Longitudinal Comparison Protection Method for AC/DC Hybrid Distribution Network Based on Waveform Similarity

With the maturity of DC transmission and distribution technology, the future distribution network will gradually develop in the direction of AC/DC hybrid distribution network (AC/DC-HDN). The unique fault coupling characteristics of AC/DC-HDN challenge the adaptability of protection methods. Based on the analysis of the fault coupling characteristics of AC/DC-HDN, this paper proposes a longitudinal comparison protection method for AC/DC-HDN based on waveform similarity. The method chiefly employs electrical quantity of the measurement point to calculate reference voltage of the corresponding reference point. Determine whether the fault location is located between measurement point and reference point or outside by determining whether the wave-form of the measured voltage is similar to that of the reference voltage or not. The longitudinal protection makes a decision on whether the fault occurs internal or external by comparing the results. Finally, the correctness of this protection method was verified by setting different location faults in PSCAD. The method can accurately determine whether the fault occurs internal or external, has a certain resistance to transition resistance, is not affected by unmeasurable load branches, and has good coping ability for calculation errors caused by noise interference.