Hybrid high-voltage direct current (HVDC) transmission has the characteristic of long transmission distance

complex corridor environment

and rapid fault evolution of direct current (DC) lines. As high fault current can easily cause irreversible damage to power devices

rapid and reliable line protection and isolation are necessary to improve the security and reliability of hybrid HVDC transmission system. To address such requirement

this paper proposes a single-ended protection method based on transient voltage frequency band characteristics. First

the frequency characteristics of the smoothing reactor

DC filter

and DC line are analyzed

and the characteristic frequency band is defined. A fault criterion is then constructed based on the voltage characteristic frequency band energy

and faulty pole selection is performed according to the fault voltage characteristic frequency band energy ratio. The proposed protection method is verified by simulation

and the results show that it can rapidly and reliably identify internal and external faults

accurately select faulty poles without data communication synchronization

and has good fault-resistance and anti-interference performance.