Modular Multi-Level Converter Model for the Analysis, the Design and the Optimization of DC Power Systems Involving Superconducting Power Cables Cooled by Liquid Hydrogen

DC power transmission technologies have achieved significant advancements, gaining widespread adoption within modern electrical systems. The use of superconducting cables in Magnesium Diboride (MgB₂) cooled by liquid hydrogen (LH2) could drastically increase the performance of DC grids, enabling higher power transport capacity and extending transmission distance, while reducing energy loss and land occupation. Today, the transport of DC electrical energy is enabled through modular muti-level converters (MMCs) capable of effectively controlling currents, voltages and power flow. Designing an optimal DC power system, along with appropriate superconducting cable design and protection apparatus, needs accurate, yet simplified, models of the converters. This study presents simplified models that apply during the fault, able to adapt to any pre-fault scenario without a need to implement complex control systems. The developed model can be easily integrated, along with a model of a superconducting MgB₂ cable, in EMT power system simulators for analysing their mutual interaction during faults and for optimizing the cable design and its protection system.