Optimal Fractional-Order Backstepping Control of Dual-Star Induction Generator Wind Energy Conversion Systems Under Wind and Parameter Uncertainties

Wind energy conversion systems based on dual-star induction generators (DSIGs) exhibit nonlinear dynamics and sensitivity to operating-condition variations, which can adversely affect power tracking, DC-link voltage regulation, and power quality. This study proposes a fractional-order backstepping control strategy optimized by the Ant Lion Optimizer (FOBC-ALO) for a DSIG-based wind energy conversion system. The fractional-order formulation provides an additional degree of freedom for shaping the controller response, while the ALO algorithm is employed to optimize the controller gains. The fractional order is selected through a sensitivity analysis, with α = 0.5 providing the most balanced performance among tracking accuracy, transient response, DC-link voltage regulation, and harmonic distortion. The proposed controller was implemented and evaluated in MATLAB 2021/Simulink and compared with a conventional backstepping controller under four simulation scenarios involving variable wind-speed profiles, machine-parameter variations, stepwise wind-speed changes, and operation without maximum power point tracking. The results show that the proposed controller consistently improves the dynamic and power-quality performance of the DSIG-based system. In the first test, the active-power response time was reduced from 1.66 to 1.32 ms, while the current total harmonic distortion (THD) decreased from 1.87% to 1.06%. Under 100% variations in the selected machine parameters, the THD decreased from 5.13% to 2.13%, while the DC-link voltage fluctuation was reduced from 10.18 to 3.02 V. For the stepwise wind-speed test, the proposed controller reduced the active-power response time by 47.99%, the ITAE by 63.70%, the DC-link voltage fluctuation by 71.90%, and the current THD by 48.69%. In the operation without MPPT, the integral of time multiplied by squared error (ITSE), integral of time multiplied by absolute error (ITAE), DC-link voltage ripple, and current THD were reduced by 41.28%, 57.67%, 74.88%, and 46.94%, respectively. Overall, the simulation results indicate that the proposed FOBC-ALO strategy improves reference tracking, transient response, DC-link voltage regulation, and current waveform quality across the investigated operating conditions. The findings provide a simulation-based foundation for subsequent real-time and experimental validation of fractional-order control for DSIG-based wind energy conversion systems.