Influence of DC transmission distance on MMC-HVDC stability under weak AC system

Abstract

The oscillation problem of MMC-HVDC under weak AC system poses a potential threat to the safe and stable operation of power grid, which is related to both of the AC and DC parameters. By comparing the stability of MMC-HVDC under different AC system strength with different DC transmission distance, it is found that when the AC system strength is too weak, there is a risk of instability under the condition of long DC transmission distance, and the correctness of this conclusion is verified by time-domain simulation. Later, the mechanism analysis of this phenomenon is carried out, the result shows that it is related to the interaction of MMC subsystems when the strength of AC system decreases.