Second‐order sliding‐mode controller design and tuning for grid synchronisation and power control of a wind turbine‐driven doubly fed induction generator

This study presents a second‐order sliding‐mode control (2‐SMC) scheme for a wind turbine‐driven doubly fed induction generator (DFIG). The tasks of grid synchronisation and power control are undertaken by two different algorithms, designed to command the rotor‐side converter at a fixed switching frequency. Effective tuning equations for the parameters of both controllers are derived. A procedure is also provided that guarantees bumpless transfer between the two controllers at the instant of connecting the DFIG to the grid. The resulting 2‐SMC scheme is experimentally validated on a laboratory‐scale 7 kW DFIG test bench. Experimental results evidence both the high dynamic performance and the superior robustness achieved with the proposed control scheme.