Nonlinear Control Strategy for DC-Link Voltage Control in a DFIG of WECS During 3φ Grid Faults

The widely used doubly fed induction generator (DFIG) in wind energy conversion systems encounters challenges related to dc-link voltage (V-dc) variations and instability, primarily from power imbalances caused by grid faults. Grid faults can occur due to factors such as insulation failure, flashover, and physical damage leading to excessive current flow. In this article, the implementation of both traditional and feed-forward controllers was first studied. A nonlinear controller for the grid-side converter aimed at regulating V-dc in the DFIG system is proposed to convert excess power due to grid faults into useful power and to protect power electronic circuits. The effectiveness of the proposed nonlinear controller was assessed through full-scale simulation using 2-MW DFIG during a grid fault scenario. Furthermore, it was validated using a laboratory-scale experimental setup with 0.75-kW DFIG. Simulation results demonstrated that the proposed nonlinear controller effectively managed V-dc variations, exhibiting reduced overshoot and rapid settling time, and kept V-dc in a safe limit compared to other methods. The experimental results mirrored these findings. These outcomes confirm that the proposed method swiftly and efficiently regulates V-dc variations during grid faults.