The Design Of The Heating Boiler Auto Control System Based On Variable Frequency Speed-Regulating Technology

With the rapid development of social economy and the increasingly improved living standard of people, the scale of city construction is unprecedentedly expanded, arousing urgent requirement for high-quality living heating system to meet the sustainingly increased need. In northern China, however, most current living heating systems for winter use are relatively still out-of-date boiler heating system, in which, the core part, namely, the control of operating fans in stokehold and water pumps is still manual and therefore hard to realize real-time adjustment according to changing pressure in the pipes and temperature of water supplied. Consequently, this fussy manual control inevitably leads to unnecessary huge waste of coal and electrical power.In this paper, a heating boiler control system based on PLC and variable frequency speed-regulating technology is designed according to Variable Frequency Reconstruct Project of Yinchuan Stokehold sponsored by Lanzhou Railway Bureau. The control system is made up of PLC, transducers, electromotor units of pumps and fans, sensors, industrial control computer and control tanks, etc. It can control electromotor starting, running and timing by means of transducers.The hardware system includes two Advantech IPC 610 industrial control computers, the upper supervisory system (USS), and a Siemens S7-300 PLC, the lower control system (LCS). The supervisory software of USS designed with WINCC(Siemens configuration software) is mainly used to develop human-machine interface of system, and realize functions such as starting/stopping of electromotors, setting of analog parameters, alarm interlocking, inquiring of historical data and reports printing, etc, while the control software of LCS designed with STEP7(Siemens PLC software toolbox) is mainly used to deal with functions such as processing analog signals, calculating parameters including the wastage of coal, PID control of temperature and pressure, and accepting control instructions from USS to realizestarting/stopping of electromotors, setting of analog parameters and control of water pumps.It is proved by field experimental operation that the frequency control system proposed not only can realize automatic control of boiler burning process efficiently, having greatly reduced energy consumption, and in the meantime effectively improved the level of boiler control management, but also has many advantages such as stable and reliable running, flexible operation, convenient maintenance, and friendly interface, etc.