A Modular Multilevel DC/DC Converter with Series-Arm Structure for MVDC Grids

This article proposes a novel modular multilevel dc/dc converter with a series-arm configuration, which can be utilized to interconnect the medium-voltage (MV) dc bus to the low-voltage (LV) dc bus. A novel series-arm structure is adopted to reduce the number of SMs. By applying quasi-square-wave modulation and phase-shifted control, bidirectional power delivery can be achieved with increased ac link frequency and mitigated dv/dt stress. On this basis, zero voltage switching can be implemented for both MV-side SM switches and LV-side full-bridge switches. The operation principle and control strategy are presented, and a 600V/100V/2kW prototype is built to validate the proposed converter.