Abstract: With the rapid development of active distribution network construction, multi-terminal power supply system has become the mainstream power supply structure. Due to the factors of grid layout design, there is a phenomenon of phase Angle difference between the two ends of distribution network closing ring. Direct closing ring will produce large impact current and affect the reliability of power supply. This paper proposes a solution based on the electromagnetic rotary power flow controller (RPFC) to achieve flexible loop closure of phase difference lines and complete emergency power control of RPFC access lines in case of system short-circuit or power off-network failure. The topological structure and working principle of RPFC are studied. Based on the principle of voltage vector superposition and instantaneous reactive power theory, flexible loop closing and emergency power control strategies of RPFC are proposed. The simulation results show that the ring-closing current and adjusting time of RPFC are only 11.95% and 18.44% of those of the dual-core phase- shifting transformer, and the RPFC shows independent power control ability in case of system failure. Finally, a 380V/40kVA RPFC experimental platform is built, and the experimental results are consistent with the simulation, indicating that RPFC achieves good control effect under flexible ring closing and emergency power conditions.