Analysis and Design Guidelines of the Isolated Modular Multilevel DC-DC Converter With the Impact of Magnetizing Inductance

The isolated modular multilevel dc-dc (IMM dc-dc) converter is one of the potential candidates for interconnection of medium- and high- voltage dc grids. One of the key components for realization of the IMM dc-dc converter is its transformer whose magnetizing inductance depends on the core material, dimensions, and airgap. Depending on the transformer design, the magnetizing inductance may vary over a wide range, adding to the complexity of the converter design. In this article, the impact of the magnetizing inductance on the converter real and reactive powers, transformer primary and secondary side currents, arm current, differential-mode current, capacitor voltage ripple, and soft-switching operation is investigated. The presented analysis is validated by a time-domain simulation in the MATLAB/Simulink software environment and experiments on a scaled-down prototype.