In　this　paper,　a　novel　bidirectional　modular　dc-dc　converter　(BMC)　with　unipolar　and　bipolar　structure　for　dc　networks　interconnection　is　proposed.　Compared　with　traditional　dc　grid-connecting　converters,　the　proposed　converter　can　realizes　high　voltage　gain　with　a　transformerless　structure　and　reduce　the　voltage　stress　across　switches.　Then,　to　solve　the　unbalanced　current　problem　among　power　units　in　the　BMC,　a　submodular　structure　is　introduced.　The　control　system　was　optimized　for　grid-connection　applications　by　introducing　the　phase-interval　operation　between　submodules　to　reduce　the　current　and　voltage　ripple　in　both　sides.　Besides,　the　control　system　can　provide　various　control　strategies,　including　output　voltage　control,　voltage　gain　control　and　power　control　to　maintain　the　voltage　level　or　keep　a　constant　voltage　gain　of　the　networks　and　performing　precise　power　control.　Finally,　simulations　of　both　sub-modular　unipolar　BMC　and　bipolar　BMC　were　implemented,　and　a　1-kW　experimental　3-level　unipolar　prototype　was　developed.　©　2018　IEEE.