Application of PID auto-tuning and cascade generalized predictive control (GPC) in large power-plant boiler

PID auto-tuning and cascade generalized predictive control (GPC) are simultaneously used to control the important control loops (such as drum water level, main steam pressure, etc.) in large power-plant boilers. By using auto-tuning, the PID parameters can always be modified quickly and effectively, while GPCs, which were used only in small boilers or to simulate or control the reheated steam temperature in large boilers, are now applied to large ones. Facing the requirements of high speed of on-line computations, the conventional GPC is modified thus the cascade GPC is obtained. The computational overhead of such a GPC is much less than which of the recursive algorithm of conventional GPC. Both the PID auto-tuning method and the cascade GPC method have very good control results in their application to a 420 t/h power-plant boiler.