Design Of Central Air-conditioning Control System Based On Fuzzy Control

With the rapid development in social and economy by the policy of reform anopening up, China will build more and more modern buildings in the future, which canprovide people comfortable environment for working. Meanwhile, it draws attentionsof the society in its enormous energy consumption. According to the research ofrelevant department, over50%of construction energy consumption is central airconditioning, about60%of the air conditioning energy consumption is in water systemof energy dissipation, which both enlarged the costs of building operation and not metthe fundamental policy standard of energy conservation and emission reduction. So itis an important issue in improve overall efficiency of air condition and energyutilization. Presently the domestic central air-conditioning water system is mostlyusing the constant flow of operation mode, the pump running at full speed, as aresult,they can not change the actual needs of cold energy, which caused a hugeenergy consumption. This paper will analyze the working principle of changing themotor speed of the central air-conditioning and water system to control the variableflow to achieve the purpose of the water flow changes by the actual load, then makeup a control scheme of water system of frequency conversion.The water system of central air-conditioning has the characteristics of nonlinear,multivariable, vulnerable to interference, and it is difficult to establish accuratemathematical model. It is difficult to achieve satisfactory control effect using theconventional PID control method. Combined with the characteristics of no accuratemathematics model and strong anti-interference abilities in fuzzy control, I put forwardthe fuzzy PID control, and design the fuzzy PID controller. After a large number ofsimulation verification, I notice that the fuzzy PID controller in the control of thecentral air conditioning chilled water temperature has a better effect than theconventional PID control. It has not only the conventional PID control precision butalso the characteristics of fuzzy control of quick response and strong anti-jamming.Finally, it introduces the hardware and software system and realizes the waterpump frequency conversion control by the Siemens S7-200PLC as the main controllerand Siemens MM440frequency converter. It also introduces the design of the main program and its control subroutine system, and analyzes the efficiency in energysaving.