With the integration of renewable energies such as offshore wind farms and the constraints of development of transmission grids, High-Voltage Direct Current (HVDC) are developing. The concept of HVDC Meshed grid has emerged in the past decade to increase reliability and strengthen interconnections between different countries. Grid interconnections of existing HVDC lines are inherently complex for technical and technological reasons related to different voltage levels caused by a staggered grid design and ongoing technological evolution. It is necessary to introduce static converters to ensure interconnection. The operating principles of early HVDC DC/DC converter topologies are now well known but deeper analysis is still required to improve transient behaviour, and other promising topologies remain untapped. Moreover, no extensive work has been done on the integration and control of DC/DC converters in mesh DC grids, a key decisive factor for their wider deployment.