Characteristics of Multiple Converters Based Traction Substations and Grid-connected Power Control Strategy

An advanced cophase traction power supply system based on three-phase to single-phase converter has been introduced to address issues of the reactive power, harmonics and unbalanced active power in the traditional traction power supply system. However, there will suffer from the problem of circulation when this converter is incorporated into. Hence, to make sure the normal operation of this advanced cophase traction power supply system, an improved droop control strategy is proposed in this paper to reduce the circulation and achieve the grid connection of multiple traction substations. As to this proposed scheme, the impedance of the traction network and the circulation and current-sharing characteristics between the traction substations are analyzed at first. In addition, the mathematical modes of the system are established with corresponding controller to obtain the compensated output voltage and phase angles between different traction substations to determine their current-sharing requirement. Then the circulation can be minimized automatically. The proposed droop control strategy is effectively and finally verified by simulation and experimental results.