A Short-Circuit Current Calculation Method Based on Zonal Linearized Norton Equivalents for High Proportion Renewable Energy Power Systems

[Objective] With the continuous increase in the proportion of renewable energy， the impact of renewable energy on short-circuit current calculations and circuit-breaker interrupting capacity verification is becoming increasingly significant. Currently， short-circuit current calculations in high proportion renewable energy power system face challenges such as insufficient accuracy of traditional methods and difficulties in obtaining renewable energy model parameters. To accurately assess the impact of renewable energy integration on system short-circuit current characteristics， this article proposes a short-circuit current calculation method for high proportion renewable energy power system based on zonal linearized Norton equivalents. [Methods] Firstly， based on typical low voltage ride through control logic， a practical voltage-current mapping model is established， dividing the renewable energy fault response into a external zone， an influence zone， and a core zone. This model only requires easily accessible grid codes or equipment parameters. Secondly， for renewable energy units in the influence zone， formulas for calculating linearized Norton equivalent parameters that dynamically vary with terminal voltage are derived， overcoming the limitations of traditional fixed parameter equivalent models. Thirdly， to improve computational efficiency for large scale systems， an adaptive zonal partitioning and iterative calculation strategy is proposed. This strategy applies detailed Norton equivalent models to the fault core and influence zones while solving with simplified models for external zones. [Results] Simulation validations on a 3-machine 9-node system and an improved IEEE 30-node system demonstrate that the proposed method yields node voltages and short-circuit currents that highly match those from MATLAB/Simulink simulations. [Conclusions] The proposed method accurately characterizes the nonlinear and multi-stage response characteristics of renewable energy during faults without relying on complex internal control parameters， providing an effective tool for short-circuit current analysis in high proportion renewable energy power system.