Analysis and experiment research on transient behavior of flexible drive train for doubly-fed wind turbine under grid fault

Wind power is a clean source of energy, but can have negative impacts on the distribution grid. More and more grid faults happened with the large-scale wind power integration. The electromagnetic characteristics of the double-fed induction generator (DFIG) wind turbine have been studied a lot under grid fault, while the mechanical characteristics studies during gird fault is rare, especially for the transient behavior of wind turbine under grid fault considering flexible characteristics of drive train. However, the flexible characteristics of the drive train affect the dynamic performance of wind turbine significantly. In order to study and research the dynamic responses of DFIG wind turbine under grid fault fully, and optimize and improve the low voltage ride though (LVRT) characteristics of wind turbine. The characteristics of inertia, damping and stiffness of the main part of the wind turbine drive train were taken account all together in this paper, and a three-mass flexible drive train model was built using spring-damping-mass modeling method. A comparative study between the flexible and the lumped mass drive train model was carried out in the frequency domain based on actual drive train parameters of a 1.5MW DFIG wind turbine. And the conclusions of flexible drive train can be taken as a two-order under damped system and torsion oscillation exist during the grid fault were drawn. A DFIG wind turbine model with flexible drive train based was built in Matlab/Simulink to verify the theoretical analysis and study the dynamic characteristics of the flexible drive train during the grid fault. And transient behaviors of wind turbine considering flexible drive train under grid fault were studied by simulation. The results of simulation indicated the correctness of theoretical analysis. Finally, the field test was carried out on the 1.5MW large scale wind turbine for the first time. The experimental results verified the theoretical analysis and simulation results.