LQG/LTR robust control system design for low-pressure feedwater heater train

The linear quadratic Gaussian with loop transfer recovery (LQG/LTR) control system design method is used to obtain a level control system for a nuclear plant low-pressure feedwater heater train. A control system design for robustness at the plant output is developed. Its performance and stability robustness are evaluated for given 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. These singular-value plots are examined. The LQG/LTR control system design procedure allows the synthesis of a low-pressure feedwater heater train level control system that meets certain frequency-domain design specifications. In this case, by only using the inherent integral type of action that deviates slightly from the ideal integral action, plant integral augmentation is avoided. Using these plant dynamics results in command following of one feedwater tank level with a slight steady-state error, which is expected. since pure integrals did not exist in the plant. The design of this robust control system shows that a desirable low-pressure feedwater heater train level control system is obtainable using the LQG/LTR procedure