Embed Size (px)
Citation preview
From Wired to In-Moving Charging of the Electric Vehicles
KISHORE NAIK MUDE1, HEMANT KUMAR DASHORA2, MANUELE BERTOLUZZO3, and
GIUSEPPE BUJA4
Department of Industrial Engineering
University of Padova
Via Gradenigo 6a, 35131, Padova
ITALY
[email protected], [email protected],
[email protected], [email protected]
Abstract: - In present years, the deployment of electric vehicles is arisen globally due to the stressing of the
environmental concerns and the demand of energy-efficient road transportation. This paper deals with the battery charging technologies for electric vehicles, giving an overview on their evolutionary process. At first,
the wired technology is reviewed and the main existing standards on it (charging modes, connection cases and
plug types) are presented. Then the wireless power transfer technology is illustrated, showing the convenience of the resonant coupling topologies in increasing the power transfer efficiency. At last, the in-moving
technology is introduced and the preliminary studies on it are addressed.
Keywords: - Conductive charging, Wireless power transfer, Conventional battery chargers, Electric vehicle.
1 Introduction The increase of oil price and environmental
issues cause the growing interest in clean vehicle technologies, such as electric vehicles (EVs) and
fuel cell EVs [1], because they provide a good
solution to reduce the environmental impacts of
transportation and energy dependency thanks to their low energy consumption and zero emissions
[2]. EVs are powered by electric batteries, which
need to be recharged drawing electric energy from the grid.
Generally two types of battery chargers (BCs)
are available: off-board and on-board. On-board
BCs are used to charge from the utility outlet at the workplace or shopping malls during the day time or
from household plug. Off-board BCs operates like a
gas station and are designed to manage a high power in order to perform fast charging.
In most of the BCs the power flows only from
utility grid to the battery, and for this reason they are often termed as unidirectional BCs (UBCs) [3];
beside circuital simplicity, UBSs enjoy of reduced
grid interconnection issues and lower battery
degradation. On other hand, some BCs manage power flowing in both directions and can work in
two operating modes, namely “recharge” mode
when they absorb energy and “generation” mode when they deliver energy to grid [4]. The
bidirectional battery chargers (BBCs) [5] implement
the Vehicle-to-grid (V2G) concept, based on the ability of BBCs of supplying to the grid the energy
stored in the battery to perform ancillary operations,
such as peak power shaving or reactive power compensation [6].
Charging of an electric vehicle is performed by
either wired charging or wireless charging [7]. Wired charging uses conductive wires between
electric supply and the charging inlet of the EV.
Even though wired charging is popular, the
problems with messy wires and safety concerns in wet environment are major drawbacks of this
system.
In recent years, wireless power transfer systems (WPTSs) applied to EV charging are gaining a
growing interest because of their advantages
compared to their wired counterpart, such as no
exposed wires, ease of charging, and fearless transmission of power in adverse environmental
conditions [8].
Low power BCs take a long time to charge the EVs batteries while the use of high power BCs
shortens the batteries operative life. These
drawbacks trouble both wired and wireless BCs, but can be overcome by in-moving charging, i.e. by
charging the batteries while the EVs are moving [9].
The paper is organizes as follows. Section II
considers the EV charging infrastructure and section III introduces the wired battery chargers. Section IV
discusses about the architectures of the power
electronic converters embedded in the BCs. Section V deals with static wireless charging while Section
VI refers to in-moving wireless charging. Section
VII concludes the paper.
Recent Advances in Energy, Environment and Financial Planning
ISBN: 978-960-474-400-8 33
2 Battery Charging Infrastructure
2.1 Electric energy replacement The replacement of electric energy onboard an
EV can be done through two methods, i) battery swapping ii) battery charging. Battery swapping
[10], consists in substituting for the customer’s
discharged battery with a fully charged one of the same type. Battery swapping stations have a short
“refueling” time, comparable with that of gas
stations, but they are very expensive and their
deployment requires a strict standardization of the layout of the batteries and of their fastening devices.
The energy replacement using battery charging
mainly follows two forms, i.e. wired and wireless charging. Wired charging is performed either using
AC charging from standard outlet or from dedicated
equipment, or from DC supply [11] while wireless
charging does not require any connection of the EVs to external devices. The classification of different
types of charging structures is shown in Fig.1.
2.2 Charging profile Usually batteries are charged in two stages: the
constant current stage and the constant voltage stage. During the first stage a constant current is
injected in the battery until its voltage reaches a
maximum value corresponding to a fully charged battery. Subsequently, as shown in Fig. 2, during the
constant voltage stage, the charging voltage is
regulated at the maximum value while the current
reduces. When current falls below a minimum threshold, the charging is completed [12].
