Modelling and Simulation of Fuel Cell Based System for Residential Applications

This episode covers a project undertaken during the third year of my undergraduate studies at Sri Ramanathan Engineering College, Tiruppur. The project involved the modelling and simulation of fuel cell based system for residential load. The report focuses on modeling, controlling and the simulation of PEMFC based power supply system for residential applications. Simulation of closed loop control of fuel cell based system is carried out in MATLAB-SIMULINK environment. Life cycle costing analysis is done to check economic feasibility of the entire system.

CARRIER EPISODE 2
MODELLING AND SIMULATION OF FUEL CELL BASED SYSTEM FOR
RESIDENTIAL APPLICATIONS.

CE2.1 INTRODUCTION.
CE2.1.1 CHRONOLOGY
This carrier episode covers a project undertaken during the third year of my undergraduate
studies at Sri Ramanathan Engineering College, Tiruppur. The duration of this project was 3
months from 12thJanuary, 2013 to 14th April, 2013. This episode contains the details of the
project work named “Modelling and Simulation of Fuel Cell Based System for Residential
Applications” as a partial fulfillment regarding to the requirements of Anna University, Chennai.
CE2.1.2 LOCATION & ORGANIZATION
Organization Name: - Sri Ramanathan Engineering College,
Affiliated to Anna University, Chennai
Location : - Triuppur, Tamil Nadu, India
CE2.1.3 POSITION
Memberof the Project.
CE2.2 BACKGROUND.
CE2.2.1 NATURE OF THE PROJECT
The nature of overall project focus on modelling, controlling and the simulation of
PEMFC (Proton Exchange Membrane Fuel Cell) based power supply for residential applications.
Renewable energy technologies has an excellent potential in India as it increase the
present power generation. Amongst all the technologies of renewable energy, the fuel cell
based power generation is obtaining extreme popularity in the residential sector mostly due to
high efficiency, excellent part load performance, cleanliness and small scale applicability.
Proton exchange membrane fuel cell or PEMFC is preferred for the utilization in residents due
to the low operating temperature and characteristics for fast startup. The analysis of total
harmonic distortion or THD of the inverter output voltage is carried out to confirm a distortion
free supply.
CE2.2.2 OBJECTIVE OF THE PROJECT
The objective of the project involved the following,
 To model and simulate fuel cell based system for residential load
 To perform a closed loop simulation of the DC-DC Converter and to provide a constant
voltage at the input of inverter
 To study 100% fuel utilization at any load

 To perform Life Cycle Costing or LCC analysis for checking the economic feasibility of fuel
cell based power supply system when used for a single family residence.
CE2.2.3 MY NATURE OF WORK.
Modelling and Simulation of Fuel cell based system is one of the major projects I have
done in my professional life. My role in the project was to Develop, Design, Model and Simulate
the DC – DC Converter with the help of MATLAB Simulinkand using the LC filter to achieve a
better reduction in the output voltage and current ripple of DC-DC Converter. I was also
involved in the load calculation for a single family residence and also checked the economic
feasibility of the system with Life Cycle Cost Analysis.
CE2.2.4 ORGANIZATIONAL STRUCTURE OF PROJECT.
FIG: 1 - Organizational Structure of Project.
CE2.2.5 STATEMENT OF DUTIES.
a. Literature survey on fuel cell, power electronic converters and control methods.
b. Develop, Design, Model and Simulate the DC – DC Converter using MATLAB Simulink
with the desired output.
c. Use of LC Filters in circuits to reduce Ripples and the harmonic distortion.
d. Load calculation for a single family residence.
e. Checking the economic feasibility with Life cycle cost analysis method.
f. Documentation and Presentation to Faculty.
CE2.3 PERSONAL ENGINEERING ACTIVITY
CE 2.3.1 COMPREHENDING THE THEORY OF THE PROJECT
As an Electrical Engineer and being a third year engineering student I have completely devoted
all my ability and had done lot of research on the working. During the literature survey it was

