The Design Of Variable Frequency Constant Pressure Gas Supply System Based On PLC

This paper takes the development of the constant pressure gas supply system of the Hongdunjie gas station of the Shan-Jing Fourth-line Natural Gas Pipeline Project as an example.Combined with the theory of motor operation and the theoretical analysis of variable-frequency speed regulation,a pressure transmitter,PLC,Inverter,motor,compressor and computer,etc.Fully automatic frequency conversion constant pressure air supply system.After a long period of testing and observation,the system is operating stably,and the pressure of the air supply to the pipe network is basically kept within the set range.The energy-saving effect of the system is obvious,the failure rate of the equipment is greatly reduced,and the expected design goals are achieved in terms of economy.This article takes the control system of the compressor group of Hongdunjie Station of the Shaanxi-Beijing Fourth-line Natural Gas Pipeline Project as the research object.The main research contents of this topic include the following aspects:(1)Analyzed the structure and principle of centrifugal compressor,flow regulation method of centrifugal compressor,motor speed formula,structure and principle of frequency converter,PLC structure and principle,and determined the method of frequency control.(2)Demand analysis of the project,analysis of changes in gas demand for the year,month,day,and hour of natural gas;comparison of supply options,choice of gas supply plan;analysis of the composition and principle of constant pressure gas supply systems.(3)According to the project prediction,the compressor,inverter,PLC,pressure transmitter,touch screen,backup power supply are selected.And complete the control system principle,control cabinet cabinet and system circuit design.(4)Completed the design of the flow chart and logic diagram of the constant pressure air supply system;completed the PLC work program design,including: system initialization design,automatic power frequency operation design,start-stop compressor design,manual control module,data acquisition Design,data output design,parameter setting design,parameter query design,print report design,etc.;finally the upper computer has been realized,with automatic frequency conversion constant pressure operation,fault alarm,data query,parameter setting,print statements and other functions.