Damping of multimodal oscillations in power systems using variable structure control techniques

Over the last three decades, efforts have been made to improve the dynamic 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 dynamics are nonlinear, nonlinear control techniques will be more effective for the control of power systems. The paper presents a technique for designing variable structure controllers (VSCs) to damp out multimodal oscillations in a multimachine power system. A novel approach of incorporating nonlinearities in the system operation at the design stage is proposed. The possibility of achieving a robust design using a simple linear model of power systems is shown. The effectiveness of the proposed VSC is demonstrated by a number of studies. Results show that a VSC performs better than a conventional power system stabiliser and both types of controllers on different units in the system co-operate in a positive manner in damping oscillations