Unified Strategy for Fault-Tolerant Operation of MMC with Multiple SMs Failure Based on SMs Grouping Management

Zhihong Bai () and Yifei Li
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Zhihong Bai: College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China
Yifei Li: College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China

Energies, 2022, vol. 15, issue 15, 1-20

Abstract: Modular multilevel converter (MMC) is distinguished by its modularity. In order to improve its reliability and avoid unscheduled maintenance, it requires the MMC to continue operating even though some of its submodules (SMs) have failed. In this paper, a grouping management method of SMs in MMC is first presented where every six SMs are conceptually grouped into a virtual subunit (SU), and on this basis, a simplified space vector modulation (SVM) implementation is developed. Then, the fault-tolerant solutions are proposed by investigating the post-fault operation of the MMC based on the virtual SU concept. It is analyzed that the SU failures can be categorized into three basic types, according to the phase where the failed SMs are located, and also multiple SM failures can be decomposed into one or multiple basic fault types. In this way, the fault-tolerant solutions are unified regardless of the number of faulty SMs. Further, the sorting capacitor voltage control is combined into the proposed methods to balance all of the SM capacitor voltages. With the proposed fault-tolerant method, the amplitude and THD of the line voltages are almost unchanged under fault conditions when compared with normal operations. The simulation and experiment verify the propositions.

Keywords: fault tolerance; modular multilevel converter (MMC); post-fault operation; space vector modulation (SVM) (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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