Modeling and Stability Prediction for the Static-Power-converters Interfaced Flexible AC Traction Power Supply System with Power Sharing Scheme

The flexible traction power supply system (FTPSS) is a promising solution to solve the electric phase break and power quality problems existing in traditional traction power supply systems. To promote the balance of train power distribution among multiple substations, power sharing control is proposed by combining average power control and P-f and Q-V droops based on virtual power decoupling method. The active and reactive power is decoupled through introducing the impedance angle without knowing specific values of the line inductance and resistance. This system level control poses new challenges to the stability of the electric railway due to complex interactions between power electronic-based substations of the FTPSS. To address this issue, the frequencydomain model of the FTPSS with power sharing control is established. Then, the eigenvalue-based stability criterion is introduced to predict the stability of the interconnected system. In particular, to obtain how the power sharing control is sensitive to some controller/circuit parameters, a parameter-oriented stability analysis method is developed through assessing the influence of the key influential factors, including the time delay of wide-area communication, the controller parameters of the power sharing scheme, the circuit parameters, the length of the traction network and the train power requirement. The time-domain simulation and the downscaled prototype experiment are conducted to validate the effectiveness of the established model and the theoretical analysis. This lays the foundation for the design and stability analysis of the FTPSS.