Research on Fault Diagnosis of Grid Forming Type Flexible DC Modular Multilevel Converter Based on Consistency Check

The flexible DC transmission system has been widely used in China's power system, and the reliability of its core equipment, the flexible DC converter valve, directly affects the safe and stable operation of the power grid. In order to ensure the safe and stable operation of the power grid, it is necessary to timely and effectively identify and locate faulty bridge arms. Based on the analysis of the working principle of the three-phase bridge of the converter, this article proposes a fault diagnosis method for the bridge arm through consistency testing. Firstly, the residual formula for the voltage of each phase bridge arm is constructed, and then the specific rules for locating the fault branch through residual threshold are introduced. Finally, the proposed method was simulated and validated using PSCAD software, demonstrating the effectiveness of the fault diagnosis method.