Failure-rate Analysis Considering Operational Condition of Half-bridge Submodule in HVDC System

The half-bridge submodule is a unit system of MMC and consists of three main circuit components: IGBT, diode, and capacitor. Failure of the part causes the submodule failure, and this failure extends to the failure of the upper system of the MMC, which eventually leads to failure of the HVDC. Therefore, the lifetime prediction of the submodule is used as an important index to predict the failure of HVDC system. However, the conventional part failure analysis considering only the type and number of parts cannot reflect the operational characteristics of the system. To overcome this problem, we design a fault-tree that reflects the operational characteristics of the half-bridge submodule and estimate the lifetime of the submodule by applying the failure-rate of MIL-HDBK-217F to the basic event. The validity of the proposed fault-tree analysis is verified by comparing with the conventional part failure analysis method.