Power Quality Impact of DC-DC Converters in Railway Systems

Energy storage systems offer a solution for energy efficiency and voltage regulation in DC railway systems. For charging the energy storage system within an electrification system, a DC/DC converter is used. The use of SiC MOSFETs in DC/DC converters allows for an increase in switching frequency, which can enhance efficiency. However, this increase can also introduce power quality issues, such as voltage oscillations and overshoot. As the number of electrification systems increases in the railway system, the number of converters also increases. In this study, various scenarios were examined in the railway system, involving the simultaneous and staggered connection of one, three, five, and nine converters. The study evaluated how these configurations affected power quality. Obtained results are presented and discussed, comparing the power quality effects according to the number of DC-DC converters and their switching configurations. According to the results, as the number of converters increases, both overshoot and oscillation values generally increase, suggesting higher voltage spikes and greater oscillations in voltage stability within the railway system. However, varying the switching times can mitigate these effects, potentially reducing overshoot and oscillations. This insight will help filter designers assess the impact of converters in railway systems.