Economic plant-wide control design with backoff estimations using internal model control

DAVID ZUMOFFEN; LAUTARO BRACCIA; ALEJANDRO G. MARCHETTI

JOURNAL OF PROCESS CONTROL

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2016 vol. 40 p. 93 - 105

0959-1524

Economic optimal operation typically involves operating as close as possible to the active constraints.However, in the presence of disturbances it is necessary to back-off from the constraints in order to avoidviolating them. The backoff approach aims at selecting the control structure that minimizes the economic loss associated with the required constraint backoffs. This paper revisits the backoff approach andproposes a framework for estimating the constraint backoffs based on well-known elements of internalmodel control (IMC) theory, such as an automatic procedure for tuning the IMC low-pass filters, a stabilitycondition, and an uncertainty representation based on diagonal input multiplicative uncertainty. Sincethe constraint backoffs are estimated using a linear dynamic model, the inclusion of input multiplicativeuncertainty allows introducing conservatism in the estimation of the backoffs, which is required in orderto avoid constraint violations. A forced-circulation evaporator benchmark problem is used to illustratethe approach.