A Novel Protection Scheme for LCC-MMC Hybrid Multi-terminal HVDC Transmission Lines

With the large-scale integration of renewable energy, power electronic equipment represented by converters is widely used in power systems. However, because of the fragility and complex fault characteristics of power electronic devices, traditional protection technologies are no longer suitable. It is urgent to propose a more reliable protection scheme to ensure the safe operation of the power system. In this paper, a novel protection scheme for LCC-MMC hybrid multi-terminal HVDC transmission lines is proposed, which is composed of four different protection principles corresponding to four fault stages, based on the fault information of wavefront, switching characteristic frequency of MMC, active injection, and differential current. The effectiveness of the proposed protection scheme is verified on PSCAD/EMTDC. Simulation results show that with the coordination of several protection methods, at least two types of protection methods can identify faults correctly most of the time after the fault occurs.