Transient modeling and stability analysis of DFIG under different power control mode

Abstract

As one of the dominant types of renewable energy generation, the transient characteristics of doubly fed induction generator (DFIG) affect the grid reliability significantly. The stator of DFIG is directly connected to the grid, and its current is strongly influenced by the output angle of the phase-locked loop (PLL). This unique structure results in the power angle of the DFIG more complex, as it cannot be simply derived from the stator voltage. Consequently, the transient process of the DFIG remains not fully characterized. To quantitatively analyze the transient stability of DFIG, a transient model of DFIG based on angle and magnitude is first established. Based on this magnitude-phase model (MPM), this study formulates the nonlinear equations for the DFIG's PLL and defines its power angle. Subsequently, a transient stability analysis method based on the equal area criterion (EAC) is developed, and its conservativeness is evaluated. The stability of the DFIG under different low voltage ride through (LVRT) strategies is compared and analyzed with the EAC, considering various rotor current-to-power angle relationships. Finally, simulations validate that the proposed MPM is accurate and applicable under transient process, and the proposed criterion can effectively estimate the stability of DFIG in transient processes.