Aerodynamic Parameter Analysis of Solar Trackers Using Aeroelastic Models and Variational Mode Decomposition

Single-axis solar trackers, known for their cost-effectiveness, have seen widespread use in recent years as a competitive electricity generation system. However, their slender forms and large wind-exposed surfaces make them highly susceptible to wind effects. Wind tunnel experiments on a scaled aeroelastic model were carried out to examine how aerodynamic damping and stiffness influence the stability of the tracker. Displacement responses under different tilt and wind direction angles were measured. The technique of variational mode decomposition (VMD) was employed for signal processing. In order to refine the decomposed signal's accuracy, particle swarm optimization (PSO) was utilized. A weighted fitness function with the simultaneous consideration of sample entropy and envelope entropy is defined and used for determining the optimal values of penalty factor (α) and the mode number (K) of VMD. Based on these, the damping and stiffness of the whole system were identified by Hilbert transform (HT). By subtracting structural damping and stiffness from those of the whole system, the corresponding values of aerodynamic damping and stiffness were finally obtained. Results show that aerodynamic damping is more sensitive to tilt angle. A relatively large value of aerodynamic negative damping can be easily found between the tilt angle of –30° and +30°. As wind speed increases, aerodynamic stiffness decreases, with a significant reduction observed at a tilt angle of ±30°. Due to the effect of aerodynamic stiffness, the vibrational frequency is found to be lower than the natural frequency that was designed for the model.