Mechanism Analysis and Damping Method for High Frequency Resonance Between VSC-HVDC and the Wind Farm

As of now, the issue of High Frequency Resonance (HFR) in the Doubly Fed Induction Generator (DFIG) with the weak ac grid have been widely investigated. However, due to the influence of time delay in the control of VSC-HVSC, the HFR can occur in the interconnected system where the VSC-HVDC connects to the wind farm as well. Based on impedance model of DFIG system and the deduced impedance model of VSC-HVDC, this paper investigates the occurrence mechanism of the HFR when the VSC-HVDC connects to DFIG based wind farm, and analyzes the mechanism that the control delay influences the stability of VSC-HVDC system. Further, to avoid the HFR, this article proposes a damping control method based on an additional voltage controller, the damping controller can fully counteract the influence of time delay so that the HFR can be damped. Also, the performance of the controller can be maintained when control delay changes. Simulation results of the VSC-HVDC system connects to a wind farm are given in this paper to verify the correctness of the occurrence mechanism and the effectiveness of the proposed damping methods.