An appreciable and significant measure of interest is currently growing up for power dc-dc converters, modernly in the industries and the civilized society and associations. In present day’s the dc-dc converters are one of the most preferred and recommended choice for the use of medium and high power utilization functions in order to achieve the objective of electronic power conversion. High voltage AC-DC, DC-AC and DC-DC converters being the essential fundamental unit of the HVDC transmission system in order to coordinate and fulfill the requirements of the power generating stations, AC grid and loading stations. Modular multilevel converter (MMC) holds some remarkable features such as modular design, scalability, reliability, tolerance of failures and larger step up and step down ratio, that make it an essential and meaningful topology for HVDC system. This paper gives an evaluation and assessment over various configurations of higher voltage DC-DC MMCs; it’s working along with characteristic attributes. Furthermore it explains the modulation and control technique considered for DC-DC MMCs.