An Approach Towards Extreme Fast Charging Station Power Delivery for Electric Vehicles with Partial Power Processing

Abstract

This article proposes an approach for realizing the power delivery scheme for an extreme fast charging (XFC) station that is meant to simultaneously charge multiple electric vehicles (EVs). A cascaded H-bridge converter is utilized to directly interface with the medium voltage grid while dual-active-bridge based soft-switched solid-state transformers are used to achieve galvanic isolation. The proposed approach eliminates redundant power conversion by making use of partial power rated dc-dc converters to charge the individual EVs. Partial power processing enables independent charging control over each EV, while processing only a fraction of the total battery charging power. Practical implementation schemes for the partial power charger unit are analyzed. A phase-shifted full-bridge converter-based charger is proposed. Design and control considerations for enabling multiple charging points are elucidated. Experimental results from a downscaled laboratory test-bed are provided to validate the control aspects, functionality, and effectiveness of the proposed XFC station power delivery scheme. With a downscaled partial power converter that is rated to handle only 27% of the battery power, an efficiency improvement of 0.6% at full-load and 1.6% at 50% load is demonstrated. Index Terms-Cascaded H-bridge (CHB) converter, dc fast charger, dc-dc power converters, dual active bridge (DAB), energy storage, fast charging station, partial power processing, phase-shifted full-bridge (PSFB), solid-state transformer (SST).

Design and Implementation of Reduced Grid Impact Charging Station for Public Transportation Applications

“…Power electronics are a fundamental part of the fast-charging station. The right choice of the power converters' topologies and the selection of the power semiconductors are the key factors in improving the efficiency and the power density of the charging units [12,13]. In [14] the electric bus was equipped with a pantograph in order to test the Flash Charge (at the bus stop), as illustrated in Figure 1.…”

Review of Architectures Based on Partial Power Processing for DC-DC Applications

“…Indeed, comparing [48] and [49], it is concluded that applying a multi-input DAB converter achieves higher efficiencies. Then, there is the auxiliary architecture proposed in [44]. However, authors conclude that the obtained converter is slightly less efficient (-0.3%) and bigger (+10%).…”

“…Then, due to its simplicity, phase shift modulation (PSM) is chosen for controlling the power flow between the source and the load. On the other hand, in order to observe the benefits of PPC architectures and based on [26], [44], the circuit shown in Figure 13 is compared to its FPC version, see Figure 14. Finally, Table 7 details the circuit parameters from Figure 13 and Figure 14.…”

“…So, if there is a high step-up/down between the source and the load, PPCs may result inadequate. Also, compared to FPC architectures, PPCs cause a larger operation range inside the power converter [44]. For example, considering the application presented in Table 6, it can be concluded that a FPC will work with a fixed input voltage and a variable output voltage.…”

Partial Power Processing Based Converter for Electric Vehicle Fast Charging Stations

“…[16][17][18][19] present PPP architectures for applications where there exist series connected elements. Last but not least, when it comes to EV fast charging applications authors from [8,20,21] propose PPP based charging units. There, the authors implement a unidirectional topology such as the phase shifted full bridge and they show that the PPP solution achieves converter rating reduction and efficiency improvements compared to its full power processing (FPP) version.…”