Comparative analysis of the performance of small H-Darrieus for different pitch control strategies

Abstract

The cyclic variations of the Angle of Attack (AoA) during the operation of H-Darrieus VAWT bring them to operate under fatigue-type loads which stakes the blade’s endurance and the lifetime of the wind turbines. At low wind speed, the AoA exceeds the stall angle and causes significant variations in aerodynamic loads on the blades. This behavior is considered one of the most recognized weaknesses of VAWT technology. To mitigate these cyclic variations, one of the approaches adopted is to prescribe either a fixed or dynamic control pitching angle to the rotor blades that prevent them from having too large AoAs. This research aims to investigate the effect of several dynamic pitch angle strategies on the aerodynamic behavior of the H-Darrieus rotor. Four pitch control strategies were pursued to explore the effect of the pitch angle on the H-Darrieus performance and the angle of attack. A novel modified pitch control strategy has been adopted to monitor the rate of change of blade direction that is relative to the incoming wind flow. Insight was devoted to investigating the impact of this parameter on the performance and self-starting capabilities of the H-Darrieus rotor, at optimum and low wind speed. 3D unsteady lifting line free vortex wake-based model was performed. The results revealed two ranges of values for the setting parameter for which the produced torque followed an increasing and decreasing trend and which is still higher than the non-pitched blades. Furthermore, at the optimal TSR, dynamic pitching control showed no significant effect on the VAWT performance, as less than 3% was achieved. At low TSR, the torque increased almost six times as compared to the fixed and zero-pitched blades.