Transfer from out-phase power supply to in-phase power supply

The out-phase power supply is transferred to in-phase power supply by applying additional breakers and converters to original structure and lines of traction substation.The phases of traction voltage become consistent by switching on / off the breakers.The converter is used as balancing device.Single-phase back-to-back converter is applied when the phase difference between two ports is ± 90°,while three-bridge three-terminal or three-bridge four-terminal converter is applied according to the connection mode when the phase difference is ±120°.The expected compensative current is generated by the balancing device according to the given formula to avoid the superposition of negative currents caused by in-phase power supply.Simulative results show that,the three-phase current of power system is the superposition of the sine fundamental wave and the high-frequency modulation wave,which is in-phase with the voltage.