The article deals with PSIM simulation results of the regenerative energy storage process with supercapacitors installed on the renewed Tatra T3A tramcars. Bidirectional supercapacitor’s current controller is connected to the filter capacitor of the tram DC converter and in the tram braking mode operates as a buck converter. The control scheme of the buck converter is suggested with two PID control loops: with filter capacitor voltage and supercapacitor current feedback. The results of PSIM simulation of tramcar braking process are given with and without overhead current fluctuations. Simulation results show the control system’s stability in both synchronous and asynchronous operation modes of the tram DC converter and supercapacitor’s current controller.