Fault Current Analysis of DFIG Considering Multi-time Scale Protection and Control under Asymmetrical Voltage Dips

The characteristics of asymmetrical short-circuit current of doubly fed induction generators (DFIGs) are different from those of synchronous generators (SGs). With the increase in the quantity and capacity of DFIGs, the analysis and calculation of the asymmetrical short-circuit current of DFIGs are vitally important for the safe and stable operation of modern power systems. Under asymmetrical fault conditions, protection circuits and control strategies of DFIGs have multi-time scale characteristics and the equivalent circuit will change accordingly. Moreover, the negative-sequence internal voltage of DFIG is controllable, which makes the analysis more complex. This paper proposed an analytical calculation method of the asymmetrical short-circuit fault current and the characteristics of fault current are analyzed considering the multi-time scale control and protection. Finally, the proposed expression is validated in MATLAB/Simulink.