3 Wired Battery Chargers Wired BCs can be installed in houses, offices,
shopping malls and public places to enable EVs
owners to charge their vehicles. Wired BCs have
direct connection to the supply by means of extension power cord plugged to the wall outlet at
one end and to the vehicle inlet at the other. They
are popular, simple in design and have high efficiency. Fig. 3 sketches a vehicle performing a
wired charge of its battery
The set of conductors, the EV connectors,
attachment plugs, and all other fittings, devices, power outlets, or apparatuses installed specifically
for the purpose of delivering energy from the
premises wiring to the electric vehicle constitutes the so called electric vehicle supply equipment
(EVSE).
The EVSE, together with the power transfer and the communication protocol used during EVs
charging are ruled by a number of national and
international standards. Some of them are
summarized in Tab.1.
3.1 Charging modes Depending on the supplied power level and on
the charging time, wired charging is classified into
Mode1, Mode 2, Mode 3 and Mode 4 [13], [14]. Mode 1: This is the cheapest and most
convenient home-based charging method, but it is
Table. 1. Different EV standards
Standard Title/ description
IEC NEC article EV charging system
SAE J2293 Energy transfer system for EV
SAE J2836
Recommended practice for
communication between PEV and
utility grid
SAE J1772 EV conductive charger coupler
SAE J1773 EV inductive coupling charging
IEC 62196
Plugs, socket outlet, vehicle couplers,
vehicle inlets and conductive charging
of EV
IEEE 15473 Inlet connecting distributed resources
with electric power system
Battery vehicle energy restoration
Batterycharging
Batteryswap
Conductive charging
Wirelesscharging
AC supply(On-board charger)
DC supply(Off-board charger)
EVSE
Outlet
Fig. 1. Electric energy replacement
v
i
t
Constant Current
ModeConstant Voltage Mode
Charging
voltage
Cutoff
currentCharging time
Fig. 2. Constant current and constant voltage (CCCV) charging
profile.
Grid
Recharging Station
BatteryCharger
BatteryPack
Fig. 3.Wired battery charging
Recent Advances in Energy, Environment and Financial Planning
ISBN: 978-960-474-400-8 34
also the slowest. EVs are equipped with on-board
BC, as well as with cords that allow the users to
charge the EV in their garage using standard
industrial plugs and wall-mounted sockets. According to Mode 1, EVs are charged from
standard 230 V household outlet with a current
limited to 16 A so that the charging power does not exceed 3.7 kW. In USA Mode 1 is prohibited
because it requires earth connection that is not a
standard feature in USA domestic electric plants. Charging times depends on the battery capacity, but
generally a battery of a compact electric car takes
around 7-15 hours to be fully charged.
Mode 2: This charging method relies on 230 V or 440 V, single phase or three phases AC mains,
with charging current limited to 32 A. As with
Mode1, dedicated plugs and sockets are not required to connect EVs to domestic wall boxes or to public
charging stations. Charging boxes and/or charging
stations and the on-board BC contain the circuitry needed to perform safety functions. Mode 2
charging takes around 3-5 hours for a full charge of
a compact car battery.
Mode 3: It typically operates with three phases 440 V AC mains and supplies up to 63 kW to the on
board BC by means of dedicated plugs and sockets.
Besides safety functions of Mode 2, charging stations and on board BCs implement suitable
protocols to synchronize their operations. As a result
of the higher available power, a BC operating in
Mode 3 provides a compact car with a full charge in less than an hour. Mode 3 charge is used by large
vehicles like electric buses, and is available in
public and commercial areas, airports, and transportation corridors [9].
Mode 4: In Mode 4 AC mains voltage is
converted in DC voltage by a rectifier installed in the charging station. An off-board BC supplies up to
400 A to the EV by means of a dedicated plug. The
Japanese standard “CHAdeMO” is the most diffused
implementation of Mode 4 charging [14]. It charges the battery of a compact car in less than 30 minutes
supplying a power of up to 50 kW.
3.2 Connection cases and plug types The methods of connecting the EV to the
recharging station and the used plugs are classified
in “cases” and “types”, respectively [15].
Case A: This method utilizes a cable with one end permanently attached to the vehicle and the
other ended with a plug to be inserted in the socket
of the charging station. Case A is typically used
with charging Mode 1 and charging Mode 2.
Case B: It uses a detachable cable assembly with
a connector to be inserted in the EV inlet and a plug
to be inserted in the supply socket. Case B1
corresponds to the connection to a wall-mounted box while Case B2 corresponds to the connection to
a charging station. Case B is typically used with
Mode 1 and Mode 2 charging. Case C: In this case one end of the cable is
permanently attached to the charging station while
the other one is terminated with a connector to be inserted in the EV inlet. Only Case C is allowed for
Mode 4 charging.
