Pilot protection based on the similarity of the traveling waves between the quadratic fitting curve and the calculated curve for the All-DC wind power transmission system

• Published in: International journal of electrical power & energy systems 2024-10, Vol.161, p.110186, Article 110186
• Main Authors: Hou, Junjie, Li, Panlong, Fan, Yanfang, Song, Guobing, Wu, Xiaofang, Qin, Xiaohua, Gao, Chao
• Format: Article
• Language: English
• Subjects: Calculated curves; Fitting curves; Initial current traveling wave difference; Pilot protection; The All-DC wind power
• ISSN: 0142-0615
• DOI: 10.1016/j.ijepes.2024.110186

•The waveform differences between the initial current forward traveling wave and the backward traveling wave are proven theoretically under internal and external faults.•The waveform similarity between the theoretically calculated curve and the fitted curve is introduced into the proposed method.•The proposed method does not require strict data synchronization and set setting values through simulation.•It can identify faults in situations with higher fault impedances, noise interference, and lower sampling frequency. The All-DC wind power generation system can effectively solve the harmonic resonance problem caused by large-scale wind power AC collection and transmission, gradually becoming a hot topic in future research. However, there are few studies on the relay protection of the All-DC wind power transmission systems. In the All-DC wind power systems, there are differences in topology, control strategies, fault characteristics, boundary characteristics, etc. At the same time, existing pilot protection has problems such as strict information synchronization requirements and selection of setting values through simulation. Therefore, the proposed pilot protection based on the similarity of the traveling wave between the quadratic fitting curve and the calculated curve for the All-DC wind power system transmission lines. Firstly, the difference of the 1-mode initial current waveform characteristics is analyzed in the time domain at both ends. Then, the least squares method is introduced to fit the differential curves of the current forward and backward traveling waves at two terminals. The differential characteristics of the differences between the fitted curve, the calculated curve, and the measured curve under the influence of internal and external errors are analyzed. Finally, the calculated value of traveling wave current during external metallicity fault is used as the standard. By comparing the fitting curve of current traveling waves and the difference in the calculation curve to distinguish internal faults from external faults. The simulation results show that the proposed protection principle can fault resistance of 2200 Ω and noise interference of 20 dB. In addition, the proposed method does not require strict data synchronization, higher sampling frequency, and setting value through simulation.