Lqg/ltr Robust Control System Design for a Low-pressure Feedwater Heater Train

This paper uses the linear quadratic Gaussian with loop transfer recovery (LQG/LTR) control system design method to obtain a level control system for a low-pressure feedwater heater train. The control system performance and stability robustness are evaluated for a given set of system design specifications. The tools for analysis are the return ratio, return difference, and inverse return difference singular-value plots for a loop break at the plant output. The nuclear industry. • Energy, is presently inves::; the classical Proportional-I: A subsystem of the nucle; received considerable atter. the feedwater plant has b; year for a BWR (boiling-vTo improve control the is used to obtain a le= feedwater heater train c: : for robustness at the plan: procedure. The singular-value pi and inverse return differe: are examined. Introduction •vith the support of the Department of :ating modern control methods to replace -tegral (PI) technique now widely in use. :r power plant, the feedwater plant, has ion. The reason for this attention is that sen responsible for three shutdowns per ater reactor). LQG LTR linear control design method >.'. control system for the low-pressure •nuclear plant. A control system design :>utput is developed using the LQG/LTR '.5 of the return ratio, return difference, ce for a loop break at the plant output The Linearized Model The nonlinear mathemiiical model of the low-pressure feedwater heater train shown in Fig. 1 is obtained using the Modular Modeling System (MMS). The nonlinear plant is linearized about a nominal operating point resulting in a state differential equation of the form