A Comparison between MPC and PI Controllers Acting on a Refrigerated Gas Plant

A refrigerated gas plant (RGP) produces sales gas (SG), which is the preferred fuel of many power plants due to economic and environmental factors. Sustaining the SG production at an optimum cost is crucial to the RGP given the operational challenges. These challenges may be alleviated by adopting a model predictive control (MPC) scheme in replacement of the current proportional-integral (PI) control scheme. In this work, a 2x2 constrained MPC scheme was developed. The process dynamics were approximated by first-order-plus-time-delay (FOPTD) models. The performance of the MPC scheme is compared with the decentralized PI control scheme in set point tracking. Although PI controllers seem to perform better than MPC controller, this is achieved at a higher operating cost and hence reducing the RGP profit margin.