Comprehensive Modeling and Analysis of Stator Turn-to-Turn Short-Circuit Faults in a DFIG

With the gradual increase in high capacity doubly fed induction generators (DFIGs) in recent years, turn-to-turn short-circuit (TTSC) faults have become a greater threat. Notably, owing to the absence of an effective fault model, the specific TTSC fault behaviors of DFIGs remain to be clarified. This study proposes a comprehensive field-circuit coupling model of stator TTSC faults inside a DFIG, which captures a two-way interaction between the circuit and field domains. Meanwhile, the control strategy for DFIG back-to-back converters is also considered in this computational model. Moreover, the nonlinear resistance of the fault arc is simultaneously calculated by using a black box model in the circuit domain. A 1.5 MW DFIG with its control system was modeled and simulated to suffer a series of TTSC faults. Fault features, including the distributions of magnetic flux density, short-circuit currents, and terminal behaviors, were revealed, and the influencing factors regarding the fault types, severities and locations were discussed. The proposed comprehensive model and the derived characteristic signatures provide insights into the development of sensitive and reliable relay protection schemes for TTSC faults in DFIGs and are expected to promote subsequent research on fault detection and diagnosis in electric machinery controlled by power electronics.