A Multiple-AC-Ports Power Electronic Transformer

Abstract

With the rapid development of clean energy production, new types of loads such as electric vehicle charging stations have been rapidly expanded in recent years, which has seriously affected the distribution grid terminal power quality. A single feeder line cannot cope with the impact load caused by electric vehicle charging stations, while upgrading the existing distribution grid is faced with high cost and insufficient land area. To deal with this problem, this paper proposes a multiple-AC-ports power electronic transformer topology, which is evolved from the cascaded H-bridge type power electronic transformer. It has multiple controllable AC ports and can use the remaining capacity of each AC feeder to multi-terminally supply impact loads at the low-voltage DC side. Therefore, it delays grid upgrade or capacity expansion, and fully utilizes the capacity of the existing distribution grid. In addition, the proposed topology has the characteristics of modularization, compactness, and easy expansion of ports. In this paper, the operation principle, energy balance mechanism and control strategy of the topology are introduced. The experimental results demonstrate the effectiveness of the proposed topology and control strategy.