Application Research Of The Distributed System Based On PLC In Boiler Supervisor And Control

The boiler is the main equipment which provides energy and power in industrial production and is widely used in the north of our country for central heating project and building supply heating. With the development of the computer and information technology, the application of computer supervisor and control system which is based on PLC arises more and more attention in industrial boiler automation.Being a kind of equipment which transform the primary energy into secondary energy and having consumed much energy and caused serious pollution, the boilers cause high energy consumption and severe environmental pollution, because they were working under non-economical condition and low automation level for a long time. Furthermore, at present, there are concentration of labor force and the separation of manufacturing and administration in the boiler industry. In order to improve the efficiency of energy utilization sufficiently, reduce the labor intensity of workers, and improve the management level of information in the enterprise, a set of supervisor and control system with enough safety, liability and high efficiency which can guarantee the boiler's automation is very necessary.The paper takes three industry hot water boilers and their related assistant control devices as object of study. Using Siemens S7-300 PLC as their core controller and making use of profibus field-bus protocol, speed regulation technology of frequency converter, network technology and redundant technology, the system construct all of control devices to be distributed supervisory and control system. Furthermore, the project realized supervisory and control of three hot water boilers by software programming and hardware building.The profibus is the field-bus standard that is used widely the industrial automation field and ET200M is used as a slave unit to be used to realize distributed I/O station in Siemens PLC systems. ET200M unit can be insert into profibus field-bus conveniently by making use of interface module IM153-2, thus, S7-300 PLC distributed supervisory control system in boiler gets possibility to be realization.Communication control for frequency converter is one new application that makes use of network technology in frequency converter technology. The technology can save much hardware costs effectively and realize speed regulation simply and reliably by the aid of frequency converter and transmit-receive of communication messages in profibus field-bus.Software redundancy is one kind of low costs redundancy technology by use of programming. The technology can improve reliability of system greatly on the basis of hardware that supports redundancy realization. When master system's failure happened, the slave system can enter into working state voluntarily to take over working task.Load adjusting automatically is used to adjust speed of all wind machines to suitable value by use of programming for the purpose of meeting requirement of system techniques. The technology reduces the energy consumption and resource waste under the guarantee of boiler burning safely. It is a key technology of energy conservation and environment protection.Besides, sequential control and safety mechanism of system ensure that the system can work safely. HMI pictures that include rich information and friendly man-machine conversation show all system data and state real-timely and provide convenience of operation and information management greatly.