  This paper presents a Generalized Modal Analysis (GMA) concept for the
small-signal stability analysis of power systems with high penetration of
Converter-Interfaced Generation (CIG). GMA quantitatively assesses interactions
between various elements in the power system, offering intuitive and
transparent physical interpretations. The method's versatility in selecting
physical quantities at different input and output ports makes it broadly
applicable. Based on the concept of GMA, the study further defines interaction
quantification indices by selecting voltage ports, examining the impact of grid
disturbances on power sources and the support from the power sources to the
grid at connection points. Numerical simulations on modified 14-bus and 68-bus
systems validate GMA's effectiveness in capturing the coupling of the dynamic
characteristics between grid elements. This research provides a theoretical
foundation and analytical framework for future analyses of power system
stability with diverse power sources.
