Feedforward DMC-PID cascade strategy for main steam temperature control system in fossil-fired power plant

Main steam temperature system has the characteristics of nonlinear, large inertia and time delay. Thus, traditional PID cascade control usually could not provide satisfied performance. As a most widely used model predictive control (MPC) algorithm, dynamic matrix control (DMC) is especially suitable for large inertia controlled object. However, DMC is vulnerable to be influenced by uncontrollable disturbances. In this paper, a new DMC control strategy based on the combination of cascade structure and feedforward compensation is proposed in main steam temperature control system. The disturbances of the load and the spray attemperator inlet temperature can be compensated by feedforward model. And the cascade structure can suppress the disturbances of spray attemperator water. Simulation results show that the novel feedforward DMC-PID cascade control strategy has remarkable dynamic performance and strong disturbance rejection ability.