Comprehensive modulation strategy for DAB-LLC bidirectional isolated converter with wide input voltage range

Purpose This study aims to enhance the DAB-LLC bidirectional isolated converter’s adaptability to wide input voltage ranges in marine hybrid power systems. It addresses efficiency losses and voltage stress caused by conventional topologies, proposing dynamic full/half-bridge switching in LLC circuits and extended phase-shift modulation in DAB circuits to achieve soft switching, reduce leakage currents and optimize power distribution. The goal is to ensure reliable energy routing, voltage regulation and electrical isolation for marine applications while minimizing losses. Experimental validation confirms the strategy’s effectiveness in maintaining stable output and high efficiency across dynamic voltage/load conditions. Design/methodology/approach This study proposes an integrated modulation strategy for a DAB-LLC bidirectional isolated converter. The LLC circuit uses dynamic full/half-bridge mode switching to extend voltage gain range and reduce DAB input voltage stress, maintaining DCX operation. The DAB circuit adopts extended phase-shift modulation to minimize leakage current RMS values and achieve full-load soft switching. Mode-switching voltage thresholds and transformer parameters are optimized to ensure efficient power distribution across wide input voltage ranges. Experimental validation confirms enhanced efficiency, stable output and ZVS operation under dynamic load/voltage conditions, demonstrating improved adaptability for marine hybrid systems. Findings Experimental tests confirm that the integrated modulation strategy can achieve a stable 80 V output within the input voltage range of 60–160 V. All switches achieve full-load zero-voltage switching, reducing losses. The dynamic mode switching has a high efficiency and reaches its peak value at the maximum input voltage. Input voltage transients and load steps show minimal output fluctuations. This strategy ensures the reliable operation of the marine hybrid system over a wide range. Originality/value This study proposes a hybrid modulation strategy integrating dynamic LLC topology switching and DAB extended phase-shift control, uniquely tailored for marine hybrid systems. To the best of the authors’ knowledge, this study is the first to optimize mode-switching thresholds for wide-voltage efficiency and ZVS-enabled reliability.