The coordinated control of circulating fluidized bed boiler with fuzzy feedforward control

An intelligent coordinated control strategy has been proposed and successfully applied to 300MW circulating fluidized bed (CFB) units in China. The paper describes an intelligent coordinated control (ICC) system to overcome the long settling time, strong coupling, nonlinearity and inconstancy encountered in CFB combustion. ICC is based on both fuzzy Feedforward (fuzzy-FF) control and the fuzzy-PID feedback control. The fuzzy-FF control path contains a set of multi-input single-output fuzzy inference systems obtained from steady-state input-output plant data and is used to improve the dynamics of CFB unit. The control output is mainly determined by the fuzzy-FF path, diminishing the control effort on the PID controllers. The fuzzy-PID controller supplies the complementary control signal component for regulation and disturbance rejection in small neighborhoods of the commanded trajectories. A self-adapting algorithm and non-uniform grid scheduling is proposed in the fuzzy-PID controller. The strategy is implemented through the function code on many typical DCS (EDPF-NT, XDPS, etc). The industrial application results show that this strategy achieves better performance in the specific range of load variations.