DAMPING OF MULTIMODAL OSCILLATIONS IN POWER-SYSTEMS USING VARIABLE-STRUCTURE CONTROL TECHNIQUES

Over the last three decades, efforts have been made to improve the dyn amic stability of power systems. Various approaches for the design of power system stabilisers (PSSs) for damping out oscillations in power systems have been reported in the literature. Since the power system d ynamics are nonlinear, nonlinear control techniques will be more effec tive for the control of power systems. The paper presents a technique for designing variable structure controllers (VSCs) to damp out multim odal oscillations in a multimachine power system. A novel approach of incorporating nonlinearities in the system operation at the design sta ge is proposed. The possibility of achieving a robust design using a s imple linear model of power systems is shown. The effectiveness of the proposed VSC is demonstrated by a number of studies. Results show tha t a VSC performs better than a conventional power system stabiliser an d both types of controllers on different units in the system co-operat e in a positive manner in damping oscillations.