Abstract：With the development of economics, the mount of power used by enterprises has exceeded greatly the mount power system can supply. It resulted in frequently power cut and the demand for power quality and safety is more and more high. There are so many important grounds such as hospitals, steel-makers, fire-controller facilities which require two power sources to realize durative of power supply. To meet the demand for uninterrupted power supply，the developing scheme of intelligent automatic switching-over double power supply system controller using P87C591 controller as main control chip was introduced . The system includes the voltage sampling, the power sources control, the man-machine interface. It is implemented with the structure and the modular programming method, programmed with Keil C. In power service equipment，based on the working principle of sampling, comparing, running software on the P87C591 controller, the micro-controller detect the power supply state and process corresponding control. If faults such as overvoltage,undevoltage，phase loss etc, was found in the normal power, the standby power would switch by the automatic transfer switch controller. The switching between two-way powers was reliably finished automatically to ensure the continuity of power supply.It is one kind double power source module which have programmable function, the automation measures, LCD display, the numerical communication .It integrates digitization , intellectualized, network-rization , which leads to automatic measurement and control process ,and reduces an artificial operation error. It is ideal product which the double power source transforms.
Keywords：double power supply；automatic switching-over； intelligent control
