Continuous Power Supply Scheme and Power Flow Algorithm of Traction Cables for Urban Railways

Continuous power supply scheme of traction cables is explored for urban railways, in which the power runs through the whole line, and two main substations are set with the same phase power supply devices, one for primary use and one for standby. The feeding section distance is modeled and solved in the cases of the unilateral and bilateral continuous power supply. The model takes the voltage loss as a constraint condition, and the maximum number of trains that the feeding section can supply is obtained by solving the model in a way of gradual increase in the number of trains. Further, the allowable value of the feeding section distance is calculated, which provides a reference for the position setting and checking of the traction transformer. To develop a layered power flow algorithm with interactive iteration, the line-based traction power supply system is modeled, and the traction power supply system is divided into the cable layer and traction layer. In this algorithm, the power flow is solved within the layer, and the variable values are modified between the layers to realize interactive iteration and obtain the final calculation results. This algorithm has the merits of reducing matrix order and increasing computational efficiency. The case analysis shows that in contrast to the traditional power supply scheme, the continuous power supply scheme can increase the utilization rate of regenerative braking energy by 99.15%, and reduce the annual electricity cost by 29.55 million yuan with the use of regenerative braking energy, and the non-recurring investment by 136.72 million yuan.