LQG LTR ROBUST CONTROLLER OF COGENERATION PLANT FOR DISTURBANCE REJECTION IN ELECTRIC FREQUENCY AND STEAM PRESSURE/

A robust controller design is considered for reducing the sensitivenes s of electric frequency and extraction steam pressure to the disturban ces imposed on a cogeneration plant by applying LQG/LTR methodology. A sample cogeneration plant that includes the dynamics of the extractio n condensing turbine and generator, actuators and valves, governor, an d PID controllers is modelled as the 15th-order differential equation for controller design. As one of the important steps in the LQG/LTR ap plication, the analysis of the natural frequency of the generator swin g is introduced to estimate the frequency band of the disturbances due to the variation in loads, and to set up the design specification of the LQG/LTR controller. In the robust MIMO controller design procedure , the singular value Bode diagram of the sensitivity transfer function matrix is shaped to reduce disturbance effects on the power system fr equency and steam pressure, according to the design specification. Cas e studies are carried out by adding a reduced 11th-order controller to the nonlinear model of the cogeneration plant. Simulation results dem onstrate the preferable performance of the LQG/LTR controller in distu rbance rejection. Copyright (C) 1996 Elsevier Science Ltd.