Mechanism modelling on the coordinated control system of a coal-fired subcritical circulating fluidized bed unit

Highlights: • A mechanism-based control model of CCS for subcritical CFB units is established. • The model can well describe the dynamic characteristics with high accuracy. • The model is validated by a 300 MW CFB unit. • A transfer function matrix of CCS is derived to design the control algorithm. -- Abstract: To improve the load following capacity of a coal-fired circulating fluidized bed (CFB) power generation unit, it is necessary to build a model for the design of the load control system, e.g. the coordinated control system (CCS). In this paper, a mechanism-based control model of the CCS with the balance between model complexity and prediction accuracy applicable for controller design is established based on the dynamic characteristics of a subcritical coal-fired CFB unit. The proposed model was applied on a 300 MW coal-fired subcritical CFB unit with the existing control system. The results showed that the model can reflect the main dynamic characteristic of power plant project with 300 MW CFB unit with the existing control system, has high precision, and can be used to design the controller of load control system. Moreover, the transfer function of coordinated control systems is derived to design the control algorithm.