Performance Analysis And Near-field Coupling Optimization Of Filter At Secondary Equipment Port

As the grid voltage continues to increase and capacity continues to increase,the electromagnetic compatibility issues in high-voltage transmission line series compensation stations and substations become more and more complicated.With the complication and intensity increase of disturbance sources at the power site,the electromagnetic compatibility problems faced by secondary electronic equipment have become more serious.The key link to solve the EMC problem is the three major factors of interference source,coupling path and sensitive equipment.For the incoming and outgoing of high-frequency disturbance signals at the device port,using a port filter is an effective two-way suppression method.The interference spectrum component is generally different from the frequency of the useful signal.The filter has a good suppression effect on these components that are different from the useful signal,so as to achieve the purpose of suppressing interference.This article aims at the current research status.First,the lightning protection device on a series of repair station platform-zinc oxide lightning arrester as the experimental research object,through the method of nonlinear function curve fitting,the residual voltage peak value of the 50-column MOV on the series compensation platform under the 20 k A lightning current was obtained.Next,I studied another small MOV under the harassment of the surge.Through experimental testing methods,simulation models calculated by two different methods are obtained.Finally,a voltage waveform comparison analysis is performed between the test waveform and the simulated waveform to ensure that the obtained simulation circuit is accurate and effective.And during the test,the modeling of the surge generator circuit of a certain manufacturer was completed,and the output waveform of the equipment was well reproduced.At the same time,the intrusion of the disturbance signal at the port of the low voltage side voltage / current acquisition device of the capacitive voltage divider transformer at the test site of an isolating switch is also studied.Considering the frequency-varying characteristics of the common-mode choke coil,the wide-band circuit modeling of the signal-port common-mode choke filter is equivalent.First,the wide-band impedance characteristics between the small choke coil terminals are tested,and the component parameters of the RLC parallel resonance equivalent circuit are extracted;According to the frequency characteristics and impedance test results of the magnetic core's magnetic permeability of the small choke coil,different power functions are used to describe the frequency change characteristics of the inductor and the frequency change characteristics of the resistance;A full-circuit simulation equivalent model of common mode and differential mode impedance of small chokecoils is established,and the simulation results are compared with the test results.Finally,a simulation circuit model of a single 2k V EFT generator under a 50? load was established.The full-circuit equivalent model of the small choke coil established is used to simulate and evaluate its suppression effect on EFT disturbance.Finally,in order to optimize the filtering performance of the EMI filter,The capacitance and frequency-varying inductance of the single-coil inductor and the common-mode choke coil are obtained by the method of three-dimensional electromagnetic field modeling and calculation.A three-dimensional model of the differential mode and the common mode of the power filter was built using the three-dimensional model of the common mode choke coil.At the same time,considering the influence of non-ideal characteristics such as the electromagnetic environment and parasitic parameters under the operation of the power filter,The near-field coupling problem is optimized.