An energy storage system, including: a first switch and a first inductor connected in series and connected to a positive electrode of an external DC system; a pre-stage bidirectional buck-boost conversion circuit, the circuit including a first terminal, a second terminal, and a third terminal; a pre-charge circuit, a fourth switch, and a super-capacitor sequentially connected in series, two terminals of a series structure resulting therefrom being connected to the third terminal of the pre-stage bidirectional buck-boost conversion circuit and the negative electrode of the external DC system, respectively; a post-stage bidirectional buck-boost conversion circuit, the circuit including a first terminal, a second terminal, and a third terminal; and a battery, a second switch, and a second inductor connected in series.