Feed Forward Wind Turbine Control Using Upwind Turbines as Sensor

This dissertation seeks to improve the performance of a downwind turbine using information obtained from an upwind turbine. Methods for using an upwind tur- bine as a sensor are examined and evaluated. Next, a feed forward optimum pitch control scheme is introduced and investigated using a series of FAST simulations. In this control scheme an upwind is used as a wind speed sensor. Wind speed measurements are passed from the upwind turbine to a downwind turbine. The downwind turbine uses the knowledge of incoming wind speed to proactively adjust turbine blade pitch. Initial simulations are promising, but ultimately the feed for- ward control system is found to be very sensitive to timing errors. This makes the control scheme impractical in real world applications. A feed forward derating con- trol scheme is then developed. In this control scheme the rotor speed of the upwind turbine is monitored for evidence of an extreme gust event. If an extreme gust is de- tected the downwind turbine is derated to mitigate the negative e ects of the gust. A series of FAST simulations show that this control scheme can reduce structural loads and rotor overspeeds in the downwind turbine. Unlike feed forward optimal pitch control, this system is insensitive to timing errors. A more sophisticated wind farm simulation tool, SOWFA, is then used to simulate and evaluate feed forward derating control. First, a verification and validation study of SOWFA is carried out. Good agreement is found between SOWFA, OVERFLOW2 and FAST results. SOWFA is then used to simulate two test cases where turbines are subjected to ex- treme coherent gusts. In both test cases feed forward derating control significantly improves performance, reducing damage equivalent loads and increasing energy capture.