Research On Zero-resistance System For Rail Potential Mitigation

In recent years,zero-resistance system(ZRS)has been proposed to overcome the shortcomings of the conventional mitigation methods of stray current and rail potential in the DC traction power system of subway.ZRS is paralleled with the existing traction power system(TPS).Through negative resistance converter(NRC),switch unit(SU)and return cable(RCA),ZRS constructs a zero-resistance path for mitigating the rail potential.However,as a new treatment scheme for the stray current and rail potential problems,the related research on ZRS is still in the preliminary stage.On the one hand,there is a lack of modeling theory for traction power system with ZRS(ZRS-TPS).On the other hand,as one of the key components of ZRS,NRC is usually equipped with additional DC power supply on the input side,which further affects the popularization and application of ZRS.Focusing on the modeling of ZRS-TPS and NRC topology,the following research is carried out in this paper.(1)Modeling of ZRS-TPS.In this paper,based on the operation principle of the ZRS in the scene of single traction interval,single line and one train,the operation principles of the ZRS with multiple traction intervals,up-down lines and multiple trains are analyzed.Secondly,the electrical network models in different scenarios of ZRS-TPS are established,and the models are solved by node voltage method and branch tearing method.The modeling of ZRS-TPS can be realized by MATLAB programming.According to the programming calculation results,the mitigation effect of stray current and rail potential for ZRS with different parameters,different train conditions and different scenes,as well as the current,voltage and power characteristics of NRC are analyzed quantitatively.(2)The topology of NRC.In order to solve the problem that the input side of the existing NRC topology usually needs to be equipped with additional DC power supply,a cascaded NRC topology in which the input side is directly connected to the DC bus of the traction substation is proposed in this paper.The operation principles and control strategies of the buck part and the negative resistance transformation part in the cascaded NRC topology are analyzed.In order to verify the basic functions of the cascaded NRC topology,a ZRS-TPS experimental platform is designed.With the reasonably designed parameters of the experimental platform,the ability of steady state output and dynamic output of NRC for various output conditions is verified through simulations and experiments.