Analysis and design of a series voltage unbalance compensator based on a three-phase VSI operating with unbalanced switching functions

A series voltage compensator for three-phase unbalanced sources is presented and analyzed. The system, based on a three-phase voltage source inverter connected in series to the supply through a three-phase delta-wye power transformer, proves to be feasible and performs as expected. A 1.3 kVA prototype was built and tested with 10.75% of unbalance and 9.01% of magnitude error ( mod MF mod =0.909). The results showed a very good correlation with the expected performance, producing a balanced line-to-line load voltage with a low harmonic content (average THD=20%), without filter. The compensator required only 168.8 VA, which shows one of the main advantages of the compensator scheme proposed.<>