Aiming at the problem that the low voltage electric power quality is not good and the double power supply switch is not standard.This paper presents a composite switch to realize the fast and flexible switching method of double power supply. The method is fast, and the switching process does not produce impulse current and over voltage, and it ensure normal operation of equipment. The switching process is coordinated by the coordination controller, and the information flow between each device is represented by the IEC61850 model. The example analysis shows that the fast and flexible switching method of the double power supply is fast and flexible.