DC pole-to-pole short-circuit behavior analysis of modular multilevel converter

This paper presents the behavior analysis of Modular Multilevel Converter (MMC) under DC pole-to-pole (PtP) Short-Circuit (SC) fault, which is an important issue in fault management, electrical system design and MMC based power system protection and control. Firstly, the transient behavior is analyzed where the conduction overlapping angle γ is defined. Secondly, seven possible SC current paths induced by different γ are identified, and the corresponding engineering SC current calculation methods for both AC and DC sides are proposed. And then, the influences of impedance distribution factor k and equivalent SC resistance R_SC on SC currents are elaborated. Finally, case study is provided to verify the effectiveness of the proposed analysis methods.