Research on Commutation Failure of DC Transmission System Based on Harmonics

The paper summarizes the micro mechanism and key influencing factors of consequential commutation failure in the HVDC transmission system, which mainly includes the harmonic impacts on the secondary commutation failure. And it quantitatively analyses the adverse effects of harmonics on commutation through the time area of commutation voltage, hence the main factors affecting the time area of harmonic voltage can be obtained. And the harmonic influence coefficient Fn is introduced to reflect harmonic voltage's influence level in the worst case of commutation. Then, a method based on harmonic voltage area is proposed to reduce the risk of secondary commutation failure, that is, through introducing the negative harmonic current feedback by harmonic voltage feedback gain index Kn to reduce the direct current at fault. The validity and practicability of the method were proved by simulation analysis.