Bi-directional high-voltage DC-DC-converter for advanced railway locomotives

Increase of power demands of DC electric locomotives requires increasing catenaries voltage (which presently is 3 kV, 1.5 kV and 0.75 kV, respectively) 4, 6, 8, 10 times and more. At the traction substation, the rectifier will be adapted. The existing traction contact network (catenaries) is kept for direct current, and the novel N-cell dc/dc bidirectional converter without transformer will be located on the electric locomotive. Each cell voltage is defined by the locomotive power train DC input level, thus balancing of capacitor voltages is not required. Simulation results of the proposed 6-cell converter have confirmed the validity of predicted properties of the converter. Realization of a 10 kW model unit has been already started. The proposed converter added with four alternating current valves and the reversible rectifier, allows implementing of the galvanic separation of the load by using the output transformer operating at raised frequency.