Sensitivity Factors in Site Calibration for Wind Turbine Power Performance Testing
Site calibration under IEC 61400-12-3 conventionally relies on wind direction and either mean wind speed or wind shear as the primary sensitivity factors. This study investigates the influence of wind speed, wind shear, inflow angle, turbulence intensity, and wind veer on the calibration relationship at a moderately complex site. Data from a reference met mast and a temporary met mast at the turbine position were analyzed. Results show that inflow angle exhibits a stronger correlation with the wind speed ratio than wind shear. Discarding data bins with low correlation improves calibration quality. At the lower blade tip height, terrain-induced flow distortion increases scatter, yielding poor calibration quality that fails to meet IEC 61400-12-3 requirements. The optimal calibration model uses wind speed as the sensitivity factor (Method 2), achieving a coefficient of determination (R²) of 0.9551 in the 190°–200° sector, compared to 0.9092 with wind shear. Using inflow angle as the sensitivity factor raises R² from 0.8802 to 0.9544 in the same sector and reduces overall Type A uncertainty. For the 200°–220° sector, Method 2 is recommended. The study demonstrates that inflow angle can serve as an effective alternative sensitivity factor, particularly in complex terrain, and that lower blade tip calibration is unreliable for power curve testing in such environments.