Stability Analysis Of "Vehicle-network" Coupled Power Supply System Of High-speed Railway With Multiple Types Of Converters

With the large number of vehicles put into operation in China,the number of vehicles has reached 3400 standard trains by the end of 2021.The interaction between vehicles and the traction power supply system is more closely,and low-frequency oscillation occurs in many places.Low-frequency oscillation often leads to vehicle traction lock,and in severe cases,it will cause the equipment on the side of the traction power supply system and the vehicle to be burned,affecting the safe operation of the vehicle.At present,the research on low-frequency oscillation of vehicle and traction power supply system(vehicle-network system)mainly considers the condition of multiple preparing vehicles.The influence of running vehicle on low-frequency oscillation of the system in the same traction network is not clear.Therefore,aiming at the low-frequency oscillation phenomenon of vehicle-network system,this paper analyzes the influence law of running vehicle under different working conditions on lowfrequency oscillation from the impedance matching,and verifies the analysis results by building a real-time simulation/experimental model.According to the analysis results,some measures are proposed to improve the stability of vehicle-network system.Firstly,the sequence impedance models of the vehicle side and the traction power supply system side are established by using the small-signal modeling method.Meanwhile,considering the different impedance characteristics of the running vehicle under different working conditions,the sequence impedance models of the running vehicle in traction and braking conditions are established respectively.In order to facilitate stability analysis,the sequence impedance model is transformed into SISO impedance model.When there are multiple preparing vehicles on the vehicle side,considering the influence of the line impedance on the impedance model of the vehicle-network system,the influence of voltage amplitude and phase angle changes at the input port of the vehicle on the vehicle impedance model and the stability of the vehicle-network system is analyzed.Then the analysis results are verified by establishing simplified circuit model of the two vehicles.Secondly,based on the impedance models under different operating conditions,the impedance characteristics of the running vehicle under traction and braking conditions are analyzed,and the influence law of traction and braking conditions on the vehicle impedance are studied by drawing the impedance ratio Bode diagram and Nyquist diagram.At the same time,the influence of different control loop bandwidths on the vehicle-network system is studied,and the analysis results are verified by building simulation model.Finally,based on the RT＿LAB real-time simulation verification platform,the phenomenon of low-frequency oscillation is reproduced,and the influence law of the running vehicle under different control loop bandwidths on the vehicle-network system is verified.According to the analysis results of the low-frequency oscillation of the vehicle-network system,a method of vehicle impedance reshaping with reverse reactive current injection is proposed to suppress the low-frequency oscillation.By establishing the vehicle model after impedance reshaping,the influence of the method on the impedance characteristics of the vehicle is analyzed,and the Bode diagram of the impedance ratio is drawn to analyze the influence of the method on the stability of the vehicle-network system,and the influence of the method on the dynamic performance of the vehicle is verified by using simulation model.