Comparison of (N+1) Redundancy and Fault Tolerance Approaches in Single-Stage Series-Connected Isolated MVAC to LVDC Converters

This paper studies fast electric vehicle chargers designed for direct connection to medium voltage AC (MVAC) grids. It is based on a modular multicell boost (MCB) structure with low-line inductor requirements and single-stage conversion with a high switching frequency transformer. This makes it an ideal candidate for use in fast EV charging stations. Each MCB cell contains a power factor correction stage and an isolated dc-dc current source converter. The preliminary study is connected considering the asymmetric secondary modulated topology that features fault-tolerant reconfiguration using healthy switches. The evaluation focuses on the power devices on the input and output sides, which are the most likely sources of failure. This study aims to improve the reliability of the charger considered. This paper looks at the feasibility of designing a fast EV charger using an (N+1) redundant cell, which is compared to the cell-level fault tolerance. The (N+1) redundancy is based on the system level, not the individual component level. The study found that using an (N+1) converter as a redundancy approach is more feasible than a fault-tolerant approach and that it is possible to design a fast electric vehicle charger utilizing this approach.