Current limiting leads to virtual power angle synchronous instability of droop-controlled converters

Synchronous instability may also occur to the P-f droop-controlled voltage source converter as well as virtual synchronous machine during large disturbance, similar to the synchronous generator's synchronous instability in conventional power systems. Moreover, the current limiting link will result in a more complicated instability process and a greatly decreased stability margin of the converter. The virtual power angle is defined in this paper to analyze the synchronous stability mechanism of a converter with respect to an infinite bus. Simulation verifies the rationality of the analysis.