Fast locating method of MMC lower tube IGBT open-circuit fault based median error between the actual and the predicted value of the capacitor voltage

Abstract

Modular multilevel converters have found a large number of applications in high-voltage and high-power DC transmission due to their modularity, scalability, multi-equality and other advantages. The two typical topologies in MMC systems are half-bridge sub-module structure and full-bridge sub-module structure. Half-bridge sub-module is widely used in MMC systems by virtue of its simple control structure, high conversion efficiency and low cost. Insulated gate bipolar transistor (IGBT) failures, especially open-circuit failures, are a major factor in the reliable operation of MMC systems. Fast and accurate positioning of the open circuit fault location and removal of the fault submodule is of great significance for handling MMC system faults. Aiming at the current situation of the fault location of the MMC system, this paper compares the error of the predicted median capacitance voltage with the actual value , and proposes an accurate diagnosis method for MMC lower IGBT tube open circuit faults. This method is suitable for one or more IGBT lower tube open-circuit fault conditions, and can quickly locate the faulty submodule within 5ms. Finally, an MMC simulation system with 8 sub-modules is built based on MATLAB/Simulink, which effectively verifies the accuracy of the proposed method.