Analysis of Torsional Oscillation Characteristics of Voltage-control Type Doubly-fed Induction Generator Based on Decoupled Damping Torque Coefficient

Virtual synchronous generator (VSG) control is used to replace the control loop of rotor side converter in voltage-control type doubly-fed induction generator (DFIG), making converter has inertia and damping characteristics, but the interaction between VSG and drive-train shaft intensifies torsional oscillation. Drive-train shaft is taken as a research object in this paper, mode decoupling method and damping torque analysis method is used to propose a damping torque analysis method that decouples the state variables of the drive-train shaft. Firstly, based on state-space equations of voltage-control type DFIG, the damping path of VSG for torsional oscillation is derived. Secondly, based on mode decoupling method, an analytical expression between state variables of drive-train shaft and damping torque coefficient is proposed to quantify the influence of VSG on torsional oscillation. Finally, the influence of control parameter in DFIG and VSG on torsional oscillation is quantified by damping torque coefficients, and the correctness of the coefficients is validated through time domain simulations.