Influence of the Power Source on the Impedance-Frequency Estimation of the 2 × 25 kV Electrified Railway

The simple increasing impedance model is usually adopted by calculation or computer simulation to represent the harmonic behaviors of the power source in the studies of impedance-frequency characteristics (IFCs) of the traction power supply system (TPSS) in electrified railways. However, this model is a little rough and sometimes even introduces inevitable errors in stability analysis, resonance estimation, and filter design, etc. This paper proposes an improved calculation method based on field tests to evaluate the impact of the power source on the equivalent harmonic impedance at the pantograph terminal seen from trains. Then two field tests are presented in detail to verify the difference between the classical method and the proposed method. The compared results proved the effectiveness of the analysis of this paper. Furthermore, the accuracy of the 2 × 25 kV electrified railway's impedance-frequency estimation was significantly improved through the proposed calculation method.