Harmonic characteristics of HVDC transmission system and its suppression method system

In this paper, firstly, the generation of characteristic harmonics and non-characteristic harmonics, the content of each harmonic and its amplitude varying with the frequency of HVDC converter are analyzed theoretically, then, the harm of harmonics to HVDC transmission lines is introduced, and some restraining measures are put forward, such as increasing converter pulsation number, installing and improving AC filter to suppress the generation of specific frequency harmonics and reduce their amplitude, so as to increase the stability of the system. Secondly, through simulation based on PSCAD/EMTDC, it is verified that 6K±1 harmonics (where K is odd) can be eliminated by increasing the converter from 6 to 12 pulsations, so as to reduce the harmonic content of transmission lines. Finally, a simulation model is built to verify that the harmonic amplitude of 12K±1 (K is a positive integer) is greatly reduced when the hybrid tuning filter is installed at 12 pulsations.