| The urban rail transit DC traction power supply system generally faces issues such as rail potential excession and stray current corrosion.Therefore,a mitigation method based on power electronics technology,called zero resistance converter system(ZRCS)has been proposed in recent years to completely solve the above problems.The ZRCS is connected in parallel with the conventional traction power supply system.By cooperating the negative resistance converter(NRC)with bipolar voltage output capability and switch units,the ZRCS establishes an equivalent zero-resistance path in the system,thus converting the traction current into a dedicated reflow cables for temporary relief from excessive rail potential and stray current corrosion.Negative resistance converter is one of the core components of ZRCS.In this thesis,a novel negative resistance converter(NNRC)is proposed,and the feasibility and mitigation performance of the zero resistance converter system based on NNRC are verified.Firstly,various types of NRC topologies are compared and discussed in detail,then the bipolar output voltage capability of NRCs is clarified through the topology modeling and working principle analysis of NRCs.In order to reduce the quantity of NRC switches,this thesis proposes a novel negative resistance converter;Further research on the practical application of the NRC with the problem of DC voltage source is carried out by adding step-down circuit to enhance the feasibility of ZRCS.Based on the research of NNRC,further research is carried out on its applicability in ZRCS,and the mitigation performance of ZRCS on rail potential and stray current is compared and analyzed through theoretical modeling;The results show that NNRC can meet the requirements of ZRCS for bipolar voltage output,and ZRCS can effectively reduce rail potential and stray current.Finally,the bipolar voltage output capability of NNRC is verified by both simulation and experiment results,and the mitigation performance of ZRCS based on NNRC is also verified.Designed and built the prototype of NNRC,and ZRCS experimental platform.The results of simulation and experiment shows that NNRC has expected bipolar voltage output capability,which can meet the application requirements of ZRCS.Also verified the mitigation performance of rail potential and stray current in ZRCS,which proves the prospect and value of ZRCS. |
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