Secondary power supply device of liquid cooling medium voltage cascade energy storage system and control method thereof

The invention discloses a secondary power supply device of a liquid cooling medium voltage cascade energy storage system and a control method thereof. The device comprises a first circuit breaker, a voltage stabilization module, a first branch loop, a second branch loop, a third branch loop and a control protection loop, the first branch loop provides AC low-voltage voltage for low-voltage side equipment of the cascade energy storage system, and the second branch loop provides DC low-voltage voltage for the low-voltage side equipment of the cascade energy storage system. The third branch loop provides direct-current low voltage for high-voltage side equipment of the cascaded energy storage system and realizes voltage isolation between the secondary power supply device and the high-voltage side equipment; and the control protection loop is used for switching off the second circuit breaker and sending a power supply fault signal to the battery management system when judging that the acquired ground potential of