Several commutation failures occurred during commissioning of a HVDC project in China Southern Power Grid

which had a great impact on both AC and DC power systems. The transient fault recording data during the commutation failure is analyzed. It is concluded that the reason of the commutation failure is the malfunction of the HVDC control system caused by the accidental failure of the extinguishing angle measurement system. Based on this inference

the detailed PSCAD model of the HVDC project is established

and the fault is simulated and reproduced

which verifies the correctness of the fault cause analysis. In order to resolve the occasional abnormality of the extinction angle measuring device

an anti-error logic link is added in the control system to shield the abnormality of the extinction angle measurement. The effect of the proposed solution is verified by PSCAD/EMTDC simulation

simulative results and actual operation show that the proposed solution is effective for abnormal measurement of extinction angle and ensures safe and stable operation of HVDC system.