Study On Traveling Wave Fault Location Of LCC-HVDC Transmission Line

LCC-HVDC(line commutated converter high voltage direct current)transmission lines are playing an increasingly important role under the influence of our country's strategy which are power transmission from west to east and large-scale interconnection.And its development prospects are broad.Therefore,studying the precise location of LCC-HVDC transmission system faults is of great significance and engineering value for timely repair of lines and improvement of power supply reliability.The traditional fault location method,using steady-state information,is more sensitive to short circuit type,transition resistance,line structure,transformer saturation and other issues.The accuracy of the ranging is low,which causes great difficulties for operation and maintenance personnel.And the traditional fault location method is difficult to apply to Long-distance transmission system.Based on previous work,this paper conducts an in-depth study on the fault location method of LCC-HVDC transmission line based on transient traveling wave,focusing on the combination of variational mode decomposition(VMD)and Teager energy operator Positioning method.The main work of this article is as follows:Firstly,the typical structure and working principle of the LCC-HVDC system are introduced,the characteristics of the transient steady-state fault of the high-voltage DC line and the characteristics of the fault traveling wave propagating on the line are explained.And the advantages of the traveling wave ranging method is further clarified on fault location of the LCC-HVDC line.Secondly,based on the reference to the Ha-Zheng HVDC transmission system,a detailed frequency-dependent characteristic analysis of the transmission line parameters,fault traveling wave propagation coefficient,wave speed and other parameters is carried out.Thirdly,aiming at the defects of VMD's own algorithm,an algorithm to optimize its parameters is proposed.It is obtained that VMD performs better than EMD in suppressing the modal aliasing phenomenon by comparing and analyzing VMD algorithm and EMD algorithm.And The principle of Teager energy operator's extraction of single signal component amplitude and frequency is discussed.Fourthly,The zero-mode wave velocity of the traveling wave of the LCC-HVDC transmission line is fitted.The traveling wave head extraction method based on the VMD-Teager energy operator and the traveling wave ranging principle of the iterative method are proposed.And the iterative process is reliable Convergence.For the positioning method proposed in this paper,by modeling and simulating the Ha-Zheng DC transmission system on PSCAD,the errors at different fault distances and different transition resistances are analyzed.And the feasibility of the proposed positioning method is verified and superiority.