The virtual synchronous generator (VSG) based on voltage/current proportional control is suitable for grid-connected converters in the absence of AC filter capacitors such as high-voltage cascade topologies. This paper focuses on the problems of insufficient voltage support capability and unstable power angle after triggering current limitation of VSG during grid voltage dips. Firstly
the working principle of the VSG based on voltage/current proportional control is analyzed. Then the mechanism of insufficient voltage support capability and power angle destabilization of conventional current loop limiting control during grid voltage dips is elucidated. On this basis
an improved transient support control strategy based on q-axis voltage feedback and voltage command correction is proposed. In a steady state
the improved control strategy is the same as the conventional control strategy
and the q-axis voltage feedback control is automatically put in to improve the power angle stability when the grid voltage dips. The d-axis and q-axis voltage commands are adjusted automatically when the current limit is reached to improve the transient voltage support capability. Finally
MATLAB/Simulink simulation results verify the effectiveness of the proposed strategy
demonstrating its capability to ensure power angle stability under current limiting while achieving adaptive grid voltage support under various sag depths.