Quick switching method and device for standby power supply

The invention discloses a quick switching method and a quick switching device for a standby power supply and realizes that influence on a load connected with a bus due to power failure is reduced through switching between a main power supply and a standby power supply. The method comprises the following steps: (1) calculating the amplitude value of voltage phasor difference between a bus and the standby power supply, as well as the phase angle difference between the bus and the standby power supply; and (2) switching the bus load to the standby power supply only when the amplitude value is lower than the ultimate value and the phase angle difference is smaller than 90 degrees. The quick switching device comprises a detection module, a computation module, a comparison module and a switching module. Through computation of real-time residual voltage, the only requirement for a user to conveniently conduct quick switching is to set the limit of the voltage difference when a circuit breaker of the standby power su