Oak Ridge National Laboratory Wireless Charging of Electric Vehicles – CRADA Report WIRELESS CHARGING OF ELECTRIC VEHICLES
Omer C. Onar, Steven Campbell, Larry Seiber, Cliff White, Madhu Chinthavali, Lixin Tang, Paul Chambon, and Burak Ozpineci Power Electronics and Electric Machinery Group (PEEM) Electrical and Electronics Systems Research Division (EESR)
1. Abstract Wireless power transfer (WPT) is a paradigm shift in electric-vehicle (EV) charging that offers the consumer an autonomous, safe, and convenient option to conductive charging and its attendant need for cables. With WPT, charging process can be fully automated due to the vehicle and grid side radio communication systems, and is non-contacting; therefore issues with leakage currents, ground faults, and touch potentials do not exist. It also eliminates the need for touching the heavy, bulky, dirty cables and plugs. It eliminates the fear of forgetting to plug-in and running out of charge the following day and eliminates the tripping hazards in public parking lots and in highly populated areas such as shopping malls, recreational areas, parking buildings, etc. Furthermore, the high-frequency magnetic fields employed in power transfer across a large air gap are focused and shielded, so that fringe fields (i.e., magnetic leakage/stray fields) attenuate rapidly over a transition region to levels well below limits set by international standards for the public zone (which starts at the perimeter of the vehicle and includes the passenger cabin). Oak Ridge National Laboratory’s approach to WPT charging places strong emphasis on radio communications in the power regulation feedback channel augmented with software control algorithms. The over-arching goal for WPT is minimization of vehicle on-board complexity by keeping the secondary side content confined to coil tuning, rectification, filtering, and interfacing to the regenerative energy-storage system (RESS). This report summarizes the CRADA work between the Oak Ridge National Laboratory and the Toyota Research Institute of North America, Toyota Motor Engineering and Manufacturing North America (TEMA) on the wireless charging of electric vehicles which was funded by Department of Energy under DE-FOA-000667. In this project, ORNL is the lead agency and Toyota TEMA is one of the major partners. Over the course of the project, ORNL and Toyota TEMA worked closely on the vehicle integration plans, compatibility, and the interoperability of the wireless charging technology developed by ORNL for the vehicles manufactured by Toyota. These vehicles include a Toyota Prius Plug-in Hybrid electric vehicle, a Scion iQ electric vehicle, and two Toyota RAV4 electric vehicles. 2. Statement of Objectives The main objective of this project is to coordinate multi-party team for the design, development, and fabrication of WPT grid side unit (GSU), coupling coils, and the vehicle side power conditioning units. The GSU includes the active front-end rectifier with power factor correction (PFC), high-frequency power inverter, and the high-frequency isolation transformer whereas vehicle side unit includes a resonant tuning capacitor, a bridge rectifier, a filter circuit, and the additional relays and contactors that are used to timely respond to the charging request or to comply with the charging protocols that a vehicle may have (CHAdeMO, J1772, or direct battery connection). The objective of this work is to demonstrate a fully automated charging process including the alignment, start charging, stop charging, and the emergency and orderly shutdown procedures while meeting at least 6.6kW power transfer over 160mm magnetic airgap while exceeding an overall (end-to-end) efficiency of 85%. After integrating ORNL developed WPT technology into demonstration vehicles, an additional objective was to validate the system operation in an independent testing laboratory (Idaho National Laboratory) for field testing of this technology which will assist in system improvements and standards development. In this project, Evatran was the commercialization partner and under ORNL guidance worked on cost and component optimization and fabrication of GSUs and also the primary and secondary coils. Evatran also worked on vehicle integrations in coordination with ORNL and other partners. Clemson University ICAR Center was the demonstration site for phase #2 deliverables of the project. Clemson University, in collaboration with Cisco Systems, also supported the radio communications developments and radio integrations to the vehicles and the WPT equipment on the vehicles. Finally, Toyota Motor Corporation is the vehicle OEM partner provided the vehicles and collaborated with ORNL on the vehicle integrations. One last objective of this project was to demonstrate in-motion wireless charging on Toyota RAV4 vehicles to prove feasibility and collect data.
LINK FULL PAPER
https://info.ornl.gov/sites/publications/files/Pub68349.pdf
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