Wind Turbine Drivetrain Test Bench Capability to Replicate Design Loads: Part II — Case Study of a Multi-MW Drivetrain

The systematic evaluation of wind turbine drivetrains using hardware-in-the-loop strategies (previously presented in Part I) is demonstrated using a state-of-the-art multi-MW drivetrain design and a 7.5-MW test bench. The test bench has the capability to apply both torque and non-torque loads to the electro-mechanical drivetrain. The proposed method to evaluate the capability of a test bench to impose the loads of interest uses design loads of the drivetrain and the test bench load application unit limits as inputs. The design loads are defined by stochastic time series of the longitudinal, lateral, and vertical forces as well as the yawing and nodding bending moments that the load application unit can concurrently apply to the drivetrain (i.e., combined loading). A total of 14 time series sets are considered to capture the minimum and maximum values of the longitudinal, lateral, vertical, and resultant forces as well as the yawing, nodding, and resultant moments. These time series are processed individually to calculate two metrics: the coverage and the capability ratio of the test bench. The former is a percentage of the time series that be applied by the test bench, and the latter indicates an excess (or deficit) in load application capability as compared with the selected design loads. The results are presented and interpreted using the previously described methodology. The findings suggest a good match between test bench capability and the loads of interest in general, and also points to challenges. These discoveries establish a basis for the experimental verification and the development of compensation methods to enhance test bench capabilities.