DC-DC converters are an important element for the future development of high voltage direct current (HVDC) grids. This paper presents a new dc-dc converter for the interconnection between different grid topologies. In particular, one elementary converter can interconnect an asymmetric monopole with a symmetric monopole. The use of two elementary converters allows the interconnection between a bipole and a symmetric monopole keeping the inherent redundancy of the bipole in case of a fault on that line. The converter is analyzed and sized for a proposed a case study. The converter is simulated in a Simulink-Matlab environment. The results prove the adequate performance of the control strategy during the power exchanges between the lines. A fault on the bipole is simulated showing the uninterrupted power transfer between the healthy pole and the symmetric monopole line bipole redundancy).