Mathematical Modeling Method and Main Protection Configuration for Stator Short-circuit Fault of Large Doubly-fed Pumped Storage Unit

The large doubly-fed pumped storage unit (DFPSU) features AC excitation and variable speed constant frequency power generation. It can be used not only for planned peak shaving and frequency modulation, but also for wide power range follow-up adjustments in response to wind and solar power fluctuations. Studying mathematical modeling methods for internal faults holds significant practical importance. It aids in understanding fault characteristics and determining the optimal main protection configuration. This study establishes a general mathematical model of DFPSU based on branch voltage and flux linkage equations, with its accuracy verified through dynamic simulation experiments. Based on this, the proposed model is applied to batch simulations using an actual large-scale unit as the analysis object, enabling quantitative analysis of the optimal stator short-circuit fault protection configuration. The recommended main protection configurations are: ‘zero-sequence transverse differential current protection + split-phase transverse differential current protection + complete longitudinal differential current protection’ or ‘zero-sequence transverse differential current protection + split-phase transverse differential current protection + double incomplete longitudinal differential current protection'. This configuration provides the most comprehensive protection coverage.