Wind Energy Assessment Using a Wind Turbine With Dynamic Yaw Control

In conducting the siting analysis of a possible on-shore or off-shore wind farm, computational tools are required to analyze the extensive wind data collected over long periods of time in order to estimate the energy that can be harnessed at that particular location. The major parameters that play a crucial role in this are the wind speed, wind direction, and presence of turbulence in the upcoming wind. However, estimation of the potential for electrical energy generation from wind at a particular site is quite complex and prone to error due to the uncertain nature of the wind. The yaw error, which is the difference between the direction of wind and the normal to the face of the rotor, can reduce the power output of a wind turbine significantly. Zero inertia assumption for the turbine rotor used by multiple assessment tools result in overestimation of the power output. For an accurate estimation of the energy that can be harnessed, the effect of directional change of the wind should be incorporated along with the other obvious parameters such as the wind speed, the effect of landscape and altitude. Most modern utility-scale wind turbines are equipped with yaw motion controller and direction measuring sensors that help change the yaw angle of the wind turbine to adjust for the wind direction. A dynamic control model and the corresponding scheme have to be incorporated in the energy estimation process. A wind energy assessment analysis for a potential off-shore wind farm in Lake Michigan is currently under way. An unmanned marine buoy, equipped with LIDAR-based data acquisition system, is deployed in Lake Michigan and data are measured at six different altitudes starting from 55 m and up to 175 m. As project participants, the authors have been working on developing a versatile, flexible and precise model and software tool to evaluate the potential for electrical energy generation. A MATLAB based program has been developed for this purpose, equipped with the capability of working with different data formats and different time averaged data sets. A dynamic model capable of considering the change in wind direction and adjusting the yaw angle has been developed as a part of the MATLAB program. The dynamic model evaluates the yaw error and implements a scheme for the adjustment of the orientation of the wind turbine in order to provide an accurate estimate of the amount of wind energy that can be converted into electrical energy. The algorithm for this dynamic model and the results obtained are discussed in this paper.