Model Circuit of Wind Farm

The amplitude of the phase-to-ground voltage for the backward system is 

The grid impedance % Z is assumed to be j2.5% (10 MVA Base). The inductance Lg is obtained as follows  

The capacity and impedance of each transformer installed in the substation S/S-L are 18 MVA and 10%, respectively. Those of the step-up transformer are assumed to be 3.5 MVA and 10%. 

The leakage inductance referred to the low-voltage side is obtained as follows  

The winding resistance is assumed to be 1% of the leakage reactance, that is, the resistive component is almost neglected in this simulation. The resistance referred to the high-voltage side is 

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