Sub-synchronous oscillation suppression strategy under virtual synchronous generator control of DFIG in series compensated grid

Doubly-fed induction generator (DFIG) in series compensation lines is susceptible to sub-synchronous oscillation (SSO) problems. This paper studies the SSO of DFIG connected under virtual synchronous generator (VSG) control strategy in a series compensation grid. The impedance model of DFIG controlled by VSG with voltage-current inner loop is firstly established, and then analyzed the influence of the outer and the inner loops on the impedance model. In stability analysis, based on the impedance model, the generalized Nyquist criterion (GNC) is used to analyze the influence of series compensation level, virtual inertia coefficient, virtual damping coefficient and voltage loop proportional parameters on the stability of DFIG power grid-connected system. According to the control structure characteristics of DFIG, the control method of additional damping at the rotor current loop output position is adopted, and the influence of additional damping control on system stability and output impedance is analyzed. Finally, the effectiveness of the compensation control method is verified by simulation analysis.