Test planning and operational modal analysis of a wind turbine tower; application to its dynamic behavior

Thorough knowledge of the wind turbine (WT) dynamics is necessary to efficiently improve its design, operation, and maintenance. Due to the wind turbine s large size, there are difficulties in measuring and excitation of full-scale WTs in general modal tests. Because of the issue, the designers may rely on finite elements and numerical models. Nevertheless, by considering the advantages of operational modal analysis relative to the experimental modal analysis, it is an efficient way to understand the dynamics behavior of WT based on the actual operation installed turbine at the site. With regard to performing operational modal analysis and achieving acceptable results, proper test planning has great importance. Initially,in this article, test planning steps will be described for the studied WT s successful operation modal test. Then the modal analysis results will be revealed, and finally, the dynamic behavior of the WT will be discussed based on the modal results.