A number of connector have been standardized
to be used in the different charging modes: Type 1: Was introduced by Yazaki and
standardized in SAE J1772, taken over by IEC
62961, for charging the EVs from a single-phase supply.
Type 2: Was introduced by Menneskes (VDE-
AR-E 2623-2-2, taken over by IEC 62961) for charging from single-phase 230 V and three-phase
440 V supply with current up to 63 A.
Type 3: Was introduced by EV Plug Alliance:
Scame/Schneider (IEC 62196) for charging from single and three-phase supply with a maximum
current of 32 A; it is endowed with a safety shutter.
It is built in two versions: Type 3A is for light EVs, like motorcycles, charged from a single-phase
supply with 230 V current limited to 16 A; Type 3C
is for full size EVs charged from single and three-
phase supply. Both versions provide for the control pilot pin.
3.3 Safety functions Rule EN 61851-1 states that for all the charging
modes, in connection Case B and Case C, the cord must contain the phase (or phases), the neutral, and
the protective earth wires. The plug at the EV side
must contain an additional pin, used by proximity detection logic of the on-board charger to check if
the EV is properly connected or not. In Mode 2 and
Mode 3 an additional wire and the relevant pin, denoted as “control pilot” are required. They are
used to perform additional functions such as: i)
continuous checking of the continuity of the
protective earth conductor ii) energization of the system iii) de-energization of the system. Optional
functions can be performed through control pilot
wire/pin: i) selection of charging rate, ii) determination of ventilation requirements of the
charging area, iii) detection/adjustment of the real
time available load current of the supply equipment
iv) retaining/releasing of the coupling, v) control of bi-directional power flow to and from the vehicle.
Recent Advances in Energy, Environment and Financial Planning
ISBN: 978-960-474-400-8 35
4 Power Electronic Converters for
Battery Chargers The basic power electronic circuitry for BCs
consists of an AC-DC converter cascaded by a DC-
DC converter. The AC-DC converter rectifies the
AC voltage from the grid to a DC voltage. The DC-DC converter controls the voltage/current supplied
to the battery according to its charging profile. In
most of commercially available BCs, the two stages are separated by an insulation stage formed by a
high-frequency inverter, a coupling transformer and
a high-frequency rectifier, as shown in Fig. 5.
The simplest AC-DC power converters are diode rectifiers. They are cheap, does not require any
control circuitry and can be realized both in single
phase and three phases versions. However, the current they draw from the grid is highly distorted
and additional input filters are required to comply
with the rules about harmonic injection in the grid.
For high power BCs the use of input filters is not viable and more sophisticated AC/DC converters
must be used.
Power Factor Correction (PFC) circuits, shown in Fig.6, are used for the single-phase BCs. They
control the current absorbed from the grid to be
nearly sinusoidal and in phase with the voltage and, at the same time, regulate the output voltage of the
rectifier. They suffer the drawbacks of needing an
output voltage higher than the peak grid voltage and
of being unable to manage bidirectional power flow. Active rectifiers are usually employed as input
stage in three phases BCs. They absorb sinusoidal
current with adjustable power factor so that, if cascaded by a bidirectional DC-DC converter, are
able of managing bidirectional power flows and to
perform V2G operations. Like PFC circuits, they
regulate the output voltage, provided that it is higher than the peak line to line input voltage.
5 Static Wireless Charging
5.1 Wireless power transfer systems Wireless power transfer systems (WPTSs) are
able to supply a load with the electric energy
absorbed by the grid without requiring any wired
connection between load and grid. WPTSs are made of two sections, transmitter and
receiver, as shown in Fig.7. Both of them consist of
a power converter, a coupling device and an
electronic control unit (ECU). Three different technologies can be utilized to
arrange a WPTS, exploiting the properties of the
electric [18], magnetic [16] [17] [19] or electromagnetic fields [20]. Magnetic-field
technology, adopted in the so-called inductive or
resonant coupling WPTSs, is most convenient for
medium- and high-power equipment because it transfers a much higher energy per unit of volume
than the electric-field technology, and does it with
much higher efficiency than the electromagnetic-field technology.
In magnetic field technology the coupling
devices are a pair of coils. The two coils are coupled each other and form an electrical transformer with
no iron core and an air-gap in between. Transmitter
power converter (TPC), fed by the grid, supplies the
transmitter coil with a high frequency current. By Faraday’s law of magnetic induction, energy is
transferred to receiver coil and, by means of the
receiver power converter (RPC), supplies the load.
