Phase shifting transformers (PSTs) are economical and effective measures to solve the problems of node voltage overruns and uneven power flow distribution caused by the large number of renewable energy sources connected to the grid. Aiming at the limitations of traditional single-core PSTs in terms of high number of taps, inability to regulate across gears, slow speed of gear switching and low accuracy, a fast-switching single-core PST (FS-SCPST) is proposed. The source-side and load-side regulating windings of the FS-SCPST can be adjusted independently to realize the decoupling of voltage magnitude and phase to a certain extent. The regulation windings of FS-SCPST are layered structure, which can effectively reduce the number of taps. FS-SCPST adopts hybrid fast switches for gear switching, which can realize millisecond arc-free switching of three access modes (forward access, reverse access, bypass) of the regulating winding. In this paper, the topology of FS-SCPST is given, its operation principle is analyzed, and the control strategy is configured. Finally, the feasibility of FS-SCPST and its effectiveness in voltage and power flow regulation are verified by simulation analysis, which highlights FS-SCPST’s potential in the field of dynamic grid stability.