A Novel Segmented-COV-Based Single-Ended Line Protection Algorithm for the Multiterminal MMC-HVDC System With No Boundary Reactor

The protection is one of the most important techniques for the modular multilevel converter (MMC) high-voltage dc (HVdc) system. The existing single-ended dc line protections are mainly based on the boundary characteristics, which are not suitable for the condition with no boundary element on the line terminal. In this article, the variation characteristics of different electric variables with fault distance changing are analyzed in the MMC-HVdc system with no boundary reactors. On this basis, a novel segmented-change-of-voltage-based single-ended protection algorithm is proposed, which is suitable for the system with no boundary element. In addition in the designed scheme, the nearby dead zone problem and return-to-inactivated problem are researched specifically. According to the proposed method, a protection device is developed, and the corresponding hardware-in-loop experiment tests are carried out to validate the properties of the developed protection device.