Applicability analysis of multi-infeed short circuit ratio in the small-signal stability analysis

The increasing penetration of renewable energy resources may lead to multiple instability issues under the ac grid with low grid strength. The short-circuit ratio (SCR), as a common index of grid strength, is still lacking the applicability discussions and the theoretical support to reflect the stability mechanism in the multi-infeed power electronic system (MIPES). To this end, this paper mainly focuses on the small-signal stability issue of the MIPES, and elaborates the theoretical basis of the multi-infeed short-circuit ratio (MISCR) including the equivalent circuit-based short circuit ratio (ESCR) and generalized short circuit ratio (gSCR) for the small-signal stability analysis. Further, it is proved that the stability criterion based on gSCR is a sufficient and necessary condition for the small-signal stability analysis in the nominal MIPES system, while the stability criterion based on ESCR still lacks of theoretical basis for the small-signal stability analysis of the MIPES. Finally, simulation results verify the effectiveness of the above conclusions by means of the IEEE 39-node topology example.