Modeling and Robust Controller Design for an Industrial Boiler

AbstractIn this paper, a practical method to design a robust controller for pressure of boiler in Mashhad Power plant using H∞ is proposed. To achieve a good performance of an industrial boiler in order to reduce fuel consumption rate and reaching higher efficiency, dynamic variables such as fuel flow, air flow and pressure of boiler must be controlled. However this dynamic model may associate with uncertainties. Uncertainties in mentioned model are caused by lack of knowledge about the dynamics of the system, pay load changes, and air flow. Thus, application of robust control methods for high precise control of pressure is inevitable. In the first step plant is identified by using experimental data by the mean of converting into a group of linear time invariant (LTI) uncertain plants. After representation of the uncertain dynamic system in general control configuration and modelling the parametric uncertainties, nominal performance, robust stability and robust performance against disturbances are analyzed by the concept of structured singular value μ. Then, using genetic algorithm an optimal controller is designed for tracking problem and disturbance rejection. This procedure gives a satisfactory controller at the presence of model perturbations. For more comparisons, quantitative feedback theory (QFT) as a well known robust control approach is also applied to the plant. Finally, nonlinear simulation has been carried out and two controllers are compared. Both optimal robust controllers guarantee robust performance of the system against the uncertainties and result in desired time responses of the output variables. By applying H∞ robust control, system tracks the desire reference inputs in a less time and with smoother time responses