| Wind energy is a renewable and clean energy source,and in the process of industrial restructuring in China,wind energy has been transformed from an auxiliary energy source,mainly electrical energy,to an alternative energy source,and will occupy a dominant position in the future development of electricity.In China,the development of wind power has a very broad prospect and its development potential is very large.After years of development,onshore wind power has formed a very mature technology and service market,and most of its convergence system transmission lines use overhead lines.However,offshore wind power has gradually become a new trend,as land and wind resources on land are becoming increasingly scarce.As the offshore wind farm convergence system consists of a large number of wind turbines and a large number of transmission lines together,and different from the onshore wind farms is the offshore wind farm convergence system transmission lines are cable lines,and most of the cable lines are buried deep under the sea.Therefore,during the operation of the offshore wind farm,it is very difficult to inspect the transmission lines after a fault occurs,resulting in a longer time required for fault recovery.Therefore,when asymmetric faults occur in the convergence system,i.e.single-phase ground fault,two-phase ground fault and phase-to-phase fault,fast and accurate positioning of the cable lines is the basis and prerequisite to ensure the safe and stable operation of offshore wind farms.In order to solve the problem of difficult fault inspection of transmission lines inside the offshore wind farm convergence system,this topic proposes a compressive sensing-based method for asymmetric fault location in the offshore wind farm convergence system,applying compressive sensing to the fault location in the offshore small wind farm convergence system,using the characteristic low sampling rate of compressive sensing to enable it to quickly locate asymmetric faults inside the convergence system.In the first step,the fault interval is determined by compressive sensing;in the second step,based on the fault interval,the zero-sequence current cannot pass through the triangular wiring method and the unique radial distribution structure of the offshore wind farm convergence system,the zero-sequence distance equation is constructed by the zero-sequence network diagram to precisely locate the asymmetric fault in the convergence system cable line.The simulation results show that the method requires only a small amount of measurement data to accurately locate asymmetric faults,has good noise immunity,and can achieve accurate location for different fault types,and is less affected by the transition resistance in the process of location.In addition,since the scale of China’s offshore wind farms is expanding and the number of turbines is rapidly increasing,the overall framework of compressed sensing in power systems is improved to further improve the applicability and accuracy of fault location methods.Firstly,the spike phenomenon is suppressed by the phase-locked loop triangular function method in extracting the fault voltage to reduce the error of the extracted voltage value due to voltage fluctuation.Secondly,the node impedance matrix and fault location coefficient are used to design a dictionary to further reduce the influence of pseudo-fault points.Finally,the Compression Sampling Matching Pursuit(Co Sa MP)algorithm is improved by combining the generalized Jaccard coefficients to improve the reconstruction accuracy of the algorithm.The ranging equation is constructed using negative sequence voltage and negative sequence impedance in the fault ranging phase to simplify the ranging steps.Simulation results show that for large-scale offshore wind farms,the method achieves 100% fault interval localization accuracy and the relative ranging error is mostly below 1%.It lays a good foundation for the application of compressive sensing in offshore wind farms. |
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