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VOL. 1, NO. 1 SEPTEMBER 2013 ISSN 2325-5987
WWW.IEEE-PES.ORG/
MAGAZINE
IEEE
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MISSION STATEMENT: IEEE Electrification Magazine is dedicated
to disseminating information on all matters related to
microgrids onboard electric vehicles, ships, trains, planes, and
off-grid applications. Microgrids refer to an electric network in a
car, a ship, a plane or an electric train, which has a limited num-
ber of sources and multiple loads. Off-grid applications include
small scale electricity supply in areas away from high voltage
power networks. Feature articles focus on advanced concepts,
technologies, and practices associated with all aspects of elec-
trification in the transportation and off-grid sectors from a tech-
nical perspective in synergy with nontechnical areas such as
business, environmental, and social concerns.
The Dependance on
Mechanical Design in
Railway Electrification
Focusing on the
ac perspective.
4Shipboard
Solid-State
Protection
Overview
and applications.
32
Cutting Campus
Energy Costs
with Hierarchical
Control
The economical and reliable
operation of a microgrid.
40
2 ABOUT THIS ISSUE
3 TECHNOLOGY LEADERS
66 DATES AHEAD
68 NEWSFEED
72 VIEWPOINT
Courting and Sparking
Wooing consumers’
interest in the
EV market.
21
Faster than
a Speeding Bullet
An overview of Japanese
high-speed rail
technology
and electrification.
11
Jacovides wins 2014 IEEE
Tansportation Technologies
Award. Pa ge 68
Cutting the Cord
Static and dynamic inductive
wireless charging of electric
vehicles.
57
Evaluating EV market interest. Page 21
Digital Object Identifier 10.1109/MELE.2013.2280833
features
departments & columns
2325-5987/13/$31.00©2013IEEE IEEE Electrification Magazine / SEPTEMBER 2013 21
HE CONCEPT OF ELECTRIFIED VEHICLES
(EVs) is the best old “new” idea that has
been around for the last century. Designs
have changed to make EVs popular, but
until now, no design has captured the pub-
lic’s imagination or gained market traction. This is because
consumers need more than facts about EVs; they need to
be wooed into making a bigger commitment to the EV.
We all know that EVs are good for us. The fact that we
all don’t have more of them in our daily diet of transporta-
tion is not the fault of automakers or consumers.
Consumers know that, like fiber, EVs make economic
sense, benefit the environment, and are enhanced with
“vitamins” like the latest technologies. All the ingredients
necessary for a healthy and significant EV penetration are
already in the marketplace.
What is missing is a certain je ne sais quoi—a winning
combination of technology, desire, and marketing to make
EVs indispensable to the average North American. Togeth-
er engineers and policy makers can make this a reality,
but they need to lead with more than just the head—they
need to appeal to the heart of the consumer as well.
Digital Object Identifier 10.1109/MELE.2013.2272481
Date of publication: 23 October 2013
Courting
and Sparking
Courting
and Sparking
Wooing consumers’ interest
in the EV market.
By Narayan C. Kar, K.L.V. Iyer,
Anas Labak, Xiaomin Lu, Chunyan Lai,
Aiswarya Balamurali, Bryan Esteban,
and Maher Sid-Ahmed
T
©Can StoCk Photo/tomwang
IEEE Electrification Magazine / september 2013
22
We Need to Talk
To move forward, sometimes you have to look back and
reassess past failures and achievements. Past generations
of EV designs grabbed the public’s attention. Innovation
and evolution are the mainstays of EV development. As
shown in Figure 1, the evolution of the EV can be traced
back to the 1830s. Scotland’s Robert Anderson built the
first prototype of an electric-powered carriage, and during
the same time period, German engineer Andreas Flocken
built the first four-wheel electric car. Pope Manufacturing
Co., Hartford, Connecticut, the first large-scale EV maker in
North America, made electric cars for the New York City
taxi fleet. These innovations propelled EV technology into
a booming industry in the United States that, by 1900, had
encompassed 28% of the road vehicle market. This
momentum was seriously dampened with the introduc-
tion of the petroleum-powered Ford Model T car. The EV
market plummeted down to near extinction because of
the predominance of internal combustion engines (ICEs)
and the availability of cheap petroleum.
Recent years have seen a rekindled interest in EVs
because of rising oil prices as well as research and devel-
opment programs that have significantly improved the
technology. Government initiatives such as the zero-
emission vehicles program in California, which has made
the technology more attractive for automakers, have also
energized the EV market. Toyota was the first automaker
to release a commercial hybrid vehicle, selling 18,000 units
in 1997. Since then, oil prices have increased steadily,
peaking at more than US$145 per barrel. Major automak-
ers have responded by developing and commercializing a
new generation of energy-efficient vehicles called plug-in
hybrid EVs (PHEVs) and all-battery EVs (BEVs).
