Design of a Robust Adaptive Control Scheme Using Singular Perturbation Technique for Grid-Connected Wind Turbine Systems

The doubly-fed induction generator (DFIG)-based wind turbine system (DFIG-WTS) is one of the most renewable energy sources used for producing electricity. Generally, a back-to-back converter connects the DFIG-WTS to the power grid. However, the DFIG-WTS operates under a wide range of intermittent wind speeds, which may result in highly variable and nonlinear system dynamics. Hence, implementing a robust adaptive control strategy becomes essential to guarantee optimal performance and stability of the system. In this paper, a detailed design and implementation of a model reference adaptive control (MRAC) scheme, with control laws derived using Lyapunov's stability method, is presented to control the rotor side converter (RSC). In the proposed control scheme, the MRAC is applied to regulate the machine rotor voltages. Due to the complexity and nonlinearity of the DFIG-WTS along with the uncertainty of wind conditions, a singular perturbation technique based on the Chang transformation method is used to reduce the studied model by decoupling it into slow and fast modes. The proposed adaptive control scheme is tested and validated on a DFIG-WTS where both the full and reduced models are studied. Simulation results demonstrate that the proposed control scheme significantly enhances system stability and dynamic performance, particularly in regulating rotor winding voltages, electromagnetic torque, rotor angular speed and flux dynamics, across a wide range of wind conditions.