Analysis on Fault Current Evolution for MMC-HVDC Grid Considering Fault Current Limiter and Grounding Mode

The rapid rise of DC side short-circuit fault current brings about great challenges on the development of modular multi-level converter based high voltage direct current (MMC-HVDC) grid. Starting from the nature that both fault current limiter and grounding mode limit current by increasing fault circuit resistance or inductance, this paper focuses on the analysis on influence of parameters in both fault current limiter and grounding mode on the evolution of DC short-circuit fault current of MMC-HVDC grid. A comprehensive current limiting effect analysis method based on transient energy flow (TEF) analysis is proposed from the perspective of macroscopic energy transfer and dissipation. In this method, two evaluation indexes of TEF suppression rate and suppression efficiency are proposed. Taking four-terminal bipolar MMC-HVDC grid as an example, the comprehensive limiting effect of TEF in each region with the change of parameters in both fault current limiter and grounding mode under the condition of DC side pole to ground fault is analyzed by PSCAD/EMTDC simulation system. The proposed method can provide a theoretical basis for the comprehensive optimization of fault current limiter and grounding mode for MMC-HVDC grid.