Bidirectional pwm converter integrating cell voltage equalizer using series resonant voltagemultiplier for series-connected energy storage cells

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IEEE SOFTWARE | EMBEDDED | MECHANICAL | ROBOTICS PROJECTS DEVELOPMENT
BIDIRECTIONAL PWM CONVERTER INTEGRATING CELL VOLTAGE
EQUALIZER USING SERIES-RESONANT VOLTAGE MULTIPLIER FOR SERIES-
CONNECTED ENERGY STORAGE CELLS
By
A
PROJECT REPORT
Submitted to the Department of electronics & communication Engineering in the
FACULTY OF ENGINEERING & TECHNOLOGY
In partial fulfillment of the requirements for the award of the degree
Of
MASTER OF TECHNOLOGY
IN
ELECTRONICS & COMMUNICATION ENGINEERING
APRIL 2016

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CERTIFICATE
Certified that this project report titled “BIDIRECTIONAL PWM CONVERTER
INTEGRATING CELL VOLTAGE EQUALIZER USING SERIES-RESONANT
VOLTAGE MULTIPLIER FOR SERIES-CONNECTED ENERGY STORAGE CELLS”
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 “BIDIRECTIONAL PWM CONVERTER
Submitted to BHARATHIDASAN UNIVERSITY in partial fulfillment of the requirement for
the award of the Degree of MASTER OF APPLIED ELECTRONICS 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 “BIDIRECTIONAL PWM CONVERTER
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:
In conventional energy storage systems using seriesconnected energy storage cells such
as lithium-ion battery cells and supercapacitors (SCs), an interface bidirectional converter and
cell voltage equalizer are separately required to manage charging/ discharging and ensure years
of safe operation. In this paper, a bidirectional PWM converter integrating cell voltage equalizer
is proposed.
This proposed integrated converter can be derived by combining a traditional
bidirectional PWM converter and seriesresonant voltage multiplier (SRVM) that functionally
operates as an equalizer and is driven by asymmetric square wave voltage generated at the
switching node of the converter. The converter and equalizer can be integrated into a single unit
without increasing the switch count, achieving not only system-level but also circuit-level
simplifications.
Open-loop control is feasible for the SRVM when operated in discontinuous conduction
mode,meaning the proposed integrated converter can operate similarly to conventional
bidirectional converters. An experimental charge–discharge cycling test for six SCs connected in
series was performed using the proposed integrated converter. The cell voltage imbalance was
gradually eliminated by the SRVM while series-connected SCs were cycled by the bidirectional
converter. All the cell voltages were eventually unified, demonstrating the integrated functions of
the proposed converter.

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INTRODUCTION:
In general, energy storage cells/modules (hereafter, simply “cells”) need to be connected
in series to form a string to meet system voltage requirements. The voltages of individual series
connected cells gradually become imbalanced due to characteristic mismatches in terms of
capacity/capacitance, self-discharge rate, and internal impedance.
The temperature gradient in energy storage modules/systems comprising numerous cells
connected in series is another major cause of voltage imbalance, because the self-discharge rate
is significantly temperature dependent. If cell voltages are mismatched, some cells with higher
(or lower) voltages might be overcharged (or over discharged) during the charging (or
discharging) process because cells are charged (or discharged) in series.
Energy storage cells, particularly lithium-ion cells, must be operated within a safety
boundary to ensure years of safe operation otherwise resulting in accelerated aging and increased
risks of hazardous consequences triggering an explosion in the worst-case scenario. Accordingly,
for energy storage modules/systems to operate safely and properly, cell voltage equalization
techniques to eliminate and/or preclude cell voltage imbalance are crucial.
In general, energy storage cells/modules (hereafter, simply “cells”) need to be connected
in series to form a string to meet system voltage requirements. The voltages of individual series-
connected cells gradually become imbalanced due to characteristic mismatches in terms of
capacity/capacitance, self-discharge rate, and internal impedance.
The temperature gradient in energy storage modules/systems comprising numerous cells
connected in series is another major cause of voltage imbalance, because the self-discharge rate
is significantly temperature dependent.

