A novel modulation strategy for isolated modular multilevel DC/DC converter's sub-module dc voltage oscillation damping

This paper focuses on the modulation strategy optimization of an isolated modular multilevel DC/DC converter (IMMDC). IMMDC sub-modules' dc capacitor and arm inductor has an inherent resonance condition, which leads to high oscillation in arm current dc component. Traditional two-level or quasi two-level phase shift operation has no damping capability to this resonance. In this paper, a novel modulation strategy and corresponding control strategy are proposed to damp this kind oscillation in IMMDC. The simulation results are provided and a down-scaled prototype has been built as well to verify the proposed modulation and control strategies.