Download II. Alternative Fuel and Fuel Cell Vehicle

International Journal of Science, Engineering and Technology Research (IJSETR)
Volume 1, Issue 1, July 2012
Simulation of Electric Vehicle Supplied by
PEM Fuel Cell with Lithium-ion Battery
Ei Sandar Aung, Zaw Lin Htun
Abstract - One of the means of transportation used for the
mobility of people in the world is a vehicle. Factors such as
global warming, dwindling fossil fuel reserves, and energy
security concerns combine to indicate that a replacement for the
internal combustion engine (ICE) vehicle is needed. To solve this
problem, the hydrogen fuel cell-powered automobile is at the top
of the list of future technologies. Fuel cell vehicles (FCVs) have
the potential of being highly efficient compared to current
vehicles. Fuel cells offer clean, quiet and efficient electrical
energy. So, fuel cell vehicles are a promising technology in
future vehicle development for they can eliminate the
environmental pollution from vehicles completely. So, the
electric system of FCV is studied. In the various types of
automobile, the essential equipment mounted on the system are
fuel cell stack, battery pack, electric motor, controller, switch,
sensor, electrical lights, etc. which are connected in electric
system. This paper aims to reduce the dangerous and accidental
cases. Moreover, simulation results of electrical system for FCV
by using Matlab/Simulink are also described.
Index Terms— Fuel cells, Hydrogen, Oxygen, Controller,
DC_DC converter, Battery, Hybrid electric vehicle
I. INTRODUCTION
Automobiles are the integral part of daily life as it
provides freedom of mobility. Automotive industries
‘solution to this problem is the electric vehicles (EVs), which
are zero emission vehicles, and the hybrid electric vehicles
(HEVs), which emit low amounts of environmentally harmful
gases such as CO, CO2 and NOx.
Electric vehicles require batteries as the energy source.
Batteries need to be recharged after electric vehicles operate
for a few hours. [1] Pure electric cars have demerits such as a
short driving distance, long recharging time, and high cost.
Thus, fuel cell vehicles (FCV), which have a longer distance
and higher transportation capability than pure electric cars.
FCV is one type of electric vehicles with fuel cell system
which is the main generating unit. A hydrogen-based, fuel cell
provides the power to give an electric vehicle the same range
as a gasoline powered vehicle. In this case, a fuel cell stack
generates the electricity by combination of hydrogen and
oxygen. [2] The products of the electrochemical process are
electricity, heat and water. Polymer Electrolyte Membrane
Fuel Cell (PEM Fuel Cell) is popular and suitable used in
vehicles. It operates within a range of relatively low
temperatures, has higher efficiency than combustion engines,
is very quiet and produces no emissions. [3]
Manuscript received Oct 15, 2011.
Ei Sandar Aung, Department of Electrical Power Engineering,
Mandalay Technological University, (e-mail: [email protected]).
Mandalay, Myanmar, 09-425269129
Zaw Lin Htun, Department of Electrical Power Engineering,
Mandalay Technological University, Mandalay, Myanmar, 09-2955560
The fuel cell vehicle, generally, contains a proton exchange
membrane (PEM) fuel cell stack with its accessories, a
DC/DC converter, battery pack, motors and motor
controllers.
II.ALTERNATIVE FUEL AND FUEL CELL VEHICLE
There are different types of alternative fuel vehicles that
are being developed, which differ on the type of propulsion
used. An electric vehicle uses only batteries and motor(s) to
drive the vehicle. A hybrid electric vehicle uses both batteries
and gas to obtain efficiency and reduced emission. Fuel cell
vehicles use fuel cells and batteries to power the cars, without
harmful emission.
A. Electric Vehicle
An electric vehicle consists of a battery that provides
energy, an electric motor that drives the wheels and a
controller that regulates the energy flow to the motor. [4] In
the early years of automotive development, electric vehicles
competed with the Internal Combustion Engine (ICE). The
advantage of the electric vehicle was that it was quiet, clean,
relatively powerful, and did not require a crank to start.
Although the range of the electric vehicle was limited, long
distance travel was not a major consideration since most autos
were owned by the wealthy and were used within the confines
of the city.
