A Novel DC Line Pilot Protection Scheme Based on Additional Current-Limiting Control of HB-MMC

The additional current-limiting control of modular multilevel converters (MMC) can effectively reduce the technical demand for DC circuit breaker (DCCB). At the same time, in cooperation with the protection, it can effectively reduce the requirements for line protection speed and improve the reliability of the protection. Therefore, a pilot protection scheme considering the influence of additional current-limiting control is established by using the ideal of integration of control and protection. Firstly, a two-stage current-limiting control strategy is proposed based on the current changing rate and amplitude, which effectively limits the fault current. Secondly, a pilot protection principle of current mutational volume is proposed, which is based on the additional current-limiting control strategy and fault current mutational direction characteristic information. Finally, the performance of the additional current-limiting control strategy and proposed protection principle are verified in PSCAD. The simulation results show that the proposed current-limiting control strategy can effectively reduce the DC fault current; The proposed protection method can reliably identify the fault. At the same time, it has a certain immunity to noise and higher fault resistance interference.