5.2 Wireless battery chargers BCs based on WPTSs offer a number of
advantages compared to the conventional chargers;
indeed, wireless charging makes it i) unnecessary any plug, cable or outlet, ii) friendly the charging
process, iii) fearless the transfer of energy in any
environmental condition, and so on. The arrangement of a wireless BC is sketched in
Fig. 8. Transmitter coil is buried in the road and the
receiver one is located on-board the EV. When the
vehicle is properly parked over the transmitter coil, the two coils are coupled and energy can be
vg
+
Vb
AC/DCConverter
DC Link
DC/DCConverter
HFInverter
HFRectifier
DC Link
Fig. 5. Scheme of principle for battery chargers
CT
Dc
D1
D3
D2
D4
Lc
+Vdcvg
ig
DC Link
Fig. 6. Power factor controller (PFC)
Mains
Power Converter
Power Converter
CouplingDevice
CouplingDevice
Load
TRANSMITTER RECEIVER
ECU ECU
+
Fig. 7. WPTS structure.
Recent Advances in Energy, Environment and Financial Planning
ISBN: 978-960-474-400-8 36
transferred from the grid to the battery, which acts
as the load of the system.
5.3 Figures of merit Figures of merit (FOMs) are useful for sizing the
WPTS and analyzing its performance. Mainly two
figures of merit [21] are considered: efficiency η and power supply sizing factor (PSSF) α. Efficiency
is defined as the ratio between the power injected in
the battery and the active power supplied by the TPC. Power supply sizing factor is the ratio between
the power injected in the battery and the apparent
power supplied by the TPC. According to the
definition, η and α are given by (1)
𝜂 =𝑃𝐿
𝑃𝑆 𝛼 =
𝐴𝑆
𝑃𝐿 (1)
The variables in (1) are PL, which is the active
power absorbed by the load, PS and AS, which are
the active and apparent power delivered by the TPC.
5.4 Inductive coupling WPTSs Magnetic WPTSs are divided into inductive
coupling WPTSs and resonant coupling WPTSs. An
inductive coupling WPTS is like a transformer but,
differently from a conventional arrangement, here the coils do not share a common core.
The circuital schemes of the inductive WPTS is
shown in Fig. 9, where V̅S is the voltage generator equivalent to the TPC, RS is its internal resistance,
LT and LR are the self-inductances of the transmitter
and receiver coils, I̅T and I̅R are the currents in the
transmitter and receiver coils, RL is the load
resistance, I̅L is the load current and M is the mutual
inductance between the two coils. From the voltage
equations of the transmitter and receiver sections, given by (2),
{�̅�𝑆 = 𝑍�̇�𝐼�̅� + 𝑗𝜔𝑀𝐼�̅�
−𝑗𝜔𝑀𝐼�̅� = 𝑍�̇�𝐼�̅�
(2)
the expressions of the FOMs for inductive WPTS can be readily obtained and are [21]
𝜂𝐼 = 𝑘2𝑄𝑅𝑄𝑇
1+𝑄𝑅2+𝑘2𝑄𝑅𝑄𝑇
(3)
𝛼𝐼 =√(1+𝑄𝑅
2)[(1+(𝑘2−1)𝑄𝑅𝑄𝑇)2+(𝑄𝑅+𝑄𝑇)2]
𝑘2𝑄𝑅𝑄𝑇 (4)
where QT and QR are the quality factors of the
transmitter and receiver and k is the coupling
coefficient, defined according to
𝑄𝑇 =𝜔𝐿𝑇
𝑅𝑆; 𝑄𝑅 =
𝜔𝐿𝑅
𝑅𝐿 ; 𝑘 =
𝑀
√𝐿𝑇𝐿𝑅 (5)
Graphs of the FOMs as a function of QR for
QT=300 are reported in Fig. 10. It can be observed
how high efficiency of power transfer can be obtained only if QR=1 and that, in any case, the TPC
must be sized for a power at least five times bigger
than the power transferred to the battery.
