Multi-Objective Parameter Optimization of LLC Converters for Shipboard Battery Energy Storage Systems Considering Efficiency and Battery-Side Current Ripple

Shipboard DC power systems increasingly employ battery energy storage systems to buffer load fluctuations, support DC bus stability, and improve power supply continuity. Accordingly, the isolated DC–DC converter interfacing the battery with the shipboard DC bus must achieve both high conversion efficiency and low battery-side current ripple. However, LLC resonant tank parameters simultaneously affect conversion losses, soft-switching characteristics, and ripple transmission, while the frequency-dependent battery impedance cannot be accurately represented by a conventional resistive load model. This paper therefore proposes a multi-objective resonant parameter optimization framework that jointly considers conversion efficiency and battery-side high-frequency current ripple. A unified converter–battery mechanistic model is established using the fundamental harmonic approximation and impedance network analysis, from which a computable battery-side ripple-current metric is derived. Multi-objective particle swarm optimization is then applied to generate a Pareto-optimal solution set and identify efficiency-oriented, ripple-oriented, and compromise designs. Experimental results obtained from a laboratory prototype verify the predicted efficiency and ripple trends, demonstrating that the proposed framework provides practical guidance for LLC resonant parameter selection in shipboard battery energy storage interfaces.