Evaluation of the effect of modal interaction higher than 2nd order in small-signal analysis

This paper attempts to obtain insight about the effect of modal interaction of higher than 2^nd order in small-signal analysis, through evaluating the effect of 3^rd order modal interaction. The indices that quantify the 3^rd order modal interaction are defined, following the modal analysis procedures used in linear modal analysis and second order modal analysis. Numerical simulation results demonstrates that, there are definitely modal interaction higher than 2^nd order, and with further higher order modal analysis, it is possible to detect more information about modal interaction, which might be useful in power system control.