The Design Of The Refrigeration System Of HVAC Based On DCS

In modern time, the air conditioning system has become an important part of people’s lives. The huge problem of energy consumption has been brought. The control effect of central air conditioning refrigeration system will produce an effect on energy consumption even on the whole building. Therefore, energy saving and optimal control of a central air conditioning system has become one of the focus of research in the field of building automation.First of all, the development status and the operational principle of central air conditioning system is analyzed. Based on the knowledge of distributed control system, the DCS-based control of central air conditioning refrigeration system has been put forward.Secondly, after analyzing the requirement of central air conditioning refrigeration system,based on the control platform of ABB AC900 F DCS, the hardware system and software system is designed, and the process station, operator station and gateway station are designed.At the same time, based on the Functional Block Diagram, at the engineer station, the design of each control strategy of refrigeration system is completed, the best parameter of the PID is founded and the configuration of the function block is completed. At engineer station, a friendly man-machine interface is designed, the hardware configuration and program configuration of control system is completed, and the real-time monitoring and feedback of important variables is realized. In order to improve the performance of the system, an advanced control strategy, predictive control, is used in the segment of super heat degree of evaporator to solve the problem of time variability and delay and the impact of interference in heat-transfer process, so that the control of evaporator is realized precisely.At last, after debugging of central air conditioning through DCS, the characteristics of real-time, rapidity, accuracy of DCS control are proved, great control effect is get, the coordinated optimization control of refrigeration system and the unit is realized, the stability and reliability of the system are improved. The simulation results of the advanced control strategy show that the performance of the controller is good, the superiority of using predictive control algorithm to control super heat degree of evaporator is proved.