Efficiency Improvement and High-Performance Control of Dual-Active-Bridge DC-DC Converter with Triple-Phase-Shift Modulation

This paper analyzes the optimal switching modes of the dual-active-bridge (DAB) DC-DC converter to minimize losses in DC-DC converters that exhibit a wide voltage range, high efficiency, and high performance. 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 TPS modulation, the DAB can decrease reactive power when dc voltages are mismatched and obtain global optimization of conduction loss and soft-switching in the full range of operation. Generation of dc-offset current in the ac link is analyzed. Static and dynamic dc-offset currents are suppressed based on TPS modulation. With direct-power feed-forward, high-dynamic control is used to improve system response to external disturbances. The digital control strategy of the whole system is designed, and optimal modulation and high-performance control are verified on the experimental prototype.