supercapacitor and battery power management for hybrid vehicle applications
DESCRIPTION
its an useful project material for eee aswell as ece students.TRANSCRIPT
1
A Main-Project Report
On
SUPERCAPACITORS AND BATTERY POWER MANAGEMENT
FOR HYBRID VEHICLE APPLICATIONS USING
MULTI BOOST AND FULL BRIDGE CONVERTERS
Is submitted to
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY ANANTAPUR,
ANANTAPUR.
In partial fulfillment of the requirements
For the award of the degree of
BACHELOR OF TECHNOLOGY
IN
ELECTRICAL AND ELECTRONICS ENGINEERING
During the year 2011-2012
Submitted By
P. GURUNADHAM 084E1A0217
S. JANARDHAN 084E1A0220
K. DILEEP KUMAR 084E1A0211
A. JAYA KRISHNA 084E1A0221
D. HARIBABU 084E1A0218
Under the esteemed mentorship of
Mr. K.MUNIGURU RAJAPRAKASH B.Tech.,
Assistant Professor,
Department of E.E.E., S.I.S.T.K
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
SIDDARTHA INSTITUTE OF SCIENCE & TECHNOLOGY
(An ISO 9001:2000 Certificate Institution)
(Approved by A.I.C.T.E. New Delhi & Affiliated to J.N.T.U.A., Anantapur)
Siddhartha Nagar, Narayanavanam road, Puttur-517583
2
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
SIDDARTHA INSTITUTE OF SCIENCE & TECHNOLOGY
(An ISO 9001:2000 Certificate Institution)
(Approved by A.I.C.T.E. New Delhi & Affiliated to J.N.T.U.A., Anantapur)
Siddhartha Nagar, Narayanavanam road, Puttur-517583
CERTIFICATE This is to certify that the MAIN PROJECT report entitled
SUPERCAPACITORS AND BATTERY POWER MANAGEMENT
FOR HYBRID VEHICLE APPLICATIONS USING
MULTI BOOST AND FULL BRIDGE CONVERTERS
has been submitted by :
P. GURUNADHAM 084E1A0217
S. JANARDHAN 084E1A0220
K. DILEEP KUMAR 084E1A0211
A. JAYA KRISHNA 084E1A0221
D. HARIBABU 084E1A0218
In the department of Electrical and Electronics Engineering, SIDDARTHA INSTITUTE
OF SCIENCE AND TECHNOLOGY, Puttur and is submitted to JAWAHARLAL NEHRU
TECHNOLOGICAL UNIVERSITY, ANANTAPUR in partial fulfillment of the requirements
for the award of B.Tech, Degree in Electrical and Electronics Engineering. This work has been
carried out under my guidance and supervision during the year 2011-12.
Project Guide: Head of the Department:
Mr. K.MUNIGURU RAJAPRAKASH B.Tech, Mr. S.RAMESHM.E.,
Assistant Professor, Associate Professor,
Department of E.E.E., S.I.S.T.K, Department of E.E.E., S.I.S.T.K
Submitted for the Viva-Voce held on: _______________
Internal Examiner External Examiner
3
DECLARATION
We here by inform that the main project entitled “SUPERCAPACITORS AND BATTERY
POWER MANAGEMENT FOR HYBRID VEHICLE APPLICATIONS USING MULTI BOOST
AND FULL BRIDGE CONVERTERS” is carried by us during the month of Feb-Mar, 2012 is
an original work submitted by us to the DEPARTMENT OF ELECTRICAL AND
ELECTRONICS ENGINEERING, S.I.S.T.K, PUTTUR.
P. GURUNADHAM 084E1A0217
S. JANARDHAN 084E1A0220
K. DILEEP KUMAR 084E1A0211
A. JAYA KRISHNA 084E1A0221
D. HARIBABU 084E1A0218
4
ACKNOWLEDGEMENT
The satisfaction that accompanies the successful completion of any task would
be incomplete without the mention of the people who made it possible, without whose
guidance, encouragement and help this venture would not have been success. The
acknowledgement transcends the reality of formality when we would like to express deep
gratitude and respect to all those people behind the screen who guided, inspired and
helped for me for the completion of my project presentation in time and up to the
standards.
