Analysis and Design for Paralleled Three-port DC/DC Converters with Democratic Current Sharing Control

This paper presents a current sharing (CS) control structure for three-port DC/DC converters. Unlike regular two-port converters, three-port converters necessitate that two of three ports to have CS control simultaneously so that the third port achieves CS by default. The parallel operation of three-port converters for space applications requires a reliable CS structure to provide uniform current distribution among the modules. Both output port CS and battery port CS are achieved by paralleling CS loop and voltage regulation loop together according to the democratically elected maximum current reference. Stability is the main challenge for three-port paralleled systems as the added CS loops should not interact with abundance of control loops. Decoupled network and bandwidth limitation assumption are applied to ensure minimum loop interactions. Small signal analysis is applied to assess CS performance and judge system stability. The proposed CS structure is tested and verified by an experimental prototype.