A study of energy storage systems for railway rolling stocks using transformers connected in series to motor windings

In order to prevent regenerative energy failure for the rolling stock, an onboard energy storage system using electric double layer capacitors (EDLC) is considered to be a promising tool. This paper proposes a new circuit configuration of an energy storage system, consisting of EDLC and its input/output auxiliary transformers connected in series to main motor windings. Our proposed system enables improved performance of the regenerative braking at the high speed region without regeneration failure. In this paper, simulation results show excellent operations of the proposed system. A mini model consisting of a 2.2 kw induction motor and IGBT inverters was tested to verify the feasibility of the proposed system.