External Reset Feedback for Constrained Economic Process Operation

Abstract

Efficiency and sustainability considerations increasingly require control systems to drive process operation as close as possible to optimally active process constraints. Because the active constraint set is changeable, override control structures are employed to transfer the control of important control objectives from one controller to another and to manage the transition between the different constraint regions. Reset windup problems can occur when these controllers have integral action with large swings (bumps) in controller output as control is transferred from one controller to another. This work considers the Shinskey–Buckley external reset feedback control structure in override control applications for a smooth transition between active constraint regions. Three example processes with increasing levels of complexity are used to quantitatively demonstrate the significant improvement in dynamic control and consequent process economic performance (compared to internal reset). The quantitative results...