Mechanism and Prevention of Commutation Failure in LCC-HVDC Caused by Sending End AC Faults

This letter analyzes the mechanism of commutation failures (CFs) caused by sending end AC faults. It is founded that the dc impulse current after fault clearance is the direct reason of CF occurring under nonserious sending end AC faults, and the controller interaction is the main reason of CF occurring under severe sending end AC faults. Moreover, a prevention strategy is proposed based on the revealed mechanism, and the validity is verified by the simulation results.