Bidirectional inventory control with optimal use of intermediate storage
Cristina Zotică, Krister Forsman, Sigurd Skogestad
Abstract
The scope of this work is to advocate the use of a decentralized control system that is able to maximize production when temporary or permanent bottlenecks occur for multiple units in series by employing the buffer inventories as intermediate storage. This bidirectional inventory control scheme has for each inventory two controllers, one for the inflow and one for the outflow, with high and low inventory setpoints, respectively. The inventory can typically be liquid (level) or gas (pressure). When production cannot be maintained without breaching physical constraints on the inventory, this control structure automatically reconfigures the loops for consistent inventory control, which means that it is radiating around the throughput manipulator to assure local consistency and feasible operation.