Research On Line Distributed Parameter Circuit Model And Its Revised Empirical Formula

In the context of the rapid development of power grid and continuous innovation of relevant technical theories,verify the correctness of new technologies and new theories and testing of most equipment in power systems is becoming more and more important.Since most of these tasks can only be performed in laboratory conditions,power grid simulation has become an important means of studying power grid.In addition,there are many protection and fault location algorithms which based on line models,and accurate line models can improve the performance of such algorithms.Therefore,establishing an accurate line model is of great significance to ensure the correctness of power grid simulation and improve the performance of algorithms such as line protection and fault location.Therefore,establishing an accurate line model can not only ensure the correctness of the power grid simulation,but also improve the performance of algorithms such as line protection and fault location.The distributed parameter circuit model in the existing line model ignores the frequency characteristics of the line parameters,therefore cannot calculate the ripple part of the transient signal.In order to improve the calculation accuracy of the distributed parameter circuit model in the ripple interval,frequency-variable parameters are introduced to modify the model and an empirical formula for calculating frequency-variable parameters is proposed.First,the frequency variable parameters are calculated using the recorded data at both ends of the line and the line mathematical model,and a suitable mathematical model of empirical formula is proposed according to the waveform characteristics of the frequency variable parameters.Then collect a large number of on-site wave recording data of different lines as samples,solve the empirical formula coefficients by function fitting,and use linear regression analysis,statistical induction and other methods to determine the function relationship between the frequency variation parameters and the various derivatives of voltage and current,and get the empirical formula of frequency change parameters.The empirical formula is used to modify the circuit model of the distributed parameter of the line,and finally the mathematical model of the modified model is obtained.Collect the actual power grid fault recording data to verify the modified model.The verification results show that the modified model can effectively deal with the complex transient signal after the fault,and the calculated value close to the actual sampled signal can be obtained for different lines.The modified model not only has the accuracy of the original model in the non-ripple interval,but also has the accuracy of the Marti model in the ripple interval.After the model is revised,the calculation accuracy in the ripple interval is significantly improved,which improves the deficiency of ignoring the frequency characteristics of line parameters in the original model.