Dynamic Model of an Interleaved Modular Multilevel DC-DC Converter for MVDC and HVDC Systems

The first comprehensive dynamic state-space model of an interleaved DC-MMC is presented. The DC-MMC is one of a new class of non-isolated modular multilevel dc-dc converters that are rapidly gaining traction for deployment in MVDC and HVDC systems. A non-linear time-averaged model of a two string interleaved DC-MMC is derived that fully represents internal capacitor voltage dynamics and converter terminal dynamics. Simulation results verify the time-averaged model exactly captures the low-frequency dynamics of a full switched converter model implemented in PLECS. The model can be used for a variety of applications, for example, rapid time-domain simulation of the DC-MMC, study of internal cell power transfer mechanisms, and analysis of harmonics and circulating currents.