Research On Dynamic Monitoirng Methods And Technique For Detecting Mechanical Damage Of Wind Turbine Blades

Wind turbine blades are key components in wind turbine, and carry an important role inenergy conversion. The safety and reliability of wind turbine blades have a very importantinfluence on energy conversion efficiency in the entire wind turbine. With the increasingcapacity of wind turbines, wind turbine blade failures pose a great threat to the safe operationof the unit. So, it is important to monitor wind turbine blades operation condition.In this dissertation, the vibration characteristics of wind turbine blade under theconditions round about the damage taking place were studied and analyzed by using themethod which was combined theoretical calculation and experimental study, and a dynamicmonitoring system based on vibration signal detection for diagnosing wind turbine bladesdamage was developed.First of all, the modes, common types and mechanism of wind turbine blade damagewere analyzed. Then, by making a comparison between the commonly methods of conditiondetection for wind turbine blades, a sort of vibration monitoring method was proposed.Secondly, on the basis of basic equations for structural dynamics, a wind turbine bladewas treated as a free cantilever beam which was entirely fixed on the root. Then the physicaland mathematical models of wind turbine blades were built. With the aid of the finite elementanalysis (FEA) software ANSYS, the model of a 15kW wind turbine blade was analyzed onthe vibration modes under the conditions round about the damage taking place, the naturalfrequencies and mode shapes were calculated. By calculating unit modal strain energychanges rate of wind turbine blades, the changes damage before and after dynamiccharacteristics of wind turbine blades were compared, and calculated damage before and afterthe first-order modal strain energy, while obtained quantitative indicators for diagnosing bladedamage location and damage extent.Finally, a 1.25m wind turbine blade was taken as the test object, and a laboratory benchfor dynamic monitoring wind turbine blades damage and a hardware system of signalacquisition were set up. Meanwhile, a dynamic monitoring and analyzing system based onLabVIEW for diagnosing wind turbine blades damage was developed, and compared withjiang su dong hua measurement system, which showed that the dynamic monitoring systemfor diagnosing wind turbine blades damage was correct and feasible.