Modulation and capacitor voltage balancing control of a three-level NPC dual-active-bridge DC-DC converter

This paper presents a converter consisting of a dual active bridge built upon three-level neutral-point-clamped legs in order to synthesize a five-level medium- or high- frequency stepped waveform on each side of the transformer. Thanks to the modulation extra degrees of freedom, the transformer current harmonic content can be reduced (less magnetic losses) and the fundamental component of the transformer primary and secondary voltages can be adjusted to minimize the reactive power (less conduction losses). A modulation strategy and control scheme to regulate the dc-link capacitor voltage balance is proposed. The topology, modulation, and balancing control are validated through simulations.