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Siqi Li, Tommy Nugyen, Weihan Li
Chris Mi, Ph.D, Fellow IEEE
Professor, Department of Electrical and Computer Engineering
Director, DOE GATE Center for Electric Drive Transportation
Unplugging the Electric Car - Wireless charging of electric vehicles with
extremely high efficiency and misalignment
tolerance
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Conventional EV Charging 1 2
Fast charging Mostly DC charging in
15 to 30 minutes.
For an EV with a 24kWh
battery pack, charging
in 15 minutes means
96kW. This is way over
the power available in
private homes.
3
Battery swapping Investment of battery
packs; standardization
is difficult; swapping
stations need a lot
investment, space and
manpower; safety and
reliability is of concern
Normal charging AC charging using
level 1 or level 2,voltage at 110V, 220V,6-10 hours per charge
Charge at home or
public space, need
large installation of
charge stations
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Wireless Charging
Issues of Con. Charging and
Battery Swapping
Electric safety is of concern:
electric shock due to rain, etc.
Charge station, plug and cable
can be easily damaged, stolen
Charge/swap station takes a lot
of space and affect the views
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Methods of WPT
Wireless Power
Transfer
电能的无线传输
Electromagnetic Induction
电磁感应式
Electromagnetic Resonance
电磁谐振式
Radiation
辐射式
Microwave
微波
Laser
激光
Ultrasound
超声波
Radio wave
无线电波
• In 1830’s, Faraday's law of induction
• In 1890’s, Tesla had a dream to send energy wirelessly
• GM EV1 used an Inductive charger in the 1990’s
• 2007, MIT demonstrated a system that can transfer 60W of
power over 2 m distance at very low efficiency
• Wireless/inductive chargers are available on the market
• Qualcomm, Delphi (Witricity), Plugless Power, KAIST, etc.
have developed EV wireless charger prototypes
Wireless market $17 Billion in 2019
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Latest Development in Wireless EV Charging
MIT 2007
Tokyo 2009
Intel 2008
Korea KAIST
Leaf 2012
Witricity/Delphi
Japan
India
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High cost
Problems and Difficulties • Magnetic field is diminishing proportional to1/r3
• Often the mutual inductance is less than 20% or 10% of the self inductance
• Analytical calculation of coil mutual inductance is next to impossible
• Further analytical method is needed
• Numerical simulation and coupled field - lumped parameter simulation is also of paramount importance
• High frequency HFSS instead of static FEM for high frequency
Large size
Need novel
design Low efficiency
five patent
disclosures
Limited distance
Sensitive to vehicle alignment
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The Topology
• Analytical
– Equivalent circuit analysis; S-parameter analysis; Analytical solutions of inductance and capacitances
• Numerical
– Finite element analysis – electromagnetic; High frequency structure simulation - HFSS
– Coupled field and lumped parameter analysis
• Experimental
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Exposed field to a human of 1.8-meter high
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
Distance [meter]
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
Ma
g_
B [u
Te
sla
]
Field exposed to a man of 1.8met height
Curve Info
Time='13250ns'
Time='13500ns'
Time='13750ns'
Time='14000ns'
Time='14250ns'
Time='14500ns'
Time='14750ns'
Time='15000ns'
Time='15250ns'
Time='15500ns'
Time='15750ns'
Time='16000ns'
Time='16250ns'
Human’s height [in meter]
Human body is exposed to maximum about 1.6uTesla in foot area
while about 0.06uT in head area.
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Experimental Verification
Max power: 8kW Max Eff.: 97%
Input voltage
Output current Input current Output voltage
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Vehicle Demonstration
• Working closely, we are making a vehicle level demonstration by end of 2013 or early 2014
• We are also working with DENSO to bench mark the design with existing wireless charging systems
• UM is also signing an agreement with Mia Motors, Inc. to commercialize the wireless charging for electric buses.