Operational boundary characterization and coordinated control of an RPFC-SVC integrated scheme for power and voltage regulation

Flexible interconnected distribution systems based on Rotary Power Flow Controller (RPFC) enable precise power flow regulation and balanced mutual power support. However, RPFC lacks inherent reactive power compensation capability, which can cause voltage violations at loop-closing points in interconnected distribution networks and restrict the bidirectional power flow operating range. This limitation hinders the full utilization of RPFC-based flexible control. To address these issues, this paper first characterizes the power operating boundary of the RPFC and defines its voltage safety margin. A flexible interconnection scheme combining the RPFC with a Static Var Compensator (SVC) is then proposed, along with a multi-timescale control strategy that accounts for their differing response characteristics. Furthermore, the influence of the RPFC-SVC combination on feeder voltage and loop-closing power flow is analyzed, revealing that voltage fluctuations simultaneously shift the center and alter the boundary of the power operating region. Finally, a simulation model of an interconnected distribution system with the RPFC + SVC configuration is developed. The results demonstrate that the proposed scheme improves both the steady-state operating range and the dynamic performance of the system, offering valuable insights for future development and application of RPFC technology.