Adaptive restart strategy of flexible DC grid suitable for double-terminal MMC

Due to the frequent occurrence of transient faults on overhead lines, the use of DC reclosing strategy can effectively improve its power supply reliability. However, when the DC grid coincides with a permanent fault, it will cause a secondary impact problem, endangering system operation and equipment safety. An adaptive restart strategy of flexible DC grid suitable for double-terminal MMC is proposed. This paper first researches the transient characteristics of pole to pole fault, then introduces the active control strategy after the fault and proposes a current reference signal with adaptive restart capability. Finally, the simulation model of typical double-terminal DC network is built in PSCAD/EMTDC. The simulation results show that the proposed adaptive restart strategy can determine the nature of the fault within 25ms, and finally restart quickly within 150ms.