A Global Redundancy Scheme for Medium-Voltage Modular Multilevel Converter Based Solid-State Transformer

摘要

Reliability and fault-tolerant operation are among the major concerns of the modular multilevel converter (MMC) based applications due to their use of a large number of power electronic devices. This paper presents a novel global redundancy scheme for medium-voltage (MV) MMC based solid-state transformers (SSTs) to deal with the submodule (SM) IGBT open-circuit failure. By sharing the same redundant SM in one phase via bidirectional switches, the proposed fault-tolerant scheme can significantly maintain the SST operation with minimum degradation and save the initial cost and volume of the system. The characteristics of the IGBT open-circuit fault with two different SM topologies are summarized in detail. The proposed global redundancy scheme can efficiently restore the system from SM failure without severe malfunction and damages. Its effectiveness is verified by simulations carried out in the MATLAB/Simulink software.