Power storage devices that attempt load leveling and energy efficiency improvement have recently drawn attention as a means of solving the problems of pantograph point voltage drop, power load variations, and regeneration canceled on DC electric railways by charging power during regeneration and discharging power during power running. The basic characteristics have been checked using a miniature system (at 400V DC) in which the electric double layer capacitor is used as power storage media and the booster chopper as a power converter that transfers power between the storage media and the overhead contact line system.

      Based on the basic characteristics obtained, a 600V DC power storage device was built, and a commercial line verification test was performed. The device was installed indoors in a car inspection section located approximately halfway between two substations (Fig.1). The storage device shown in Fig.2 was set to discharge to the train when the overhead contact line voltage dropped below a preset voltage, and to charge from both substations when the stored power in the device decreased. As Fig.3 shows, the overhead contact line voltage in the car inspection section did not fall below the target value of 550V, demonstrating good voltage compensation control. In the future, this research will be extended to implementation of the storage device on 1500V DC sections.

      This study was sponsored by the Ministry of Land, Infrastructure and Transport.

Fig.1 Test section of the power storage device

Fig.2 Storage device installed in the car inspection section

Fig.3 Example of compensation when the overhead contact line voltage drops