Equivalent Modeling of Three Phase Short Circuit Current Calculation of Direct-Drive Wind Farms Considering Internal Distribution Characteristics

With the increasing integration of wind power into the power grid, the accurate equivalent calculation and modeling of short circuit currents in wind farms are critical for analyzing and setting relay protection parameters of wind power system. However, the traditional single-machine multiplication method applied in direct-drive wind farms (DDWFs) fails to adequately account for the internal characteristics of these stations, thereby introducing errors in the calculation results. This paper proposes a novel calculation model for steady state currents during three phase short circuit faults in DDWFs, considering the distribution characteristics of internal generating units. A piecewise function equation is derived to describe the entire process of current-voltage behavior of the generating unit in DDWFs during three phase short circuits. The equivalent circuit model is formulated as a combination of equivalent impedances and controlled current sources. The accuracy and reliability of the proposed calculation model are validated through comparative test cases under various scenarios.