BACKUP POWER SUPPLY SYSTEM AND STARTUP CONTROL METHOD THEREOF

This application provides a backup power supply system and a startup control method thereof. When an on/off-grid controller is powered off, a first control circuit provides a low level signal as an off-grid signal for a second control circuit of an inverter. In this way, when a voltage on a direct current side meets an inverter startup voltage value condition, the inverter preferentially performs an off-grid black start, and after the startup is complete, the inverter runs in off-grid mode and outputs an alternating current voltage to quickly supply power to a backup load. Before the inverter is started with off-grid mode and outputs the alternating current voltage, if it is detected that a voltage on an alternating current side meets a minimum off-grid output voltage value condition and a high level signal is received as an on-grid signal, the inverter may directly switch to on-grid startup, to complete quick startup. When a voltage of a power grid meets an undervoltage protection voltage value condition, the on/off-grid controller may directly start with on-grid mode and run in on-grid mode, turn on the first switch circuit, and send the high level signal as an on-grid signal, to quickly supply power to the backup load and provide a voltage for the alternating current side of the inverter.