The co-phase traction power supply system (CTPSS) introduces a large number of power electronic devices on the power supply side, which makes the train-grid electrical coupling relationship complicated and prone to system instability. In this paper, the dq-frame impedance of the CTPSS is derived. Neglecting DC voltage fluctuations, the co-phase supply units (CPSUs) can be equated to single-phase inverters, while the electric multiple units (EMUs) are equated to single-phase rectifiers. Then, based on the dq frame impedance measurement method for single-phase systems, the modeling approach is validated by frequency-domain simulation. In addition, the stability of CTPSS is discussed according to the Generalized Nyquist Stability Criterion (GNSC). Finally, the CTPSS model is constructed in MATLAB simulation platform, and the experimental results verify the correctness of the proposed theoretical model.

Generalized Nyquist stability criterion,Co-phase traction power supply system,dq-frame impedance,stability analysis