Research of protection for AC transmission lines based on characteristic of grid-side inverter

With the advantage of saving resources and high utilisation, DC transmission becomes the vital part of the sustainable development. However, due to the control strategies of grid-side inverter, the fault characteristics of the grid will change dramatically, which influences the reliability of grid protection. By establishing the model in PSCAD, the fault characteristics of the inverter was obtained and the effects on current protection was analysed here. The results reveal that the magnitude of fault current was directly influenced because of being connected with the inverter. The grid inverter can make a difference in selectivity and reliability of current protection. In order to solve this problem, the paper constructs the equivalent model of the inverter and attains the unique feature that the fault component impedance measured in the location of protection decreases with the increasing distance of fault location. According to the characteristics, a targeted fault component impedance protection is designed. The feasibility and effectiveness of this protection is verified by simulation in PSCAD model.