Centralized Locating Strategy of Fault Current Limiters in MMC-Based Multiterminal HVdc Grid

Abstract

In this article, a centralized locating strategy of fault current limiter (FCL) in high-voltage direct current (HVdc) grid is proposed and analyzed. By employing FCLs at the output sides of modular-multilevel-converters (MMCs), the proposed centralized locating strategy could reduce the number of FCLs in multiterminal high-voltage direct current (MTdc) grid. A typical application scenario based on Zhangbei–Beijing four-terminal HVdc grid is introduced in this article. Mathematical model of the proposed strategy is built and numerical solutions are calculated. Then, the simulation model is built in PSCAD/EMTDC and different locating strategies of FCL are studied. Simulation results verify the rationality of theoretical analysis. Also, calculation and simulation results demonstrate that the proposed centralized strategy has similar current-limiting performance with the conventional distributed FCL locating strategy. When the proposed strategy is applied, the MMCs could be protected from overcurrents. What is more, the reliability and reconnection of partial system after faults are ensured. The healthy part of MTdc grid could maintain continuous operation and transmit active power as normal. When applying different FCL locating strategies, the total investment of FCLs is calculated and compared. Calculation results prove that the proposed centralized locating strategy can effectively reduce the investment of FCLs compared with the conventional distributed strategy and is more suitable for MTdc grid.