Modeling And Optimal Control Of Combustion Process Of Biomass CFBB

In renewable energy,biomass energy is the only carbon-containing energy,and biomass direct-fired power generation is a very important way to achieve large-scale biomass utilization.At present,the use of circulating fluidized bed combustion of biomass fuel in China has been able to achieve.This technology has features of strong fuel adaptability,wide water adaptability,strong load regulation,low cost and energy saving and environmental protection.Segment biomass direct-fired power generation boiler is the best choice in current stage.However,the combustion system of biomass CFBB is a non-linear,large lag and strong coupling thermal process.Conventional PID control method is difficult to realize the automatic control of biomass circulating fluidized bed boiler.Therefore,a fuzzy control strategy based on decoupling compensator is designed for this problem.Firstly,the thermal process of biomass circulating fluidized bed boiler is analyzed,and the characteristics and control requirements of CFBB thermal process are introduced.The transfer function matrix model of combustion system is obtained by identifying the control loop model of bed temperature and main steam pressure based on the least square principle.Through analysis and calculation,it can be seen that there is a strong coupling between bed temperature and main steam pressure system.In view of the serious coupling between bed temperature and main steam pressure,two decoupling methods,simplified diagonal decoupling and feedforward decoupling,are adopted to remove the coupling relationship between them.The single-loop control of bed temperature control by feeding rate and main steam pressure control by primary air is realized.Aiming at the characteristics of non-linearity,time-varying and large delay of CFBB combustion system,three kinds of fuzzy control methods are designed for bed temperature and main steam pressure circuit respectively on the basis of decoupling principle.Fuzzy controller could have an ideal control effect for the system without precise mathematical model,non-linearity and time-varying.Three kinds of fuzzy control methods are simple fuzzy control,fuzzy PID control and fuzzy control based on Smith predictor.They are used to control the bed temperature and main steam pressure loop respectively.The control effect of these three kinds of fuzzy control methods is compared with that of conventional PID control.The response speed,stability and robustness of the Smith predictor based fuzzy controller are the strongest.The performance of simple fuzzy control and conventional PID control is poor.Fuzzy control strategy based on decoupling method is adopted in this paper.The experimental results show that this method can meet the requirements of decoupling,and can adapt to the complex characteristics of CFBB combustion system to achieve fast and stable control effect.