5.5 Resonant coupling WPTSs In resonant coupling WPTSs, the inductances of
the coils are compensated by capacitors inserted
either in series or in parallel to the coils and by tuning the resonant frequency of the coil-capacitor
branches to the working frequency of the TPC. Four
fundamental topologies of resonant WPTSs can be arranged: series-series (SS), series-parallel (SP),
parallel-series (PS) and parallel-parallel (PP),
depending on how the capacitors are inserted in the
two sections. In [22] performances of the four topologies have
been analyzed and their FOMs derived. It resulted
that the compensation at the transmitter side reduces the PSSF while compensation at the receiver side
improves the efficiency of the WPTS. Best
efficiency performance is achieved by SS topology,
RS IT
VS VRj wM IR - jwM IT
+++
LR
RL
IRLT
VT
Fig.9. Schematics of inductive WPTS
T r a n s . c o i l
R e c e i v . c o i l
R e c t i f i e r
G r i d
H F I n v e r t e r
R e c t i f i e r & C h o p p e r
B a t t e r yP a c k
Fig. 8. Wireless battery charging
Recent Advances in Energy, Environment and Financial Planning
ISBN: 978-960-474-400-8 37
whose circuital scheme is reported in Fig. 11, characterized by the following FOMs
𝜂𝑆𝑆 = 𝑘2𝑄𝑅𝑄𝑇
1+𝑘2𝑄𝑅𝑄𝑇; 𝛼𝑆𝑆 = 1+𝑘2𝑄𝑅𝑄𝑇
𝑘2𝑄𝑅𝑄𝑇 (6)
The FOMs in (6) are graphed in Fig.12. The
graphs show that implementation of resonant WPTS increases the efficiency and decreases the PSSF
compared to inductive WPTS and that these
enhancements are nearly unaffected by QR, provided that it is bigger than 1.
5.6 Coil coupling From (3) - (6) it appears that FOMs of the coil
coupling is strictly dependent on the coupling coefficient k. Therefore, design of the coils has a
crucial role in WPTSs and the usage of different coil
structures is well investigated in literature [23], [24]
with the aim of maximizing k and reducing its dependence on coil distance and/or misalignment.
To enable higher coupling coefficient and to
direct the magnetic flux lines in proper direction, ferrite cores are used. Ferrite cores are utilized
because of their properties of high magnetic
permeability, useful in directing the flux, and low
electrical conductivity that mitigates the magnetic losses under high-frequency flux cycles.
Different ferrite core structures are illustrated in
literature, for example, in [22], cores having the I, C
and E sections shown in Fig. 13, have been tested
and compared.
5.7 Power electronics requirements In 2013, SAE International J2954™ Task Force
for Wireless Power Transfer of Light Duty, Electric
and Plug-in Electric Vehicles, standardized the working frequency of WPTSs to 85 kHz. This
frequency is much higher than the frequency of the
electrical grid so that it is generated by a high frequency inverter (HFI) that constitutes the output
stage of the TPC. As it happens with conventional
BCs, the input stage of the TPC is formed by an
AC-DC converter that can be a simple diode rectifier, a PFC circuit or an active rectifier.
Requirements for the power switches used to
build the HFI are much more demanding than those posed by conventional industrial inverters because
of the higher commutation frequency. In order to
reduce losses and increase efficiency, WPTSs take advantage of modern power switches built with
wide band gap (WBG) materials [26], [27].
Compared to Si, the WBG materials have higher
junction operating temperature, higher thermal conductivity and lower thermal expansion
coefficient, where the latter two properties make the
packaging of the WBG power devices more reliable over a larger range of temperatures. Moreover, a
WBG junction has a high breakdown field that
benefits the WBG power devices of a thinner
voltage blocking layer so that they have a lower on-
(a)
(b)
Fig.10. FOMs of inductive WPTS (a) Efficiency (b) PSSF
10-2
10-1
100
101
102
0.2
0.4
0.6
0.8
Effic
iency
QR
10-2
10-1
100
101
102
101
102
103
104
Pow
er
supply
siz
ing facto
r
QR
RS IT
VS VRjwMIR -jwMIT
+++ LR
RL
IRLT
CRCT IL
Fig.11. Schematics of resonant SS WPTS
Fig. 13. Sections of I (blue), C (blue+yellow), and E (blue+yellow+green) cores.
(a)
(b)
Fig.12. FOMs of resonant WPTS (a) Efficiency (b) PSSF
10-2
10-1
100
101
102
0.2
0.4
0.6
0.8
1
Effic
iency
QR
10-2
10-1
100
101
102
101
Pow
er
supply
siz
ing facto
r
QR
Recent Advances in Energy, Environment and Financial Planning
ISBN: 978-960-474-400-8 38
resistance and, consequently, lower conduction
losses. The thinner blocking layers and the higher
drift velocity of the free charges reduce the parasitic
capacitance of the WBG power devices and this gives them the ability of switching at very high
frequencies.
These characteristics can be profitably exploited also in the designing of the rectifier embedded in the
RPC, given that it operates at the same frequency of
the HFI. On the other hand, the DC-DC converter that supply the battery does not require particular
components to be built because its switching
frequency is usually lower.
6 In-moving Wireless Charging After development of static WPTSs, the next step
is to make a WPTSs able to charge EVs while they are moving on the road. Such a technology would
improve easiness of charging and reduce the cost of
EVs. Indeed, the most costly component of an EV is
the battery. A long range EV needs a big battery which is expensive and heavy. The ability to charge
the EV while it is moving enable the use of a
smaller and cheaper battery, achieving a long driving range without any waste of time at the
charging station.
