1122 / 2019-05-20 23:12:26

Active Protection Scheme for MTDC System Based on Full-Bridge MMC Converters

protection,VSC based multi terminal HVDC

Multi-terminal DC (MTDC) system is considered as an important revolution of the power system with large-scale renewable energy sources integration. The dc line protection is one of the key techniques for the system reliability and security, whose main technical difficulty lies in quick and reliable faulted lines identification. In this paper, a fault control method based on Full-Bridge MMC converters without blocking IGBTs is proposed. All of dc lines current will be limited to 0 by this method after fault. With the help of control method, the current from a specific converter station is regulated to 0.2pu. According to the direction of current flow, the faulted line can be identified. Therefore, an active protection scheme is elaborated. The fault control strategy and active protection scheme is analyzed using EMT simulations under variation of the fault location, type and resistance. The investigations are carried out in a German Ultranet three-terminal DC system with full-bridge modular multilevel converters in symmetrical monopole configuration.