understood that the Electricity sector in India has an installed capacity of 211.766 GW as on
December, 2012. All the Non Renewable Power Plants comprise of about 87.8% and all the
Renewable Energy sources comprise of about 12.20%. The vastness of production of electricity
by the usual sources will definitely result into severe pollution in the environment and also for
the cause of greenhouse effect in the world. Therefore, in order to fulfill the constant increase
in the demand of power and for decreasing the emissions that are connected with the
combustion of fossil fuel and all the other negative effects, dependency on the renewable
energy sources has increased. For this, the Fuel cell is considered as one of the most promising
source of renewable energy as it has an extra benefit of supplying incessantly in every season as
long as the continuity of the fuel is maintained, while solar and wind power are very much
subjected to weather conditions.
Fuel Cell:-
Fuel cell is an electrochemical device that converts chemical energy into electrical energy
directly without any emission of gases. The Schematic Diagram of fuel cell is shown in Fig 1.
The chemical part that is involved in this device is gases. There are two gases used by fuel cell to
generate electrical current, those are fuel gas and oxidant gas. The fuel gas is fed to anode and
the oxidant is fed to cathode. The fuel gas of fuel cell ishydrogen gas and the oxidant gas is
purely oxygen or air. The byproducts of fuel cell operation usually are water and heat. Thus
fuel cells are pollution free, noise free sources of energy.
There are two chemical reactions involved in the operation of fuel cell. The first reaction
occurred at the anode electrode. The chemical reaction equation is as shown in Eq. (2.1)
The hydrogen molecules split into two protons (H+) and two electrons (e-). These
twoelements will flow to cathode. The protons flow through electrolyte membrane while
the electrons flow through external circuit. At cathode, the second reaction occurred
after the protons and the electrons arrive to the cathode electrode. The chemical reaction
equation at cathode is as shown in Eq. (2.2)
Two protons combine with an atom of oxygen producing water. To join those two elements,
the electrons are required. This reaction is an exothermic reaction where the energy from
these elements is released in form of heat .Therefore the equivalent equation for this chemical
reaction is shown in Eq. (2.3)
FIG 1:- Working of Fuel Cell FIG 2:- Equations

Block Diagram
FIG 3: Block Diagram
The block diagram of the entire system which incorporates a source, DC-DC converter,
Inverter, Filter and a Load is shown in Fig. 3. A DC-DC converter is essential to step up the low
output voltage obtained from the stack of Fuel cells to a higher level. The Inverter
converts the high output voltage obtained from the DC-DC converter to a single phase
AC voltage which is converted to a sinusoidal voltage using filters. The voltage obtained is fed to
the load. The output of the Fuel Cell is highly unregulated and falls as the load on the
Fuel Cell is increased. Hence a Closed loop of the Full Bridge DC-DC Converter is
performed which provides a constant voltage at the output of the Full Bridge Converter
irrespective of the change in the load on the Fuel Cell. Filter is used at the output of the
inverter to filter out the unwanted harmonics in the supply voltage.
CE 2.3.2 ENGINEERING KNOWLEDGE AND SKILLS APPLIED IN THE PROJECT
This report focuses on modeling, controlling and the simulation of PEMFC based power
supply system for residential applications. Simulation of closed loop control of fuel cell based
system is carried out in MATLAB-SIMULINK environment. Simulation model consist of PEMFC,
full bridge DC-DC converter and a single phase PWM inverter followed by an LC filter. My
project supervisor guided me and helped me to understand the concept and working of
MATLAB Simulink operations which assisted me for the design and development of the DC –DC
Converter. During the development of the DC – DC Converter,I have installed a PI Controller in
feedback loop to remove steady state error in the output voltage and Pulse Width Modulation
control scheme is applied in order to control the ON and OFF durations of the switch.
The total harmonic distortion (THD) analysis of the Inverter output voltage is carried out
to confirm a distortion free supply. Life cycle costing analysis is done to check economic
feasibility of the entire system.

CE 2.3.3 ACCOMPLISHMENT AND TASK PERFORMED
Proton exchange membrane fuel cell (PEMFC) is preferred for residential use due to its
low operating temperature and fast startup characteristics.
As mentioned above, the project is about modeling, controlling and stimulating the PEMFC
based power system for household applications. First of all I started with the design and
modelling of DC – DC Converter with MATLAB Simulink and obtained the desired output with
the help PWM Control Scheme and PI Controller.
DC – DC Converter.
Here I have used a FULL Bridge DC – DC converter. The DC- DC Converter is required to boost
the low voltage of fuel cell to a higher DC Voltage and to provide a constant link voltage to
inverter.
My scope involved is to design and model DC-DC converter with providing constant Output
voltage of 363V irrespective of load. However after several experiments in the MATLAB, the
specification of the full bridge dc – dc converter were found and are as below,
Input Voltage from Fuel Cell = 65 – 37 V
Output / Input power = 6 KW
Switching Frequency = 10 KHz
Duty cycle = 45%
Transformer turns ratio = 1:10.