I express out deep sense of gratitude to our project guide
Mr. K.MUNIGURU RAJAPRAKASH, B.Tech, Asst. Professor, for his guidance and
supervision at all levels of my project presentation. I indebted to his valuable suggestions
and sustained help in completion of my project presentation.
I express my deep sense of gratitude to Mr. S. RAMESH, M.E., Head of the
department of Electrical and Electronics Engineering for his valuable guidance and
constant encouragement given to me during this presentation
First and Foremost, I express my sincere gratitude to out honorable chairman
Dr. K.ASHOKA RAJU Ph.D., and also deep sense of gratitude to our honorable
principal Dr. USHAA ESWARAN Ph.D., for having provided all the facilities and
support in completing my project presentation successfully.
. I also thankful to All staff members of EEE department, for helping me to
complete this presentation by giving me valuable suggestions. I express my sincere
thanks to All my friends who have supported me in the accomplishment of this project
presentation.
Last but not the least, the one above all of us, the omnipresent God, for answering
our prayers for giving us the strength to plod on despite our constitution wanting to give
up and throw in the towel, thank you so much Dear Lord. Thank you for showing us the
path . . .
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CONTENTS
Abstract 1 +8
1. Introduction 2
1.1 Energy storage unit 5
1.2 Comparison of supercapacitor with lithium-ion (general capacitor) 7
1.3 Advantages and limitations of supercapacitors 8
1.4 Proposed block diagram 9
1.5 Power Flow 10
2. Effectiveness of battery-supercapacitor combination in electric vehicles 12
2.1. Energy management 14
2.1.1 Energy management functions can be separated into two groups 15
2.2 Component Modeling 16
2.2.1 Battery Bank 16
2.2.2 Supercapacitor Bank 17
2.2.3 Electrical Load 18
2.3 Vehicle energy storage system using supercapacitors 18
2.3.1 System specifications 18
2.3.2. The topology of bi-directional DC/DC converter 20
2.4 Vehicle application requirements 21
3. Ultracapacitor-battery interface for power electronic applications 23
4. DC/DC converters topologies and modeling 26
4.1. Multi boost and Multi full bridge converters modeling 27
5. Design for experimental results 31
5.1 Experimental setup at reduced scale 34
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6. Simulation results 36
6.1 General 37
6.2 Introduction to Matlab 37
6.3 The Matlab System 38
6.3.1 Desktop tools and development environment 38
6.3.2 The Matlab mathematical function library 39
6.3.3 The Matlab language 39
6.3.4 Graphics 39
6.3.5 The Matlab external interfaces 39
6.3.6 Matlab documentation 39
6.3.7 Matlab online help 40
6.3.8 The role of simulation in design 40
6.3.9 Sim power systems libraries 41
6.3.10 Matlab Library 43
6.4 Full bridge converter simulation circuit for Np = 2 43
6.5 Boost converters simulation results 47
6.5.1 Simulation circuit for boost converter 47
6.6 full bridge converters simulation results 51
Conclusion 55
References 56
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LIST OF FIGURES
1. Converter topologies for ECCE Hybrid Vehicle 4 +8
(a). first solution 4
(b). second solution 4
2. Overview of energy storage unit Battery 5
3. Supercapacitor equivalent circuit 8
4. Electric vehicle/hybrid electric vehicle system using supercapacitors 9
5. Power flow to the ESU 10
6. System configuration of the supercapacitor implemented 19
7. The bi-directional DC/DC converter(full-bridge type topology) 20
8. (a). Multi boost Converter topology 27
(b). Multi full bridge converter topology 28
9. (a). Multi boost control strategy 30
(b). Multi full bridge control strategy 30
10. Full bridge converter with chopping devices 33
11. Boost and full bridge converters experimental setup 34
(a). Boost converters setup for Np = 2 34
(b). Full bridge converter setup for Np = 1 35
12. Full bridge converter simulation circuit for Np = 2 44
13. (a). Super capacitor modules voltages 45
(b). Super capacitor modules currents 45
14. (a). Battery current control result 46
(b). DC-link and active load currents 46
15. Simulation circuit for boost converter 47
16. Super capacitor modules experimental and simulation voltage results 48 (a). First module voltage 48
(b). Second module voltage 48
8
17. Super capacitor modules experimental and simulation current results 49
(a). First module current 49
(b). Second module current 49
18. DC-link voltage and current experimental validation 50
(a) