Transient Stability Assessment of a DFIG-WTG System Using Trajectory Sensitivity Analysis

A methodology has been presented to assess the transient stability of grid-tied type-3 wind turbine generator systems based on the concept of trajectory sensitivity theory. The objectives here are to estimate the critical clearing time (CCT) and critical values of parameters for doubly fed induction generator-based wind turbine generator (DFIG-WTG) system and identify the parameter that has the highest influence on the system stability. To achieve them, the recently developed reduced-order model of DFIG-WTG system amplifying the dynamics of the phase-locked loop synchronization is considered. The model is numerically solved for computing the sensitivities of the state trajectories with respect to a pre-defined set of parameters. Consequently, the norm of the vector of sensitivities is used as an indicator of the stability margin for the DFIG-WTG system. Following this, the inverse of the maximum value of sensitivity norms obtained from two different simulations is extrapolated to estimate the CCT as well as the critical values of parameters for the DFIG-WTG system. Finally, extended case studies based on trajectory sensitivity analysis have been conducted to demonstrate the application of the methodology for multi-DFIG-WTG systems.