A Fault Location Strategy for IGBT Open-Circuit Fault in Modular Mutilevel Converter

Modular Multilevel Converter (MMC) contains many Submodules (SM). Open-circuit fault of the switching devices which are connected in SM will result in the rise of the interphase circulating current, DC side voltage ripple, and other corresponding deteriorations. At present, many proposed methods which focus on the submodule inner switching fault are not quite easy to achieve in reality. Considering the previous studies, a more reliable and precise fault-location method requires to be introduced. In this paper, modal analysis is carried out first, then proposed a fault location method to solve the switching open-circuit fault. The method includes two components, one implements Fourier Decomposition on circulating current to locate the faulted phase, and then detects the instant value of capacitor voltage in the faulted phase as mentioned to locate the faulted SM. The efficiency of the fault location strategy is finally demonstrated in simulation and proved to be feasible.