Fault Management in Meshed MVDC Grids Enabling Uninterrupted Operation

Abstract:
The increase of renewable energies as well as the integration of new types of loads - charging infrastructure for e-mobility or heat pumps - and electrical energy storage systems pose major challenges for the distribution grid, especially at the medium-voltage (MV) level. The power flow needs to be dynamically controlled for stable grid operation. New MVDC grids can supplement existing AC grids and serve in two ways, (1) interconnect and stabilize MVAC grids, and (2) link new renewable sources and major loads. In the literature, many concepts were discussed, but the fault-current management is still a significant problem for the realization of such DC grids. This paper presents a prospective structure of a meshed MVDC grid with fault handling capability based on only three core components: Modular Multilevel Converters for the coupling to AC grids, Power-Flow Controllers and disconnector/grounding switches. The proposed protection scheme enables a fast and reliable fault isolation, as well as a fault ride-through under certain conditions.