Front end converter with integrated pfc and dc–dc functions for a fuel cell ups with dsp-based control

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IEEE SOFTWARE | EMBEDDED | MECHANICAL | ROBOTICS PROJECTS DEVELOPMENT
FRONT-END CONVERTER WITH INTEGRATED PFC AND DC–DC FUNCTIONS
FOR A FUEL CELL UPS WITH DSP-BASED CONTROL
By
A
PROJECT REPORT
Submitted to the Department of Computer Science & Engineering in the
FACULTY OF ENGINEERING & TECHNOLOGY
In partial fulfillment of the requirements for the award of the degree
Of
MASTER OF TECHNOLOGY
IN
COMPUTER SCIENCE & ENGINEERING
APRIL 2016

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CERTIFICATE
Certified that this project report titled “FRONT-END CONVERTER WITH INTEGRATED
PFC AND DC–DC FUNCTIONS FOR A FUEL CELL UPS WITH DSP-BASED
CONTROL” is the bonafide work of Mr. _____________Who carried out the research under
my supervision Certified further, that to the best of my knowledge the work reported herein does
not form part of any other project report or dissertation on the basis of which a degree or award
was conferred on an earlier occasion on this or any other candidate.
Signature of the Guide Signature of the H.O.D
Name Name

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DECLARATION
I hereby declare that the project work entitled “FRONT-END CONVERTER WITH
INTEGRATED PFC AND DC–DC FUNCTIONS FOR A FUEL CELL UPS WITH DSP-
BASED CONTROL” Submitted to BHARATHIDASAN UNIVERSITY in partial fulfillment
of the requirement for the award of the Degree of MASTER OF SCIENCE IN COMPUTER
SCIENCE is a record of original work done by me the guidance of Prof.A.Vinayagam M.Sc.,
M.Phil., M.E., to the best of my knowledge, the work reported here is not a part of any other
thesis or work on the basis of which a degree or award was conferred on an earlier occasion to
me or any other candidate.
(Student Name)
(Reg.No)
Place:
Date:

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ACKNOWLEDGEMENT
I am extremely glad to present my project “FRONT-END CONVERTER WITH
INTEGRATED PFC AND DC–DC FUNCTIONS FOR A FUEL CELL UPS WITH DSP-
BASED CONTROL” which is a part of my curriculum of third semester Master of Science in
Computer science. I take this opportunity to express my sincere gratitude to those who helped me
in bringing out this project work.
I would like to express my Director, Dr. K. ANANDAN, M.A.(Eco.), M.Ed., M.Phil.,(Edn.),
PGDCA., CGT., M.A.(Psy.) of who had given me an opportunity to undertake this project.
I am highly indebted to Co-Ordinator Prof. Muniappan Department of Physics and thank from
my deep heart for her valuable comments I received through my project.
I wish to express my deep sense of gratitude to my guide
Prof. A.Vinayagam M.Sc., M.Phil., M.E., for her immense help and encouragement for
successful completion of this project.
I also express my sincere thanks to the all the staff members of Computer science for their kind
advice.
And last, but not the least, I express my deep gratitude to my parents and friends for their
encouragement and support throughout the project.

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ABSTRACT:
This paper presents the development of a boost converter with integrated power factor correction
(PFC) and dc–dc functions for a proton exchange membrane fuel cell (PEMFC) uninterruptable
power supply (UPS). Through the use of a passive resonant soft-commutation cell, which besides
providing improvements in efficiency and reduced electromagnetic interference, produces a
naturally controlled supercapacitor charger circuit. Supercapacitors are employed in order to
provide a proper startup of the PEMFC and to improve its dynamic response. The control
strategy is implemented using a digital signal processor and is based on the average current
control method for sinusoidal input current imposition ensuring, therefore, a high input power
factor and low harmonic distortion of current.
The main features of the proposed solution are the use of a PEMFC as an energy storage system,
which replace the battery banks commonly used in UPS systems, eliminating the common
drawbacks related to working life and maintenance issues, and the use of a front-end converter
with integrated PFC and dc–dc functions eliminating the necessity of using an additional and
dedicated dc–dc converter for the PEMFC. During power failure or even in conditions of severe
voltage sags on the ac mains, the PEMFC is activated assuring the continuous power supply to
the electronic load connected to the dc link. In this paper, the authors present the full study
description including experimental results that corroborate with the theory herein presented.