Does Our Relationship Have a Future?
Today, conventional ICE vehicles are a modern necessity on
which society relies. However, large numbers of automobiles
in use around the world have caused and continue to cause
serious health and environmental problems. Air pollution,
global warming, and the rapid depletion of the Earth’s petro-
leum resources are problems of paramount concern.
According to Navigant Research, “The average price of
fuel for conventional vehicles will likely continue to rise
through the remainder of this decade, driving demand for
electrified (hybrid, plug-in hybrid, and all electric) vehicles”
[1]. So far, this prediction is being fulfilled. This is corrobo-
rated by Pike Research’s findings of increasing EV sales
and market penetration around the world, as noted in Fig-
ure 2. In 2012, Japan led sales of pure electric cars with a
28% market share of global sales, followed by the United
States with a 26% share, China
with 16%, France with 11%, and
Norway with 7%. Plug-in hybrid
sales in 2012 were led by the Unit-
ed States with a 70% share of
global sales, followed by Japan
with 12% and The Netherlands
with 8%. According to a recent
report from Navigant Research, a
total of 21.9 million EVs will be
sold worldwide during the period
from 2012 to 2020.
Making a Long-Term
Policy Commitment
The significant reduction in fossil
fuel usage and CO2 emissions is a
well-known and attractive feature
of EVs that has enabled their mar-
ket penetration. The public and the
industry understand the impor-
tance of reducing carbon foot-
prints. They know that the trans-
portation sector, as a whole, has a
significant carbon footprint, and
only governments, at various lev-
els, have the power to regulate that
footprint through legislation. In
the United States, for example, the
Corporate Average Fuel Economy
(CAFÉ) regulation compels, or you
1801–1900
EVs Enter the
Marketplace
1901–1950
EV
Production inks
1951–1999
High Oil Prices—
Renewed
Interest in EVs
Since 2000
Increased
Interest in EVs
Figure 1. The evolution of EVs.
700,000
600,000
500,000
400,000
300,000
200,000
100,000
0
Number of Vehicles
2011 2012 2013 2014
Year
2015 2016 2017
Africa/Middle East
Western Europe
North America
Asia Pacific
Latin America
Western Europe
Figure 2. Global annual light-duty vehicle sales through 2017, as forecasted by Pike Research.
IEEE Electrification Magazine / september 2013 23
could even say “drives,” automakers
to improve their motor vehicles’
mileage capabilities every year. Ulti-
mately, this will encourage manufac-
turers to introduce more EVs into
their product lineup because meet-
ing the standard will become
increasingly difficult with standard
ICE vehicles. Figure3 shows the CAFÉ
standards put forward by the U.S.
government from 2011 through 2025,
as documented in 2017–2025 Model
Year Light-Duty Vehicle GHG Emis-
sions and CAFÉ Standards. Figure 4
shows a short-term forecast of the
EV market through individual com-
pany shares. On the basis of this
forecast, Toyota is predicted to lead
the market with a 38.5% share fol-
lowed by Ford, Nissan, Honda, and
General Motors. It is estimated that
EV sales will begin to grow rapidly
after 2015 and reach a combined 7
million per year by 2020 and 100 mil-
lion by 2050.
The International Energy Agency
has put forward a positive and
ambitious road map to achieve
widespread adoption and use of EVs
and PHEVs worldwide by 2050. The
road map targets a 30% reduction in
global CO2 levels by 2050 relative to
2005. The reduction is to be imple-
mented through efficiency improve-
ments and electrified transporta-
tion, with an EV share of at least
50% of the global light-duty vehicle
sales. To achieve that target, policy
support is critical to ensure that the
initial cost is as affordable as possible
and that an adequate charging infra-
structure exists. Furthermore, collabo-
ration between public and private sec-
tor companies must be established
and strengthened through research
programs, standards, and infrastructure development.
Electric Machines—
More than Just a Pretty Face
Electric machines have proved their ability to provide equal
mechanical power at relatively high efficiencies when
compared with ICEs over the past few decades. This, along
with their ability to mitigate fuel consumption and green-
house gas emissions, is a substantial reason to replace ICEs
with electric machines. This has created a demand for a
new generation of electric machines that meet electrified
transportation’s specific needs. Every EV has at least one
electric machine, and some have multiple motors depend-
ing on their drivetrain architecture. The annual production
of e-motors for EVs is forecasted to reach millions this
decade, based on forecasts by analysts who track hybrid
and EV production plans. Navigant Research predicts the
global market for electric drive motors in light-duty vehi-
cles to grow from a little less than US$1 billion in annual
revenue in 2013 to more than US$2.8 billion in 2020.
