The regenerative power in DC electric railways is generated during braking and is shared between vehicles. The sharing contributes to the reduction of the overall power consumption. When there is no powered vehicle running nearby, a light-load regenerative brake control is activated to prevent overvoltage. In that case, the regenerative power cannot be used effectively. Therefore, an appropriate bus voltage can be set as a means of reducing the light-load regeneration control and increasing the regenerative power.
In this study, to effectively utilize the regenerative power, we conducted verification tests on the Yokohama line by changing the bus voltage of DC substations, and determined an appropriate bus voltage that would not affect the train operation. To clarify this voltage, it is necessary to clarify the pattern in which the regenerative power is used. It requires a detailed analysis of the regenerative energy, powering energy, and feeding loss related to the operating energy. This study revealed that lowering the voltage facilitates the transfer of regenerative power to other feeding lines, and quantitatively demonstrated that reducing the amount of restricted regenerative braking energy increases the regenerative energy. The relationship between regenerative energy, power-running energy, and feeding loss was shown, as well as the factors that reduced the operating energy. This method is effective on railway lines where an amount of the restricted regenerative braking energy is generated, such as the Yokohama Line. If the half-tap extra-high-voltage transformer is set to a voltage that lowers when changing one tap from normal on the Yokohama Line, the regenerative power can be further increased without affecting the train operation and the operating energy can be reduced.
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