Synchronous Instability Mechanism of P-f Droop-Controlled Voltage Source Converter Caused by Current Saturation

Under large disturbances, P-f droop-controlled voltage source converters may lose synchronous stability, just like synchronous generator. Moreover, the current limitation leads to a more complicated instability mechanism and decreases stability margin greatly. This letter describes a virtual power angle instability problem and analyzes its mechanism from the virtual power angle characteristic curves of a converter with respect to an infinite bus. Simulation verifies the rationality of the analysis.