Mechanism And Suppression Measures For Low-Frequency Oscillation Of Traction Power Supply System

Our electric locomotives always use AC-DC-AC traction drive system, which is using PWM pulse width modulation technology and transient direct current control strategy. Compare to the conventional AC-DC electric locomotives, it has many advantages, such as higher power factor, more stable intermediate DC voltage, and less low harmonic content. However, since its wider distribution of harmonic frequencies and the rectifier control system using the vehicle network system parameter, the likelihood of the occurrence of oscillations car network will increase. So, well electric match between locomotive and traction network must be fully considered in the design process, otherwise it will lead to low-frequency oscillations of traction power supply system, and even cause parking accident, seriously affecting the normal order of railway transport.Low-frequency oscillations appear in many electric locomotives in China, which lead to traction blocked from normal operation, such as HXD1electric locomotive at East Lake Station, CRH5EMU at Beijing depot, CRH1EMU at Shanghai (Nanxiang) etc.In order to analyze the mechanism of the low-frequency oscillations, and study the key factors affecting the stability of the interconnected system of traction power supply system, the AT power supply for high-speed railway operations is analyzed. Then, based on multi-conductor transmission line, the chain network model and π-type circuit model are established, the traction network parameters are calculated with matlab program as well. The simulation model of HXD1locomotive is built based on the four-quadrant PWM converter works and transient strategy.Hurwitz and impedance ratio criterion are introduced in this paper to analyze the stability of interconnected systems, which are composed of the locomotives and traction network. Combining with the established simulation model, the paper analysis and simulate the reason of the low frequency oscillation of the systemUnder the condition of the simplified grid parameters, and on the basis of Hurwitz and impedance ratio criterion, this paper analyzes the matching relation between the electric locomotive side converter control system parameters and traction network system parameters. By analyzing the interconnected system simulation and combining with field test results, low frequency oscillation mechanism is analyzed and appropriate measures are proposed to solve the problem of low frequency oscillation.