Basic requirements for supplying energy to electrical locomotives are voltage control, low amplitudes of harmonics and optimum reliability of supply. Saving loss energy is an essential contribution for climate protection. European rules for this are much more severe than those from the USA. Research on concepts for electrical locomotives that utilize recuperation of deceleration energy is done by many companies and in many countries. This thesis starts with a basic description of the uncontrolled three-phase diode bridge circuit (B6U). It continues with 6-pulse, 12-pulse, and 24-pulse rectifier circuits. Finally, the diode is replaced by a controlled thyristor in order to accomplish closed loop control of the voltage. In next part we describe sub-stations with a two-way rectifier/inverter at thyristor technology being composed of a rectifier bridge and an inverter in anti-parallel connection for voltage control. Through this circuit topology, the energy produced by deceleration can be fed back into the grid. Realization by a pulse-with-modulation inverter is described, too. All investigations are done by simulation using the program PSCAD/EMTDC. Simulation results are compared to measurements obtained at two different projects; we observe good coincidence. Therefore, the program PSCAD/EMTDC proves to be reliable and efficient tool for computer-aided development of energy supply plants.