Transient Characteristics and Quantitative Analysis of Electromotive Force for DFIG-based Wind Turbines during Grid Faults

For doubly-fed induction generator (DFIG)-based wind turbines (WTs), various advanced control schemes have been proposed to achieve the low voltage ride through (LVRT) capability, whose parameters design is significantly reliant on the rotor electromotive force (EMF) of DFIG-based WTs. However, the influence of the rotor current on EMF is usually ignored in existing studies, which cannot fully reflect the transient characteristics of EMF. To tackle with this issue, this study presents a comprehensive and quantitative analysis of EMF during grid faults considering various control modes. First, the DFIG model under grid faults is established. Subsequently, the transient characteristics of EMF are analyzed under different control modes (that is, rotor open-circuit and connected to converter). Furthermore, the EMF transient eigenvolumes (that is, accessorial resistance item, transient decay time constant, and frequency offset) are quantitatively analyzed with the typical parameters of MW-level DFIG-based WT. The analysis results contribute to the design of the LVRT control scheme. Finally, the analysis is validated by the hardware-in-the-loop experiments.