Analysis And Suppression Of High-order Resonance Of Traction Power Supply System Of High-speed Railway

In order to meet the high-capacity and high-efficiency requirements of electrified railways,more and more AC-DC-AC high-power electric locomotives have been put into use.Electric locomotives have the characteristics of moving,time-varying,nonlinear,etc.,and there is a nonlinear strong coupling relationship with the traction network.When the impedance of the electric locomotive does not match the resonance of the distributed capacitance and inductance of the transmission line of the traction network,at a certain frequency,the traction power supply system will be unstable.One of the unstable phenomena is that the locomotive often runs on the railway.higher harmonic resonance occurs.High-order resonance will not only produce resonance overvoltage and affect the normal operation of electrical equipment,but its resonance current will also interfere with the communication lines along the railway.In this paper,the impedance analysis method is used to study the high-order resonance problem of the traction power supply system by establishing the closed-loop transfer function of the vehicle-to-grid system,and an effective resonance suppression scheme is proposed.The main work of this paper is as follows:Firstly,the traction power supply system of the AT power supply mode and the structure of the AC-DC-AC electric locomotive are introduced;according to the topology and control strategy of the electric locomotive,the simplified equivalent output of the electric locomotive under the dq coordinate is established by the impedance analysis method Impedance model and equivalent input impedance model of the traction network.Starting from the main circuit and control system,the equivalent impedance ratio of the vehicle-to-grid system is derived.Secondly,the generalized Nyquist criterion is used to analyze the influencing factors of high-order resonance in the traction power supply system,mainly the number of electric locomotives and control parameters.Grid-electric locomotive" co-simulation model to verify the correctness of the analysis results.Finally,the structure and control strategy of the single-phase active filter that can be used in the traction power supply system of high-speed railway are introduced;the small-signal impedance model of the active filter is established,based on the traction network and the mathematics of the electric locomotive built earlier The model analyzes the influence mechanism of the active filter on the high-order resonance of the traction power supply system;proposes a high-order resonance suppression scheme for the traction power supply system that reshapes the impedance of the active filter,and uses the virtual impedance adaptive parameter design to improve the virtual impedance.The adaptability of impedance to dynamic system is verified by building a simulation model of traction power supply system with active filter added.The results show that the impedance reshaping of the active filter can change the impedance characteristics of the system,effectively eliminate the harmonics of the traction power supply system and suppress the resonance;and the adaptive parameter design of the virtual impedance can cope with the dynamic changes of the traction power supply system.Make the system more stable.