A. Sadowska, P.J. van Overloop, C. Burt, and B. De Schutter, "Hierarchical MPC-based control of an irrigation canal," in Transport of Water versus Transport over Water - Exploring the Dynamic Interplay Between Transport and Water (C. Ocampo-Martinez and R. Negenborn, eds.), Cham, Switzerland: Springer, pp. 169-187, 2015.
We discuss the problem of controlling an irrigation canal to accommodate fast changes in the canal state in response to events such as offtakes announced with no time lag or sudden weather changes. Our proposed approach comprises a hierarchical controller consisting of two layers with decentralized PI controllers in the lower layer and a centralized MPC-based event-driven controller in the higher layer. By incorporating the hierarchical controller structure we achieve a better performance than with the PI controllers only as currently in use in the real world, while barely increasing the communication requirements and remaining robust to temporary communication link breakdowns as the lower layer can work independently of the higher layer when the links are being restored. The operation of the higher-layer controller relies on controlling the head gate and modifying the settings of the local controllers. This way, an acceleration of water transporting is attained as the controller allows for rapid reactions to the need for more water or less water at a location. Specifically, when there is a sudden need for water, the storage in some of the pools is used to temporarily borrow water. Alternatively, when there is too much water at a location, it can be stored for some time in upstream or downstream pools before the PI controllers manage to remove the water. We show how the proposed control approach works in a simulation-based case study and compare it with the standard control method currently in use. This demonstrates that employing the new hierarchical controller ensures a better performance.