each of the first full bridge circuit, the second full bridge circuit and the third full bridge circuit configured to be used as an inverter circuit or a rectification circuit, and the charging and discharging interface circuit switchably connected with a mains network and a workload; and wherein

when the energy storage unit is discharged, the first full bridge circuit is combined with the resonant network for implementing soft-switching, to be configured to invert a low-voltage direct current (DC) of the energy storage unit into a high-frequency low-voltage alternating current (AC), and boost the high-frequency low-voltage AC into a high-voltage AC through the resonant network, and then transmit the high-voltage AC to the second full bridge circuit; the second full bridge circuit configured to rectify the high-voltage AC into a high-voltage DC, the third full bridge circuit configured to invert the high-voltage DC into a power-frequency standard voltage AC, and then output the power-frequency standard voltage AC from the charging and discharging interface circuit to the workload; and

when the energy storage unit is charged, the mains network inputs the power-frequency standard voltage AC from the charging and discharging interface circuit, the third full bridge circuit configured to rectify the power-frequency standard voltage AC input from the mains network into the high-voltage DC, the second full bridge circuit combined with the resonant network for implement soft-switching, to be configured to invert the high-voltage DC into a high-frequency high-voltage AC, depressurize the high-frequency high-voltage AC into the low-voltage AC through the resonant network and transmit the low-voltage AC to the first full bridge circuit, the first full bridge circuit configured to rectify the low-voltage AC into the low-voltage DC, and the low-voltage DC input to the energy storage unit for charging the energy storage unit.