An in-moving WPTS consists basically of a magnetic WPTS where a special track (instead of
the transmitter coil) is built under the road surface.
This track produces a magnetic field which is linked
with receiver coil. Like in static WPTS, power is transferred inductively from transmitter track to the
receiver coil and higher efficiency is achieved if the
track and the receiver coil resonate with suitable capacitors at the HFI frequency.
The main requirements of in-moving WPTSs are:
i) simple construction for ease of maintenance, ii)
good field focusing towards receiver coils for high efficiency, iii) ability of self-compensation when
multiple receiver coils draw power from the track,
iv) containment of electromagnetic field (EMF) under defined limit around the track for pedestrian
safety, and v) low overall cost. Different in-moving
WPTSs designs have been proposed by many researchers to satisfy these requirements.
6.1 On line electric vehicle Korea Advanced Institute of Science and
Technology (KAIST) proposed online electric vehicle (OLEV) which passed through many
generations as different shapes of ferrite cores such
as U-type, E-type and I-type have been used [28].
Present generation uses I-type core for transmitter
track and plate core for receiver coil. Supply lines
are twisted to each other (Fig. 14(a)) and creates alternating poles in the track (Fig. 14(b)), this
arrangement reduces leakage inductance and
unwanted EMF. In the receiver side, there is a pair of receiver coils which covers consecutive poles to
complete the magnetic path.
The main asset of this arrangement is the use of
narrow transmitting track and wide receiver coils [29]. The transmitting poles produce magnetic field
which spreads in wide area towards the coils and
this effect is helpful to achieve lateral tolerance in the placement of the EV over the track. Moreover,
the series of magnetic poles with alternating polarity
helps to reduce unwanted EMF and leakage inductance. The measured power efficiency of the
prototype resulted 74% with 20 cm air gap.
6.2 Moving field WPTS An alternative to the installation and the
supplying of a long transmitter track is to have
multiple coils deployed along the vehicle path and a
suitable switching arrangement to supply them one
by one, as sketched in Fig. 15. This solution is denoted as moving field WPTS [30], [31]. In the
Power supply rail
Air-gap
Lateral displacement
Pickup plate
Pickup Moving direction
Is
Pickup coil (+) Pickup coil (-)
Power supply cables Bottom plate
Top view
Side view
Cross-sectional view
Power supply rail
Pickup
Magnetic flux
Magnetic PoleN
Magnetic PoleS
Magnetic PoleN
Magnetic PoleS
Fig. 14. A basic overview of OLEV.
Ls , Cs
Cp1 Cp2 Cp3 Cp4 Cp5
Sp1 Sp2 Sp3 Sp4
Lp1 Lp3Lp2 Lp4
+V0
-V0
DC power lines
SL1 SR1 SL2 SL3 SL4SR2 SR3 SR4
Fig. 15 Schematic of the Moving Field IPT system
Recent Advances in Energy, Environment and Financial Planning
ISBN: 978-960-474-400-8 39
figure, each of the transmitter coils is denoted by its
self-inductance Lpi while the receiver coil and the
relevant compensating capacitor are denoted as Ls
and Cs, respectively. Switch Spi alternatively connects one terminal of the ith coil to two voltage
lines, one positive, denoted as +V0 and the other
negative, denoted as -V0, so that a high frequency square wave voltage is applied to the coils.
According to vehicle position, transmitter coils
get activated one by one. Smooth transition of current from the jth coil to the (j+1)th is carried out
by means of the switches SRj and SL(j+1) and of the
capacitor Cp(j+1). The length of receiver coil is twice
that of a transmitter coil to close the magnetic path maintain continuity in power transfer.
6.3 Parallel coil compensation Like moving field WPTS, parallel coil
compensation WPTS relies on many transmitter coils distributed along the vehicle path, but in this
case they are connected in parallel and supplied by a
single inverter, as shown in Fig. 16. The coils have high self-inductance and the supply frequency is
also high, so that only a low current flows in the
coils in normal conditions. When the receiver coil
approaches a transmitter coil, its reactance is reflected into the transmitter side. The receiver coil
is connected to a capacitor and they are tuned so
that, at the HFI frequency, their reflected impedances compensate completely the transmitting
coil reactance.
Reactance compensation causes an increase of the current in the transmitter coil that, in turn, builds
up a strong magnetic field and enables the power
transfer [32], [33].
Compensation using the reactance of receiver coil is an attracting solution to eliminate switches
and sensors otherwise required to supply only the
transmitter coil faced with the receiver one. Moreover, since the magnetic field generated by a
transmitter coil is very low when no receiver coil is
coupled, unwanted EMF remains inherently under control.
