Reactive Characteristics in Subsystem-Level Small-Signal Stability Analysis of Multi-Converter Systems

Journal article, 2026

This paper investigates the impact of converters’ reactive characteristics on small-signal stability assessment in multi-converter systems. A reactivity index is defined and introduced as a complementary measure to the passivity index, which forms the basis of subsystem-level stability analysis. Passivity theory alone may be insufficient to fully assess instability risks in such systems. In particular, the reactive characteristics of the converters and the connecting grid are used to identify system resonances, while active characteristics (passivity) indicate the potential for destabilization of those resonances. Theoretical findings are validated through time-domain simulations.