Grid-Forming Control Strategy for the Emergency Power Supply Mode of the “Grid-Source-Storagetrain” Collaborative Power Supply System Based on Virtual Synchronous Generator

Aiming at the emergency power supply requirements of the traction power supply system under extreme conditions, this paper studies the grid-forming control strategy of the emergency power supply mode for the “Grid-Source-StorageTrain”(GSST) collaborative power supply system in the case of dynamic changes in railway loads. Firstly, the energy flow topology of the GSST collaborative power supply system is determined. The power grid, renewable energy, energy storage system, and trains are integrated to achieve collaborative power supply of multiple components. In the face of the complex situation where the impedance of the traction network changes dynamically due to the movement of the train during emergencies and the static loads also increase or decrease, a control strategy combining quadrature proportional resonant (QPR) control, virtual synchronous generator (VSG) control, and virtual impedance is proposed. Subsequently, the Bode diagram is drawn by using the impedance and transfer function analysis method to analyze the optimization effect of the virtual impedance during the dynamic changes of the load. Based on the small signal stability analysis method, the root locus diagram is drawn to explore the influence of key parameters on the system stability and dynamic performance. Finally, a simulation model is constructed under typical working conditions such as the change of the traction network impedance caused by the movement of the train and the increase or decrease of the static load, and a comprehensive verification of the performance and adaptability of the control strategy is carried out. The research shows that this strategy can provide an independent and stable emergency power source for the traction power supply system. The virtual impedance improves the high frequency response characteristics of the system and enhances its stability. Under dynamic working conditions, the power supply waveform is good, the voltage deviation is less than 5 %, the frequency deviation is less than 1 %, and the emergency capacity is sufficient, ensuring the reliable operation of the system under extreme conditions.