The traction motor is key to the synergy of the electric
powertrain. Selecting a suitable existing motor is a
70
60
50
40
30
20
CAFÉ
Small Passenger Cars
Regular Passenger Cars
Light-Duty Trucks and Vans
Heavy-Duty Trucks
10
0
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
Year
S
mall Passen
g
er Car
s
R
e
g
ular Passen
g
er Cars
Ligh
t-
D
uty
T
ruc
k
s an
d
V
an
s
H
eav
y
-
D
ut
y
T
ruc
ks
Figure 3. CAFÉ standards for each model year in miles per gallon through 2025. (Data courtesy of
the National Highway Traffic Safety Administration and the Environmental Protection Agency.)
Toyota—38.5%
Ford—12.3%
Nissan—10.6%
Honda—9%
GM—8.9%
Fisker—5.5%
Tesla—2.5%
Hyundai—2.5%
Volkswagen—2.4%
BMW—1.5%
Diamler—1.4%
Meyers Motors—1.2%
Other—3.8%
38.5
3.8
1.2
1.4
1.5
2.5
2.4
2.5
5.5
8.9
9
10.6 12.3
Figure 4. EV market shares by company, forecasted by Ceres/Citi Investment.
IEEE Electrification Magazine / september 2013
24
challenge for designers. It is important to recognize that
motor choice cannot be made without careful consider-
ation of the integration of its controller and associated
power electronics. Some automakers have decided to
confront this issue by designing, developing, and
producing their traction motors in-house, rather than
purchasing off-the-shelf machines from specialist suppli-
ers. The off-the-shelf motors, no matter how extensively
they are adapted for a specific application, can compro-
mise the efficiencies of the propulsion system.
As in Any Relationship,
There Must Be Compatibility
Proper selection of electric machine type is based on key
features such as the energy source in the vehicle, space
and vehicle dynamics, efficiency, reliability, cost, and the
major operating requirements of the machine. The major
operating requirements of the traction motor include a
wide speed range, impulsive response, high efficiency over
a wide torque and speed, high torque at low speeds, fault
tolerance, and high power density. Among the major auto-
makers, there is no general consensus as to the type of
electric machine best suited for vehicles, but induction and
permanent magnet (PM) machines are the two types cur-
rently used in EVs and are expected to continue to domi-
nate the market.
These machines fundamentally vary in their rotor
architecture (Figure 5). The induction machine rotor con-
tains conducting bars that cut the stator field and develop
a voltage that drives a current and produces a secondary
field. The rotors in PM machines use magnets to generate
the rotor’s magnetic field exclusively, without the need
for excitation current or any of the losses associated with
it. These machines are found to have higher efficiency,
torque density, and heat dissipation capability than their
induction machine counterparts. PM motors are widely
used in today’s EVs, including the Ford Focus, Toyota Prius
(Figure 6), Chevy Volt, and Nissan Leaf, because of their
superior performance over the induction machines. Remy
is one of the PM e-motor manufacturers whose motors
are used by GM, BMW, and Mercedes two-mode hybrids,
as well as a growing list of commercial vehicles. Active
areas of research on PM machines include studying the
effect of rotor and stator configurations on harmonics
and the causes and mitigation of demagnetization.
The advantages of PM machines are offset by the
increasing price and supply disruptions of magnets due to
geopolitical issues. This challenge has inspired companies
such as Tesla and Remy to develop next- generation induc-
tion machines for vehicles that will be lighter and more
efficient than the magnet-type machines. The convention-
al induction motors use aluminum rotors. However, the
electrical conductivity of copper is 60% more than alumi-
num, making it an enticing substitute. Using copper mate-
rial can also reduce the motor operating temperatures by
5–32°C. These data suggest that the lifetime of motors
using copper rotors may be extended by 50% or more. An
example of the use of the copper rotor induction
machines is in the latest generation of U.S. Army heavy-
duty hybrid EVs (HEVs) powered by four 520-V, 140-hp
induction machines with die cast copper rotors.
Another Innovation Suitor on the Horizon
The switched reluctance motor (SRM) is another candi-
date for traction motors, apart from the widely used
induction and PM types. To date, SRMs have been
applied in heavy-duty vehicles, and research is in prog-
ress to implement them into the lightweight vehicles.
The SRM is a doubly salient machine with no winding
or magnet on the rotor. It features a simple, rugged
structure with fault-tolerance ability, high-speed opera-
tion capability, high power density, and relatively low
manufacturing cost. Despite these advantages, SRMs do
present some challenges. For example, torque ripple
and acoustic noise need to be addressed through funda-
mental design improvements to develop a viable SRM-
based electric propulsion system.
The Power Couple: Torque and Input
Regardless of the type of machine selected, to achieve the
performance desired, a suitable drive is required. The drive
consists of a bidirectional converter and its control. At the
(a)
(b)
Figure 5. Cross sections of the various traction motor technologies:
(a) an induction motor and (b) an axial flux SRM.
