Gas-fired Boiler Control System Design With The Siemens PCS7System

With the advancement of science and technology and environmental protectionrequirements, natural gas as a new energy industry has being increasingly used. Boiler is amulti-input, multi-output, multi-loop, nonlinear interconnected object, there are many cross-impact on input parameters and output parameters. Boiler automation control, according tothe parameters of the dynamic characteristics, is an integrated multi-loop control system. Ifyou lack the necessary detection and control method, without an appropriate configuration ofthe automatic control system, it is difficult to improve the thermal efficiency of the boiler, andthe energy consumption is also large. Therefore, accelerating the transformation of boilercontrol system to improve its automatic level is a very realistic task.The master’s degree thesis focuses on gas-fired boiler water level control, combustioncontrol systems, self-tuning fuzzy PID controller design. The gas-fired boiler structure isintroduced, and the main control system, control strategic logic are analyzed. Achieve thetarget of gas-fired boiler monitoring and automatic operation via the Siemens PCS7system.(1) Water level control system. By comparison, two-element level control system on onehand to ensure the stability of the drum level, avoiding the internal and external disturbanceon the water level control, on the other hand to achieve the safe operation of the boiler.(2) Combustion control system. Combine oxygen trim control and parallel positioningcontrol together in debugging stage; make sure the oxygen content of the flue gas emissioncontrol in2%to3%level. In the mean time, these setting avoid the investment of online gasanalysis instrumentation and subsequent maintenance. After commissioning, the settings ofuse parallel positioning control, Maxon PLC controller, butterfly valve with servo motor asactuators, ensuring high reproducibility and combustion adjustment precision, allowscompanies to save the cost of production, and ensure the efficiency of boilers operation.(3) Self-tuning fuzzy PID controller. PID control applies for a variety of linear time-invariant systems; it is simple and fast with good stability. But for nonlinear systems withmuch interference, the PID adjustment is limited. The advantage of fuzzy control is designerno need to master the mathematical model of the controlled object, but can complete controlof the process according to the existing knowledge and experiences. The disadvantage is thatthe dynamic characteristics of a large steady-state error or bad. A self-tuning fuzzy PIDcontroller is the combination of fuzzy control and PID control which can make up for theshortage of a single control system. Especially for boiler, which is multi-input, multi-output,multi-loop, nonlinear interconnected objects, it is well applied. (4) Realize remote monitoring and operation of the gas boiler with Siemens PCS7system. SIMATIC Manager is a program developed by Siemens, which can realize the remotemonitor and control of the boiler system. I design dual-controller architecture to ensuresystem stability and timeliness. Basic Process Control System modules and fail-safe modulesare installed separately, to achieve the high reliability of the input output signal management.Industrial Ethernet and Profibus system combined in the net frame layout, reducinginstallation costs and maintenance costs.