Protection Method for AC/DC Hybrid Distribution Network Based on Line Integrity Judgment

AC/DC hybrid distribution networks facilitate the flexible integration of renewable energy sources. However, due to the influence of power electronic devices and control strategies, the sensitivity and reliability of protection methods for AC/DC hybrid distribution networks face challenges. This paper proposes a protection method based on line integrity judgment. First, taking the lumped parameter R-L line model as an example, the protection principle based on line integrity judgment is analyzed. Second, a protection principle implementation method suitable for AC/DC hybrid distribution networks is proposed. The reference point voltage is calculated using the electrical quantities at the measurement point, and the fault location is determined by comparing the similarity between the voltage waveforms at the measurement point and the reference point. Cosine similarity is introduced to quantify the waveform similarity. Finally, by comparing the fault judgment results from both ends of the line, it is determined whether the fault is internal or external to the line. A simulation model is built using PSCAD/EMTDC, and the simulation results show that the proposed protection method can accurately distinguish fault locations and exhibits good adaptability to different control strategies.