This paper presents the modeling and control of a DC/DC bidirectional converter suitable for medium voltage and power applications in Multi-Terminals HVDC (MT-HVDC) grids. Moreover its use as DC circuit-breaker is described. This is a new concept, against the contemporary studies of DC breakers, which could help for the implementation of MT-HVDC networks. The proposed multilevel topology is based on Dual Active Bridge (DAB). The overall control of the DC/DC converter is achieved by using a nonlinear control based in Lyapunov theory.