Study On The Icing Forecast Of Wind Turbine Blade And The Influence Of Icing On The Output Of Power Generation

Operating experience shows that, icing of wind turbine blades will influence theiraerodynamic characteristics, thus resulting in the decline in the output of the generators.Therefore, it is significant both practically and theoretically for the grid’s safety and stability toforecast the icing situations of wind turbine blades and study their influences on the output ofthe wind turbine. Based on the existing problems in the calculation methods of blade icing, thispaper mainly contributes to the improvement the calculation methods of the air flow field ofblades, the local impact coefficient of supercooled water droplets, and the partial freezecoefficient of liquid water. Besides, it explores the influences of icing on the output power ofgenerators. Details are as follows:(1) The great differences of the airfoil airflow field between different parts of blade have asignificant influence on the icing distributions on the blade surface. The existingthree-dimensional calculation model can obtain the airflow field on different parts of the blade,however, it demands long time and huge storage space, which greatly influences the feasibilityof icing forecast of blades. This paper introduces the relative velocity to the existingtwo-dimensional airfoil airflow calculation model, which can ensure the accuracy and decreasecalculation time.(2) Local collision coefficient of supercooled water droplets is an important parameter inthe icing forecast of blade. At present, Lagrangian method is the main calculation approach.Nevertheless, as different coordinate systems are adopted in calculating supercooled waterdroplets trajectories and airflow field, the calculation process is complex and the efficiency islow. In this paper, the coordinate transformation is avoided by establishing differential equationsof supercooled water droplets trajectory under rectangular coordinate system based on thecalculation results of the airflow filed. The results show that the proposed approach can enhancethe calculation efficiency at no loss of accuracy.(3) The freezing coefficient of liquid water on the icing surface plays a decisive role in theicing type of blade. The Messinger icing model neglects the influence of airflow shear force andwater film flowing on the local freezing coefficient during the freezing process of liquid water.For further improvement, the water film flow model on the icing surface is established based on the balance of the stress of icing surface water film. By using the improved model, the localfreezing coefficient of the liquid water on icing surface is calculated and the calculationaccuracy is promoted.(4) The icing form is determined by the icing density when the freezing coefficient ofliquid water on the icing surface is convinced. At present, the icing density was set as a fixedvalue in the icing calculation at home, and the influence of meteorological factors on icing formwas not considered. In this paper, the automatic prediction of blade icing was achieved byintroducing the Macklin icing density empirical formula and adopting the timing simulationmethod.(5) The relative humidity of atmosphere cannot be regarded as a calculation parameter ofblade icing forecast. According to the live cloud droplet spectrum collected by wind powerplant and the parameters of wind speed and temperature which were real-time monitored, theicing forecast in different parts of the blade is achieved in this paper. And by adopting thepractical icing condition of blade in wind power plant and the airfoil icing test of blade in thephytotron, the effectiveness and accuracy of the icing forecast calculation method of blade inthis paper were verified.(6) Blade icing is the main reason for the decline of output power of generators. Inconsideration of the present condition that the output power condition of wind power generatorunit can’t be forecasted during the icing period, this paper proposed an approach to establish thethree-dimensional airflow field calculation model of icing blade based on aerodynamic theory.This paper firstly comes up with the idea to study the influence of icing on the output power ofthe unit based on the aerodynamic characteristics. The accuracy of the model is verified, whichprovides an effective method for the forecast of the output power of unit during the icing period.