Multiport Modular Multilevel Converter for DC Systems

Multiport HV DC-DC converters are required to facilitate future HVDC infrastructure with the ability to interconnect and manage power flow between multiple HVDC networks. Existing topologies offer limited modularity and scalability, making them difficult to implement in the fast-growing HVDC industry. In this paper, a multiport modular multilevel converter (MP-MMC) is proposed as the first truly modular multiport HV DC-DC converter. The MP-MMC is made up of multiple subconverters that can be controlled individually with de-centralized controllers, allowing easy reconfiguration and high reliability of the converter power circuit. The MP-MMC is compared with other prominent multiport HV DC-DC converters based on modularity, reliability, semiconductor effort, magnetics requirement, and fault-blocking performance. Operation and performance of the MP-MMC are verified by simulation.