Study On Modeling And Low Frequency Oscillation Suppression Method Of High-Speed Railway EMUs And Traction Network Coupling System

With the rapid expansion of China’s high-speed railways,the operating power and density of EMUs continue to increase,which greatly improves the railway transportation capacity.However,the low-frequency oscillation phenomenon occurs frequently during the high-density running of EMUs.This problem may cause the lock of EMUs,which seriously affects the order of EMUs and endangers the passenger’s personal safety.In view of the complex electrical coupling between the traction network and EMUs,this paper takes the high-speed railway EMUs and traction network coupling system as the research object,and studies its model and low-frequency oscillation problem suppression method.Firstly,the high-speed railway EMUs and traction network coupling system is divided into two parts: the traction power supply system and the EMU.The composition and principle of traction substation,AT station and traction network are introduced,and their simulation modules are established respectively.The topology of the traction converter,the working principle of the four-quadrant converter,the transient current control strategy and the SPWM modulation method are introduced.Based on MATLAB/Simulink software,the simulation model of high-speed railway EMUs and traction network coupling system is established and the simulation results verify its effectiveness.Secondly,the stability analysis method based on impedance ratio is introduced,which is introduced into the stability analysis of the high-speed railway EMUs and traction network coupling system,and the low-frequency oscillation problem is explained reasonably.Based on this method,several important parameters of the EMU,such as the size of load,the parameters of voltage loop and switching frequency,are analyzed respectively to influence the stability of the system.Thirdly,the basic principles and characteristics of fuzzy control theory are introduced.Combined with this theory,a transient current control strategy based on fuzzy PI is proposed,and the design method of fuzzy PI controller is given.Compared with the transient current control strategy,this strategy has better dynamic and static characteristics.And it can effectively suppress the low-frequency oscillation of the high-speed rail network coupling system.The strategy is verified by MATLAB/Simulink simulation.Finally,the hardware-in-the-loop real-time simulation platform of the high-speed railway EMUs and traction network coupling system is built.The platform is mainly composed of RT-LAB real-time simulator and NI-cRIO 9030 controller.The RT-LAB real-time simulator is used to simulate the topological part of whole system.The NI controller is used as the control link of the four-quadrant converter.The experimental results verify that the proposed strategy can suppress low frequency oscillation obviously.