Coupling Short-Circuit Ratio Calculation Method Based on the Source Network Load Correlation Thevenin Equivalent

The short-circuit ratio is a key index used to measure the voltage support capability of new energy grid-connected systems, which contradicts its accuracy and practicability. The current short-circuit ratio index (SCR-U) does not consider the influence of the coupling impedance between power supply and load on the short-circuit ratio in the calculation process. This paper derives the coupled short-circuit ratio (SCR-O) based on SCR-U and the coupled equivalent impedance. The coupled critical short-circuit ratio (CSCR-O) is then numerically obtained based on the maximum transmission power, and the extreme value of the critical short-circuit ratio is calculated to provide a numerical basis to determine the accuracy of SCR-U and SCR-O. Finally, simulations demonstrate the superiority of the coupling short circuit to the short-circuit ratio index. It can provide more accurate results and reflect the system’s real-time voltage stability.