This paper presents a crowbar identification criterion for short-circuit current (SCC) calculation of doubly fed induction generator (DFIG) in large power grids. Based on the transient process of SCC flowing through rotor side converter (RSC) during the fault, this paper derives a practical non-time-domain crowbar criterion under symmetrical and asymmetrical faults, which is only related to terminal voltage and could be adapted to the existing iterative calculation method of SCC. Moreover, the proposed criterion is used to perform steady-state SCC calculation including grid side converter (GSC) in power grid to verify its necessity and effectiveness. The manufacturer-based PSCAD simulation and hardware-in-the-loop simulation are conducted to prove the accuracy of the proposed method.

For the past decades, practical calculation method of short circuit current (SCC) contributed by doubly fed induction generator (DFIG) under asymmetrical short circuit fault is deficient due to its control strategies and unlinear equipment. Asymmetrical SCC of DFIG is much more complicated and may be higher than that of a symmetrical fault in some situations. To address the problem, analytical derivations of SCC under asymmetrical faults are presented by establishing current equations between DFIG windings and converter controller or crowbar protection. Each frequency component could be directly extracted from time-domain expressions. Furthermore, clear mathematical models of asymmetrical peak and steady-state SCC used for practical calculation of power systems are proposed. Simulation results verify the effectiveness and robustness to different parameters and fault conditions of the proposed method. Finally, the influences of possible parameters on characteristics of asymmetrical SCC are summarized based on the proposed method.