Power system damping from energy function analysis implemented by voltage-source-converter stations

Because weakly damped system oscillations can endanger the secure operation of power systems, this paper is a study on how damping can be increased. As the power system is nonlinear, an energy function approach, patterned after the direct method of Lyapunov function, is used in the analysis. The analysis develops an energy function W and shows that a real power term (proportional to local frequency) and/or a reactive power term (proportional to the line voltage differentiated with respect to time) increase the rate of diminution of the energy function W. This implies effective damping of power swings by such power signals and is verified by simulations of a multi-machine system model. The damping signals are introduced by voltage-source-converter (VSC) stations.