A novel active line conditioner for a three-phase system

A novel configuration for an active line conditioner is proposed for correcting voltage unbalances in a three-phase AC power system. The proposed system injects a correction voltage V_inj with proper magnitude and phase in one phase to guarantee balanced voltages at the load terminals. The negative voltage components in the input supply are effectively nullified by the injected voltage. The kVA requirement of the proposed active line conditioner is small, typically 3% for a 10% unbalance in the input supply. The dynamic cancellation of the negative sequence voltage component by the proposed scheme drastically improves the performance of induction-motor-type loads connected to a weak AC system. A thorough analysis of the scheme along with suitable design guides is presented. Selected experimental results on a laboratory prototype active line conditioner are detailed