A hybrid energy storage system and its control strategy based on a bidirectional resonant converter

With the continuous expansion of clean energy integration, hybrid energy storage systems (HESS), which are capable of smoothing power output, have garnered increasing attention. The dual active bridge converter, known for achieving electrical isolation and soft-switching capability, is commonly employed in HESS. To broaden the voltage gain range and reduce the current ripple on the energy storage device side, this paper proposes a novel HESS topology based on a current-fed bidirectional resonant converter. Firstly, the converter topology and its equivalent circuit are presented. Its switching modes and operational principles are analyzed, leading to the derivation of an equivalent circuit model, a voltage gain expression, and the characteristics of the low-voltage-side current ripple. Subsequently, a decoupling control strategy is proposed. This strategy independently controls the power transfer of the super capacitor and the battery by adjusting the duty cycle of the corresponding full bridge on each energy storage side. The power share of each port is dynamically regulated according to the power allocation command. Simulation results verify that the proposed system achieves zero voltage switching (ZVS) for all switches and exhibits fast dynamic response along with good stability during load transitions and power command changes.