A Study on the Analysis of Fault Current in Bipolar MVDC System Using Modular Multilevel Converter

As power systems evolve with the integration of renewable energy sources and the rise in DC loads, there is growing interest in hybrid AC/DC power transmission systems. Historically, AC transmission has dominated due to its efficiency in long-distance power delivery and ease of transformation. However, advances in power conversion technology and the increasing prevalence of DC-based loads, such as electric vehicles, have led to a shift towards integrating DC systems into the grid. While this integration offers benefits like excellent system responsiveness, DC systems also present challenges, particularly in transient fault analysis due to power converters' complex, discontinuous dynamics. This paper focuses on a bipolar mediumvoltage DC (MVDC) system modeled using Full-Bridge Modular Multilevel Converters (FB-MMC) in MATLAB/Simulink. By comparing the fault current characteristics of the bipolar MVDC system with an RLC equivalent impedance model of the converter, the study identifies key factors affecting fault current behavior. It validates the accuracy of the proposed model. The findings contribute to developing technologies necessary for stable and efficient MVDC system operation.