Fixed (Trackside) Energy Storage System for DC Electric Railways Based on Full-SiC Isolated DC-DC Converters

Abstract

At present, in several European railway networks using traditional DC electrification systems, it is not possible to increase traffic nor to operate locomotives at their nominal power ratings. Trackside energy storage systems (TESSs) can be an alternative solution for the creation of new substations. A TESS limits contact line voltage drops and smooths the power absorbed during peak traffic. Thus, the efficiency of the power system can be increased while limiting costs and the environmental impact. This paper proposes a new topology of a TESS based on full-SiC isolated DC/DC converters associated with lithium-ion batteries and galvanic isolation, offering major advantages for operational safety. In the event of a fault, the input and output terminals of the converters are electrically separated, and the contact line voltage can never be directly applied to the batteries. In addition, the use of SiC MOSFETs makes it possible to obtain excellent efficiency with a high switching frequency. The first part of this paper presents the main characteristics of an elementary TESS module, while the second part proposes a sizing methodology for the typical case of a 1.5 kV DC line, which shows the limits of using TESSs to reinforce a power supply. Finally, the experimental results of an elementary module prototype are presented.