Transient Stability of Power Systems Integrated with VSCs

The transient stability issue of power systems with high penetration of power electronic converters has raised growing concerns. In the literature, the issue was investigated mainly by numerical simulation, which, however, can neither give analytical insights into the stability mechanism nor provide accurate information on the stability boundary. This issue is investigated analytically in this letter. It is found that the converter output alters the power angle characteristics of generators; the converter's synchronization requirement limits the maximum power angle of the generator, which proves to be the leading cause of a new type of transient instability. Also, a quantitative method is provided to accurately predict the stability boundary.