New Topology Design and On-line Charging and Discharging Technology of Substation DC System

Abstract

The substation DC system uses battery packs as a backup power source. It needs to be regularly checked for capacity. In the existing topology, batteries are connected in series as a power source. When checking capacity discharge, an additional backup power supply must be built to replace it, which is costly and complicated to operate. To this end, this paper proposes a new battery topology. The previous 54 series batteries were divided into 3 packs, with each consisting of 18 batteries. The three battery packs are connected in parallel to the DC bus through bidirectional DC/DC converters. The automatic charging and discharging control strategies of the battery packs under the new topology are studied. The system can automatically charge and discharge batteries through bidirectional DC/DC converters, and conduct online capacity testing of battery packs. Simulation results show that the designed new topology not only realizes the online verification of battery capacity but also saves the test cost. The power supply reliability of the DC system of the substation is also greatly improved through the redundant structure.