Pole-to-Pole Fault Protection of Hybrid-MMC-based MVDC Distribution Systems

DC fault handling is a critical design and operation issue for DC distribution systems. DC distribution protection should be rapid due to the fast growth of fault currents, and cost-effective high speed DC breakers are challenging, especially in medium voltage DC (MVDC) distribution systems. A hybrid MMC (Modular Multilevel Converter) based DC fault protection and restoration method is proposed for pole-to-pole fault protection of MVDC systems. The converter topology and associated control are able to interrupt DC fault current rapidly and isolate DC fault with zero-current turn-off by DC disconnectors. Furthermore, the proposed method includes fast converter restarting and DC system reconnection after fault removal. Simulation results of the pole-to-pole fault protection in a MVDC distribution system show satisfactory performance.