Electric
Motor
Controller
Battery
Transmission
Wheels
Figure 1. Power-train in electric vehicle
Figure 1 is a block diagram of a typical EV. Electric
vehicles [4] use electric motors for propulsion. The demise of
the original electric vehicles was largely due to the limitations
of its power source. Batteries in those days had low levels of
energy per unit weight and time. Batteries usually need
several hours to fully charge. In addition, the electric motors
used to drive the vehicle, in the early days, were heavy and
inefficient, further compounding the problem.
B. Hybrid Electric Vehicle
Any vehicle that has more than one power source can be
classified as hybrid electric vehicle (HEV), but here the term
is used for vehicles that combine electric drive with a heat
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International Journal of Science, Engineering and Technology Research (IJSETR)
Volume 1, Issue 1, July 2012
engine using fossil-fuel energy sources. HEVs use both
electric motor with batteries and an IC engine to power the
vehicle. Currently, there are two main configurations of
components of a hybrid system which are called series and
parallel hybrids.
Fuel Cell
Converter
Battery
Generator
Controller
Electric
Motor
Transmission
Electric Motor
Wheels
Engine
Battery
Transmission
Figure 4. Fuel Cell Vehicle Configuration
III. FUEL CELL STACK AND WORKING PRINCIPLE
Wheels
Figure 2. Power-train in Series Hybrid Electric Vehicle [5]
In the series hybrid, the mechanical output of the heat
engine is used to generate electrical power by means of a
generator, similar to that used in a conventional car, shown in
Figure 2. The generator produces sufficient electrical power
to propel the car. It is possible to run the engine at close to
constant speed and share its electrical output between
charging the battery and supplying the power to drive the
wheels.
Engine
Battery
Transmission
Controller
Wheels
The fuel cells used in this vehicle group are PEM fuel
cells from, containing six sub-stacks, one of which consists of
140 cells, as shown in Figure 5. The current configuration has
the six sub-stacks divided into two parallel groups of the three
sub-stacks in series. This configuration yields a maximum of
315 V as shown in Figure 5. This value was selected because
it is relatively close to the 288 V of the battery pack. The
alternate configuration consists of the six sub-stacks being
divided into three parallel groups of two sub-stacks in series.
This configuration would have a maximum output of 210 V,
which is too far below the nominal level for the battery packs.
The cells’ peak power is 14.25 kW per sub-stack, and
85.5kW total .Fuel cell efficiencies vary between 50 percent
at 0.6V/cell and 67 percent at 0.8V/cell. Specific energy is
dependent on the quantity of hydrogen available to feed the
fuel cell. current density is 0.94A/cm at 0.6V/cell.
Electric Motor
Figure 3. Power-train in Parallel Hybrid Electric Vehicle [5]
An HEV with a parallel configuration has both a
mechanical connection between the engine and transmission
as in conventional vehicles and an electric motor coupled to
the transmission. These two drive-trains are independent of
each other as shown in Figure 3. The engine is smaller than
would be used for steady highway driving. The battery
provides auxiliary power for both acceleration and
hill-climbing, and also accepts regenerative braking energy.
C. Fuel Cell Vehicle
A fuel cell vehicle can be considered as a series HEV
using hydrogen as the alternative fuel. Electricity for both the
on-board batteries and the electric motor is supplied by the
fuel cell that works like the generator in series HEVs. Fuel
cell vehicles are the promising technology for they can
eliminate the environment pollution from vehicles
completely. A fuel cell is much more efficient than
conventional energy sources, because it converts chemical
energy of the fuel directly into electricity without going
through an intermediate combustion step.
Figure 5. 315 Volts Fuel Cell Configuration
The core of the fuel cell system is the PEM fuel cell stack.
As shown in Figure 5, the PEM fuel cell is composed by a fuel
electrode as the anode and an oxidant electrode as the
cathode. The two electrodes are made of porous carbon
materials. They are separated by an ion-conducting polymer
electrolyte in the form of a thin plastic sheet. This polymer
electrolyte, the proton exchange membrane, has the
proprieties of both a proton conductor and an electron
insulator. The membrane is impermeable to air. Integrated
assembly is called the membrane electrode assembly (MEA).
