Date of Award
Master of Science (MS)
Full-scale wind turbine nacelle testing with Hardware-In-the-Loop (HIL) configuration allows full operational certification testing with native nacelle controllers, as opposed to open-loop testing which requires significant modification of the controller to bypass missing subsystems when the nacelle is mounted on the test bench. Implementation of Hardware-In-the-Loop testing involves running a real-time simulation of a full turbine model in parallel with the test bench in order to account for the missing rotor, tower, platform, and actuators. For successful implementation of this method, first, the simulation model should be able to capture the dynamic characteristics of the turbine accurately while also meeting the real-time requirements. Second, the deviations resulting from the different boundary conditions between the drivetrain in a full turbine and the test bench environment should be mitigated. In the first part of the study, a sensitivity analysis is performed using a baseline wind turbine model to determine the minimum drivetrain fidelity level necessary to capture the dynamics with a focus on the torsional characteristics that are crucial for performing electro-mechanical certification tests. The results show that the torsional dynamics are dominated by the flexibility of the main shaft and the gearbox supports. The rest of the components can be significantly simplified thereby reducing the total number of modes and degrees of freedom for real-time execution. In the second part of the study, the reduced drivetrain model is utilized in a comparative analysis to quantify the deviations in torsional dynamics resulting from the rigid connections and test bench components (motor, reduction gearbox, and the load application unit) replacing the tower and rotor, respectively. It is found that the different mechanical interfaces can shift the first torsional mode of the drivetrain by as much as 19% which can significantly impact electro-mechanical responses. The feasibility of exploiting the test bench speed controller to introduce virtual inertia, damping, and stiffness and compensating for such differences is studied. It is demonstrated that the controller can be tuned to perform pole placement and match the torsional frequencies between the coupled test bench-nacelle and the full turbine. Finally, the performance of the tuned controller is verified using two case studies: a) free response to characterize the torsional responses in a low voltage ride through scenario, and b) forced response to evaluate its ability to track a highly dynamic speed profile resulting from a turbulent wind profile.
Heinold, Kirk Christopher, "Considerations for Testing Full-Scale Wind Turbine Nacelles with Hardware-in-the-Loop" (2021). All Theses. 3506.