Supercapacitors system for balancing power-supply gap in railway electric vehicles

The supply catenary lines for electric vehicles, and specifically for urban streetcars, may be subject to a series of discontinuities which could determine the power switch-off of the traction converter, due to protections intervention. The proposed system, based on a two-quadrant DC/DC converter, a supercapacitors bank and a suitable control system, can compensate the discontinuity of the supply line, providing a stable energy source to electric drives. As a result, vehicle drivability and passenger comfort improve, commercial speed increases and number of failures reduces. Moreover, weight, size and cost of the traction converter can also be reduced, as required input capacitance needs not being overdimensioned. Performances are evaluated by means of numerical simulation of a real urban vehicle undergoing a supply line discontinuity.