Nonlinear modeling and control for an evaporator unit

This article presents a nonlinear modeling approach describing the enthalpy dynamics between the inlet of the economizer and the outlet of the evaporator in a once-through boiler. The model is used to design an LQG controller for the steam quality at the evaporator outlet and to estimate the firing power, which constitutes a disturbance to the process. Robustness properties of the overall controller design are evaluated and the results are presented in simulations utilizing a high-fidelity model acting as the real plant.