IEEE Electrification Magazine / september 2013 25
machine level, during motoring, the goal is to provide the
terminals with the proper voltages to meet the torque com-
mands that the driver is imposing through the action of the
pedal. Additionally, many vehicles employ regenerative
breaking, which uses the electric machine as a generator to
convert the energy produced by the action of slowing the
vehicle and using it to charge the battery pack. With hybrid
vehicles, a supervisory control is necessary to determine
the power flow through the system as there are multiple
energy sources, the battery, and ICE that work differently
during various modes.
To control any machine, a relationship must be estab-
lished between the input excitation and the resulting
torque. The torque in an electric machine arises from the
interaction of magnetic fields in the stator and rotor, and
the generation of these fields depends on a coupled and
complicated interaction of the current and flux linkage of
the internal windings. The most commonly adopted ac
electric motor control in EVs is the vector-control technique,
which is capable of mathematically
separating the component of cur-
rent directly responsible for torque
generation (Figure 7). This is done by
projecting all the three-phase quan-
tities along two axes: the direct (d)
axis, which is in line with the field,
and the quadrature (q) axis, which is
perpendicular to it. To find these
axes, it is necessary to determine
the position of the rotor online.
In a PM motor drive, when the
motor operates under base speed,
the controller calculates the refer-
ence d- and q-axis current using a
maximum torque-per-ampere tech-
nique to ensure the efficiency and
torque production of the motor.
Over base speed, a field-weakening
method is used to estimate the cur-
rent reference and ensure the
power limit is not exceeded. The
reference d- and q-axis voltage is
generated taking into consideration cross- coupling terms,
which arise from the aforementioned coupled electrical
interaction, and then converted back to the three-phase
quantities. Pulse-width modulation is used to generate a
gate signal for the power electronic switches to create the
required voltage waveforms (Figure 8).
To meet the advanced requirements of fast dynamics,
field-oriented vector or direct-torque control is also the
solution for induction machines. With rotor-flux-oriented
control in a squirrel cage induction motor, the unstable
portion of the natural speed–torque characteristics vanish-
es, and hence, there is no chance of instability due to cer-
tain types of load torques. The additional advantage is the
fact that the maximum torque-producing capability of the
machine is dictated by thermal considerations only. The
electromagnetic torque response becomes as fast as a sep-
arately excited dc machine of identical torque rating but
with a reduced size and weight. The only disadvantage
in a field-oriented controlled induction motor drive is the
dc-dc Converter Motor Inverter Generator Inverter
Generator
Motor
Filter
Capacitors
Inductor
Battery
IPM
+
–
Figure 6. A block diagram of the Toyota Prius e-motor drive system [5].
ac Motor Current
Sensors Powertrain EV Battery
Encoder/
Resolver
Position/Speed
Calculation
MTPA/FW
Hysteresis
Current/Sine
PWM
Voltage Power
T1 – T6
i
c
i
d
T
abcodq
i
q
i
d
i
q
T
e
i
b
i
a
Signal
T
e
Z
e
Figure 7. Overall schematic of three-phase ac traction motor drive.
IEEE Electrification Magazine / september 2013
26
higher cost in realizing and
implementing the complex control
strategies in real-time field applica-
tions. Indirect rotor field-oriented or
vector-controlled induction motor
drives, where rotor position is esti-
mated instead of measured, are
widely used in EVs/HEVs for high-
performance applications.
An SRM requires special convert-
er topology, as it is fundamentally
different in structure from other ac
machines. Variable-frequency con-
trol, such as the hysteresis current
controller, and current control based
on fixed switching frequency, such
as the propotional–integral control,
have been developed and employed
widely. Researchers have also pro-
posed adaptive/intelligent control-
lers employing artificial intelligence
techniques such as fuzzy logic, slid-
ing mode control, emotional control,
neural networks, and evolutionary
algorithms and their combinations. These methods have
proven effective in applications that require four quadrant
operations, tracking capability, robustness to load distur-
bance, and less steady-state error, such as HEVs’ or EVs’
traction applications [6] (Figure 9).
Multifaceted Technology for Power Electronics:
Integrated Motor Drive and Battery Charger
Conventional battery chargers have been either on- or off-
board chargers. The onboard chargers have limitations of
cost, power handling capacity, and charging time. An inte-
grated charger topology using the power electronics
already available on board can be used for battery charging
when they are not used for traction, and this can lead to
fast-charging technology [7]. The challenge is to design
power electronic converters that are compatible with the
motor and the battery pack, which usually are manufac-
tured by two different companies. The companies design-
ing the motor-drive system and the battery pack for the
same vehicle can be coordinated by the original equip-
ment manufacturer (OEM) in such a case. Because the bat-
tery is only charged when the vehicle is parked using the
same power electronics converter, reduction in the initial
vehicle cost and space used can be achieved. Moreover, in
such a case, the motor windings can also be used as filters
to improve power quality issues. Figure 10 shows a futuris-
tic system that is expected to be on board vehicles for fast
charging and traction application.
