Two-Level Control of Doubly Fed Induction Generator Using Flatness-Based Approach

In this study, implementation of flatness-based control on doubly fed induction generator (DFIG) is investigated. Flatness-based approach is well adopted to control systems in two-level control structure where the tasks of planning, trajectory generation, and tracking the desired trajectories can be easily separated. As a result, the system is decoupled into two trivial linear systems. While in vector control the trajectories are found using PI controllers, in the proposed control structure the trajectories are computed directly, through algebraic equations. Desired active and reactive power are used to develop the set points for trajectory generation. Tracking of the desired trajectories is guaranteed through feedback linearization. The two-level control structure enables active power control and the opportunity for wind plants to contribute in frequency regulation. The proposed control shows promising results in tracking the desired reactive power and the active power across a variety of scenarios and in providing ancillary service to support the frequency regulation of the grid.