Development of an Equivalent Wind Plant Power-Curve

Wind turbine manufacturers publish and certify power curves for their turbines. These turbine power curves are used for planning purposes and estimating total wind power production. When a wind plant consisting of many turbines connects to the utility grid and starts operation, the focus shifts to the entire plant’s performance. An equivalent wind plant power-curve becomes highly desirable and useful in predicting plant output for a given wind forecast. The National Renewable Energy Laboratory (NREL) has worked with a utility to collect detailed data from a large wind power plant to develop such an equivalent power curve. This paper will (1) summarize available data, methodology, and the results of this work; (2) discuss the validation process; and (3) explore the applicability of such an approach on other wind power plants without detailed data. Performance of a single wind turbine can be characterized by a power curve − a graphical representation of the turbine electric power output as a function of the hub-height wind speed. With such a curve, turbine power output and energy production can be predicted without detailed knowledge of turbine operations and its control schemes. An equivalent power curve for the entire plant can serve the same purpose for plant and system operators to predict the plant output for a given wind speed. However, unlike the singleturbine power curve, a single curve cannot capture all the nuances of a wind plant consisting of tens or even hundreds of turbines. A model consisting of a set of power curves is required to fully characterize the complex input/output relationship of a wind plant to account for the effects of different wind directions, local terrain, and asymmetric turbine layout in a wind plant. NREL has obtained data from a large wind plant for the development of such a model. The data include plant output, wind speed, and direction from meteorological towers, and nacelle anemometer readings and power output from each turbine. From this extensive dataset, the distributions of wind speed and power production of all turbines are analyzed over a wide range of wind speeds. From these distributions, a model is constructed to generate an equivalent power curve for the plant.