DFIG Wind Farm Modeling for Subsynchronous Control Interaction Analysis

Single doubly fed induction generator (DFIG) model is adopted in present subsynchronous control interaction (SSCI) analyses because of its ease of use. But, there are hundreds of wind turbine generators (WTGs) under different operating conditions in practical wind farms. A two-DFIG model is employed in this paper to check the influences of different system factors on SSCI. These analyses indicate that resonant frequency of SSCI predominantly depends on the leakage inductances of the generator and transformer. It indicates that the impedance of the resonant circuit mainly consists of the above inductances and the series capacitor. Thus, in the sense of resonance, the whole system can be simplified into an LC circuit. According to the resonant power conservation of this LC circuit, a multi-DFIG model can be aggregated into a single-DFIG model. Eigenvalue analysis and simulation results show that the proposed single-DFIG model possesses acceptable precision in the representation of SSCI in a multi-DFIG system.