Research On Equivalent Model And Storage Capacity Of Doubly-Fed Wind Farm

There are enormous reserves of wind energy resources all over the world. If the wind power could be made full use of, which could greatly improve the world energy structure, reduce global energy supply and environmental issues, make significant contribution to sustainable development. However, with the growing size of wind farms, the negative impact of wind power characteristics on the grid becomes more significant, the impact of large-scale wind farms integration with system on system stability and power quality can not be ignored. If these problems can not be solved suitably, it will not only endanger the load-side power and may even lead the entire network to collapse, which seriously hindered the use of wind energy and wind power development.By taking doubly-fed induction generator wind power system as the research object,this paper focuses on the differences and changes in output power which caused by wind speed changes of each wind turbine in the large scale wind farm which integrated to the system. And it also study on some basic technical issues such as building equivalent model for Doubly-fed wind farms in operation and how to use the wind energy storage device to improve the output of wind power.Firstly, the article analyzed differences between doubly-fed induction generator and asynchronous machines in equivalent circuit and transient mathematical model. By introducing equivalent weighted arithmetic of asynchronous generators, equivalent parameters of doubly fed induction generator are calculated and its applicability is discussed. Then equivalent model and the actual model of wind farms are built in the Matlab / Simulink simulation platform, in which the wake effect, the effect of transformers connecting with double fed induction generator and connecting lines are taken into account. The simulation results matches with theoretical analysis, which confirmed that weighted method could be Suitable for double-fed wind farm equivalent within a certain range.Secondly, based on characteristic function of wind power generation unit's output power and the probability distribution function of wind speed in wind farm, a method to calculate the required energy-storage capacity for long-term stable power output of large-scale wind farm is proposed, which could mitigate the impact of instable power output of grid-connected large-scale wind farm on system. The scope of the method is also discussed. The proposed method is verified by the data from actual wind farm. By contrast with other output strategies, the superiority of the method is indicated. It analyzed different factors which influences the reasonable value of storage capacity, established the reasonable value range of storage capacity, which could provide reference for planning wind farm.