A method to coordinate decentralized NMPC controllers in oxygen distribution networks

• A new updating price technique is presented to be used in the price-driven coordination methods on nonlinear systems.
• Coordination method is formulated as feedback loop control.
• The performance is as good as the ones achieved by a centralized NMPC controller.
• Changes in the structure of the NMPC controllers are minimal, it is only necessary to add an extra term in the cost function.

This paper deals with the optimal operation of large scale systems composed by local processes liked by shared resources. A decentralized architecture plus a coordinator, which guarantees the satisfaction of the global constraints of the process, is presented. The decomposition of the control problem into smaller ones is based on Lagrangean decomposition and on price coordination methods to update the prices. A coordination method that allows formulating the price assignment as a control problem is presented besides a formulation based on market behaviour. Both approaches are driven by the difference between the total shared resources available and demanded by the local NMPC controllers. One advantage of this approach is that in the low layer only requires adding an extra term in the cost function of the existing NMPC controllers. Moreover, there is no communication between local controllers, only between each local controller and the coordinator.