State estimation of a boiler model using the unscented Kalman filter

The state estimation of a 300 MW drum-type boiler is examined, using an unscented Kalman filter to improve estimation accuracy by preserving the nonlinearities of the boiler equations. The boiler is modelled by a system of differential state equations for the dynamics of the circulation loop and another set of partial differential equations for the heat exchangers such as the superheaters, reheater and economiser. These modelling equations are the results of first principle balance equations, which have a form that is unsuitable for the extended Kalman filter method because of errors between the linear and nonlinear propagation of the boiler states and the difficulties in obtaining the Jacobian of the state model for the propagation of model uncertainties. An unscented Kalman filter is used to circumvent this problem as it treats the system model as a black box. Filtering results from simulated plant data are presented to demonstrate the effectiveness of the filter application.