Admittance Modeling of DFIG-WT with Stator Current Control Considering PLL and DC Bus Dynamic

Direct stator current control (SCC) has wide application prospect in wind power systems based on doubly-fed induction generation (DFIG) duo to the advantage that the reference current is not affected by generator parameter drift. However, the oscillation characteristic between SCC-controlled DFIG and series compensation line seriously hindering the safe consumption of wind power. In this paper, the small signal transfer law of SCC-DFIG is deeply analyzed. Moreover, the admittance models are established to accurately characterize the frequency domain characteristics of SCC-DFIG by taking into account the influence of multi-time scale dynamic characteristics such as phase locked loop (PLL), dc bus dynamic and frequency coupling. Theoretical analysis and simulation results show that the grid-connected oscillation risk of SCC-DFIG is higher than DFIG with rotor current control (RCC). The stability evaluation results can provide reference for the formulation of inhibition strategy and stable operation of SCC-DFIG.