Fast Back-up Protection Scheme of Receiving-End Hybrid LCC-VSC DC Transmission Lines

Hybrid multi-terminal DC transmission technology combines the advantages of the two converter technologies and has broad development prospects. The fault characteristics of the transmission line of the multi-terminal hybrid system are different from the traditional single DC system. The fault characteristics of the hybrid multi-terminal DC transmission line are analyzed in this paper. it is found that there are current imbalances on both sides when the transmission line faults, and the backup protection time requirements of the LCC branch and the VSC branch are different. The traditional differential undervoltage protection and current differential protection is difficult to serve as backup protection for the entire transmission line. In order to solve the problem, a dual-acceleration inverse time overcurrent protection scheme based on single-end electrical quantities is proposed as a fast backup protection for the transmission line traveling wave protection. The scheme of different setting values at both ends to solve the problem of current imbalance on both sides was used in this paper. The inverse time limit feature can be used to cooperate with the main protection of two branches at the same time. Therefore, the protection scheme is less affected by distributed capacitance and transition resistance. Finally, simulation results prove the effectiveness of the scheme. © 2021, Electrical Technology Press Co. Ltd. All right reserved.