. Regarding that the Single-phase voltage sags are the most frequent types of voltage sags, the faulted phase will supplied by the two healthy phases in the most cases of voltage sags. This results in a more successful operation under very deep single-phase voltage sags. Even if one phase is lost, the proposed compensator will continue to supply all three phases of the sensitive load. The proposed voltage sag compensator is validated using digital simulation case studies with PSCAD/EMTDC software.