Decentralized suboptimal load-frequency control of a hydro-thermal power system using the state variable model

State space modelling and synthesis of decentralized suboptimal load-frequency control for hydro-thermal power systems are described in this paper. The state space models are derived by the partial fraction technique for reheat steam turbines, hydro turbines and hydro governors having numerator dynamics. Decentralized suboptimal load-frequency controls are synthesized by using the method of minimum error excitation and their performance is analysed as a function of tie-line power level. It is shown that the suboptimal control with feedback of some, but not all, of the remote area state variables is a feasible alternative to the optimal control, whereas local control without feedback of any remote state variable is inadequate for stabilizing the system.