Simulation on Voltage Unbalance Reduction in Railway Electrification System by Different Special Transformers

In recent years, electric railway system becomes an efficient mass transportation in large urban areas. A railway electrification system supplies electric power to railway trains through the transformers. Therefore, the transformer is a key component to help reduce problems of the unbalance of voltage and current in the power grid. As electric trains have their power delivered on a single-phase system, the single-phase transformer causes the unbalance of voltage and current in the power system network, with which the railway electrification system is connected. In order to alleviate these problems, special transformers, i.e. Scott transformer and Le-Blanc transformer, have been proposed to be used in the railway electrification system. This paper focuses on developing the special transformer models for using in DIgSILENT PowerFactory software. The developed models have been verified with a simple train system in order to study the effectiveness of reduction of voltage unbalance factors from the three types of transformers. In addition, the developed special transformer models can be applied in a large-scale power system network for power quality problem analysis.