Disturbance Estimator based NonLinear MPC of a Three Phase Separator

This paper presents a nonlinear predictive controller with a feed-forward action applied to a three-phase separator used in the petroleum industry. Two tools are used in order to include the feed-forward action in the NMPC, a disturbance estimator and a disturbance predictor. Moreover, a supervisory control changes the objective function characteristics of the NMPC depending on the type of disturbances acting on the process. The separator advanced controller, which is capable to maintain all process variables in pre-defined zones, uses a practical nonlinear model predictive controller (PNMPC) developed in the Department of Automation and Systems (Federal University of Santa Catarina). The performance of the proposed strategy is compared to a traditional PI Zone controller used in industry and to a different NMPC based on a Hammerstein model. All the case study simulations are developed with a complete phenomenological nonlinear model of the separator. The obtained comparative results show that the proposed strategy gives the best results, allowing good oscillation attenuation under slug perturbations.