Overvoltage Research and Insulation Coordination for HVDC Transmission System Based on Medium-Frequency DRU-MMC

Currently, the application of HVDC transmission system based on medium-frequency DRU-MMC is a research hotspot. In the design of the medium-frequency DRU-MMC system, overvoltage protection and insulation coordination are crucial issues that must be addressed. Furthermore, the influence of frequency on the overvoltage characteristics of the DRU-MMC system also holds research value. Given the limited research on overvoltage-related topics of DRU-MMC systems both domestically and internationally, this paper proposes an overvoltage protection scheme suitable for medium-frequency DRU-MMC systems. Based on the comprehensive reference to traditional DC engineering and the research achievements of the characteristics of the DRU-MMC system itself, the paper investigates the impact of frequency selection in the medium-frequency system on the overvoltage of the DRU-HVDC system using PSCAD/EMTDC. It was found that the influence of frequency on overvoltage does not follow a specific pattern. Depending on the location of the fault and the type of fault, the trend of overvoltage variation with frequency differs, making it impossible to draw definite conclusions.