655 / 2019-04-20 15:13:26

Research on post-fault time sequence of MTDC with MMCs

Fault analysis,MMC,Multi-terminal HVDC (MTDC),Post-fault time sequence,Short-circuit current

Nowadays, flexible HVDC transmission develops towards a direction of multi-terminal or meshed grid. When analyzing the post-fault transient responses of mutli-terminal HVDC (MTDC), the coupling effect of multiple converters is more and more important. Due to the non-linear characteristics and different control sequences of each convertors, the contribution of fault current from each convertor station cannot be simply added, and the time sequence of different converters should be considered. Hence, the time sequences of each convertor station are discussed and studied in this paper. A time sequence diagram is peoposed to segmentize the post-fault procedure, and the transient currents are calculated segment by segment. A multi-terminal DC transmission system based on modular multi-level converter (MMC) is modeled in PSCAD/EMTDC and used to test the calculation results. The results show that the calculation error of fault current is within a reasonable range, which verifies the correctness of the theory.