On the other hand, this technique requires to
design the TPC for an apparent power much higher
than the active power transferred to the battery,
therefore some different series-parallel
combinations are under study to achieve lower PSSF and higher efficiency.
7 Conclusions The paper deals with the latest achievements in
the field of EV battery charging. At first
conventional BCs, which are already available in the
market and have been installed in a number of cities around the world, are considered. An overview is
given about their architecture and about the
standards released by international bodies about power levels and connection means between the
EVs and the recharging stations.
Subsequently, static wireless BCs are dealt with. Nowadays only few firms are proposing this
solution on the market, mostly with low power
product aimed at domestic charging. A description
of their working principles and a comparison of the features of the inductive and of the resonant
chargers are given, showing as the resonant
architecture outperform the inductive one from the point of view of efficiency and sizing power of the
TPC.
Lastly, in-moving wireless BCs are considered. Even if they are still object of research, the
performances of first prototypal plants suggest that
they will have an increasing role in freeing the EVs
from the limits of the available battery charging technology.
References:
[1] A.Y.Saber and G.K.Venayagamoorthy, “One
million plug-in electric vehicles on the road by
2015,” Proc. IEEE Intell. Trans. Syst. Conf, 2009, pp. 141–147.
[2] C.C.Chan, ‘‘The state of the art of electric,
hybrid, and fuel cell vehicles,” Proc of IEEE, vol. 95, no. 4, pp. 704-718, 2007.
[3] C.C.Chan and K.T.Chau, “An overview of
power electronics in electric vehicles,” IEEE Transactions on Industrial Electronics, vol. 44,
no. 1, pp. 3-13, 1997.
[4] M.C.Kisacikoglu, B.Ozpineci and L.M.Tolbert,
“Examination of a PHEV bidirectional charger system for V2G reactive power compensation”,
Proc. of IEEE Applied Power Electronics Conf.
and Exposition, 2010, pp. 458-464. [5] A.Emadi, Y.J.Lee and K.Rajashekara, “Power
electronics and motor drives in electric, hybrid
electric, and plug-in hybrid electric vehicles,”
Inverter
Pickup coil
Strong magnetic field at coupled coil
Weak magnetic field at uncoupled coils
Supply line
Transmitting coils
Fig. 16. Basic conceptual layout of magnetic field containment
technique of IPT
Recent Advances in Energy, Environment and Financial Planning
ISBN: 978-960-474-400-8 40
IEEE Transactions on Industrial Electronics,
vol. 55, no. 6, pp. 2237-2243, 2008.
[6] D.P.Tuttle and R.Baldick, “The evolution of
plug-in electric vehicle grid interactions,” IEEE Transactions on Smart Grid, vol. 3, no. 1, pp.
500–505, 2012.
[7] A.Khaligh and S.Dusmez, “Comprehensive topological analyses of conductive and
inductive charging solutions for plug-in electric
vehicles,” IEEE Transactions on. Vehicular. Technology, vol. 61, no. 8, pp. 3475–3489,
2012.
[8] G.A.Covic and J.T.Boys, “Inductive Power
Transfer,” Proc. of IEEE, vol. 101, no. 6, pp.1276-1289, 2013.
[9] Ji.Kim, Jon.Kim, S.Kong, H.Kim, I.Suh,
N.Suh, D.Cho, Jou.Kim, and S. Ahn, “Coil Design and Shielding Methods for a Magnetic
Resonant Wireless Power Transfer System,”
Proc. of the IEEE, vol. 101, no. 6, pp.1332-1342, 2013.
[10] O.Worley and D.Klabjan, “Optimization of
battery charging and purchasing at electric
vehicle battery swap stations,” Proc. of IEEE Vehicle Power and Propulsion Conference
(VPPC), 2011, pp. 1-4.
[11] http://en.wikipedia.org/wiki/SAE_J1772. Retrieved on 13/10/2014.
[12] R.C.Cope and Y.Podrazhansky, “The art of
battery charging,” Proc. of IEEE. Battery
Conference, 1999, pp. 233–235. [13] SAE International, “SAE’s J1772 ‘combo
connector’ for ac and dc charging advances
with IEEE’s help,” [Online]. Available http://ev.sae.org/article/10128.
[14] CHAdeMO, “What is CHAdeMO?” (2010).
[Online].Available:http://chademo.com/01_What_is_CHAdeMO.html.
[15] “New SAE International Quick-Charge EV
Connector Standard Gaining Momentum”
(Press release). SAE International. 2011-08-04. Retrieved on 13/10/2014.
