Design Of Control System For Central Air Conditioning Water System

With the economic development,people pay more attention to the pursuit of quality of life and put forward higher requirements to the performance of air conditioning.air conditionings have become widely used in shopping malls,office buildings,subway stations and so on.The widespread use of air conditionings,especially the central air conditionings,further increase energy consumption.And in the era of energy shortage,energy saving optimization of central air-conditioning water system becomes extremely important.In this dissertation,the control system based on S7-300 series programmable logic controller(PLC)is designed for energy-saving control of central air conditioning water system.This paper introduces the working principle and variable flow control method of central air conditions,as well as the current research status of control strategies at home and abroad;the distributed control system based on S7-300 PLC is designed,as well as drive circuit and control circuit;Besides,under the programming environment of STEP7,the subroutines of inverter communication,fuzzy PID and water pump variable frequency operation and the bypass operation control are designed;then,using MCGSE configuration to complete the monitoring screen.Furthermore,the communication network of PROFIBUS-DP and Ethernet are constructed,which realizes the data communication between PLC and frequency converter with PROFIBUS-DP network and the communication between PLC,touch screen and computer with Ethernet network;Considering system's hysteresis and nonlinear characteristics,a Fuzzy-PID controller based on fuzzy control theory is proposed.Simulations are presented to verify the superiority and feasibility of the control algorithm.Simulations results are presented to show that the proposed controller can make the system obtain good transient and dynamic performance,anti-interference quality and robustness;The two layers of communication control network enhances the system's integration and openness,which makes the operation and monitoring on the system become more convenient.Meanwhile,the workload of the field debugging was reduced.Long-term stable operation results show that the energy consumption is greatly reduced by regulating the flow of water system.