Fault Location Of HVDC Transmission Line Based On Traveling Wave Principle

In modern power technology rapid development era,UHV DC transmission has its single benefit,in the spread space,great ability transmission occupies an important position.But UHV DC transmission distance is far more than ac power,and after a poor geographical environment and climate regions,therefore the accident risk is big,high detection difficult.UHV DC transmission line fault location technique for improving power supply reliability and economy,as well as accurate positioning points,has an important value.This paper studies the fault location of UHVDC transmission lines.Firstly,based on the engineering parameters of cloud-Guangzhou UHVDC transmission,this paper builds the model of cloud-Guangzhou UHV DC transmission system with ±800 k V,analyzes the waveform of the model in normal operation and fault respectively,and verifies whether the voltage and current waveform meets the standard and meets the requirements of fault location research.Secondly,the basic theory of transmission line traveling wave is analyzed.On this basis,the two-ended and single-ended traveling wave ranging principles are compared.Then,aiming at the inherent defect of Variational Mode Decomposition(VMD)algorithm,Grey Wolf Optimization(GWO)is proposed to get the optimal decomposition layers of different signals so as to avoid mode aliasing.Aiming at the problem that time-frequency resolution of S transform is not accurate enough,a Generalized S-Transform(GST)is proposed to improve time-frequency resolution for accurate time calibration.A fault location method combining GWO algorithm with VMD and GST is proposed.The linear mode signal is obtained by using Kellenbell decoupling voltage traveling wave,and the optimal VMD decomposition layers are obtained by using GWO algorithm for the linear mode signal.Then,the coupled signals are understood by the VMD,and the natural modal components of different frequencies are obtained.Then,the time-frequency analysis of the high frequency natural modal components is carried out by GST,and the instantaneous energy spectrum is obtained.The wave velocity is fixed and the fault distance is calculated by double terminal positioning method.The accuracy and reliability of the proposed method are verified by simulation examples under different conditions,and the accuracy is higher than that of similar methods.Finally,fixed wave speed is used to solve the problem of positioning error.A fault location method considering the influence of wave velocity is proposed.Based on the analysis of frequency characteristics,the fitting of the relation between wave velocity and frequency change is realized to avoid the use of fixed wave velocity.The frequency and time of traveling wave head were extracted by GWO optimization combined with VMD and GST.The wave velocity at the corresponding frequency is mapped by the relation between wave velocity and frequency,and the proposed fault location method considering the influence of wave velocity is applied to carry out the simulation example.The results of the example show that the positioning error of this method is further reduced,and it has higher accuracy and better adaptability than other different wave velocity processing methods.