• Analyzed the adaptability of distance protection by fully considering the fault control strategies. • The proposed method fully considers the influence of fault severity during the FRT control stage. • A control and distance protection coordination method for DEWFS is proposed. • The proposed method has a certain robustness and is less affected by fault resistance. Since the PV-side voltage source converter (PVVSC) and the sending-end modular multilevel converter (SEMMC) are connected by AC lines, they constitute a double-ended weak-feed system (DEWFS). Under the traditional negative sequence cooperative control strategy, it will induce incorrect action of traditional distance protection. Therefore, an improved distance protection considering the negative-sequence control coordination strategy is proposed. Firstly, the adaptability of distance protection of DEWFS under the traditional fault cooperative control strategy is analyzed. Secondly, considering the influence of fault severity on the control effect, a switch strategy between negative sequence voltage suppression (NSVS) and negative sequence impedance angle reconstruction (NSIAR) on the MMC side is proposed. Finally, combined with the composite sequence network analysis to obtain the additional impedance angle provoked by the fault resistance, and the correct action of the traditional distance relay is realized. The simulation results suggest that the proposed method has high resistance to fault resistance and can realize accurate identification of internal and external faults within 60 ms, and it has certain robustness. Moreover, the proposed negative sequence control strategy did not affect other fault ride-through (FRT) control of the DEWFS while ensuring the safe and stable operation of the DEWFS.
Hou et al. (Tue,) studied this question.