Operational characteristics and blade fatigue life analysis of a novel variable-pitch wind turbine under natural wind conditions

This study was designed to investigate the nonlinear load behavior and fatigue life of distributed small wind turbines in natural turbulent wind fields through an in-situ field experiment. A test platform was deployed in a representative wind resource area in Hohhot, Inner Mongolia, using a self-developed 5 kW variable-pitch wind turbine prototype to perform synchronous high-frequency monitoring of wind speed, direction, and blade root loads. The aerodynamic loads were estimated via blade element theory, and rain-flow counting was used to identify the stress cycle history at the blade root, followed by fatigue life prediction using S-N curves and Miner's linear damage model. A comparative study was conducted on two cases with comparable mean wind speeds but contrasting turbulence intensities. The analysis revealed that increased turbulence intensity significantly amplifies stress fluctuations, raising fatigue damage by 45.7% and reducing blade life by about 31.7%. The results further indicate that adjusting the pitch angle can effectively reduce excessive power output and peak structural loads, confirming the practical control performance of the newly developed pitch actuator. The research offers both measured data and theoretical insights for improving structural reliability and predicting fatigue life of small-scale wind turbines.