Transient Stability Analysis of Grid-forming Converter Based on Virtual Synchronous Generator

In recent years, the proportion of grid-forming converters based on virtual synchronous generator (VSG) has gradually increased in power systems, but the transient synchronization stability after it is connected to the power grid lacks in-depth research. The transient synchronous stability mechanism of VSG is studied in this paper. The transient synchronous stability model of the VSG during grid voltage dropping faults is established. Based on the phase portrait curve method, the instability mechanism of the VSG and the influence of voltage variation on its transient synchronization stability are studied. According to the reactive power and voltage coupling effect, an enhancement measure is proposed to improve the transient synchronization stability by automatically changing the command value of output active power. Finally, through the electromagnetic transient simulation model built in PSCAD/EMTDC, the transient stability mechanism of the VSG grid-connected system and the availability of enhancement measures during grid faults are respectively studied.