A sequential loop closing approach to the ALSTOM gasifier problem

Abstract

A sequential loop closing technique combined with high-frequency decoupling was applied to the design of a control scheme for a gasifier unit that forms part of an integrated gasification combined cycle power plant. The data describing the plant were provided by ALSTOM, in the form of three locally linearized state-space models. Although the initial analysis tests were frustrated by the extremely ill-conditioned nature of the model data, which yielded erroneous results when used with standard test procedures, it was possible to design a control system for the gasifier at the 100 per cent load condition by making use of certain scaling and decoupling algorithms. The robustness of this control scheme was then assessed by applying it (unchanged) to the 50 and 0 per cent operating conditions. The resulting closed-loop systems were simulated and the results obtained show that the controlled system performed quite well at all load conditions, albeit with the violation of input constraints in the face of pressure disturbances.