Automatic working mode
(1) Self switching and self restoring mode: The controller monitors two power sources. When both power sources are working normally, the load is powered by the commonly used power source; When the common power supply fails (power outage or phase loss), the controller issues a switching command to automatically switch the power supply to the backup power supply, and the load is powered by the backup power supply at this time; When the common power supply returns to normal, the controller issues a switching command again to return the load power supply from the backup power supply to the common power supply.
(2) Self switching and non self restoring mode: Its working mode is similar to self switching and self restoring, but it only automatically returns to the common power supply when the backup power supply also fails, otherwise it will continue to be powered by the backup power supply to the load.
(3) Grid generator mode: When the common power supply fails, the controller outputs a generator start command, and after a short delay, the common power supply is disconnected, and the load is powered by the generator; When the common power supply returns to normal, the controller outputs a generator shutdown command and the power supply automatically switches to the common power supply, and the load returns to the mode of being powered by the common power supply.
Manual mode
In manual mode, the power supply cannot switch automatically and requires manual operation. There are mainly three methods: common power supply, backup power supply, and power-off and reconnection.
Common power supply: forcing the common circuit breaker to close and the backup circuit breaker to disconnect.
Backup power supply: forcing the backup circuit breaker to close and the common circuit breaker to disconnect.
Power outage and subsequent disconnection: Simultaneously force the disconnection of both the common circuit breaker and the backup circuit breaker, or close all circuit breakers that were disconnected due to a fault.

2、 Application of PLC
PLC control system, Programmable Logic Controller， It is an electronic device designed specifically for industrial production that uses a type of programmable memory to store programs internally, execute logical operations, sequence control, timing, counting, and arithmetic operations for user facing instructions, and control various types of machinery or production processes through digital or analog input/output. It is the core part of industrial control. PLC has the characteristics of high reliability, strong anti-interference ability, powerful functions, flexibility, easy learning and use, small size, and light weight.
At present, PLC controllers have been widely used in various industries such as steel, petroleum, chemical, power, building materials, machinery manufacturing, automobiles, textiles, transportation, environmental protection, and cultural entertainment both domestically and internationally. Their usage can be roughly classified into the following categories: logic control of switch values, analog control, motion control, process control, data processing, communication, and networking. The dual power switch mainly controls the actuator (circuit breaker) through the switch value to achieve the purpose of switching power supply. Using PLC instead of dual power controller can fully meet the function.

3、 Design of Dual Power Control Scheme Based on PLC

4、 The advantages of using PLC as a dual power controller
(1) Stable and reliable performance. The input and output circuits of PLC are electrically isolated from the internal CPU, and their information is transmitted through optocouplers or electromagnetic devices. In addition, the CPU board has shielding measures against electromagnetic interference. Therefore, it can ensure that the operation of PLC programs is not affected by external electrical and magnetic interference and can work normally. The components used in PLCs are mostly contactless and highly integrated, with a relatively small quantity, which provides a material basis for their reliable operation. In the design and manufacturing process of mechanical structures, many measures have been taken to ensure the safe and reliable operation of PLCs, which can guarantee their resistance to vibration and impact. The working mode of PLC is scanning and interruption, which ensures that it can work in an orderly manner, avoiding the 'risky competition' that often occurs in relay control systems. Its control results are always determined, and it can also handle urgent controls in emergency situations, ensuring timely response to emergency situations and reliable operation of PLC.
(2) Scheme economy greatly reduces costs. Some domestic dual power controllers can cost thousands of yuan, while some foreign brand controllers can cost tens of thousands. Using a Gumei PLC for dual power controllers not only ensures reliable performance, but also greatly reduces costs. After programming the dual power program in one go, there is no need for repeated programming, and the program used before can be directly applied to subsequent projects.
(3) The human-machine interface is more user-friendly, with beautiful graphics and simple control. Traditional dual power controllers are mostly digital tubes or simple LCD displays, controlled by buttons. Using a 7-inch touch screen from Gu Mei to create a more user-friendly human-machine interface makes it easy to operate, and customers can also create personalized interfaces according to their own needs.