Multivariable control of a steam boiler

This thesis is devoted to apply a Multi-Input Multi-Output (MIMO) controller to a specific Steam Boiler Plant. The considered plant is based on the descriptions obtained from the input/output data of a referenced steam boiler in the Abbot combined cycle plant in Champaign, Illinois. The objective is to take all the useful input/output data from the steam boiler according to its performance and capability in different operation points in order to model the most accurate plant for control. The conceived case of study is based in a modification of a model proposed by Pellegrinetti and Bentsman in 1996, considering to be tested under a benchmark proposed by the Control Spanish Association (CEA). Initially, taking into account only the input and output data of the system, black box modeling techniques were used to obtain different models of the plant. The first approach was to obtain a transfer function model to apply a Internal Model Controller (IMC). However the result was not as expected because the controller becomes considerable difficult to tune given the big quantity of poles and zeros of the resulting IMC controller. Hence this technique was dismissed. On a second stage, it was obtained a model of the plant in state space representation to apply a Linear-Quadratic Regulator (LQR) technique to understand how the system behaves with this state space model design. Given that the description of the system in this form was more accurate the obtained results were better for this type of controller making it better suited to fulfill the needs of the plant. This work covers all the steps followed to use the Internal Model Controller (IMC) and the Linear-Quadratic Regulator (LQR) techniques to study the behavior of a steam boiler system in an industrial environment. The obtained results are exposed and explained with the aim of describing which one of the two used methods is better suited for the control of the plant. Finally a budget and impact studies are presented to explain which could be the resources needed in order to apply this type of controllers effectively in a steam boiler plant, being able to extrapolate the obtained results to be applied to other type of processes in the same sector (heat exchangers, distillation columns, etc.)