Short circuit current calculation of Doubly Fed Induction Generator

Based on the basic voltage and flux equations of the Doubly Fed Induction Generator, this paper derived expressions of short-circuit current of wind turbines, which are expressed by transient equations of stator and rotor flux. The transient equations of stator and rotor flux were functions of initial values of stator and rotor flux and transient time constants of stator and rotor windings. The initial value of stator flux was calculated, considering the influence of stator resistance, and the rotor flux equation under steady state condition was used to calculate the initial value of rotor flux. Transient behaviors of the stator and rotor flux were analyzed when three-phase faults occurred at terminals of generators, then the transient equations of stator and rotor flux and detailed equations of the short-circuit current of DFIG could be obtained. DIgSILENT/PowerFactory program was used to execute electromagnetic transient simulations when three-phase faults occurred at terminals of generators and at the power system respectively. Simulation results show that it is efficiently to use the equations of short-circuit current proposed by this paper to calculate the short-circuit current of DFIG. As the stator and rotor resistances are considered in the equations of the short-circuit current, calculation results are closer to simulation results, and all differences are less than 4%.