Influence of Resistive SFCLs on Relay Protection of a Hybrid HVDC Incorporating LCC and VSC

The hybrid HVDC with line commutated converter (LCC) and voltage source converter (VSC) can efficiently realize large-scale power transmission and new energy consumption. This paper studies the effects of resistive superconducting fault current limiters (SFCLs) on the hybrid HVDC’s relay protection. The resistive SFCLs are positioned at the LCC and VSC to reduce the DC fault currents within tolerable levels, and the pilot protection is configured in the hybrid HVDC to conduct the fault identification and enable the fault clearance. The control scheme and protection configuration of the hybrid HVDC are theoretically presented. The quantitative impact of the resistive SFCLs on the pilot protection is investigated in a 320 kV HVDC system using the MATLAB platform. The effects of different SFCL sizes and fault resistances on the fault current gradient and the integration of the fault current component are analyzed. The ideas for establishing the starting and directional elements of the pilot protection in the hybrid HVDC are proposed.