Gain-scheduled control of a fossil-fired power plant boiler

The objective is to optimize the control of a coal fired 250 MW power plant boiler. The conventional control system is supplemented with a multivariable optimizing controller operating in parallel with the conventional control system. Due to the strong dependence of the gains and dynamics upon the load, it is beneficial to consider a gain-scheduling control approach. Optimization using complex-μ synthesis results in unstable LTI controllers in some operating points of the boiler. A gain-scheduling approach allowing for unstable fixed LTI controllers is applied. Gain-scheduling which interpolates between unstable controllers is not allowed using traditional schemes. The results show that a considerable optimization of the conventional controlled system is obtainable. Also the gain-scheduled optimizing controller is seen to have a superior performance compared to the fixed LTI optimizing controllers operating alone