Complex Short Circuit Ratio to Evaluate Grid Robustness for Inverter Integration

So far, the short circuit ratio (SCR) has been widely used to assess grid robustness at inverter points of interconnection. However, its mathematical and geometric foundations have not been fully established, and its applicability across various X/R ratios and power factors remains an open question. This paper provides a geometric interpretation of the SCR based on the two-dimensional direct-quadrature axis framework from the perspective of voltage stability. The analysis incorporates the grid’s equivalent impedance, specifically accounting for the X/R ratio, as well as the inverter’s power factor and the reactive power contribution of shunt filter capacitors. The proposed method is validated through multiple case studies conducted under diverse conditions using an electromagnetic transient (EMT) model derived from a real power system. Simulations are performed with the Power System Computer Aided Design/Electromagnetic Transient including DC (PSCAD/EMTDC<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TM</sup>) platform.