Sliding mode control strategy for DFIG

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Sliding mode control strategy for DFIG

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Sliding Mode Control (SMC) is a robust control strategy widely applied to Doubly Fed Induction Generators (DFIGs) in wind energy systems. DFIGs are popular in wind turbines due to their variable-speed operation and improved energy efficiency. However, they face challenges like parameter uncertainties, grid disturbances, and mechanical stress.

SMC, known for its insensitivity to parameter variations and external disturbances, is particularly effective for DFIG control. The strategy works by forcing the system state to "slide" along a predefined surface, ensuring stability and fast dynamic response. In DFIG applications, SMC is primarily used for rotor-side and grid-side converter control.

For rotor-side control, SMC helps regulate torque and stator reactive power independently, enhancing fault ride-through capability. On the grid side, it ensures stable DC-link voltage and accurate power injection into the grid, even under unbalanced conditions.

The key advantage of SMC in DFIGs is its ability to handle nonlinearities and disturbances without requiring precise system modeling. However, designers must address chattering—a high-frequency oscillation inherent in SMC—through techniques like boundary layer approximation or higher-order sliding modes.

Applications of SMC in DFIGs are particularly valuable in weak grid conditions or during voltage sags, where conventional PI controllers may underperform. Future trends include hybridizing SMC with adaptive or intelligent control methods to further improve DFIG performance under complex operating scenarios.