The feeding transformer for electric railway converts three phase electric power to a pair of single phase electric power for driving electric cars. In some cases, however, not a pair of single phase power feeding but only a single phase power feeding is required. For example, a single phase power feeding is suitable for a car depot from the viewpoint of preventing voltage fluctuation at three phase voltage.
For this reason, authors have developed a small mode of single phase feeding power conditioner (SFC).
SFC is made of a pair of self-commutated inverters, which connect the two phases of secondary side of feeding transformer, coupled with a DC side capacitor.
Two inverters operate independently at Main-phase and Teaser in order to control reactive power. On the other hand, the power control circuit of SFC controls active power of Main-phase load and Teaser load. This means that the power control circuit delivers active power from the larger load circuit to the smaller one via the DC capacitor. Then SFC can keep balance of active power between Main-phase load and Teaser load.
This paper describes the principle of unbalanced voltage compensation using SFC and test results using a SFC model.