Research on the Protection Action Strategy for Multi-Terminal AC/DC Converter with Fault Blocking Capability

The multi-terminal AC/DC converter with fault blocking capability is widely used in the power system. In this paper, based on the topology of the multi-terminal AC/DC converter using clamp double sub-module (CDSM), the principle of blocking DC fault current is analyzed under the high-voltage DC bipolar short-circuit fault. The impact of the protection action strategy on the discharge path of the submodule capacitors of AC/DC converter is discussed. Different exit sequences and the locking time of the dual active bridge (DAB) converter and DC/AC inverter are discussed, and the protection action strategy is provided for multi-terminal AC/DC converter. Finally, simulation results are provided for the different protection action strategies.