Decoupled Power Control of SEIG-WECS System Using Nonlinear Flatness-Based Controller

This paper presents a nonlinear flatness-based approach for simultaneous control of the active and reactive power of a self-excited induction generator (SEIG) in wind energy conversion system (WECS). The proposed flatness-based controller (FBC) generates the control outputs which are applied to the current-controlled voltage source inverter (CC-VSI) and gearbox. A differential flatness theory is exploited to derive the flat outputs of the SEIG generator as well as to prove that the overall system is differentially flat one. This enables a transformation of this system into the linear canonical (Brunovsky) form and facilitates the design of the controller. The design methodology of the flatness-based controller relies on using a flux-based mathematical model of the SEIG in rotating $dq$ reference frame. The set points of the active and reactive powers are converted into system variables using a high-level reference trajectory generator (HLRTG). The proposed approach provides an efficient decoupled control for both the active and reactive power of the SEIG generator. The efficiency of the proposed control system is confirmed through simulation experiments.