Dynamic Characterization of Wind Turbine Gearboxes in Operational Conditions

The gearbox is one of the key subsystems in a typical wind turbine. It has the task to transfer power from the low speed shaft connected to the rotor to the high speed shaft connected to the generator. Larger wind turbines require more power and gearboxes with higher load capacity need to be designed and a deep knowledge into gearbox dynamics becomes of fundamental importance. When dealing with a machine in operating conditions with several rotating components, components are introduced in the signal that make the application of standard techniques such as Operational Modal Analysis very difficult and in some cases almost impossible. For this reason, new techniques to tackle with these conditions were investigated in the past, such as Order Based Modal Analysis. This method represents an extension of standard OMA to extract a modal model from measurement on a machine during run-up (or run-down) conditions. The applicability limits of standard OMA are here demonstrated on the data acquired on a 13.2 MW wind turbine gearbox testing facility during controlled run-up conditions. The advantages of the proposed methodology will be demonstrated by firstly applying it on data simulated using a validated model of the testing facility. The additional challenges that need to be faced when applying the method to real data will also be presented.