Research Of Distribution Of Mass Blocks On Shaft Load Shedding And Operation Performance Of Vertical Axis Wind Turbine

H-type vertical axis wind turbine has become one of the focuses in recent years for its advantages of no yaw mechanism,simple structure and convenient maintenance,However,the periodic variation of attack angle of blade in the rotation result in the periodic fluctuation of radial load of shaft,which limits the development of large vertical axis wind turbines.In order to reduce the radial load of the shaft,a load reduction method based on mass block dynamic distribution is proposed based on three NACA0018 blades wind turbine.The load shedding operation law of the mass block is determined by theoretical analysis and numerical simulation,in addition,the influence on the structure of the main shaft and the performance of the wind turbine is analyzed.Finally,the test device of load shedding operation law of the mass block is built,and the feasibility of the load shedding operation law is verified by trial in part.The main contents and conclusions of this paper are as follows:1)Taking the three NACA0018 blades vertical axis wind turbine as the research object,the relationship between the mass blocks distribution and the radial load of the turbine’s shaft is analyzed theoretically.On the basis of fluid simulation,the load shedding operation law of the mass block is obtained with the target of minimizing the radial load of the shaft.When the mass reaches 0.075kg,the radial load of the original wind turbine shaft can be reduced by 97.1%and the deformation of the shaft can be reduced by 99.7%.2)Considering that the installation of the mass block will prolong the start-up time of the wind turbine,this paper proposes a method to shorten the start-up time based on the mass block,and studies the operation law of the mass block in the start-up phase of the wind turbine.The results show that the mass block can reduce the starting time of the wind turbine by 40.6%compared with the wind turbine whose mass block is fixed at the initial position of the load shedding operation law.In addition,in order to quickly switch the operation law of the mass block from the start-up phase to the stable operation phase of wind turbine,the mass block transition displacement curve is designed.The results show that the mass block can also reduce the load of the shaft in the process of transition curve.3)Under the load shedding operation law of the mass block,the steady speed of the wind turbine is simulated and analyzed by using the UDF.It is found that the mass block basically does not affect the average speed of the wind turbine in stable operation stage,but it can significantly reduce the speed fluctuation of the wind turbine,and the CV of the fluctuation intensity is reduced by 48.1%.4)The test platform of mass block’s load shedding operation law is developed.The PID control algorithm is designed and simulated by MATLAB software to determine the optimal values of PID parameters:K_P=40,K_i=0,K_d=20,so that the system can reach a stable state in 0.3s.The results show that the actual operation curve of the mass block can follow the theoretical load shedding operation law curve in real time.