Research on power coefficient of wind turbines based on SCADA data

Power coefficient Cp is an important parameter for wind turbine design and operational control. Wind speed is the basic calculation parameter of the power coefficient. Since the anemometer is fixed on the nacelle, the measured wind speed is different from the wind speed in front of the wind rotor. Calculation error will produced if the directly measured wind speed is used to calculate the power coefficient. In this paper, a calculation model of the wind speed in front of the wind rotor is presented based on the SCADA data and the aerodynamic theory. Two power coefficient calculation methods are proposed. One is based on the statistical data and the other is based on the real-time data. An actual calculation result for a 2 MW wind turbine shows that the power coefficient is near or greater than 0.593 (the theoretical maximum value) if the directly measured wind speed is used during the maximum power point tracking (MPPT). After wind speed correction, the power coefficient is reduced to 0.397 that is more realistic. When using the real time data, the power coefficient is time-varying even in the region of MPPT, since wind speed is time-varying and the wind rotor rotational speed regulation is delayed due to the wind rotor moment of inertia.