Research On The Model Free Adaptive Control Of Circulating Fluidized Bed Boilers Combustion Process

Circulating Fluidized Bed Boilers (CFBB) combustion is a new techoology of coal cleaning combustion with high burning efficiency, low pollution and wild fuel adaptability. It has broad prospects and strong trend of sustainability to promote the development cogeneration industy. CFBB is a complex system of distribution parameters, nonlinear, time-variation, strong delay and multivariable coupling, it's hard to build a precise mathematic model in conventional method, and some conventional method which is well operated on general boiler can not yield ideal result. The automatic control of CFBB has become a main bottleneck for its widely commercial application. In this thesis, Model Free Adaptive Control(MFAC) is proposed to slove the difficulities in this fileld. MFAC is concerned the advantage of indepence on mathmatical models, decoupling, adaptive and robust in rejecting. In the view of above questions, this dissertation does some reseach on advanced process control of CFBB. The main work of this dissertation are as follows:The principle, development and dynamic performance of CFBB are briefly introduced, and the research and application of advanced process control for CFBB home and abroad are summarized systemically.Second, deep study of the structure of CFBB and technical flow and summarize various kinds of CFBB models. Predigesting the progress of CFBB combustion system model is thoroughly investigated and a viable control parameter and algorithm of models is developed for practical uses.The structure and algorithm of MFAC is discussed in details and modified the structure and parameters tuning of the MFAC applied to the typical large inertia and large time delay characters of first order and second order plants. Fuzzy logic was introduced to tune parameters and simplify the MFAC. Comparing the new type MFAC to the old one on example of typical large inertia , time-variation, large time delay charcters of first order plants, the result was presented that new type MFAC with fuzzy logic is better than the old one with good dynamic performance.The fuzzy Model Free Adaptive Controller is used for the control of bed temperature and main steam pressure. The simulation results show the Fuzzy Model Free Adaptive Controller has good adjustability on the characteristic changing of controlled Proeess. Based on this, a coordinated control system of bed temperature and main steam pressure is developed. Th control system can not only satisfy the demanding of control in bed temperature and main steam pressure, but also assure the stabilization of primary air. The simulation proves the feasibility and validity of this control system.The works of this thesis are summarized and some prospects are made in the end.