A Direct Power Feeding System for AC railway Networks Using Modular Multilevel Converter

Traditional railway power supply systems impose substantial power quality problems (PQ) on the utility network, such as unbalance, harmonics and a large amount of reactive power. This paper proposes a topology based on three-phase to single-phase modular multilevel converters (MMC) to obviate these problems. The MMC based traction substations (TSS) are connected directly to the utility grid through the three-phase side of MMC. The proposed system symmetrically transfers active power from three-phase grid to the single-phase overhead catenary system (OCS) which compensate negative sequence current (NSC), reactive power and harmonics simultaneously. Eliminating bulky traction transformers (TT), integrating OCS, removing the neutral sections and increasing the train speed are the advantages of the proposed system. The precise simulations are provided to verify the performance of the proposed method.