Abstract：To address the large inrush current during the switching of a virtual synchronous generator（VSG）

from off-grid to grid-connected，and the stability issues of traditional pre-synchronization schemes，a control

method for the phase-locked loop（PLL）pre-synchronization unit to be cut off in non-grid-connected time was

proposed. First，based on the VSG's rotor motion and excitation equations，the main factors affecting the inrush

current at closing were identified. Then，considering the physical model of virtual reactance and the characteristics

of virtual power output，a virtual power pre-synchronization scheme combining virtual reactance and band-pass

filtering was developed. Finally，the effectiveness of proposed method was verified through 2 kW simulations and

experiments. Results show that proposed method enables smooth switching between off-grid and grid-connected

modes and allows for the removal of the pre-synchronization unit at any time after grid connection，demonstrating

good stability.

      Key words：virtual synchronous generator（VSG）；closing；inrush current；pre-synchronization；virtual power；virtual reactance；smooth transition

     Format Citation:丁津津，彭勃，张峰,等. 基于虚拟功率的非计划性VSG并离网平滑切换控制策略[J].电气传动,2026,56(06):16-21. DING Jinjin，PENG Bo，ZHANG Feng,et al. Control strategy for seamless unplanned transition between grid-connected and islanded modes of VSG based on virtual power [J].Electric Drive,2026,56(06):16-21