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If cell voltages are mismatched, some cells with higher (or lower) voltages might be
overcharged (or overdischarged) during the charging (or discharging) process because cells are
charged (or discharged) in series. Energy storage cells, particularly lithium-ion cells, must be
operated within a safety boundary to ensure years of safe operation otherwise resulting in
accelerated aging and increased risks of hazardous consequences triggering an explosion in the
worst-case scenario.
Accordingly, for energy storage modules/systems to operate safely and properly, cell
voltage equalization techniques to eliminate and/or preclude cell voltage imbalance are crucial.

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EXISTING SYSTEM:
A buck–boost bidirectional battery equalizer composed of MOSFET switches with body
diodes and a large inductance inductor. This nondissipative equalization design has many
advantages such as high equalization efficiency due to the nondissipative current diverter,
bidirectional energy transferring capability, and a modular design

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PROPOSED SYSTEM:
In this paper, a bidirectional PWM converter integrating voltage equalizer for series-
connected energy storage cells is proposed. The proposed integrated converter can be derived by
combining a traditional bidirectional PWM converter and a series-resonant voltage multiplier
(SRVM) that functionally operates as a voltage equalizer and is driven by an asymmetric square
wave voltage generated at a switching node of the PWM converter. The bidirectional converter
and voltage equalizer can be integrated into a single unit without increasing switch count, thus
realizing not only system-level but also circuit-level simplifications.

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ADVANTAGES:
 High voltage gain
 Isolation between input and output

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BLOCK DIAGRAM:

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TOOLS AND SOFTWARE USED:
 MPLAB – microcontroller programming.
 ORCAD – circuit layout.
 MATLAB/Simulink – Simulation

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APPLICATIONS:
 Electric vehicles and grid-connected applications

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CONCLUSION:
A bidirectional PWM converter integrating a cell voltage equalizer has been proposed in
this paper. The proposed integrated converter is basically the combination of a traditional
bidirectional PWM converter and SRVM that functionally performs cell voltage equalization. An
asymmetric square wave voltage generated at the switching node of a converter is exploited to
drive the SRVM, hence the SRVM itself is a switchless circuit. The two functional elements (i.e.,
bidirectional converter and equalizer) can be integrated into a single unit without increasing the
switch count, hence realizing system- and circuitlevel simplifications

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REFERENCES:
[1] M. Uno and K. Tanaka, “Accelerated charge-discharge cycling test and cycle life prediction
model for supercapacitors in alternative battery applications,” IEEE Trans. Ind. Electron., vol.
59, no. 12, pp. 4704–4712, Dec. 2012.
[2] S. M. Lambert, V. Pickert, J. Holden, X. He, and W. Li, “Comparison of supercapacitor and
lithium-ion capacitor technologies for power electronics applications,” in Proc. Power Electron.
Mach. Drives, Apr. 2010, pp. 1–5.
[3] M. Uno and K. Tanaka, “Spacecraft electrical power system using lithiumion capacitors,”
IEEE Trans. Aerosp. Electron. Syst., vol. 49, no. 1, pp. 175–188, Jan. 2013.
[4] K. Nishijima, H. Sakamoto, and K. Harada, “A PWM controlled simple and high
performance battery balancing system,” in Proc. IEEE Power Electron. Spec. Conf., Jun. 2000,
pp. 517–520.
[5] Y. S. Lee and M. W. Cheng, “Intelligent control battery equalization for series connected
lithium-ion battery strings,” IEEE Trans. Ind. Electron., vol. 52, no. 5, pp. 1297–1307, Oct.
2005.

Bidirectional pwm converter integrating cell voltage equalizer using series resonant voltagemultiplier for series-connected energy storage cells

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Bidirectional pwm converter integrating cell voltage equalizer using series resonant voltagemultiplier for series-connected energy storage cells