Experimental Characterization of a Grid-Loss Event on a 2.5-MW Dynamometer Using Advanced Operational Modal Analysis: Preprint
This paper experimentally investigates a worst case grid loss event conducted on the National Renewable Energy Laboratory (NREL) Gearbox Reliability Collaborative (GRC) drivetrain mounted on the 2.5MW NREL dynamic nacelle test-rig. The GRC drivetrain has a directly grid-coupled, fixed speed asynchronous generator. The main goal is the assessment of the dynamic content driving this particular assess the dynamic content of the high-speed stage of the GRC gearbox. In addition to external accelerometers, high frequency sampled measurements of strain gauges were used to assess torque fluctuations and bending moments both at the nacelle main shaft and gearbox high-speed shaft (HSS) through the entire duration of the event. Modal analysis was conducted using a polyreference Least Squares Complex Frequency-domain (pLSCF) modal identification estimator. The event driving the torsional resonance was identified. Moreover, the pLSCF estimator identified main drivetrain resonances based on a combination of acceleration and strain measurements. Without external action during the grid-loss event, a mode shape characterized by counter phase rotation of the rotor and generator rotor determined by the drivetrain flexibility and rotor inertias was the main driver of the event. This behavior resulted in significant torque oscillations with large amplitude negative torque periods. Based on tooth strain measurements of the HSS pinion, this work showed that at each zero-crossing, the teeth lost contact and came into contact with the backside flank. In addition, dynamic nontorque loads between the gearbox and generator at the HSS played an important role, as indicated by strain gauge-measurements.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy Wind Power Technologies Office
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1170353
- Report Number(s):
- NREL/CP-5000-63501
- Resource Relation:
- Conference: To be presented at the Conference for Wind Power Drives, 3-4 March 2015, Aachen, Germany
- Country of Publication:
- United States
- Language:
- English
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