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International Journal of Science, Engineering and Technology Research (IJSETR)
Volume 1, Issue 1, July 2012
Charging
Discharging
Relay
Switch
Battery
Fuse
Box
Fuel Cell
Controller
Auxiliary
System
Fuel Cell
Stack
DC-DC
Converter
Power
Inverter
Generating
Charging
Electric
Motor
Distribution
Figure 7. Overview of Electric System Used in Fuel Cell Vehicle
Figure 6. Basic Principle of PEM Fuel Cell
A PEM fuel cell uses a simple chemical process to
combine hydrogen and oxygen into water, producing electric
current in the process. As illustrated in the diagram, it works
something like electrolysis in reverse:
 At the anode the hydrogen molecules give up
electrons and form hydrogen ions, a process which is
made possible by the platinum catalyst.
 The electrons travel to the cathode through an external
circuit, producing electrical current. This current can
perform useful work by powering any electrical
device (such as an electric motor).
 The proton exchange membrane allows protons to
flow through, but stops electrons from passing
through it. As a result, while the electrons flow
through an external circuit, the hydrogen ions flow
directly through the proton exchange membrane to
the cathode, where they combine with oxygen
molecules and the electrons to form water.
 In this way, hydrogen fuel’s natural tendency to
oxidize and form water is utilized to produce
electricity and useful work.
 No pollution is produced and the only resulting
products are water and heat. The chemical reactions
in the PEM fuel cell can be described as:
Anode: 2H2→4H++4e(3.1)
Cathode: O2+4H++4e-→2H2O
(3.2)
Overall: 2H2+ O2→2H2O
(3.3)
Equations 3.1, 3.2, and 3.3 are used to determine the
amount of hydrogen, oxygen and water needed or produced in
the reaction.
After completion of the reaction, the rest of hydrogen
exhausts out at the hydrogen-side out port, and air passes out
through air-side out port with water vapor. Water vapor
produced at the air side is then separated from the air gases
outside the cell with a water separator for recovery.
IV. OVERVIEW OF ELECTRIC SYSTEM USED IN FUEL CELL
VEHICLE
Electric system and its security play an important role in
fuel cell vehicle construction. Electric vehicle depends on
electricity for generating system, charging system, lighting
system and others. The electric vehicle system includes
generating system, charging system, power distribution
system, lighting system and other electrical systems. The
overview block diagram of electric system used in fuel cell
vehicle is shown in Figure 7.
A. Permanent Magnet Synchronous Motor
The electrical motor is a 288 V, 100kW interior
permanent magnet synchronous motor (PMSM) with the
associated drive (based on AC6 blocks of the
SimPowerSystems Electric Drives library). This motor has 8
pole and the magnets are buried (salient rotor's type). A flux
weakening vector control is used to achieve a maximum
motor speed of 12,500 rpm.
PMSM is equivalent to an induction motor, where the air
gap magnetic field is constant. PMSM offer a number of
advantages in designing modern motion control systems. A
PMSM is largely maintenance free, which ensures the most
efficient operation. PMSM has speed or torque characteristics
ideally suited for direct drive of large horsepower, low rpm
loads.
B. DC-DC Converter
The DC/DC converter is voltage-regulated. The DC/DC
converter adapts the low voltage of the battery (200 V) to the
DC bus which feeds the AC motor. A DC-DC converter is a
device that accepts a DC input and produces a DC output
voltage. It would be step-down (Bust) converter to lower
input voltage, or step-up (Boost) converter to increase input
voltage.
C. Lithium-ions Battery
• The battery is applied a 13.9 Ah, 30 kW lithium-ion
battery stack. During cell discharge, lithium ions (Li+) are
released from the negative electrode that travels through an
organic electrolyte toward the positive electrode. In the
positive electrode, the lithium ions are quickly incorporated
into the lithium compound material. The process is
completely reversible.
