Risk Assessment of First Commutation Failure Caused by Single-phase Harmonic Voltage

Commutation failure is a research hotspot in the field of line commutated converter-based high voltage direct current transmission (LCC-HVDC). Current studies primarily focus on commutation failures caused by AC system faults, while research on harmonic voltage-induced commutation failures requires further exploration. First, starting from the mechanism of commutation failure and combining the analysis of a commutation process involving two stages, this study refines the classic definition of commutation failure. Then, taking singlephase harmonic voltage disturbances at the receiving-end converter bus as an example, the commutation voltage time area method is employed to comprehensively analyze harmonics of different orders, amplitudes, and phases. This approach identifies critical intervals of harmonics that may trigger the first commutation failure. For scenarios involving multiple harmonic disturbances in a single phase, a numerical evaluation method is proposed to determine whether commutation failure occurs. Finally, the effectiveness of the proposed risk assessment method is validated using the electromagnetic transient simulation platform (PSCAD/EMTDC).