Study On Permeability Characteristics Of High-order Harmonics In Traction Substation

While AC-DC-AC electric locomotives and EMUs are widely used in China’s electrified railways,the impact of high-order harmonics on traction power supply system cannot be ignored.After high-order harmonics are transmitted to traction substation through catenary system,it is easy to generate harmonic permeation between different voltage levels and harmonic lateral transmission between the same voltage levels by traction transformer and self-use transformer.The problem of permeation of high-order harmonics in traction substation needs to be further studied.In order to figure out permeability characteristics of high-order harmonics while there is an electrical coupling between traction transformer(TT)and self-use transformer in traction substation,in this paper,a comprehensive high-order harmonics permeate model of traction substation(CHHPM of TS)which include V/v TT and inverse-YNd11 wiring transformer is derived.Using the field measured data of traction substation,the correctness of CHHPM of TS was verified on MATLAB software.Then,based on the harmonic model: 1)This paper discusses lateral transmission of high-order harmonics between the two phases in the secondary of V/v TT.The process of lateral transmission of high-order harmonics based on the mechanism of impedance effects was explained.Meanwhile,a harmonic lateral transmission coefficient(HLTC)was defined to describe the degree of high-order harmonic lateral transmission between the two phases of TT.2)Combined with the distribution characteristics of phases of traction load,the amplification characteristics of harmonic voltage of common-phase in low-voltage three-phase system was studied.A harmonic amplification coefficient(HAC)was defined to describe the amplification state of high-order harmonic.The study shows that HLTC is related to harmonic order,system short circuit capacity and TT capacity,and TT capacity affects the value of HLTC more.Specifically,the smaller the transformer capacity is,the larger HLTC value is,and the greater the lateral transmission of high-order harmonics is.HAC is only related to amplitude and phase of traction load.From perspective of probability,the common-phase harmonic voltage is often in an amplified state.