Common-Mode Current Reduction of Paralleled Dual Converters for Bipolar DC Distribution

Asymmetrical operation is a main challenge for the application of bipolar dc distribution systems. As a promising solution, paralleled dual converters balance the dc pole voltages without the penalties of increased power ratings by integrating a center-tapped transformer. The interleaving operation of dual converters could realize the harmonics cancellation of neutral line current, which is elaborated by harmonics distribution analysis presented in this paper. Moreover, phase shifting strategy is used to offer an additional degree-of-freedom (DoF), the resultant 2DoF modulation strategy is able to significantly suppress the common-mode (CM) current, which could reduce the size of CM choke and improve power density of converter. The validity and benefit of 2DoF strategy for dual converters are verified by both simulation and experimental results.