Automatic Control System Of Residential District Heating

Development of economic has improved the quality of our life. It isnecessary for north people to supply heating in winter. As heat source ofcogeneration are in short supply for some remote towns, distributed heatingsupplying systems are built nearby residential district. There are three problemsneed to be solved. Firstly, boilers discharge too much dust and soot emissionwhich gives rise to a destruction of the environment. Secondly， energyefficiency is still low, consuming too much coal and other resource. Thirdly, theability of heat exchange station control system is in short，the quality of heatingsupplying is in not so good too. According to these situations, designed aautomatic control system which depend on gas boiler as heat source.The heating system uses the S7series programmable logic controller, theheat source net consist of four2.1MW gas boilers. gas boiler control shouldensure the safety firstly, therefore, in the process of boiler starting and stopping,the controller only enter the next step when the result of last step is detected only,closure in the program is necessary. In order to monitor the device moreconveniently, set touch screen as human-computer interaction interface.Net of this system is constructed by PROFIBUS and MPI. PROFIBUShelps to realize communication between the master station and the slave stations.Upper machine communicate with S7-300as master station through MPI. Thereare10slave stations, they are S7-200. Due to the field device is far fromcentral room, using optical fiber as communication medium, at the same timereduces the interference. The content of the set of hardware and software for communication are expounded.All constructions in this residential district are tall buildings, in order toavoid the secondary network vertical imbalance and balance water conservancyconditions，divide secondary heating net vertically. Secondary network equippedwith a frequency converter to realize circulation of pump speed, and then thecycle of secondary network flow can be controlled; electric energy can be savedat the same time. Prediction of supplied water temperature based on temperatureoutside in advance is helpful. Due to man-made and nature factors, secondarynetwork need replenishing water. PID control algorithm can achieve stabilizingpressure of secondary network with a high degree of accuracy.Kingview software is chased as monitoring configuration of upper PC.Configuration interfaces includes the process of the whole system, boilermonitoring interface, circular monitoring interface, replenishing watermonitoring interface, the system data reports, alarm records, current time curve,etc. Each part can show both detailed parameters of the systems and can bestetted according to these parameters. Kingview has its own style to write datadown, introduce an easier way to read historical data by EXCEL.In this article, hardware involved has been illustrated; their type andspecification are explained too.