Increasing the Efficiency of Wind Turbines through Understanding of Their Transient Responses

Global demand for renewable energy is increasing, and wind power is the fastest growing source of renewable energy. Current control methods for wind turbines are designed for steady-state wind and are unable to capture the extra energy from turbulence. To capture more energy from unsteady wind, the complex flow over a pitching blade needs to be understood. This award supports fundamental research to understand wind turbine response to time-varying wind and blade pitch facilitating the creation of new control laws for wind turbines.

The research objective of this project is to understand the transient response of wind turbines to control law and time varying wind and blade pitch. In turbulent flow, the wind turbine response and the control law are inter-connected and must be treated as a complete nonlinear, time-varying system. For this reason, understanding how the control law affects the overall system response is included in the research objective. To achieve the research objective, load cell measurements of lift force, drag force, and moment of wind turbine blades under unsteady wind and blade pitch conditions will be collected at the large closed return wind tunnel facility at the University of Minnesota. A fan driven by a variable frequency drive producing a maximum wind velocity of 38 m/s controls the wind speed. The pitch blade angle will be controlled by an electric motor in the range of -2 to +4 degrees. The frequency content of the time-varying wind and blade pitch motion inputs will cover the range of interest in the wind spectrum. Control laws to be investigated include torque-based control and state-based control.