The feeding transformer for AC electric railways converts three-phase electric power into a pair of single-phase electric power supplies for driving electric cars. To prevent the fluctuation of three-phase voltage, however, a single phase feeding suits car depots. Authors have developed a single-phase feeding power conditioner (SFC) for unbalanced voltage compensation. This paper describes the principle and test results of using SFC. SFC is made of a scalene Scott-connected feeding transformer and a pair of self-commutated inverters, which connect the secondary side of a transformer and are coupled with the DC side capacitor. Each inverter operates independently in order to control reactive power. On the other hand, SFC controls active power from larger to small load phase circuits via the DC capacitor to keep the active power balanced.