Design of the PID controller for circulating fluidized bed boiler combustion system

Circulating fluidized bed (CFB) combustion system is a long time delay and strong coupling multivariable system. It is difficult to build an accurate mathematical model. So using conventional controllers cannot achieve the desired performance. Through analysis of the control structure of the CFB combustion system, this paper presents a two-degree-of-freedom PID controller based desired dynamic equation (DDE) method and a partially decentralized PID controller based on dynamic matrix control (DMC) for the CFB combustion system. Both methods do not depend on the accurate mathematical model and can improve the control performance of systems with large time delays. These methods were applied to a domestic 75 t/h circulating fluidized bed boiler combustion system. Simulation results show that the proposed methods can achieve better disturbance rejection ability and robustness compared with conventional methods.