Abstract
In the single-phase AC railroad electrification, the voltage unbalance and voltage fluctuation of three-phase electric power system have to be reduced. For suppression, three-phase power is converted to two-phase power by a three phase-to-two phase transformer, and the electric power is received from a powerful or high-tension source.
However, in the case of the newly AC electrified railroad projects, it is likely that a strong power supply may not be available locally. Further, recently, re-generative braking has come to be applied to electric rolling-stocks. The result is poor when a three phase-to-two phase transformer is used to reduce the unbalance power. So, in some cases reactive power compensation may be found more profitable than a three phase-to-two phase transformer.
This paper describes a theoretical study and results of tests on a mini-model which utilizes reactive power compensation on primary-side of the modified wood-bridge connected transformer. On AC electrified railroad, in which two single-phase loads change independently of each other, reactive power compensation capacity differs for each of the three phases. Therefore, reactive power capacity has to be controlled separately for each phase. Authors examined a method of detecting two single-phase loads to control voltage variation and found the test results about the mini-model satisfactory.