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INTRODUCTION:
DUE to the remarkable technological development observed in recent years, several industrial
processes have begun to depend entirely on the use of electronic devices. In this context, it has
become inadmissible the occurrence of interruptions in power supply regarding various fields of
work and services, among which one can cite telecommunications systems, devices employed in
hospital emergency rooms, and flight control systems. In this sense, many companies invest in
research studies, which focus on the development of solutions that avoid energy supply
interruptions to their systems. The devices manufactured for this purpose were denominated as
uninterruptible power supply (UPS), which commonly present a high power factor (HPF) front-
end converter followed by a dc–ac or dc–dc stage (depending on the application) and uses
rechargeable batteries such as sealed lead-acid or nickel cadmium, which use toxic heavy metals
such as cadmium, mercury, and lead.
In addition, the unpredictable working life along with limited charge–discharge cycles increase
the cost concerning maintenance and replacement. On the other hand, fuel cells (FCs) are
emerging as a reliable power source, since it is inherently clean and presents very high overall
efficiency (40–60%). Unlike batteries, performance characteristics of the FCs such as great
tolerance to high temperatures (from –40 °C to +50 °C), lower maintenance requirements,
scalability, and higher power density, make them a very attractive alternative to UPS systems.
Due to the fact that FCs do not have the capacity to respond immediately to fast load changes or
to startup as soon as it is required, supercapacitors can be used in conjunction with the FC. It is
important to highlight that they only supply the energy for short periods, which is necessary to
allow the FC to achieve steady state. One can also conclude that they are also very attractive for
battery storage systems, since the batteries provide energy only during longer interruptions
improving, therefore, their working life. In this context, this paper presents a single-phase HPF
frontend converter suitable for an online UPS system using a proton exchange membrane fuel
cell (PEMFC) as an energy storage system. Different to ordinary FC UPS as shown in Fig. 1(a)

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and also observed in the proposed system, shown in Fig. 1(b), consists of a boost converter with
integrated PFC and dc–dc functions, so a dedicated dc–dc converter for the connection of the
PEMFC is not needed. A self-resonant zerocurrent and zero-voltage-switching pulse width
modulated cell (SR-ZCS-ZVS-PWM) is used, therefore, besides the soft commutation of
switches S1 (main) and S2 (auxiliary), the charge circuit for the supercapacitor bank is also
ensured. A supercapacitors bank is able to operate without hindrance at 60% to 100% of rated
voltage. Normally, a dedicated control is needed to achieve this condition, such as the smoothing
control method presented or the sliding mode control shown in this context, one must emphasize
that in the proposed system there is no need for a dedicated energy storage control on the
supercapacitors.
The power diode D1 , which connects the supercapacitors bank with the boost inductor LB ,
provides the path for the transference of the stored energy to the output capacitor when the main
switch S1 is OFF and diode D0 is forward biased, therefore, controlling the voltage level across
the supercapacitors terminals in a natural flowing manner. The amount of energy processed by
the SR-ZCS-ZVS-PWM commutation cell is transferred to the supercapacitors bank every
switching cycle. In steady state, the supercapacitor supplies energy to the load only when the
input ac voltage is lower than its terminal voltage and, hence, diode D1 is forward biased. Under
a power failure condition on the ac grid, the switch S3 is turned ON and the supercapacitors
provide the necessary condition for the startup of the PEMFC.

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EXISTING SYSTEM:
Conventional step-up converters, such as the boost converter and flyback converter, cannot
achieve a high step-up conversion with high efficiency because of the resistances of elements or
leakage inductance; also, the voltage stresses are large. A boost converter (step-up converter) is a
DC-to-DC power converter with an output voltage greater than its input voltage. It is a class of
switched-mode power supply (SMPS) containing at least two semiconductors (a diode and a
transistor) and at least one energy storage element, a capacitor, inductor, or the two in
combination. Filters made of capacitors (sometimes in combination with inductors) are normally
added to the output of the converter to reduce output voltage ripple.

