Regenerative Braking Energy Utilization Analysis in AC/DC Railway Power Supply System With Energy Feedback Systems

In the power supply system with an energy feedback system (EFS)s, the energy from EFS (
$W_{F}$
) will flow to rectifiers, which is circulation flow (CF). However, the efficiency of CF between substations has been rarely studied. Besides, the relationship between the train operation and regenerative braking energy (RBE) utilizing efficiency is not clear. In this article, the energy flow structure of the AC/DC railway power supply system including CF is established. In the double-train system, promoting CF when the trains’ distance is long can be beneficial to power utilization efficiency. Chengdu Metro Line 9 is analyzed as a multitrain system based on the iterative AC/DC power flow algorithm. The key to energy saving includes reducing the energy consumption of on- board resistance and the DC traction network (TN) loss. Compared with the catenary and rail system, the fourth-rail system can promote system energy efficiency by 23.5% at most. The CF and energy fed to main substations (MSs) count for less than 2% and 8% of
$W_{F}$
. When the headway time is short, RBE should be avoided feedback to EFS, while the feedback power of EFS should be advocated when the headway time is long. The results can help guide the operation of urban rail to save energy.