Gaining Traction in a Relationship
One idea to improve the performance of the EV drivetrain is
to add multiple machines. It then becomes a matter of
Current
Sensors
SRM Powertrain EV Battery
Position
Signal
Signal
Processing
Voltage
Regulation
Parameters
Adjustment
Power
PWM
D
i
c
∗
T
e
∗
I
e
i
b
i
a
Signal
θ
e
ω
e
Figure 8. An overall schematic of the three-phase switched reluctance motor drive.
Figure 9. The development of a motor control algorithm.
IEEE Electrification Magazine / september 2013 27
determining if the advantages of having multiple machines
outweigh the cost of adding them in. The main advantage
is expected to be a significant increase in vehicle efficiency,
especially in heavy-duty vehicles such as buses where
space is less of a concern. One motor can be used when the
transit bus is empty, and the other motors can be added
when the load on the bus exceeds the rating of the other
machine(s). Such a motor-drive system will result in sym-
metric loading of all machines, operating them near their
rated conditions, which can yield better motor efficiency.
The added complexity to the system amounts to the neces-
sity of adaptive-control strategies and planetary gear sys-
tems and clutches for the mechanical connections.
Multimotor technology is currently being used in the
Mercedes SLS AMG electric drive. Four compact PM syn-
chronous motors with combined ratings of 552 kW and
1,000 Nm, weighing 45 kg and a reaching a maximum
speed of 13,000 r/min, make up the drivetrain. It uses a
unique concept of transmission, allowing each motor to
selectively drive all four wheels. This helps in individual
wheel torque distribution; however, it is only achievable
under the significant disadvantage of unsprung masses
with wheel hub motors.
Another recent innovation under investigation is the
integration of the traction motor housing inside the wheel
rim. This in-wheel motor design (Figure 11) saves signifi-
cant space and eliminates the need for a transmission,
differential, and related mechanical parts. This reduces
energy losses due to friction. The in-wheel motors also
improve traction by allowing precise control over each
wheel, and they allowed greater flexibility in vehicle
design since there is no need to mechanically link the
wheels to a common driveshaft. They show great promise
in increasing the overall efficiency.
In Innovation, Marketing, and Consumer
Wooing, It Always Comes Down to
Chemistry: The Li-Ion Battery
The successful deployment and mass adoption of EVs
depends greatly on cost and performance. One of the big
hurdles presently faced by EV manufacturers is the
disproportionately high manufacturing cost associated
with the EV battery pack. For instance, Allan Mulally, CEO
of Ford Motors, indicated that the manufacturing cost of a
battery pack for a Ford EV could range anywhere between
US$12,000 and US$15,000 per car, while the car itself sells
for US$22,000. Clearly, to achieve long-term competitive-
ness, this battery problem needs to be solved.
From lead-acid battery technology, with specific energy
as low as 30 Wh/kg in the late 19th century, to the currently
used lithium ion (Li-ion) batteries, various battery
chemistries chosen as energy storage systems (ESSs) for the
transportation sector are numerous. The main require-
ments of a battery are: 1) high power density to ensure
rapid vehicle acceleration and the ability to use regenera-
tive braking power; and 2) high energy density to ensure an
extended drive range. Low cost, extensive cycle life, and
safety are other key requirements.
Li-ion batteries are the latest trend in battery chemis-
try. With the nominal values of cell voltage of 3.2–3.65 V,
specific energy of 130–150 Wh/kg and power density of
2,300–2,400 W/kg, these batteries are considere d to be one
of the best performers for automotive applications to date.
Li-ion batteries contain multiple anodes and cathodes. By
choosing the structure carefully, power and energy appli-
cation requirements can be well satisfied. Despite its
many advantages, there is always a tradeoff between per-
formance and cost. The major disadvantage of Li-ion bat-
teries is their high cost, which accounts for more than
one-third of the total vehicle cost. Other disadvantages are
aging, requirement of thermal protection, and immature
technology compared to lead-acid or nickel metal hydride
(NiMH) batteries.
Battery Technology Roadmap
The quest for improved EV battery technologies goes as far
back as the 1970s. One of the first commercially feasible
technologies adopted by automakers was the NiMH bat-
tery. NiMH batteries became the choice for early hybrid
vehicles because they have a higher energy density and
Battery Pack dc–dc
Converter
Motor Inverter
and Battery
Charger
ac Motor/
Filter
Charging Inlet
from ac Grid
Figure 10. Futuristic integrated power electronics for a traction motor drive and an on-board fast battery charger.
IEEE Electrification Magazine / september 2013
28
are lighter than lead-acid batteries of comparable power.
They are commonly used in many hybrid vehicles today,
including the Toyota Prius and Honda Insight. After testing
several alternatives, Toyota announced in 2009 its contin-
ued use of NiMH batteries in many of its hybrid vehicles.
