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High Efficiency Wireless Charging of Electric Vehicles for Safe and Economic Future Transportation. Chris Mi , Ph.D, Fellow IEEE Professor, Department of Electrical and Computer Engineering Director, DOE GATE Center for Electric Drive Transportation - PowerPoint PPT Presentation
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Chris Mi, Ph.D, Fellow IEEEProfessor, Department of Electrical and Computer Engineering
Director, DOE GATE Center for Electric Drive Transportation
University of Michigan-Dearborn, (313)583-6434; mi@ieee.org
High Efficiency Wireless Charging
of Electric Vehicles for Safe and
Economic Future Transportation
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
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
Definition of WPT
Wireless power transfer (WPT) Inductive power transfer (IPT) Contactless power system (CPS), Wireless energy transfer Strongly coupled magnetic resonance High-efficiency inductive-power distribution The essential principles are the same given the
distances over which the power is coupled is almost always within one quarter of a wavelength and therefore, the fundamental operation of all of these systems can be described by simple coupled models
Grant Covic and John Boys, “Modern Trends in Inductive Power Transfer for Transportation
Applications,” IEEE journal of emerging and selected topics in power electronics, vol. 1, no. 1, march
2013
Methods of Wireless Power Transfer
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
Predicted Wireless
Charging Market
$17 Billion in 2019
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 designs
and methods to
study these systems
Low efficiency
Limited distance
Sensitive to vehicle alignment
A Wireless Power Transfer System
Secondary controlled WPT
Covic, G.A.; Boys, J.T., "Inductive Power Transfer," Proceedings of the IEEE , vol.101,
no.6, pp.1276,1289, June 2013.
Equivalent Circuit Series-Series
1 111 1
22 2
2
1( )
0 1( )
m
m L
R j L j LCV I
Ij L R R j L
C
Series-Series Resonance Structure
L1, L2 – Self inductance
Lm – Mutual inductance
L1= L1σ +Lm; L2= L2σ +Lm
Power Transferred
Power of output side
Power of the input side
Efficiency
2 22 1
2 2 2 21 2
( )| |
| [ ( ) ] |m L
Lm
V L RP I R
Z Z L
22
21 2 1 2
( )| [ ( ) ] | cos
m L
m
P L RP Z Z Z L
Calculated
efficiency
21 2
1 1 1 21 2
| || | | | cos cos
| ( ) |m
V ZP V I
Z Z L
0 1 2 3 4 5 6 7 8 9 100
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
System Topology at UMD Key inventions:
- Optimized multi-coil design for maximum coupling, with bipolar architecture- LCC topology for soft switching to further increase efficiency and frequency- Distributed circuit parameters to minimize the capacitor size and voltage rating- Bidirectional LCL Power factor correction circuit to maximize the front end efficiency
and reduce system cost- Foreign object detection and electromagnetic field emissions for human and animal
safety for the developed system.
11
Double-sided LCC Compensated Wireless Power Transfer
S1
C1 CO
D1
Battery Pack
+-
LoS3
S2 S4
L1
D2
D3
D4
Vin VoutA
B
L2
Sending Side Receiving Side
C2
i1 i2
M+
+ ++
Lf1Cf1
+Cf2
Lf2+
iLf1 iLf2
Topology
• Important Characteristic:
• The output current at resonant frequency:
• The output power can be expressed as:
2 2 _1 120 0
mLf Lf
f f
U LI I k U
L L
2 2 _1 1 220
Lff
LP U I k U U
L
Comparison of Coil Design
(a) Circular pads, (b) flux-pipe pads (c) DD-DDQ bipolar pads
Trong-Duy Nguyen, Siqi Li, Weihan Li, Chunting Chris Mi, Feasibility Study on Bipolar Pads for Efficient Wireless Power
Chargers, IEEE Applied Power Electronics Conference, Fort Worth, TX, USA, March16-20, 2014
Typical Misalignment
Door-to-door (right-left)is more difficult Front-rear is easier to align
Z (height)
Rectangular bipolar pads
Rectangular Unipolar pads
