The AC electrified railway systems have the power quality problems such as the harmonic currents pollution, the reactive power consumption, and the load imbalance because the locomotives show the characteristics of nonlinear and single-phase electrical loads. These power quality problems have a bad effect on not only AC electrified railway systems but also other electric systems connected together. A railway power quality conditioner (RPQC) is able to provide a novel solution to these power quality problems in the AC electrified railway systems. In this paper, a novel RPQC control algorithm based on the synchronous-reference-frame (SRF) is proposed. The proposed RPQC control algorithm can compensate effectively the harmonic currents, the reactive power, and the load imbalance. The validity and the effectiveness of the proposed RPQC control algorithm are illustrated through the simulations.