Cross-phase voltage sag compensator for three-phase 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 them 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 capacitors 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 be 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. Beside the single-phase voltage sags, the compensator can compensate for any balanced and unbalanced voltage sag accompanied with phase jump. The proposed voltage sag compensator is validated using digital simulation case studies with PSCAD/EMTDC software and experimental results from a laboratory-scale prototype.

► A new three-phase voltage sag compensator is introduced. ► The compensator uses cross-phase direct ac–ac converters requiring no intermediate elements. ► The proposed compensator compensates the faulted phase using the healthy phases. ► It can compensate for different types of voltage sags and phase jumps and one phase outages. ► The operation of the proposed compensator is validated by experimental results.