Adaptive Passivity-Based Control of Forced Subsynchronous Oscillation in DFIG-Based Wind Farms

The forced sub-synchronous oscillation (FSSO) accident in Hami, Xinjiang, has the new characteristics of time-varying frequency. It is significantly different from the previous negative damping sub-synchronous oscillation, which has aroused widespread concern. In this paper, the generation mechanism of FSSO is analyzed, and an oscillation suppression strategy based on adaptive passivity-based control (APBC) is proposed. Firstly, the propagation path of inter-grid harmonic disturbance source in doubly-fed induction generator (DFIG) unit is analyzed based on the mathematical model. The generation mechanism of FSSO under the excitation of disturbance source is analyzed using an equivalent disturbance equation, and through analysis of the relationship between bandwidth stability and damping state, a design concept for suppression strategy is proposed. Secondly, the RSC control strategy is designed by introducing the PBC theory. Based on the disturbance suppression and damping compensation effect of the APBC, the overall control framework and oscillation suppression strategy are proposed. Finally, considering the influence factors such as wind speed, line series compensation degree and the number of online wind turbines, a FSSO simulation model of wind farm is built, which verifies the effectiveness of the suppression strategy proposed in this paper. Moreover, the well engineering application prospects is verified by the actual FSSO example in Hami area.