Dynamic virtualization of a small scale wind turbine

The use of wind turbines for clean energy generation has grown rapidly in recent years due to their cost-effectiveness and mature manufacturing technology. However, these structures experience complex and nonlinear conditions during operation, which necessitates early damage detection. As a result, it is important to use both numerical and experimental methods to characterize the dynamic properties of wind turbines. Experimental Modal Analysis (EMA) is typically used to conduct laboratory tests on scaled models, while Operational Modal Analysis (OMA) is used for full-scale wind turbines. OMA enables the implementation of structural health monitoring strategies to assess wind turbine conditions and detect potential damages. Additionally, experimental data can be used to update numerical models through a dynamic virtualization process. This thesis focuses on analyzing a scaled wind turbine specimen using EMA and exploring the potential of OMA for wind turbine health monitoring. This dissertation summarizes a six-month work experience at Siemens Digital Industries Software. The primary objective is to estimate the modal parameters by integrating test and numerical techniques. To accomplish this, a numerical model is developed and validated using mathematical modeling techniques and simulation tools that replicate the wind turbine's dynamic response. The tower model is initially developed in Simcenter 3D and preliminary modal properties are estimated. Subsequently, experimental modal analysis is carried out using a modal impact hammer and acquired data is used to estimate the modal properties via Simcenter PolyMax. To assess the reliability of the numerical results, modal data from the finite element analysis are compared to modal test outputs. The tower FE model is successfully updated using the Model Update tool in Simcenter 3D, which employs a genetic algorithm for optimizing the model parameters, to better fit the numerical and experimental results. The modal analysis reveals that the first five mode shapes for the wind turbine comprise the first and second tower bendings in both the fore-aft (FA) and side-side (SS) directions, representing the fundamental tower mode shapes for a wind turbine. The entire wind turbine system is then subjected to numerical and experimental modal analysis. Two types of tests are conducted: experimental modal analysis and operational modal analysis. It is noteworthy that the dynamic behavior of the structure is primarily influenced by the dominant blades, resulting in the presence of only the first bending in the tower's fore-aft and side-side directions. The results of both numerical and experimental analyses indicate that the primary mode shapes for the wind turbine are the tower bending, the first three flap-wise modes, as well as the two edgewise modes and the second group of flap-wise modes. Finally, operational modal analysis is carried out with rotating blades to verify the applicability of this technique and compare the results with the experimental and numerical ones. The outcomes of the tests validate the previous results and demonstrate the reliability of this innovative modal testing technology.