Multi-vehicle accessed railway vehicle-grid system stability analysis and optimization based on OLTC

The interaction between Electric Multiple Units (EMUs) and the traction network can lead to oscillation problems due to electrical mismatch. The stability between the EMUs and the traction network is difficult to ensure because of the multiple operation points and variable operation modes of EMUs. To analyze the system stability, impedance-based methods are commonly used. However, existing impedance-based stability analysis methods require identifying system transfer functions, which can introduce under- or over-fitting problems. To address this issue, this paper introduces an optimized open-loop based stability analysis method for multi-vehicle accessed vehicle-grid system, which effectively assesses the impact of vehicle operating points and modes on system stability. In addition, we propose an On-Load Tap Changer based method to enhance the voltage stability of railway traction networks. By optimizing traction network voltage, the impedance characteristics of vehicles are also modified, thus enhancing system stability. Finally, we validate the efficacy of the proposed method through case studies based on an actual railway train schedule diagram.