Power supply seamless switching device and method of electrified railway traction substation

The invention discloses a power supply seamless switching device and method of an electrified railway traction substation. Four paths of voltages, namely two-phase voltages of buses a and b of a contact network and voltages of a bus I and a bus II of a power supply, and four switching position signals, namely switches 201A and 201B of a low-voltage side of a main transformer 1B and switches 202A and 202B of a low-voltage side of a main transformer 2B are accessed to the switching device. During application, the current running mode of the traction substation is identified according to access quantity, automatic charging is achieved to prepare for switching if the running mode is normal, and discharging is performed to lock a switching function if the running mode is abnormal; three switching modes of parallel automatic switching, parallel semi-automatic switching and series switching can be performed; an optimal switching-on mode can be selected according to a real-time relation between the bus voltages of the power supply and the bus voltages of the contact network during switching on; and six modes of parallel rapid switching, rapid switching, same-phase lead phase angle switching, same-phase lead time switching, residual voltage switching and long delay switching can be performed, and uninterruptible power supply switching of two power supplies of the electrified railway traction substation can be achieved.