Recently, manufacturers have extensively started using
Li-ion as the preferred energy source, especially in EV and
PHEV applications.
In 2008, Li-ion batteries were considered too costly to
be used on a wide scale, costing around US$1,200/kWh to
deliver specific energy of 110 Wh/kg and power density of
1,000 W/kg. However, with the invention of new electrode
and electrolyte materials, the technology was advanced
and the cost reduced to US$700–800/kWh in 2011. The
specific energy and power density increased significantly
to more than 120 Wh/kg and 1,800 W/kg, respectively.
Currently, these batteries cost about US$400–500/kWh
and have a specific energy of 130–140 Wh/kg and a
power density of 2,400 W/kg. Their life is around 3,500
cycles. In 2015, the target cost for Li-ion batteries is
US$200–300/kWh for a PHEV. Specific energy and power
density targets are as high as 250–300 Wh/kg and
3,500W/kg, respectively, in 2020, with a cost target of
US$100–150/kWh. The electric range targeted is approxi-
mately 150 mi in 2020. As of now, the range is approxi-
mately 38–40 mi for a midsize PHEV like the Chevy Volt
and approximately 100 mi for a full EV like the Mitsubishi
i-MiEV. Figure 12 explains the technological advancement
and future targets for Li-ion batteries from 2008 to 2020.
Harvesting Energy: Lessening Burden on the Battery Pack
Energy harvesting is another answer to reduce the load
on the battery pack. The generation of electricity on
board a vehicle without chemical conversion can sig-
nificantly enhance the autonomy of electric driving
and extend the life and improve the performance of
energy storage devices. The e-tire concept is one of the
energy harvesting methods using the deflection of the
tire while the vehicle is in motion [8]. More specifically,
this new concept uses local changes in pressure and
shape of a vehicle tire to generate
electricity. The idea uses the prin-
ciple of electromagnetism to gen-
erate electricity inside the tire of
a vehicle in a new way that is yet
to be exploited in electrification
of vehicles. The rolling of the
wheel on the road causes local
changes in the tire’s symmetric
shape and makes it flat at the
contact area with the road sur-
face, as shown in Figure 13(a).
The dynamic deflection changes
the radial distance between the
wheel axis and the circumfer-
ence area of the tire when it is in
contact with the ground. This
localized deflection in the tire
(a) (b)
Figure 11. An in-wheel motor layout: (a) the overall cross section of the in-wheel motor with the tire and (b) the various components of the in-
wheel motor.
Specific Energy (Wh/Kg)
2008 2010 2012 2014 2016 2018 2020
Year
Power Density (W/Kg) Cost (US$/kWh)
2
00
8
2010
2012
2014
2016
2018
Yea
r
Figure 12. The forecasted power density, specific energy, and cost of Li-ion batteries through 2020.
IEEE Electrification Magazine / september 2013 29
can be utilized by adopting a
number of linear generators incor-
porated in a vehicle wheel, as
depicted in Figure 13(b).
How Fast Can You Charge?
Supported by government incentives,
the market for EVs can grow if ade-
quate fast-charging facilities are
placed in convenient permanent loca-
tions, such as gas stations. Such large-
scale installations of charging stations
will advance the charging infrastruc-
ture and technology for EVs. It will
also create a trend of charging the EVs
at permanent charging stations just
like filling up gasoline in the existing
gas stations for gasoline vehicles. The
advancement in charging technology
has to go hand in hand with the
advancement in battery technology,
as the battery should be able to han-
dle the high inrush of power from
such fast-charging dc stations.
These vehicles connected simul-
taneously to the grid consume a large
amount of electrical energy. This
demand for electrical power can lead
to extra-large and undesirable peaks. Also, power-quality
problems, such as poor power factor and higher total har-
monic distortion during charging and discharging, may
cause equipment malfunction and component failures. It
is an economic and safety concern to the utility compa-
nies as transformers and feeders are prone to overloads.
Hence, the effect of harmonics alone would be a reason to
shut down the power transfer between the grid and the
vehicle. Also, the effect of load increase and its inherent
low power factor on the distribution systems should be
considered. As the number of cars
increases, load increases and,
hence, it might worsen the current
trend of harmonic distortion.
Higher-efficiency Level 3 sus-
tainable charging stations are
expected to mitigate issues of
charging time, quantity of power
consumed, and power quality.
Moreover, the market for EVs can
expand if adequate fast-charging
facilities are provided in perma-
nent locations such as gas sta-
tions and provided with high-
amperage connections from a
mixed power system containing
onsite solar power generation and
the grid. Such large-scale installa-
tions of charging stations will
advance the charging infrastruc-
ture and technology for EVs and
create a trend of charging EVs at
permanent charging stations just
like filling up gasoline in the exist-
ing gas stations for gasoline vehi-
cles. Figure14 shows one such
futuristic fast-charging station.
