Design and tuning of fixed-switching-frequency second-order sliding-mode controller for doubly fed induction generator power control

A pulse-width modulation-based second-order sliding-mode control (2-SMC) scheme for the rotor-side converter feeding a doubly fed induction generator (DFIG) is presented. It is aimed at achieving both high robustness to DFIG parameter variations and close tracking of a predefined rotor speed-dependent optimum power curve, while preserving a fixed switching frequency. In addition, it eludes the appearance of chatter. Tuning equations are also derived to adjust all its gains and constants. The proposed 2-SMC algorithm is evaluated as part of a sensorless scheme on the mathematical model of a 660-kW DFIG via numerical simulation. Its operation in terms of robustness and dynamic performance is then compared with that of a classical PI-based vector control (VC) strategy. The validity of the suggested 2-SMC scheme, as well as its superior performance in comparison with its PI-based VC counterpart, are corroborated through experimentation carried out on a 7-kW DFIG test bench.