Solid-State Transformer Based Fast Charging Station for Various Categories of Electric Vehicles With Batteries of Vastly Different Ratings
A. C. Nair, B. G. Fernandes
Nov 1, 2021
Citations
6
Citations
Journal
IEEE Transactions on Industrial Electronics
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Key Takeaway Key Takeaway: The SST-based fast charging station effectively charges various electric vehicle categories with batteries of different voltage and power ratings, reducing unbalance and enabling use of lesser current-rated devices.
Abstract
This article proposes a solid-state transformer (SST) based power electronic architecture for fast charging three categories of plug-in electric vehicle with batteries of vastly different voltage and power ratings. The SST accomplishes integration to a medium-voltage grid and isolation to the charging ports without the use of an LFT. Delta connected cascaded H-bridge (CHB) is used as the active front-end rectifier and quad active bridges (QABs) are utilized for the isolated dc–dc conversion stage. In the proposed architecture, an additional winding called balancing winding is provided in each of the medium-frequency transformers of the QAB. The balancing winding of the transformers are paralleled such that a circulating current flows among the transformers of the three phases, which eventually reduces the unbalance in the delta-connected clusters. Hence, the magnitude of zero-sequence current required to balance the cluster powers for a certain level of unbalance is also reduced. As a result, the total current in the devices of the CHB decreases and devices with a lesser current rating can be used. The control philosophy and detailed analysis of the system are given in the article. Experimental results with a scaled-down prototype are presented to verify the claims.