During cell charge operation, lithium ions move in the
opposite direction from the positive electrode to the negative
electrode. Lithium-ion batteries have high specific energy,
high specific power, high energy efficiency, good
high-temperature performance, and low self-discharge. The
components of Li-ion batteries are also recyclable. These
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International Journal of Science, Engineering and Technology Research (IJSETR)
Volume 1, Issue 1, July 2012
characteristics make Li-ion batteries highly suitable for EV
and other applications of rechargeable batteries. [6]
V. SIMULATION OF ELECTRIC VEHICLE SUPPLIED BY
PEM FUEL CELL
Fuel cell vehicle powertrain is shown in figure. This
model shows a multi-domain simulation of a FCV power train
based on SimPowerSystems and SimDriveline. The motive
power of FCV is an electric motor, in order to increase the
drive train efficiency and reduce air pollution. It provides the
advantages of the electric motor drive.
A .Fuel Cell Stack Parameters Determination
For the simplified model, four parameters (Eoc, V1, i0 ,
NA) are to be determined which requires at least four
simultaneous equations. The following sets of equations are:
(1)
V1  E oc  NA ln i 0  R ohm I nom
Figure 10. FCV Electrical Subsystem/ Fuel Cell Stack
I

(2)
Vnom  E oc  NA ln  nom   R ohm I nom
 i0 
(V  Vnom )( I max  1)  (V1  Vmin )( I nom  1)
(3)
NA  1
ln( I nom )( I max  1)  ln( I max )( I nom  1)
R ohm 
i0


V1  Vnom  NA ln( I nom )
I nom  1
(4)
 V1  E oc  R oh m 


NA

e
(5)
nFVnom
100
h(H 2 O(gas)) N
(6)
Figure 11. Fuel Cell Stack Parameter
Figure 8. Fuel Cell Vehicle
Figure 9. Fuel Cell/Electrical Subsystem
Figure 12. Fuel Cell Vehicle/ Electrical Subsystem/Electrical Measurement
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International Journal of Science, Engineering and Technology Research (IJSETR)
Volume 1, Issue 1, July 2012
Figure 17. Simulation Waveforms of the Scope of Electrical Measurement
Figure 13. Fuel Cell Vehicle/Energy Management Subsystems
Figure 18. Simulation Waveforms of the Scope of Energy Management
System
Figure 14. Fuel Cell Vehicle/Energy Management Subsystems/Power
Management
Figure 15. Simulation Waveforms of the Scope of Car
VI. DISCUSSIONS AND CONCLUSION
The large number of automobiles in used around the
world has caused and continued to cause serious problems for
environment and human life. The construction of the fuel cell
vehicle includes electric motors, power electronics,
embedded power train controller, energy storage system. So,
the electric system of fuel cell vehicle is simulated. The
electric system involves generating system, charging system
and power distribution system. In generating system, battery
pack and fuel cell stack are used for operating the system. The
transportation system is very important to the entire world
today. As the limitation of fossil fuels and the high
consumption rate of this energy for transportation, inclination
of vehicle industry toward other sources of
energy is
inevitable. So fuel cell vehicles (type of electric vehicle) is a
good solution.
REFERENCES
[1]
I.J.M. Besselink, P.F. van Oorschot, E. Meinders, and H. Nijmeijer,
Design of an efficient, low weight battery electric vehicle based on a
VW Lupo 3L, Battery, Hybrid and Fuel Cell Electric Vehicle
Symposium & Exhibition, Shenzhen, China : 2010.
[2]
Frano Barbir, PEM Fuel Cells -Theory and Practice ( Elsevier
Istambul 2005) 1-14.
Nathan J. English and Ramesh K. Shah, Technology Status And
Design Overview Of A Hybrid Fuel Cell Engine For A Motorcycle,
Second International Conference on Fuel Cell Science,
Engineering and Technology, 2004 - 2457.
C. C. Chan and K. T. Chau. Modern Electric Vehicle Technology.
Oxford University Press, New York, 2001.
Iqbal Husain, 2003, "Electric and Hybrid Vehicles Design
Fundamentals", Printed Edition, CRC Press LLC, London, UK.
[3]
[4]
[5]
Figure 16. Simulation Waveforms of the Scope of PM Synchronous Motor
Drive
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International Journal of Science, Engineering and Technology Research (IJSETR)
Volume 1, Issue 1, July 2012
[6]
Ron Hodkinson and John Fenton, 2001, "Lightweight
Electric/Hybrid Vehicle Design", Reed Educational and
Professional Publishing Ltd, Butterworth-Heinemann, Oxford.
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