Second-order sliding-mode controller design and tuning for grid synchronization and power control of a wind turbine-driven DFIG

This paper presents a second-order sliding-mode control (2-SMC) scheme for a wind turbine-driven doubly-fed induction generator (DFIG). The tasks of grid synchronization and power control are undertaken by two different algorithms, designed to command the rotor-side converter (RSC) at fixed switching frequency. Effective tuning equations for the parameters of both controllers are derived. A procedure is also provided that guarantees bumpless transition between the two controllers at the instant of connecting the DFIG to the grid. The resulting 2-SMC scheme is evaluated via real-time hardware-in-the-loop (HIL) emulation over the virtual prototype of a 660-kW DFIG. HIL results evidence both the high dynamic performance and the superior robustness achieved with the proposed control scheme.