Distributed Array of GPS Receivers for 3D Wind Profile Determination in Wind Farms

D. Chen, L. Heng, D. Jia, G.X. Gao

Abstract:	Wind energy is currently one of the fastest growing sources of renewable energy. Wind turbines are able to generate clean electricity without harmful emissions to the environment. The versatile nature of wind and the resulting uncertainty in predicting the wind power generation is the main barrier for wind energy penetration into the electricity grid. Existing sparsely located expensive anemometer masts are not sufficient for detailed wind sensing. Wind farms often have uneven flow conditions due to complex or large terrain. For example, the Roscoe Wind Farm in Texas covers 100,000 acres of land with 627 turbines. In addition, wake effects from neighboring turbines are not negligible. The new generation of wind turbines in the 10MW class is as high as 200 meters at the blade tip, causing the traditional 60-meter masts no longer suitable. Sensing the wind profile densely, accurately, in three dimensional, and inexpensively is critical for both optimizing the installation of wind turbines on a wind farm, and predicting and optimizing the power generation. This paper presents a new method of wind profile sensing based on a distributed array of GPS receivers. In our wind sensing system, GPS receivers, inertial measurement units, wireless communication transceivers and pitot tubes are equipped in wind speed sensing payloads and deployed on helikites, aerostats at a cross between a kite and a blimp. Multiple helikites are strung together vertically and are allowed to float freely in the air at varied altitudes. This architecture allows for the system to not only to determine a 3D wind profile, but also to be very scalable as increasing the number of helikites will enable larger areas covered or higher resolutions of the wind profile. The 3D wind profile is determined by the wind speed sensed by each helikite. The helikite always aligns its direction with the direction of the airstream, and thus the pitot tube can correctly determine the wind speed relative to the helikites. Positioned at the head and tail of the helikite, the GPS receivers will be aligned into the direction of the wind. The direction of helikites can be accurately derived from differential GPS carrier phase measurements and the inertial measurements. In addition, the GPS measurements, as well as some of the inertial measurements, can be used to calculate the true position and velocity of the helikite with respect to the ground. The difference between the true velocity of helikite and the relative wind speed is the wind speed with respect to ground. A wind profile is then generated from the collection of the data. Finally, the system is tested on a local wind farm to verify the effectiveness of the system and algorithm in determining an accurate wind profile. Collected airspeed data from our GPS-based wind sensing system are compared to anemometer data to evaluate deviation from wind speed ground truth.
Published in:	Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013) September 16 - 20, 2013 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	84 - 91
Cite this article:	Chen, D., Heng, L., Jia, D., Gao, G.X., "Distributed Array of GPS Receivers for 3D Wind Profile Determination in Wind Farms," Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013), Nashville, TN, September 2013, pp. 84-91.
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