Generalized short circuit ratio for multi-infeed LCC-HVDC systems

The relationship between the short circuit ratio (SCR) and static voltage stability is analyzed in this paper. According to eigenvalue decomposition method, a concept named generalized short circuit ratio (gSCR) has been proposed for multiinfeed HVDC (MIDC) systems to mathematically measure the connected AC strength from the voltage stability point of view, which can overcome the rule-of-thumb basis of existing multiinfeed short circuit ratio (MISCR) concept. In gSCR, two indices, the critical gSCR (CgSCR) and the boundary gSCR (BgSCR) are developed to quantitatively evaluate if the connected AC system is strong or weak, in which CgSCR=2 and BgSCR=3 are two critical values for strength criterion. Finally, simulations are conducted to validate the effectiveness of the proposed gSCR. The results show that some system parameters like equivalent AC impedance angle have little effect on the two critical values.