Challenges in testing and monitoring the in-operation vibration characteristics of wind turbines

This paper aims at discussing the main challenges in testing and monitoring the in-operation vibration characteristics of wind turbines by presenting the results of the analyses performed using analytical models, aeroelastic simulations and infield vibration measurements. Within the scope of the research, the dynamic behavior of a 2.5 MW - 80 m diameter - wind turbine was monitored by using three different measurement systems namely, conventional strain gauges, photogrammetry and laser interferometry, while the turbine was both at parked condition and rotating. The modal parameters were extracted for several operation conditions and wind speeds. Similar modal analyses were also conducted on the response time histories which were generated by using an analytical mass-spring-damper model and an aeroelastic simulation tool. The main challenges in analyzing the dynamic properties of wind turbines, possible reasons of the uncertainty in the estimated modal parameters and the applicability limits of the utilized identification algorithms are discussed based on the results of these investigations.