Summary of Research on Multi-infeed Short Circuit Ratio in AC and DC Systems

Multi-infeed Short Circuit Ratio (MISCR) is a useful index which can evaluate the interaction between AC and DC in multi-infeed AC/DC systems. However, it cannot accurately analyze the influence of high nonlinearity and be applied in new aspects such as DC hierarchical connection. This paper tries to make a brief survey on MISCR. Firstly, based on the definition of MISCR proposed by CIGRE DC working group, the variation of short-circuit ratio before and after forming multi-infeed system is introduced. Then the influence of contact impedance between DC drop point, system equivalent impedance and DC power on MISCR is explained in detail. Also, the application of MISCR on voltage stability, dynamic overvoltage and harmonic resonance is summarized. Finally, the shortcomings and current improvement of MISCR are presented, which provide a foundation for further research on multi-infeed AC/DC system.