Study And Application Of Mimo Decoupling Internal Model Control In Boiler Combustion Process

With the rapid development of society and economy, the demand of automatic control system to the boiler industry is increasing greatly. Improving boiler efficiency has become an objective in that man interests. However, at present the working conditions of most boilers in industry are complicated and variable. The practical working status differs greatly from what designed originally. It is unable for modern plants to meet the needs of economical management only by regulation of the traditional manipulation and control methods.In this paper, boiler combustion control system is studied as its thesis, considering the feature of coupling and phase lag, according to the requirement of modern boiler industry, multivariable decoupling internal model control developed rapidly at present is applied to decouple controlled variables (stem pressure, composition of oxygen in the flue gas and negative pressure in the combustion chamber) and manipulated variables (fuel, fed air, drawn air). Fed air is made into proportion with fed fuel in order to ensure the economic demands and safety of boiling process, fed air is proportional to drawn air so that negative pressure in the combustion chamber is constant at the desired value. This paper take QingDao LaiXi brewery boiler combustion system as an example, Matlab simulink realt shows that the method is practicable.The main contents of the research in this paper are as follows:1. The boiler process flow and control request is expound, boiler combustion process and controlled variables are demonstrated in detail, and the complexity of control is shown. 2. Multivariable decoupling IMC based on SISO IMC is presented, the designed controller has the function of decoupling and IMC at the same time, Genetic Algorithm is used to approximate model during the controller design to calculate easily and to ensure this method more practical.3. The boiler in Qingdao Laixi Brewery is taken as an example to simulation with Matlab, The method shows that the designed controller is simple in structure,convenient to adjust parameters, It makes the system not only with good performance of set point tracking, disturbance rejection and robustness, but also reduces bad influence while satisfying technical demand.4. In the final control system, Siemens SIMATIC S7-200 is used as the control element, and the system is programmed with VC++.Finally, the further prospect to the research work is made.