Assessment of non-linear modal interaction in stressed power networks using the method of normal forms

This paper reports on the experience in the analysis of non-linear effects arising from the interaction between the fundamental modes of oscillation in power systems. The approach used is based on a flexible representation of the power system derived from the utilisation of a modified normal form approach. First, a brief introduction to the method of normal forms is presented; then a non-linear model of the power system that includes the representation of second-order effects is proposed for the analysis of non-linear effects in a classical model of the power system. This approach is general and can be extended to allow for the analysis of higher dimensional non-linear systems. Based on this formulation, approximate closed form time-domain solutions are utilised to evaluate the influence of non-linear modal interaction on system behaviour. The procedures developed are tested on a 46-machine, 190-bus practical system. © 2002 Elsevier Science Ltd. All rights reserved