Vibration Performance Analysis Of Wind Turbine Blades Covered With Ice And Study On Ice Operation Control Strategy

The blades are the main components of wind turbines that absorb wind energy.The blades of wind turbines operating in cold areas will freeze,and the ice on the blades will directly affect the service time of the blades.Therefore,the wind turbine blade ice type and the influence of blade ice on the wind turbine have become the main research focus.In this paper,the ice-covered wind turbine in the blade tip area is taken as the research object,and the quasi-three-dimensional model of ice-covered wind turbine is established.The vibration performance of ice-covered wind turbine and the corresponding power control and adjustment strategy are studied by using the methods of fluid mechanics,structural dynamics and automatic control theory.The accuracy of numerical simulation of ice-coated blade vibration in tip area was verified by hammer test.The main research contents and conclusions are as follows:(1)Based on the equation of conservation of ice mass and energy,a structured grid was used to calculate the overlying ice shape of the two-dimensional airfoil of a model wind turbine.The numerical results show that the ice thickness and ice area of the tip airfoil are positively correlated with the relative incoming flow velocity,the content of liquid water in the air and the average diameter of droplet particles,but negatively correlated with air temperature.(2)The quasi-three-dimensional model of ice-tipped blade was established.In this paper,a model fan with rated power of 100 W is used as the research object during vibration numerical calculation and test.The numerical results show that the tip ice reduces the first three natural frequencies of the wind turbine and increases the possibility of resonance in the lower order.With the increase of the law of aerodynamic load and centrifugal force load,the blade parameters will also change correspondingly,and the low-order vibration frequency of wind turbine decreases while the high-order vibration frequency increases.The increase of centrifugal force load law has a greater effect on the vibration frequency of wind turbine with tip ice.(3)In order to verify the accuracy of the vibration frequency trend obtained by numerical calculation,the leading edge and trailing edge of the blade tip area were tested for the mold ice-covered vibration characteristics.The test results showed that: The variation law of vibration frequency of mold icing on the trailing edge of blade tip is consistent with that of icing on the leading edge of blade tip,that is,the first three orders of natural frequency decreases after icing,and the last two orders of natural frequency increases after icing,and the natural frequency shows a downward trend with the increasing length of icing.(4)Through the numerical calculation of the model wind turbine,it is found that the ice will cause serious power loss of the wind turbine.In the numerical calculation of the control strategy,this paper adopts 1.5MW wind turbine which is closer to the actual situation as the research object.In simulink,the fixed-blade variable speed control method is used to continuously increase the speed of the ice-covered wind power generation system,and maintain its power output to reduce the output power of the wind turbine,so as to simulate the ice-covered situation of the wind turbine.In the simulation process of wind turbine,it is found that if no control measures are taken for the wind turbine,the wind turbine will stop eventually,so as to ensure that the wind turbine will not stop for a long time.