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PROPOSED SYSTEM:
This paper presents a single-phase HPF frontend converter suitable for an online UPS system
using a proton exchange membrane fuel cell (PEMFC) as an energy storage system. A self-
resonant zerocurrent and zero-voltage-switching pulse width modulated cell (SR-ZCS-ZVS-
PWM) is used, therefore, besides the soft commutation of switches S1 (main) and S2 (auxiliary),
the charge circuit for the supercapacitor bank is also ensured. A supercapacitors bank is able to
operate without hindrance at 60% to 100% of rated voltage. Normally, a dedicated control is
needed to achieve this condition, such as the smoothing control method presented. In this
context, one must emphasize that in the proposed system there is no need for a dedicated energy
storage control on the supercapacitors. The power diode D1, which connects the supercapacitors
bank with the boost inductor LB, provides the path for the transference of the stored energy to the
output capacitor when the main switch S1 is OFF and diode D0 is forward biased, therefore,
controlling the voltage level across the supercapacitors terminals in a natural flowing manner.
The amount of energy processed by the SR-ZCS-ZVS-PWM commutation cell is transferred to
the supercapacitors bank every switching cycle. In steady state, the supercapacitor supplies
energy to the load only when the input ac voltage is lower than its terminal voltage and, hence,
diode D1 is forward biased. Under a power failure condition on the ac grid, the switch S3 is
turned ON and the supercapacitors provide the necessary condition for the startup of the
PEMFC.

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ADVANTAGES:
 There is no need to use an external battery bank, which has a short working life and low
scalability, as well as an associated charger circuit.
 There is no need to use a dedicated dc–dc converter for the PEMFC which, thus, reduces
cost.
 The use of nondissipative switching cell improves the overall efficiency and can reduce
electromagnetic interference (EMI).
 The supercapacitors bank is continuously connected to the system, which guarantees zero
switching delay between the ac power supply and the startup of the PEMFC.
 The commutation energy is used for charging the supercapacitors, which presents a
higher charge–discharge cycle when compared to batteries.
 The supercapacitors bank naturally operates under 60% to 100% of rated voltage, so there
is no need to implement a dedicated control technique to assure the working life of the
supercacitors, making the proposed system simple.

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BLOCK DIAGRAM:

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TOOLS AND SOFTWARE USED:
 MPLAB – microcontroller programming.
 ORCAD – circuit layout.
 MATLAB/Simulink – Simulation.
APPLICATIONS:
 Uninterruptible power supply (UPS).

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CONCLUSION:
This paper presents the development and analysis of a singlephase front-end converter with
integrated PFC and dc–dc functions for online FC UPS. The elimination of dedicated dc–dc
converters, as well as batteries and associated charging systems, results in significant size and
cost reduction and in improving the reliability and working life of the system. The dynamic
performance of the proposed FC UPS system was improved using a decoupling supercapacitors
bank which is continuously connected to the system assuring conditions for the prevention of
critical operation situations during the startup of the FC along with zero switching delay of the ac
power to the PEMFC. The DSP-based control technique is based on the average current control
method for sinusoidal input current imposition and dc-link voltage control. Theoretical analyses
were presented and corroborated with experimental results. It was shown that high input power
factor, low harmonic distortion of current, and improved dc-link voltage regulation for the
connection of other electronics loads can be achieved. Special attention was given to the
dynamic performance analyses of the proposed solution under conditions of ac power supply
interruptions showing that the FC is activated assuring the continuous energy supply.

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REFERENCES:
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IEEE Appl. Power Electron. Conf. Expo., 2013, pp. 1852–1858.
[2] K. Kirubakaran, S. Jain, and R. K. Nema, “DSP-controlled power electronic interface for
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3853–3864, Dec. 2011.
[3] S. B. Silva, M. A. G. Oliveira, and M. M. Severino, “Sizing and optimization photovoltaic,
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[4] W. Zhang, D. Xu, X. Li, R. Xie, H. Li, D. Dong, C. Sun, and M. Chen, “Seamless transfer
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[5] Y. Zhan, Y. Guo, J. Zhu, and H. Wang, “Power converters and controllers for UPS
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[6] M. P. Shreelakshmi and V. Agarwal, “An energy efficient and environment friendly elevator
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Front end converter with integrated pfc and dc–dc functions for a fuel cell ups with dsp-based control

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Front end converter with integrated pfc and dc–dc functions for a fuel cell ups with dsp-based control