Analysis, Design, and Performance Optimization of a Bidirectional Three-Level Neutral-Point-Clamped Dual-Bridge Series Resonant DC–DC Converter for Energy Storage Systems

In this paper, an isolated bidirectional three-level neutral-point-clamped dual-bridge series resonant converter (3L-NPC-DBSRC) is proposed for the wide-voltage range dc-dc applications in energy storage systems, which consists of a neutral-point-clamped (NPC) three-level bridge on the primary side, a LC-type series-resonant tank, and a full bridge on the secondary side. The proposed 3L-NPC-DBSRC is able to realize increased voltage gain and reduced harmonic components in the primary-side high-frequency-link voltages and currents. By using fundamental harmonic analysis (FHA), the steady-state operation principles of 3L-NPC-DBSRC are thoroughly analyzed in both forward and backward power-flow directions. Furthermore, a control algorithm based on globally optimal condition (GOC) is proposed for achieving zero-voltage switching (ZVS) in all switches and minimum root-mean-square (RMS) ac-link current, thus simultaneously reducing the switching and conduction power losses, and eventually resulting in high overall efficiency. Finally, to verify the effectiveness of the proposed 3L-NPC-DBSRC and its control method, both simulations and experiments are carried out on a designed example.