Capacitor monitoring for modular multilevel converters
The modular multilevel converter (MMC) is attractive for medium-or high-power applications because of the advantages of its high modularity, availability, and high power quality. Reliability is one of the most important challenges for the MMC consisting of a large number of submodules (SMs). The capacitor monitoring in each SM of the MMC is an important issue, which would affect the performance of the MMC. This paper proposed an effective monitoring method for the capacitance in each SM of the MMC. The proposed method reveals the relationship between the arm average capacitance and the capacitance in each SM of the arm, which can be used for capacitance estimation with a simple algorithm. The simulation studies with the professional tool PSCAD/EMTDC are conducted with the proposed method. The study results show the effectiveness of the proposed method.