Unified power flow controller (UPFC), static synchronous series compensator (SSSC) and phase shifting transformer (PST) can change line parameters and control power flow, which have been used in the practical power system. This paper aims to summarize and prospect the research about the application of these devices. Firstly, the basic principle and the structure of these power flow control equipment are analyzed, and their practical projects are introduced. Secondly, the research status of these devices is summarized from five aspects: control strategy, fault protection, locating and sizing, converter and measurement. Finally, the typical application scenarios of power flow control devices in power grids are forecasted, and the trend of future power flow control technology is prospected.