Load Analysis And Load Reduction Control Optimization Of Large Wind Turbine Based On FAST

In this paper,based on the industry authoritative data,the trend of large-scale wind turbines was firstly explained by analyzing the development status of wind power industry home and abroad,and the urgent need for fatigue load analysis and load reduction optilization under such conditions was pointed out.Then,an authoritative wind turbine simulation modeling software named FAST,developed by the National Renewable Energy Laboratory(NREL),was introduced.On this basis,FAST and Simulink were combined to build a collective pitch control simulation model for NREL 5 MW wind turbine,also a variable gain PI collective pitch controller was designed for this wind turbine.The simulation results and analysis showed that it is no obvious effect to reduce the fatigue load simply by optimizing the performance of the collective pitch controller.Based on the previous content,the simulations according to the IEC wind turbine certification standard was completed in this paper,the load distribution law of the wind turbine under various load conditions were grasped by analyzing the load situations of the key parts,so that dangerous locations,where the fatigue damage is prone to occur,can be identified.Then the related theory and general flow of structural fatigue danage estimation were systematically summarized、and the fatigue damage caused by the load of the blade root was roughly estimated.Finally,according to the results of load analysis and fatigue damage estimation,the corresponding control optimization strategies were proposed for the load of key parts like blade roots:Firstly an optimized scheme about pitching below the rated wind speed was designed,and the optimal advancing pitch section was selected according to the comprehensive evaluation of fatigue damage and power generation;Secondly,combined with the power and load control objectives,the PI parameters of the individual pitch controller were optimized in each wind speed segment above the rated wind speed,then the variable gain scheduling function of the individual pitch controller could be fitted;Thirdly,the load feedback loop was added to further reduce the peak load of the blade root based on the variable gain PI individual pitch strategy.The simulation results showed that,the advancing pitch strategy effectively weakened load and power fluctuation near the rated wind speed,while the variable gain PI individual pitch controller,with load feedback added,significantly reduced blade fatigue damage compared to collective pitch.