Current order‐based emergency control strategy for subsequent commutation failure elimination in HVDC

Abstract

Subsequent commutation failure (CF) elimination in line-commutated-converter–based high-voltage direct current (LCC-HVDC) is an essential issue of AC/DC hybrid power systems. Since methods based on improving HVDC control systems or advancing the firing angle have inherent limitations, adjustment of the DC current order is regarded as an effective emergency control strategy for HVDC that has been put into operation. However, existing methods sometimes result in failed CF elimination due to improper control timing of DC current. In order to determine proper control timing, novel voltage indexes are put forward in this article to identify stability or instability of the hybrid system. Then, the DC current order is adjusted in real time to eliminate subsequent CF according to the evaluation results given by the proposed voltage indexes. The control strategy is simulated in the PSCAD/EMTDC platform as well as actual power system, and the simulation results compared with those of existing schemes verify the effectiveness and advancement of the proposed strategy on subsequent CF elimination.