A Novel Protective Scheme to Improve Half-Bridge MMC Operation against DC Fault Condition

High-Voltage Direct-Current (HVDC) systems are an attractive solution for long distance power transmission. Among the various types of converters, Modular Multilevel Converter (MMC) has been identified as a modern converter choice for HVDC systems. Also, HVDC systems have been used widely and it is essential to conduct studies on the field of DC-side faults which are considered as big challenges in HVDC technology. Not only has it impacted the DC side converters, but also the AC system’s stability is entirely affected. In this paper, a novel protective scheme is proposed through which it can block the AC-feeding phenomenon during DC fault, by applying this protective scheme the AC grid will remain stable during non-permanent DC fault as well as prevent damage of electrical equipment. This paper presents the DC fault analysis and proposes a novel protective scheme to protect HVDC transmission lines against DC fault while maintaining AC side grid stability. Detailed simulation results verify the performance and effectiveness of the proposed method.