A Fault Detection Method Based on Successive Variational Mode Decomposition for the Energy Absorption Branch of Modular DC Circuit Breakers

Modular DC circuit breakers (MDCCBs) are key equipment for modular multilevel converter (MMC) high voltage DC (HVDC) grids, and they need an energy absorption branch (EAB), which consists of many metal-oxide varistors (MOVs), to achieve fault current suppression. The reliability of the EAB directly influences the reliability of the MDCCBs. However, the existing fault detection methods of the EAB are unsuitable for the whole fault suppression period. To this end, this article proposes a fault detection method based on successive variational mode decomposition (SVMD) for the EAB of MDCCBs. The proposed method is as follows. First, the branch current in each EAB submodule is intercepted to obtain a preprocessed current. Second, the preprocessed current is decomposed by the SVMD, and the highest frequency component is selected as the faulty feature component. Third, an inrush factor is built by the faulty feature component to achieve EAB fault detection. Last, the performance of the proposed method is evaluated by a four-terminal symmetric bipolar MMC-HVDC simulation system with MDCCBs and the record data from the Zhangbei MMC-HVDC grid project. The study results show the effectiveness of the proposed method, and some comparisons are made among several state-of-the-art methods to validate the superiority of the proposed method.