Anomalous Commutation Failure Phenomenon in Multi-Infeed HVDC Systems

Commutation failure theory of HVDC system is proposed and its reason is analyzed. Faults at inverter bus in multi-infeed HVDC system can cause local commutation failure and even concurrent commutation failure. Anomalous commutation failure is simulated with six kinds of ac system strength, and it is more and more serious at first as the system strength increases then become less serious as the strength becomes stronger. Coupling impedance is changed to get its relationship with anomalous commutation failure.