Model development, state estimation, and controller design of a nonlinear utility boiler system

The purpose of this paper is to develop a dynamic nonlinear model and to design controller for the CPS Energy´s Spruce Unit # 1 natural circulation drum boiler. This nonlinear four state boiler model will be based on physical parameters obtained from construction data and steam tables. This model will be utilized to study the steady-state and dynamic behavior of the system. Then we develop an Unscented Kalman Filter (UKF) that is capable of estimating both measurable and non-measurable states. The UKF state estimates will be compared against the two measurable outputs of the system which are the drum water total, V_wt and drum pressure, p. The other two estimates will be compared against the two non-measurable states, which are the quality in the riser outlet, a_r, and the steam volume under of liquid level in the drum, V_sd. Finally, a controller will be developed to regulate the states by solving an optimization problem with constraints. Computer simulations are also presented to illustrate effectiveness of our results.