Unified Modulation Strategy with DC-Bias Mitigation for Dual Active Bridge Converters

This paper aims to tackle the persistent dc-bias problem that arises in the high-frequency link of dual active bridge converters (DAB). Such issue occurs frequently during transient processes like start-up, load or voltage fluctuations, and power direction alterations. A unified eliminating strategy, solely based on modulation, is proposed and validated. Through the independent control of half-bridges using four triangular carriers that are updated asynchronously, this method ensures automatic dc-bias elimination, obviating the need for transient calculations, and is effective for all existing multiple phase-shift strategies. Finally, the proposed method is verified by the comprehensive experimental results.