Research On Modeling Methods And Efficient Algorithms For Electromagnetic Pulse Response Of Transmission Lines

With the rapid development of the modern industrial level,the space electromagnetic(EM)environment becomes gradually complicated,which obviously increase the probability of the electronic and electrical equipment being attacked by the electromagnetic interference.The transmission line(TL),which is a signal-connecting and wave-guiding structure frequently employed in modern electronic and electrical equipment,could turn into an important path for the external EM energy to enter the equipment irradiated by an incoming interference.On this point,the coupling strength between the TL and external electromagnetic pulses(EMPs)directly affects the operating status of the entire equipment.In order to ensure the safe and stable operation of the electronic and electrical equipment,it is necessary to conduct in-depth and comprehensive research on the EM response characteristics of the TL excited by EMPs.At present,scholars at home and abroad have conducted certain discussions on this issue.Based on the previous work,this dissertation conducts in-depth research on the modeling method and efficient algorithm of EMPs response of TL with regard to four aspects:transient response analysis of the frequency-dependent TL,EM reciprocity solution of the field-to-line coupling problem,TL modeling in special structures,and lightning EM effects calculation of the power TL network.The main work and innovations of this dissertation are summarized as follows:(1)The fast calculation method for analyzing the transient response of the TL system with frequency-dependent characteristics is proposed.Firstly,a hybrid algorithm combining TL equation,matrix pencil method(MPM)and piecewise linear recursive convolution(PLRC)technique is constructed for the case of a STL terminated with the complex frequencydependent network,which overcome the difficulty of constructing the state variable equations of complex frequency-dependent networks.The correctness and efficiency of this hybrid algorithm are verified by numerical examples.It is seen that the whole analysis process can be accelerated with an improved calculation accuracy.Then,the extended MPM(EMPM)which avoids the secondary processing of the correlation matrix of the sampled data,are proposed to implement the analysis of port equivalence problems in multi-port systems.Finally,for analysis of the EM effects of multi-conductor TLs(MTL)system grounded by complex frequency-dependent networks,an efficient algorithm combining TL equations,EMPM and PLRC technique is proposed to complete the fast evaluation of the EM response of this model.(2)The application range of EM reciprocity theorem in the analysis of the field-line coupling problem of TL is expanded.Firstly,the current distribution along the lines of the STL and MTLs with mismatched loads is studied in the test phase,and the frequency domain expression of the test current and the corresponding time domain expression composed of the original excitation wave and multiple reflection waves are deduced.Then,the EM reciprocity calculation formula for calculating the induced voltage of the STL with mismatched terminations is improved;further,a new calculation method and formula of the induced voltage at the terminal of the MTLs is proposed,and the relevant elements in the formula are redefined.Afterwards,the equivalence of the formulas which are derived from testing and receiving stages and used for calculating the induced voltage at the terminals of TL irradiated by plane wave is verified by theoretical analysis;meanwhile,the validity and correctness of the proposed calculation method for solving the induced voltages of MTLs are verified by numerical examples terminated by different loads(pure resistance and frequency-dependent load).Finally,the EM reciprocity calculation formulas of induced voltages of the STL and MTLs excited by the vertical/horizontal electric dipoles as well as lightning are deduced,and the EM coupling problems of the corresponding numerical examples are analyzed.(3)A variety of modeling techniques for TLs in special structures is developed.Firstly,based on the perturbation technique,a time-domain perturbation solution model of the TL equation is established by equivalently treating the non-uniform TL as the superposition of the uniform TL and its perturbation.The validity and correctness of the proposed model are verified by two examples of TLs where the height of line changes with sinusoidal or random tendency.Then,the Tikhonov regularization technique is introduced into the solution process of the generalized TL model,so as to achieve a stable solution of the high-frequency field-toline coupling process of the TL.Meanwhile,the calculation efficiency is improved by optimizing the steps of regularization parameter solution that is the most time-consuming part of the solution process,then the proposed method is further extended to realize the analysis of the high-frequency field-to-line coupling problem of MTLs.Finally,the electromagnetic topology(EMT)method is used to model the complex TL network and realize the synchronous calculation of lightning overvoltage at each junction in the TL network,and the model error of EMT method is analyzed theoretically.(4)The efficient hybrid algorithms for analyzing the lightning effects of complex TL networks are established.Firstly,in response to the need for rapid calculation of the lightning EM fields at a single observation point,a time-domain acceleration technology based on MPM is proposed,which achieves a significant improvement in computational efficiency;at the same time,a frequency domain fast solution method combining the segmented sampling technique and MPM is proposed,which offers a great saving of computing time under the premise of avoiding over-sampling and under-sampling.Then,the calculation of the lightning EM fields at the observation points around the overhead TL(OTL)is accelerated by MPM,and the calculation results are embedded in the TL equation in the form of equivalent excitation sources to complete the time domain fast calculation of the lightning-induced voltages of the OTLs.Finally,aiming at the frequency domain solution of lightning effects of TL network,an efficient hybrid algorithm combining segmented sampling technique,EMT and MPM is constructed.The feasibility of this hybrid algorithm is analyzed theoretically,and its efficiency and correctness are verified by numerical examples.