As the cost of installing and operating wind generators has dropped, and the cost of conventional fossil-fuel-based generation has risen, the economics and political desirability of more wind-based energy production has increased. High wind-power penetration levels are thus expected to augment in the near future raising the need for additional spinning reserve to counteract the effects of wind variations. This solution is technologically viable, but it has high associated costs. Our study presents a different solution to short-term wind-power variability, using advanced power electronic devices combined with energy-storage systems. New control schemes (designed to filter power swings with a minimum of energy) were designed, modeled and verified through experimental tests. We also determined the procedure to extract the corresponding perunit model parameters for simulations and test purposes.
We first reviewed D-Q transformations with emphasis on modeling of the system and control algorithm. System components were then designed using criteria similar to those used to design medium-voltage power products. We tested a proof-of-concept for performance of the power converter in a scaleddown isolated system using real wind-power data. Tests were conducted under realistic system conditions of wind-penetration level and energy-storage levels, to better characterized the impacts and benefits of the Power Stabilizer. We described the scaleddown isolated electric power system used in the testing. We also analyzed the performance of the wind-farm model and the synchronous machine?s governor to gain an insight into the model system?s limitations.
Simulation results carried out in Mathematical Laboratory (MATLAB) and Power Systems Computer Aided Design (PSCAD) were compared to experimental data to verify the performance of the power converter under different system conditions and algorithms. Power limiters were also contrasted and evaluated for frequency deviations and attenuated power fluctuations. In summary we can say that, among all the power limiters considered in our study, the adaptive high pass filter presented the best performance in terms of system robustness and effectiveness.
Wind-Energy Outlook
Wind power has been used for at least 3000 years, mainly for milling grain, pumping water, or driving various types of machines. However, the first attempt to use wind turbines for producing electricity date back to the 19th century. In 1891, Poul La Cour in Demark built an experimental wind turbine driving a dynamo. The oil crisis of the 1970s revived interest in wind turbines. Nowadays, the power is the fastest growing source of energy in the world and its growth rates have exceeded 30% annually over the past decade [1]. Cumulative global wind-energy generating capacity approached 40,000 MW by the end of 2003 [2]-[3]. The main drivers for developing of the wind industry in the United States are
?????????? Federal Renewable Energy Policies, particularly the Production Tax Credit (PTC) that provides a 1.5 cent per kilowatt-hour credit for electricity produced from a wind farm during the first 10 years of operation. This wind energy PTC expired December 31, 2003 but will be reinstated through 2005 as part of a major tax
package (H.R. 1308).
?????????? State-level renewable energy initiatives, such as the Renewable Portfolio Standard, or green pricing.
The Database of State Incentive for Renewable Energy [4] gives more information on incentives. These government initiatives, together with technological advances, plus the need for a new source of energy capable of meeting the world?s growing power demand and the rising prices of conventional fossil fuel-based generation, make the wind power one of the most promising industries in the future.
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