LQG/LTR control system design for a low-pressure feedwater heater train with time delay

An LQG/LTR control system design is formulated for a nuclear reactor feedwater heater train with output time delay. This approach involves factoring the feedwater heater train plant into nonminimum and minimum-phase components to allow the design of a robust controller for the minimum-phase component of the plant using the LQG/LTR technique. The nonminimum phase component takes the form of an all-pass filter containing the RHP zeroes of the first-order approximation of the time-delay component. Using this nonminimum phase all-pass filter, certain singular-value multiplicative error bounds can be established to obtain a stable control system when using the LQG/LTR design technique on the minimum-phase component of the plant. Novel analysis methods using singular values are integrated into the conventional singular-value performance and stability robustness analysis procedure. These methods allow computation of the maximum allowable time delay before instability occurs for both SISO and MIMO (single-input-single-output and multiple-input-multiple-output) control systems