An Adaptive Reclosing Scheme for MMC-HVDC Systems Based on Pulse Injection From Parallel Energy Absorption Module

Modular multilevel converter (MMC) based high voltage direct current (HVDC) transmission system is one of the important development trends of DC power grid. After fault isolation, the traditional reclosing method of MMC-HVDC system is directly reclosing DC circuit breaker (DCCB). Once the fault point still exists, DCCB will be tripped again. This method will make the DC system suffer from the secondary strike of fault in a short time, and seriously endanger the service life of DCCB. In order to overcome the drawbacks of the traditional reclosing schemes, this paper proposes a novel adaptive reclosing scheme based on pulse injection from parallel energy absorption module. When dc fault current is interrupted by DCCB, the fault energy stored in current-limiting reactors (CLR) and dc lines is transferred to energy absorption module automatically. By switching on IGBTs embedded in absorption module for a short time, a voltage pulse is injected directly into the faulty line without interference from CLR. Then the nature of fault is identified and the fault distance can also be calculated in the case of permanent faults. The simulation results verify the effectiveness of the proposed reclosing scheme.