[16] S.Y.R.Hui, W.X.Zhong and C.K.Lee, “A
critical review on recent progress of mid-range wireless power transfer,” IEEE Transactions on
Industrial Electronics, vol. 29, no. 9, pp. 4500-
4511, 2014. [17] L.Jiangui, Y.Qingxin, C.Haiyan and W.Junhua,
“Study and application of contact-less electrical
energy transmission system,” Proc. of IEEE
Vehicle Power and Propulsion Conference, 2008, pp. 1-4.
[18] C.Y.Xia, C.W.Li, and J.Zhang, “Analysis of
power transfer characteristic of capacitive power transfer system and inductively coupled
power transfer system,” Proc. of Int.
Conference on Mechatronic Science, Electric
Engineering and Computer, 2011, pp. 1281-
1285. [19] R.J.Parise, “Model to predict performance of
all electric transportation with wireless power
beams,” Proc. of Energy Conversion Engineering Conference, 2002, pp.731-736.
[20] W.C.Brown, “The history of power
transmission by radio waves,” IEEE Trans. on microwave theory and techniques, vol. MTT-
32, n. 9, pp. 1230-1242, 1984.
[21] K.N. Mude, M. Bertoluzzo and G. Buja,
“Design of contactless battery charger for electric vehicle, Proc. of IEEE AFRICON,
2013, pp.1099-1104.
[22] M.Bertoluzzo, K.N.Mude, and G.Buja, “Characteristic Evaluation of Wireless Battery
Chargers for Electric Vehicles,” Proc. of IEEE
Electromotion, 2013, pp. 1-5. [23] S.Mutashar, M.A.Hannan, A.S.Salina, and
A.Hussain, “Design of spiral circular coils in
wet and dry tissue for bio-implanted micro-
system applications,” Progress In Electromagnetic Research, Vol. 32, pp.181-
200,2013
[24] J.T.Boys and G.A.Elliot, ”An appropriate magnetic coupling coefficient for the design
and comparison of ICPT pickups,” IEEE Trans.
on Power Electronics, vol. 22, no. 1, pp. 333-
335, 2007. [25] M.Chigira, Y.Nagatsuka,Y.Kaneko, S.Abe,
T.Yasuda, and A. Suzuk, “Novel Core
Structure and Iron-Loss Modeling for Contactless Power Transfer System of Electric
Vehicle,” Electrical Engineering in Japan, Vol.
184, no. 2, 2013. [26] H.Zhang, L.M.Tolbert and B.Ozpineci, “Impact
of SiC devices on hybrid electric and plug-in
hybrid electric vehicles,” IEEE Trans. on
Industry Applications, vol. 47, no. 2, pp. 912-921, 2011.
[27] H.Jain, S.Rajawat and P.Agrawal,
“Comparision of wide band gap semiconductors for power electronics
applications,” Proc. of Int. Conf. on
MICROWAVE, 2008, pp.878-881. [28] S.Lee, J.Huh, C.Park, N.S.Choi, G.H.Cho, and
C.T.Rim, “On-Line Electric Vehicle using
Inductive Power Transfer System,” Proc. of
IEEE Energy Conversion Congress and Exposition (ECCE), 2010, pp. 1598 – 1601.
[29] J.Huh, S.W.Lee, W.Y.Lee, G.H.Cho, and
C.T.Rim, “Narrow-Width Inductive Power Transfer System for Online Electrical
Recent Advances in Energy, Environment and Financial Planning
ISBN: 978-960-474-400-8 41
Vehicles,” IEEE Transactions on Power
Electronics, vol. 26, no. 12, pp. 3666 - 3679,
2011.
[30] J.A.Russer, M.Dionigi, M.Mongiardo, and P.Russer, “A Moving Field Inductive Power
Transfer System for Electric Vehicles,” Proc.
of IEEE European Microwave Conference (EuMC), 2013, pp. 519-522.
[31] J.A.Russer, M.Dionigi, M.Mongiardo, and
P.Russer, “A Bidirectional Moving Field Inductive Power Transfer System for Electric
Vehicles,” Proc. of 11th International
Conference on Telecommunication in Modern
Satellite, Cable and Broadcasting Services
(TELSIKS), 2013, pp. 17-20.
[32] K.Lee, Z.Pantic, and S.M.Lukic, “Field
containment in dynamic wireless charging systems through source-reciever interaction,”
In proc. of IEEE Energy Conversion Congress
and Exposition (ECCE), 2013, pp. 3658- 3663. [33] K.Lee, Z.Pantic, and S.M.Lukic, “Reflexive
Field Containment in Dynamic Inductive
Power Transfer Systems”, In proc. of IEEE Transactions on Power Electronics, vol. 29, no.
9, pp. 4592 – 4602, 2014.
Recent Advances in Energy, Environment and Financial Planning
ISBN: 978-960-474-400-8 42