The utility companies can own/
manage these charging stations,
which will reduce their power-
quality concerns, as they will have
greater control over these moni-
tored charging stations. Level 3
charging infrastructure costs
between US$30,000 and US$160,000.
It is expected that commercially
available EVs will be charged within
15–30min to approximately 80% of
the battery capacity using a dc fast-
charging station.
The Energy That Comes when
Couples, Transportation Policy,
and EV Charging Resonate
While some researchers are trying to
solve the EV battery problem
through improvements in battery chemistry, others are try-
ing to solve the problem by alternate means external to the
battery. Accordingly, recent studies have shown the feasibil-
ity of charging EVs wirelessly with greater than 90% effi-
ciency from utility supply to battery. This technology has
come to be broadly known as inductive power transfer (IPT),
and its application to electrified transportation for static
and in-motion charging is gaining much attention world-
wide from OEMs, government agencies, and academic insti-
tutions. The proponents of IPT-based EV charging aim to
reduce the battery size and, by
extension, its associated cost by
ensuring that it is charged more fre-
quently and seamlessly. The
increase in charge frequency would
be accomplished through opportu-
nity charging, whereby EVs could
easily charge up while stopped at a
stop sign, traffic light, bus stop, or
even while driving over an electri-
fied section of roadway.
At the heart of IPT-based EV
charging systems are two of the
oldest and most well-known laws
of classical electromagnetics:
Ampere’s law and Faraday’s law of
induction. The fundamental differ-
ence between the modern magnetic
(a)
(b)
Figure 13. Energy harvesting through
a novel e-tire concept. (a) An overall side
view of the e-tire with 16 linear generators in
the wheel. (b) A cross-sectional view show-
ing the linear generator.
Figure 14. Futuristic sustainable PV-based
fast-charging stations.
IEEE Electrification Magazine / september 2013
30
induction and the conventional low- frequency magnetic
induction that has now been in use for nearly a century in
devices such as transformers and close proximity chargers
is the use of matched high-frequency (i.e., >60Hz) reso-
nances at the source and receiver devices involved in the
energy exchange so as to facilitate efficient power transfer
across larger distances.
The distance and alignment between the primary
and secondary inductive structures plays a critical role
in all magnetically coupled systems but especially in
modern IPT systems. The magnetic coupling coefficient
is a figure of merit that quantifies the amount of mag-
netic energy generated at the primary that ends up
being captured by the secondary. Conventional induc-
tively coupled systems are tightly coupled, having cou-
pling coefficients in the range of 0.92–0.98. On the other
hand, in IPT-based wireless EV chargers, the large sepa-
ration and misalignment possible between primary and
secondary result in coupling coefficients that are typi-
cally in the range of 0.1–0.4, making such systems very
loosely coupled. In turn, this very loose magnetic cou-
pling results in very large leakage fields. These stray
fields are lost from the perspective of transferring power
from the primary to the secondary and also produce
large inductive reactances that can be modeled as being
in series with the windings of the primary and second-
ary magnetic structures. These large reactances severely
limit the flow of primary and secondary currents; con-
sequently, capacitive compensation of primary and
secondary and operation at resonance are necessary to
reduce the reactances to manageable levels.
From Figure 15, it can be seen that the design of a
practical contactless EV charging system based on loosely
coupled resonant IPT involves at least four main chal-
lenges: 1) the design of the low-loss and high-coupling
electromagnetic structures that will participate in the
magnetic energy exchange; 2) the design of an efficient
high-power and high-frequency circuit, known as the IPT
power supply, capable of driving the entire system; 3) the
processing and conditioning of the received power on the
secondary side; and 4) the automated control of the entire
system [9]. With a formal SAE standard (SAEJ2954) on
wireless charging due to be completed in 2015 [10], much
work is presently being undertaken by different institu-
tions to make wireless EV charging a practical and
attractive reality that has the potential of significantly
alleviating—if not eliminating—the “range anxiety” that
has until now made consumers so reluctant to fully
embrace EVs [11]. Figure 16 shows one such 6-kW, 20-kHz
IPT system that was developed for conducting research
Primary Side Magnetic Coupling Secondary Side
Power Supply
Input
Voltage
Secondary
Controller
Magnetic
Field
Sink
Energy
Coupling
Network
Power
Processing/
Conditioning
Electrical
Load
High-
Frequency
Electrical
Energy
Source
Energy
Coupling
Network
Primary
Controller
Magnetic
Field
Source
Figure 15. A simplified system diagram of an IPT-based EV charger.
Inverter
Controller
Secondary Magnetic Pad
Primary Magnetic Pad
Test Load
Figure 16. The fully functional contactless EV battery charger. Figure 17. Electric machine testing in progress at the University of
Windsor.
