Impact of DC fault blocking capability on the sizing of the DC-DC Modular Multilevel Converter

The capability of DC-DC converters of blocking DC faults is an important issue for the development of HVDC meshed grids. This paper analyzes the impact on the converter design of including such characteristic for the DC-DC Modular Multilevel Converter. Steady state and transient analysis are proposed and tested, showing how the converter should be oversized to include this feature. From this analysis it is concluded that including the fault blocking capability has an impact on the power losses and the investment in semiconductors but not in the investment on capacitors. The converter presents better indicators for low DC transformation ratios demonstrating the interest of the topology for these applications. However for those ratios, the impact of including fault blocking capability is the highest.