Application of Resistance SFCL in MTDC Grid with Reclosing Protection Strategy

Resistive superconducting current limiter (RSFCL) is an effective technical means to solve the short-circuit current problem of DC transmission system. Aiming at the problem of large fault current and fast rising speed in multi terminal DC system (MTDC) with modular multilevel converters (MMC), a new protection strategy based on RSFCL is proposed to isolate the fault area quickly. Through analyzing the quench and recovery characteristics of RSFCL, the quench resistance meeting the reclosing requirements is determined, of which recovers to superconducting in 300 ms. The coordination principle and operation sequence of RSFCL, DC circuit breaker (DCCB) and MMC converter are analyzed for setting up the protection strategy. Taking the bipolar short circuit fault of overhead line in a three terminal flexible DC project as an example, the rationality of the proposed protection strategy is verified in PSCAD/EMTDC software. The simulation results show that the coordination strategy can help to quickly isolate the fault area, carry out fault ride through of non-fault station, accelerate the restart of fault pole converter, and reduce the outage time of MTDC grid.