Efficiency improvement and high-performance control of dual-active-bridge DC-DC converter with triple-phase-shift modulation

For dc-dc converter with wide range of voltage, high efficiency and high performance, this paper analyzes the optimal switching modes of the dual-active-bridge (DAB) dc-dc converter to decrease the loss. By solving the multi-objective constrained conditional extremums with the Karush-KuhnTucker (KKT) method, a triple-phase-shift (TPS) optimal modulation with full range of operation, global continuity, and simple calculation is obtained. By adopting the TPS modulation, the DAB can decrease the reactive power when the dc voltages are mismatch and obtain global optimization of conduction loss and soft-switching in the full range of operation. The generation of dc-offset current in the ac link is analyzed. The static and dynamic dc-offset currents are suppressed based on the TPS modulation. With the direct-power feed-forward, a high-dynamic control is used to improve the system response to the external disturbances. The digital control strategy of the whole system is designed, and the optimal modulation and high-performance control are verified on the experimental prototype.