DC side short circuit transient simulation of DC traction power supply system

In urban railway transit, DC traction power supply system is adopted. Accurate analysis of DC side short circuit transient is important for design of new DC traction electrification system and assessment of the suitability of protection arrangement and power equipment. The model of the transformer/rectifier was analyzed. The method based on Kron´s tensor analysis was utilized to reformulate circuit equations automatically after switching operation. Parabolic curve-fitting approach was used to determine the accurate switching time, and variable time step 4^th-order Runge-Kutta procedure was adopted to solve the differential equations. The accuracy was demonstrated by comparison with a case study of a practically measured fault current profile. And the impacts of the ratio DC side resistance to AC side inductance and the ratio DC side inductance to AC side inductance on the short circuit transient were analyzed. It is shown that close-up short circuit faults cause large transient peak fault currents and high rate of rise of fault currents. It is also shown that DC side short circuit transient is significantly affected by the ratio DC side resistance to AC side inductance and the ratio DC side inductance to AC side inductance.