Abstract
The high-frequency isolation (HFI) charging DC port can serve as the interface between unipolar/bipolar DC buses and electric vehicles (EVs) through the two-power-stage system structure that combines the front-end three-level converter with the back-end logical link control (LLC) resonant converter. The DC output voltage can be maintained within the desired voltage range by the front-end converter. The electrical isolation can be realized by the back-end LLC converter, which has the bus converter function. According to the three-level topology, the low-voltage rating power devices can be adapted for half-voltage stress of the total DC grid, and the PWM phase-shift control can double the equivalent switching frequency to greatly reduce the filter volume. LLC resonant converters have advance characteristics of inverter-side zero-voltage-switching (ZVS) and rectifier-side zero-current switching (ZCS). In particular, it can achieve better performance under quasi-resonant frequency mode. Additionally, the magnetizing current can be modified following different DC output voltages, which have the self-adaptation ZVS condition for decreasing the circulating current. Here, the principles of the proposed topology are analyzed in detail, and the design conditions of the three-level output filter and high-frequency isolation transformer are explored. Finally, a 20 kW prototype with the 760 V input and 200–500 V output are designed and tested. The experimental results are demonstrated to verify the validity and performance of this charging DC port system structure.
Highlights
As solutions of energy crisis and environmental pollution, electric vehicles (EVs) that can run on alternative resources of energy have increasingly attracted attention for investigations of decreasing fossil fuel consumption and reducing greenhouse gas emissions [1,2]
Electric vehicle technologies involved with hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and plug-in pure electric vehicles (PPEVs), such as the Toyota Prius and
This paper proposes a high-frequency isolation (HFI) charging DC port topology
Summary
As solutions of energy crisis and environmental pollution, EVs that can run on alternative resources of energy have increasingly attracted attention for investigations of decreasing fossil fuel consumption and reducing greenhouse gas emissions [1,2]. The commercial success of EVs relies heavily on the presence of high-efficiency charging stations to increase mileage and shorten charging time [3,4,5]. A large number of high-power charging stations need to be constructed to solve consumers’ need for long-distance transport with electric vehicles (EVs). The construction of these facilities is a key factor in attracting more consumers to the use of EVs [6,7,8,9,10].
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