Design of universal variable-structure controller for dynamic stabilisation of power systems

A study on the application of variable-structure control techniques for improving power system dynamic stability is presented. The basic concepts and design criteria of variable structure control are briefly discussed. The procedure of designing a variable-structure controller for a synchronous machine connected to infinite busbar using a simple linear model obtained by linearising nonlinear characteristics of the system is explained. The effect of variation of machine output power, transmission line reactance and infinite bus voltage on the design of the controller is investigated. A controller algorithm that guarantees proper operation irrespective of machine output power, transmission line reactance and infinite bus voltage is discussed. The performance of the controller is verified using a more elaborate synchronous machine model in which the effect of damper windings is treated. The results of the simulation studies show that with the proposed controller the stability of the power system is improved significantly