Research on Active Current-Limiting Control and Fault Characteristics of DC Distribution Network

The DC distribution network based on the hybrid modular multilevel converter (MMC) has the ability of active current-limiting control, which plays an active role in fault clearing of distribution network. However, the fault characteristics of the DC distribution network become complicated because of the active current-limiting control. It brings new problems to the fault detection and judgment of relay protection. According to the structural features of the hybrid MMC, the start-up strategy and control objectives of the active current-limiting control are analyzed in this paper. The improvement suggestions are put forward to maintain the operational safety of the power grid, as well as meet the application requirements of the relay protection. Moreover, The characteristics of the short-circuit current of the DC distribution network are analyzed based on the active current-limiting control. Meanwhile, the influences on the relay protection are estimated. Finally, the effectiveness of the proposed current-limiting control strategy and the correctness of the fault characteristic analysis results are verified by simulation tests.