Feasibility Analysis Of Superconducting Devices For Wind Power Integration

In recent years,with the exhaustion of fossil energy and the deterioration of the environment,more and more countries begin to attach importance to the development of renewable energy.Among renewable energy sources,wind power technology is relatively mature and has higher cost efficiency and resource efficiency,making it one of the fastest growing secondary energy sources in the world now.With the continuous development of wind power technology,the capacity of single wind turbine is increasing day by day,and more and more transmission lines are needed to transmit wind power in large wind farms.The increase of transmission lines will not only increase the loss of power,but also increase the construction cost of wind farms.However,as a new and increasingly mature power transmission technology,superconducting cables have a power transmission capacity of 3-5 times of that of traditional lines under the same cross-sectional area.For DC power transmission,the transmission loss is less than one tenth of that of traditional lines and for AC power transmission,the transmission loss is only half of that of traditional lines.Therefore,it has certain potential economic merit if superconducting cables are applied to wind power integration.However,in order to analyze the feasibility of superconducting cable in the field of wind power integration,it is necessary to consider not only its economy,but also its safety and reliability.When the power grid or the wind farm has a short circuit fault,the strong fault current may cause the whole superconducting cable to quench,thus causing a serious impact on the wind farm and the power grid.For applying superconducting cables to wind power integration,the transient characteristics of the superconducting cable in response to the transient conditions of the wind farm should be analyzed in detail,so as to determine the feasibility of the superconducting cable for wind power integration.This thesis introduces the classification and development trend of wind power generation technology,describes the main electrical wiring structure of large wind farm in detail,puts forward the scheme of grid-connected wind farms with application of superconducting cables,analyzes and compares the advantages and disadvantages of the topological structures of the permanent magnet direct-drive wind power system,expounds the control strategy of machine side,grid side and unloading circuits.Furthermore,this thesis introduces the internal structure and working principle of superconducting cables and the internal structure and working principle of resistive and saturated iron-core superconducting fault current limiters.By means of performance comparison of these two kinds of fault current limiters,the detailed physical and mathematical models of the selected one are derived and explained.Finally,this thesis uses PSCAD/EMTDC and MATLAB to build the simulation platform,analyze the transient characteristics of superconducting cables in response to the transient conditions of the wind farm,discuss whether superconducting cable can recover full power transmission state after some transient conditions.The results indicate that the application of superconducting devices in wind power networks has some advantages with certain feasibility.