Compact Galvanic Isolated Modular Multilevel High Voltage DC/DC Transformer and its Control Scheme in Full DC System

With the large-scale development of renewable energy sources, the limitations of conventional alternative current collection and HVDC transmission schemes are becoming apparent. The DC collection and transmission scheme for renewable energy sources eliminates reactive power and power angle stability issues, and allows for transmission over much longer distances. It is a highly promising solution for the future renewable energy development in desert, Gobi, and arid regions. Under existing conditions, high voltage DC/DC transformers have become a crucial component of the full DC solution. To address this issue, this paper discussed the compact galvanic isolated modular multilevel high voltage DC/DC transformer (MMHVDCT) and its control scheme in full dc system. Case studies based on practical HVDC scenario are also given to demonstrate the effectiveness of the discussed DCT.