The Single-Ended Protection of Flexible HVDC Transmission Line Based on Traveling Wave Power Amplitude Ratios Using S-Transform

The fast and reliable protection is one key technology of flexible HVDC transmission system. The traditional flexible DC line protection is mainly based on single-ended fault characteristics, whose reliability is greatly affected by DC fault. In this paper, a single-ended protection of flexible HVDC transmission line based on line-mode power is proposed. The frequency-domain characteristics of line-mode power traveling wave under internal and external fault are analyzed theoretically. The line-mode power is converted by S-transform, the amplitude differences between the low and high frequencies are analyzed, and the amplitude ratio of low frequency to high frequency is constructed for the protection criterion. The simulation results on Zhangbei four-terminal ± 500 kV flexible HVDC transmission system by PSCAD illustrate the effectiveness of proposed algorithm under different fault types, fault locations and transition resistances, which can withstand the transition resistance 1000 Ω and 20 dB noise.