Utility-scale battery energy storage systems undergo frequent charge–discharge mode transitions, inducing severe power surges that threaten power converter reliability and grid interface stability. Existing solutions primarily address steady-state power smoothing or mode transitions in residential-scale inverters. Consequently, the rapid bidirectional power reversals inherent in utility-scale storage systems remain largely underexplored. This paper identifies a transient power surge mechanism in dual-active-bridge (DAB) based storage converters, revealing that phase-shift discontinuity during mode reversal is the root cause of instantaneous power spikes. A composite control strategy is proposed, integrating a transient phase-shift feedforward compensator with an adaptive virtual impedance regulator. Unlike conventional mode-switching methods that rely on control loop replacement, the proposed approach maintains a unified control architecture and dynamically reshapes the transient power trajectory via pre-positioned phase-shift adjustments and impedance regulation. A 500-kW energy storage converter hardware-in-the-loop platform is constructed.Experimental results demonstrate that the proposed method reduces the peak power surge by 74.6%, shortens the switching transient duration from 1.21 s to 0.28 s, and limits DC bus voltage deviation to within ±3.8%. Furthermore, the proposed method exhibits superior transient suppression performance compared with conventional PI-based mode switching and droop-only control under various states of charge (SOC) and power deficit conditions.
