A power flow calculation method for over-zone power supply in electrified railways connected to weak external power grids

Electrified railways in mountainous areas are prone to operate in adverse scenarios of over-zone power supply (OZPS). Compounded by the presence of a weak external power grid, the voltage of the power grid and the traction network is susceptible to marked fluctuations, posing great threats to the safe operation of electric locomotives. Therefore, calculating the power flow of the traction power supply system (TPSS) connected to weak power grids in OZPS scenarios is of great importance for addressing the power quality problems, and thus ensuring the safe operation of electrified railways. In this context, a fine-grained power flow calculation method for OZPS in electrified railways connected to weak external power grids is proposed in this paper. Firstly, this paper decouples the external power system (EPS) from the TPSS and both the EPS and the TPSS are modeled. Then, by alternatively iterating the coupled “EPS-TPSS” system, a joint power flow calculation method is developed, which characterizes the interactions of power and voltage between the EPS and the TPSS. Thus, the power flow of both the EPS and the TPSS are calculated. A comparative analysis between the proposed method and conventional method demonstrates that the proposed method more accurately captures the power interactions between the two systems. Furthermore, calculation results are compared with those obtained with Simulink and tested across multiple systems. The findings indicate that the proposed method achieves better accuracy and adaptability compared with the conventional methods.