An Improved Fault Ride Through Scheme and Control Strategy for DFIG-Based Wind Energy Systems

This paper proposes a fault ride through scheme for doubly-fed induction generator (DFIG)-based wind energy systems. The proposed framework combines the robustness properties of fractional order sliding mode control (FOSMC) with the active/reactive power control capability of dynamic voltage restorer (DVR) and high-power density of superconducting magnetic energy storage (SMES) devices. The FOSMC is formulated using a novel sliding manifold to control the series active filter and generate appropriate voltage for injection into the stator terminal so as to maintain the dynamic stability of the DFIG in the presence of grid faults. The DVR is used as a cost-effective solution to compensate for grid-induced voltage sags. The SMES is used as a grid-enabling device that instantaneously stores and discharges high levels of power to mitigate the sudden drop in the power resulting from the grid fault. The effectiveness of the proposed approach is demonstrated using a DFIG-based wind energy system subjected to both symmetrical and unsymmetrical faults.