Dynamic Characterization Testing of Wind Turbines

The U.S. Department of Energy (DOE), in conjunction with the U.S. wind industry, is supporting the development and commercialization of utility-grade wind turbines. Under the Certification Program, the DOE, through the National Renewable Energy Laboratory (NREL) will assist the U.S. industry in obtaining American Association for Laboratory Accreditation (A2LA)-type certification for their class of wind turbine. As part of the Certification Program, NREL is conducting a suite of certification tests that are specified by the International Electro-technical Commission standards. One emerging certification requirement is to characterize the dynamic behavior of the wind turbine's operation. Therefore, the purpose of the dynamic characterization tests is to document the wind turbine's fundamental dynamic characteristics under critical operational modes and fault conditions in light of turbine design specifications. Some of the dynamic characteristics that we determine from testing include the conformation of fundamental structural vibration frequencies and the system's dynamic response to typical rated and extreme modes of operation. This paper discusses NREL's approach in designing and implementing a dynamic characterization test for commercial wind turbines. One important objective of the dynamic characterization test is to provide a Certification Agent with test data to show that the wind turbine's mechanical equipment is operating within design vibration limits. For NREL's industry participant, the test results are an indication of the wind system's overall quality of mechanical operation that can be used to compare with established industry standards for a wind system's response under typical and extreme operating conditions.