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Design of an Integrated Battery Charging System for both Wired and Wireless Charging for Battery Electric and Hybrid Vehicles

Elshaer, Mohamed A
http://orcid.org/0000-0002-8759-2816
http://rave.ohiolink.edu/etdc/view?acc_num=osu16064084627996

Abstract Details

2020, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
With the continuous drop in the HV battery cost, Electric Vehicles are forecasted to become increasingly affordable. However, with more services being added to electric vehicles, the onboard system complexity and cost continues to increase. Currently, plug-in electric vehicles require an onboard conductive charger to regulate the power delivered to the HV battery and isolate the HV bus from the AC grid. In some cases, electric vehicles may offer the option for supplying AC power to connected loads thus providing the flexibility of using the onboard HV battery as a mobile source. Moreover, with increased consumer demand for hands-free charging, wireless power transfer can potentially be considered as an addon option to serve as an HV battery charger. Unfortunately, due to the limited onboard space and the high cost of the power conversion system, adoption of the wireless power transfer technology has not gained traction. This dissertation provides a comprehensive study outlining the challenges with adding a wireless HV battery charger to battery-electric and plug-in hybrid vehicles. Through system architecture analysis, a case is made for why there is a need to consolidate the redundant onboard circuit blocks through system-level integration. Opportunities for reducing the onboard bill-of-material cost and reducing the size of the onboard electronics are provided. Moreover, the technological challenges with the overall power conversion efficiency as it pertains to a highly integrated system are discussed. Also, the challenge of realizing system interoperability with the public charging infrastructure for the wireless power transfer system is addressed. Battery electric and plug-in hybrid vehicles capable of wirelessly charging the HV battery have the advantage of charging while in motion, during frequent stops, and automatically in public designated parking areas. With such flexibility in receiving power, the battery size can be reduced, allowing for a reduction in vehicle weight and cost. While the wireless power transfer (WPT) technology has matured to the point that standards are being developed for it, the monetary cost of this technology remains high. Innovation in both the ground infrastructure and onboard vehicle electronics remains a necessity. There is a need for new methodologies and test procedures to enable the development of new vehicle systems that are interoperable with the public ground infrastructure. These design guidelines need to provide enough flexibility for innovation to occur in both the ground and vehicle subsystems. The dissertation starts with analyzing the state-of-art HV battery charging architecture for a wireless-capable plug-in electric vehicle. Through system analysis, an optimal onboard charging architecture is proposed to minimize the size and bill-of-material cost of the onboard electronics. The methodology proposed by SAE J2954 for qualifying the interoperability of product ground assemblies and product vehicle assemblies is analyzed in detail. Challenges in realizing system interoperability between an optimized highly integrated vehicle assembly and the public infrastructure are discussed. The wireless power transfer figure-of-merit (FOM) is redefined to consider the impedance matching capability. The ratio between the energy stored in the magnetic field and transferred power is derived to optimize the driving point impedance, which in turn determines the efficiency of the system. Furthermore, it will be shown that when the ground assembly (GA) and vehicle assembly (VA) are independently characterized, the magnetic coupling and power transfer between them can be quantified with relatively high accuracy. The goal for this work is to formulate the mathematical equations needed to describe a resonator by an equivalent source, thus allowing independent characterization of the transmitter and receiver subsystems. A new methodology for designing and testing wireless power transfer systems for electric vehicles is proposed. To realize a technologically-neutral way for developing the transmitter and receiver parts of the system, a technique for constructing a separate equivalent circuit model for each subsystem using a scan of the magnetic field is proposed. Through the utilization of a reference source, impedance constraints are developed so that the transmitter side of the circuit is designed and tested independently from the receiver side of the circuit and vice versa. Finally, a systematic approach for optimizing the onboard system architecture is provided. Through system simulation and hardware validation, it will be demonstrated that a highly integrated onboard battery charging architecture can achieve full interoperability with the public wireless charging infrastructure without sacrificing the performance of either the onboard conductive charger or wireless power transfer system. A novel topology for integrating the receiver coil of a wireless power transfer system with the electric vehicle’s onboard bidirectional conductive charger is proposed. Through component sharing between the two subsystems, a reduction in the overall size and cost of the onboard electronics is achieved. Furthermore, by utilizing GaN HEMT devices, the DC-DC stage achieved an efficiency of 95.6% when transferring 5 kW via the onboard charger and 93.4% when transferring 7.7 kW via the wireless power transfer system. Conclusions and recommendations for future work are presented.
Jin Wang (Advisor)
Lee Robert (Committee Member)
Zhang Julia (Committee Member)
Illindala Mahesh (Committee Member)
213 p.
Electrical Engineering
Wireless Power Transfer, Integrated on-board charger, WPT, CLLC, Bi-directional DC-DC, Plug-in EV

Recommended Citations

Citations

  • Elshaer, M. A. (2020). Design of an Integrated Battery Charging System for both Wired and Wireless Charging for Battery Electric and Hybrid Vehicles [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu16064084627996

    APA Style (7th edition)

  • Elshaer, Mohamed. Design of an Integrated Battery Charging System for both Wired and Wireless Charging for Battery Electric and Hybrid Vehicles . 2020. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu16064084627996.

    MLA Style (8th edition)

  • Elshaer, Mohamed. "Design of an Integrated Battery Charging System for both Wired and Wireless Charging for Battery Electric and Hybrid Vehicles ." Doctoral dissertation, Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu16064084627996

    Chicago Manual of Style (17th edition)

osu16064084627996
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This open access ETD is published by The Ohio State University and OhioLINK.