Multi-terminal medium voltage DC grids fault location and isolation

Voltage source converters (VSCs) are highly vulnerable to DC fault current; thus, protection is one of the most important concerns associated with the implementation of multi-terminal VSC-based DC networks. This study proposes a protection strategy for medium voltage DC distribution systems. The strategy consists of a communication-assisted fault location method and a fault isolation scheme that provides an economic, fast and selective protection by means of using the minimum number of DC circuit breakers. This study also introduces a backup protection which is activated if communication network fails. The effectiveness of the proposed protection strategy is analysed through real-time simulation studies by use of the hardware-in-the-loop approach. Furthermore, the effects of fault isolation process on the connected loads are also investigated. The results show that the proposed strategy can effectively protect multi-terminal DC distribution networks and VSC stations against different types of faults.