Controller Structure Identification Method for Doubly-Fed Wind Turbine Generators Based on Mapping Between FRT Response and Control Loops
Accurate electromagnetic transient (EMT) models of doubly-fed induction generator (DFIG) wind turbines are essential for grid stability analysis under large disturbances, yet encapsulated commercial controllers prevent structural access. This paper proposes a controller structure identification method based on the mapping between fault ride-through (FRT) response morphology and control loop actions. Using measured FRT responses from nine mainstream DFIG types under symmetrical and asymmetrical faults—with voltage sags to 0.9, 0.75, 0.5, 0.35, and 0.2 p.u. and swells to 1.2, 1.25, and 1.3 p.u., and durations of 2000, 1705, 1214, 920, 625, 2000, 1000, and 500 ms—typical response features are categorized. Mapping relationships between each FRT stage and control loop actions are established, and identification criteria for active power, reactive power, and FRT control loops are constructed via excitation signal and operating condition combinations. A white-box EMT model is built from the identification results and validated on a hardware-in-the-loop platform against manufacturer black-box models and actual controllers. Results show the proposed method achieves high modeling accuracy across different DFIG types and operating conditions, outperforming the WECC generic model, particularly in reproducing full-process FRT responses including active/reactive power spikes, oscillations, and recovery behaviors.