Research on the causes of resonance of DC bus voltage in subway power supply system

Electric traction is adopted in subway, and its safe operation depends on the stability and reliability of the power supply system. With the increasing traffic density and the high-density grid-connected application of new energy systems, the electrical characteristics of the subway power supply system often change greatly. Not only the traction side may have special loads similar to the line short circuit, but also the DC bus may produce resonance. Therefore, it is necessary to explore the mechanism of DC bus voltage resonance from the construction of subway power supply system circuit. Firstly, the mathematical model of the third-order nonlinear non-autonomous state equation of the AC-side rectifier transformer circuit is established. Then, by adding a time dimension, the third-order non-autonomous system is transformed into a fourth-order autonomous system. The rich dynamic behaviors of the system under different excitations are obtained by numerical analysis, and the three-dimensional phase diagram, phase plane diagram, Poincare map and bifurcation diagram are analyzed in depth. Finally, the chaotic waveform obtained by simulation is compared with the field measured oscillation voltage waveform after 24-pulse rectification.