On modelling approaches for receding-horizon control design applied to large-scale sewage systems

In this paper, receding horizon control of large-scale sewage systems is addressed considering different modelling approaches, which include several inherent continuous/ discrete phenomena (overflows in sewers and tanks) and elements (weirs) in the system. This fact results in distinct behaviours depending on the dynamic state (flow/volume) of the network. These behaviours can not be neglected nor can be modelled by a pure linear representation. In order to take into account these phenomena and elements for the design of the control strategy, a modelling approach based on piece-wise linear functions (PWLF) is proposed and compared against a hybrid modelling approach previously reported by the authors. Control performance results and associated computation times considering both modelling approaches are compared by using a real case study based on the Barcelona sewer network. Results have shown an important reduction in the computation time when the PWLF-based model is used, with an acceptable suboptimality level in the closed-loop system performance.