Cascade control of a process plant using predictive and multivariable control

A cascade control arrangement on a chlorine-producing plant was investigated, in which the inner loop consists of multivariable control of three compressors, while an outer pressure control loop is implemented by predictive control. The authors report on a theoretical/simulation study, which is based on a nonlinear model of a real plant. The design work was done on a linearized model, obtained at a typical plant operating condition. It is anticipated that the plant will be equipped with a fault detection and identification (FDI) sub-system, and this study is part of a program to demonstrate that the control system can usefully exploit the information available from this FDI sub-system