Sliding mode control with three-level rotor-side converters in DFIG-based wind energy systems: Comparison study

This study examines a variable-speed wind energy conversion system based on a doubly-fed induction generator (DFIG). The rotor is regulated using power electronic converters, whereas the stator is directly connected to the grid. A comprehensive mathematical model is developed to support the control design process. The main objective is to investigate the effectiveness of sliding mode control (SMC) when applied to the DFIG. In particular, the performance of SMC is evaluated using both two-level and three-level rotor-side converters. The results indicate that the combination of SMC and three-level converter topology reduces current ripple and harmonic distortion, while enhancing the dynamic response compared to the two-level case. Furthermore, a comprehensive comparison between SMC and conventional PI control strategies is conducted. The results highlight the superior accuracy and performance of SMC, demonstrating excellent tracking of setpoints for various system variables. This is further confirmed by its robustness to machine parameter variations and its precise regulation of both active and reactive stator powers.