Negative sequence current accumulation difference based wind farm collection line protection for MMC-HVDC system

During the fault of the wind power collection line of the MMC-HVDC system, the amplitude of the fault current may be limited due to the control of the converter, which leads to the severe limitation of traditional protection. In this paper, based on the difference of negative sequence current accumulation, a new protection scheme for wind farm collection lines is proposed. First, the negative sequence current equivalent circuit of the wind farm collection line is constructed. Then, the distribution characteristics of negative sequence current at different fault locations are identified. On this base, a novel protection scheme based on transient negative sequence current accumulation difference using interconnected blocking signals is proposed. The RTDS simulation results show that the protection scheme can accurately identify faults of different types and locations.