FIG 4:- Closed Loop Control of Full Bridge Converter.
During the design and modelling with the help of MATLAB Simulink the Transformer Primary
voltage (Vo) is obtained and is as Fig 5.Then I have used PI controller in feedback loop to control
the switching operation so that input to the inverter can be controlled and maintained constant
to 363 V. The output voltage of DC-DC converter is (then) sensed and compared
continuously with the reference voltagei.e. 363 V. The difference between the reference and
the measured voltage is used as an error signal and the error signal is fed to a Proportional
Integral (PI) circuit. I have compared this amplified error signal with a high frequency saw tooth
signal to generate appropriate PWM control signalsfor controlling ON and OFF durations of
switches. By controlling ON and OFF durations of switch constant and regulated output of 363V
is obtained which is shown in Fig.6.
FIG 5:- Transformer Primary Voltage.FIG 6:- Converter Output Voltage.
However there were several dips in the converted output voltage and to reduce the dips, and
get constant and steady output to feedthe inverter I have used a LC filter which removes ripples
and dips in the output voltage.
Fig 7 shows the output voltage waveform of dc to dc converter after smoothening by the L and
C

FIG 7:- Full Bridge DC – DC Converter Voltage waveform
Thus the closed loop control of the full bridge dc to dc converter reduces the steady state
error.And aboosted and regulated output of 363V was obtained at the output of dc to dc
converter as shown above.
Also by considering the wattage of each households, the peak load for residential is calculated.
After the project completion, withthe Life Cycle Cost Analysis (LCCA)the economic feasibility of
the system was also calculated.The analysis permits to evaluate the cost incurred during the
lifespan of the system discounted at an interest rate over the time. The cost analysis was done
for 20 years.
CE 2.3.4 PROJECT COORDINATION
This work of the project was under taken by the sequence of several tasks of community
amongst my fellow team members and me. I was responsible for the Design part of DC- DC
Converter and some for determining the peak load of residential. Documentation of the project
was also taken care and I was very sure about changing and modifying all the amendments. All
of my three members who were included in the project with me, helped me in my part of job in
the project.
CE 2.3.5 IDENTIFIED PROBLEMS AND SOLUTIONS
CE 2.3.4.1 PROBLEMS
The problem that I faced was while designing the DC – DC Converter. Selection of
models with proper ratings in MATLAB, setting of frequency of pulse generators, selection of
duty cycle, turns ratio of transformer, Feedback loop design. I had never worked on the
designing part of Converter earlier and in this project I had to design it, I had to refer several
reference books, Technical articles and Technical papers to understand design topology. It was
(not easy) challenging for me to complete the design on myself.
CE 2.3.4.2 SOLUTIONS
However, my team members and my project supervisor was a constant support system
to me and finally I was able to complete the designing part smoothly and systematically.
CE 2.4 PROJECT REVIEW
CE 2.4.1 PROJECT OVERVIEW
Fuel cell is a device that is electrochemical and which switches the chemical energy into
the electrical energy directly without any types of gas emission. This project was made for the
betterment of the society. This project presents the design and simulation of 6 KW PEMFC
based power supply system for a Residential Application. A PEMFC is well suited for residential

use due to its low operating temperature, no harmful emissions, low operating noise and
its ability to respond to variations in the load. The simulation of the Closed loop system shows
that the using a power electronic converter (Full Bridge DC-DC Converter), the variations
of the Fuel Cell Voltage can be regulated for changing load conditions. A Sinusoidal
PWM H Bridge Inverter is used to obtain a distortion less 230 V rms output voltage.
Sinusoidal PWM technique is used to reduce lower order harmonics whereas higher ones
are eliminated using LC Filter. It is important to ensure that the Output of Inverter is distortion
free because an addition of nonlinear load in the system affects the voltage quality. Thus with a
less distortion initially, the effect on voltage quality due to addition of the nonlinear loads will
be reduced. According to IEEE 519 standard a general permissible THD in voltage should
be less than 5%. The THD obtained in my work is 0.6%.