Non-unit traveling wave protection for flexible HVDC lines based on the ratio of the waveform fitting residual

作者：Li, Haifeng; Jiang, Huimin; Liang, Yuansheng^*; Xu, Yongzhi; Wang, Gang

来源：ELECTRIC POWER SYSTEMS RESEARCH, 2023, 218: 109199.

DOI：10.1016/j.epsr.2023.109199

• Flexible HVDC system
• Line protection
• TW fitting
• Non-unit protection
• Fault waveform

To solve the problems of sensitivity and rapidity of flexible DC line protection from the perspective of the time domain waveform difference of the fault traveling wave (TW), a mathematical analysis of the waveform char-acteristics of the fault-generated TW of the flexible HVDC line is developed in this paper. Moreover, the dif-ference in the time domain expression between the voltage TW is obtained under internal and external faults. To extract the features of the voltage TW waveform, the Levenberg-Marquardt method is used for data fitting according to two fitting functions corresponding to the internal and external faults. Then, a non-unit travelling wave protection scheme based on the ratio of these two fitting residuals is proposed. Finally, extensive simu-lations based on PSCAD/EMTDC show that the scheme can reliably identify all the faults of the DC line within 1 ms and has a high sensitivity and strong robustness under noise interference and different operation modes.