Elimination of voltage imbalance between the split capacitors in three-phase half-bridge switch-mode rectifiers

The voltage imbalance between the split capacitors in three-phase half-bridge switch-mode rectifiers is observed and the elimination of the imbalance is proposed in this paper. It is found that adding a DC bias to the source current of each phase can resolve the voltage imbalance problem. The elimination strategies are developed by thoroughly analyzing all possible conducting paths of the DC bias currents and their effect on the voltage imbalance. The proposed elimination control loop is implemented on a prototype system and the experiments show satisfactory results.