Five Studied Cases
Case 1:
480x1000Case 2: 600x800
Case 3: 693x693
Case 4: 800x600
Case 5: 1000x480
Ferrite bar dimension
( L x W x H *)
Sender771.4 x 16 x
16600 x 16 x 16
589.1 x 16 x 16
415.4 x 16 x 16
360 x 16 x 16
Receiver925.7 x 16 x
16720 x 16 x 16
589.1 x 16 x 16
498.5 x 16 x 16
432 x 16 x 16
Number of ferrite bars 7 9 11 13 15
Coil
Sender 480 x 1000 x 6 600 x 800 x 6 693 x 693 x 6 600 x 800 x 6 1000 x 480 x 6
Receiver 480 x 1000 x 8 600 x 800 x 8 693 x 693 x 8 600 x 800 x 8 1000 x 480 x 8
Coils: Similar area
Ferrites: Similar volumeY (w
idth)
X (depth / length)
Z (height)
X & Y Misalignment
0.00 100.00 200.00 300.00 400.00y_misalligned [mm]
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Coup
ling
1_2_S2R2_X600xY800_noShield_dyKy (front-to-rear misallignment)Curve Info
Ky_600x800Ky_693x693Ky_800x600Ky_480x1000Ky_1000x480
The topology with bigger Y-size has
a better Y-misalignment tolerance
0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00x_misalligned [mm]
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Coup
ling
1_1_S2R2_X600xY800_noShield_dxKx (door-to-door misallignment)
Curve Info
Kx_480x1000Kx_600x800Kx_693x693Kx_800x600Kx_1000x480
1. The maximum coupling coefficient
decreases with the increase of coil’s
X-length
2. X-misalignment tolerance
increases with the coil’s X-length
Y (width)
X (length)
Z (h
eight)
Angular Misalignment
Typically, when a driver parks an EV, the worst angular misalignment can be limited at about 30°
Coupling coefficient vs x, y, theta
X
Z
YFinite element analysis using Maxwell 3D
Coupling Coefficient Profile versus Door-to-door and Front-to-rear Misalignments
Safety issues
With chassis - maximum misaligned position
Range of flux density
is within 1-1.2 meters,
=> It is safe to install
this WPC in an
electric vehicle
chassis, typically
about 1.8meter door-
to-door size
with chassis - perfectly aligned position
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 2.00Distance [meter]
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
Mag
_B [u
Tesla
]
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.
21
Experimental Verification
Max power: 8kW
Max Eff.: 97%
Input voltage
Output currentInput currentOutput voltage
Experiment Results
Xmis=0mm, Gap =200mm Xmis=300mm, Gap =200mm Xmis=125mm, Gap =400mm
(Rectifier + PFC) + Buck + Wireless
PFC – power factor correction >0.98 Buck for charge control WPT: fixed frequency, auto-tuned system.
WPT
System Efficiency for Different Vbat
Dynamic In-Motion Charging
Buried tracks
Results of Foreign Object Test #1
Experiment Result: the gum wrapper was burned and there left an
imprint, which means the temperature is high.
Conclusions
Misalignment tolerance was analyzed and discussed Two kinds of coupling coefficient detection methods were
proposed 8 kW wireless charger prototype with 200mm gap and
300mm door-to-door misalignment tolerance had been built and tested
Coupling coefficient maintains at 18.8%~31.1% With a 200mm gap, 95.66% efficiency (at about 8kW)
from DC to DC was obtained at desired position 95.39% efficiency (at about 4kW) at 300mm X-
misalignment and 200mm Gap
Department of Energy- GATE Program
DENSO International US China Clean Energy Center GATE Industrial Partners
- Chrysler, Ford, DENSO International, Mathworks, dSPACE, ANSYS, Hp Pelzer, EDTA, PSIM, GaN Systems
Acknowledgement
IEEE Workshop and TPEL Special Issue on Wireless Power
2015 WoW Sponsored by six Societies of IEEE PELS, IAS, IES, VTS, MAG, PES June 5-6 (Fri.-Sat.), 2015, Daejeon, Korea Held just after the 2015 ECCE-Asia (June 1-4) in Seoul General Chairs: Dr. Chun Rim, Dr. Chris Mi TPC: Dr. John Miller http://www.2015wow.org
IEEE Transactions on Power Electronics (Guest-EIC) IEEE Journal on Emerging and Selected Topics on Power
Electronics (Guest-EIC)
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