In order to deal with the excessive current in valve side of flexible HVDC resulting in phase jumps during the transition from closed-loop control in a grid-connected mode to open-loop control in an island mode

a novel control strategy for the transition from grid-connected to island operation based on phase synchronization is proposed. Firstly

the dq axis components of grid-side voltage at the instant of transition are captured and used as the initial reference values for the dq axis components in the island open-loop control. During the process

by dynamically adjusting the amplitude of reference wave

the real-time tracking of grid side voltage by reference wave is realized

thereby ensuring phase synchronization. Once the daxis and q axis components of reference wave reach their preset values

the reference wave is stabilized to realize the stable control. To verify the effectiveness of the proposed strategy

a simulation model for Zhoushan five-terminal flexible HVDC project is constructed on RTDS platform. The simulation results clearly show that the proposed control strategy based on phase synchronization can effectively resolve the phase jumps during the transition from grid connected to island operation

which significantly enhances the stability of this transition process.