Abstract: With the rapid development of voltage source converter based high voltage direct current (VSC-HVDC) transmission, dozens of VSC-HVDC projects with different voltage ratings have been built worldwide during the last decade. According to the development history of AC grids, it is an irresistible trend to develop large-scale HVDC grids. However, DC/DC converters must be utilized to act as DC transformers in HVDC grids. Therefore, highly efficient and low-cost high-voltage high-power DC/DC converter is currently one of the key fundamental techniques needed by the HVDC grids. In order to satisfy the technical requirements of interconnecting HVDC lines with different voltage ratings, this paper developed a series of capacitive energy transfer (CET) principle based DC/DC topologies by modifying the classic low-voltage DC/DC converters. The topology evolution rules and current commutation mechanism were presented. Compared to conventional DC/DC converter topologies, the CET topologies were able to reduce the component count, improve conversion efficiency, and reduce the weight and size of the converter. At last, simulation and experimental results validated the effectiveness of the CET principle based DC/DC converter.