Hybrid-Bridge-Based Dual-Active-Bridge Converter With an Asymmetric Active-Neutral-Point-Clamped Three-Level Bridge

Hybrid-bridge based dual-active-bridge (DAB) converter comprised of three-level (3L) and two-level (2L) full-bridge (FB) is promising to be a good candidate for medium voltage DC (MVDC) grids. By applying a corresponding modulation strategy proposed in this paper with multiple working patterns, a wide voltage conversion gain can be obtained. However, given that the conventional neutral-point-clamped (NPC) DAB converter has potential risk losing the control of the voltage conversion gain in backward and forward modes, an asymmetric active-neutral-clamped (A-ANPC) 3L structure is employed in the proposed converter to overcome this issue. Afterwards, to ensure a smooth working pattern transition, a simplified control strategy is proposed. The backflow power remains constant regardless of working conditions, and the zero-voltage-switching (ZVS) can be achieved for all power switches under the proposed modulation strategy. The operation principle, characteristics, and performances of the proposed converter are analyzed in detail and experimentally verified.