IEEE Electrification Magazine / september 2013 31
on the primary side power supply topologies most
commonly used for EV charging applications. The system
shown has been tested at 3 kW over a 7-in air gap and
achieved 93% efficiency as measured from the dc link of
the inverter to the load being energized.
Electric Powertrain Testing:
Measuring the Endurance of a Relationship
The accurate testing and validation of the components
and control algorithms is a major stage in research and
development of various technologies for electrified trans-
portation. Generally, the drivetrain tester is a regenera-
tive system that can be used to test the electric machine,
power electronics, control algorithms, and battery perfor-
mance by inputting the vehicle drive cycle and engine
characteristics. D&V, Horiba, AVL, and A&D Technologies
have all developed products specifically to test hybrid
and EV components, such as the one in Figure 17. The
centerpiece of the system is a powerful dynamometer
capable of applying the load torque for the drive cycle. To
support the dynamometer, all systems include a
variable- frequency drive, which feeds off a variable dc
link that can be used to model the battery. Most systems
are regenerative in nature; that is, when the machine
under test is braking and generating energy, it is fed back
to the dc link where it can be used to help power the
testing machine itself. This recycling of power means
less has to be pulled from the mains, which reduces the
cost of long tests. This is a big issue for an endurance test
that can last for days.
That missing je ne sais quoi to make EVs indispensable to
the average North American consumer can be found in
accessible charging infrastructures, reliable long-life batter-
ies, and increased mileage. Consumers want to be wooed—
they want a relationship with EVs. Vehicle manufacturers
want a better-quality EV to offer consumers to increase mar-
ket penetration. Engineers and policy makers, to make this
relationship a reality, need to appeal to more than just con-
sumers’ minds and go beyond testing and performance sta-
tistics and test results. They also need to appeal to the hearts
of\consumers to woo them into making the long-term com-
mitment and the emotional and financial investment in EVs.
Consumers know that EVs are healthy and good for them—
they just want a bit more romance in the relationship.
For Further Reading
Nearly 22 million electric vehicles will be sold from 2012 to
2020. [Online]. Available: www.navigantresearch.com/
newsroom/nearly-22-million-electric-vehicles-will-be-
sold-from-2012-to-2020
Corporate average fuel economy [Online]. Available:
https://en.wikipedia.org/wiki/Corporate_Average_Fuel_
Economy
Electric & plug-in vehicle roadmap [Online]. Available:
www.iea.org/publications/freepublications/publication/
EV_PHEV_brochure.pdf
Y. Sato, S. Ishikawa, T. Okubo, M. Abe, and K. Tamai,
“Development of high response motor and inverter sys-
tem for the Nissan Leaf electric vehicle,” in Proc. SAE
World Congress, 2011-01-0350.
M. Olszewski, “Evaluation of the 2010 Toyota Prius
hybrid synergy drive system,” Oak Ridge National Labora-
tory, Washington, DC, Rep. FY2011, Mar. 2011.
C.-L. Tseng, S.-Y. Wang, S.-C. Chien, and C.-Y. Chang,
“Development of a self-tuning TSK-fuzzy speed control
strategy for switched reluctance motor,” IEEE Trans. Power
Electron., vol. 27, no. 4, pp. 2141–2152, Apr. 2012.
S. Haghbin, K. Khan, S. Zhao, M. Alakula, S. Lundmark,
and O. Carlson, “An integrated 20-kW motor drive and
isolated battery charger for plug-in vehicles,” IEEE Trans.
Power Electron., vol. 28, no. 8, pp. 4013–4029, 2013.
A. Labak, G. A. Nazri, and N. C. Kar, “Novel design of
electric tire concept incorporating permanent magnet
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Transportation Electrification Conf., pp. 1–6, 2013.
O. H. Stielau and G. A. Covic, “Design of loosely coupled
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Biographies
Narayan C. Kar is with the Centre for Hybrid Automotive
Research and Green Energy (CHARGE), University of Wind-
sor, Canada.
K.L.V. Iyer is with the Centre for Hybrid Automotive
Research and Green Energy (CHARGE), University of Wind-
sor, Canada.
Anas Labak is with the Centre for Hybrid Automotive
Research and Green Energy (CHARGE), University of Wind-
sor, Canada.
Xiaomin Lu is with the Centre for Hybrid Automotive
Research and Green Energy (CHARGE), University of Wind-
sor, Canada.
Chunyan Lai is with the Centre for Hybrid Automotive
Research and Green Energy (CHARGE), University of Wind-
sor, Canada.
Aiswarya Balamurali is with the Centre for Hybrid
Automotive Research and Green Energy (CHARGE), Univer-
sity of Windsor, Canada.
Bryan Esteban is with the Centre for Hybrid Automo-
tive Research and Green Energy (CHARGE), University of
Windsor, Canada.
Maher Sid-Ahmed is with the Centre for Hybrid Auto-
motive Research and Green Energy (CHARGE), University
of Windsor, Canada.
