With the sharp increase in the demand for traction power in high-speed railways and the rise in train operation density, the problem of voltage fluctuation in the traction network has become increasingly prominent. When the position of the train changes dynamically, the voltage of its access point is coupled and affected by multiple factors such as the impedance of the traction network, load distribution and regenerative braking energy feedback, which may lead to voltage drop or even equipment failure. Aiming at the problems such as the disconnection between traction calculation and power supply system modeling and the unclear dynamic coupling mechanism in traditional research, a dynamic coupling framework integrating traction calculation and the circuit model of multi-conductor traction networks is proposed. Firstly, based on the calculation of train traction, the relationship between train power and position variation is obtained, and a dynamic load model is constructed. Then, based on the traction network structure, an electromagnetic coupling model of contact lines, return lines and rails is constructed, and a real-time mapping relationship of train position - power - voltage is established to break through the limitations of the static load assumption.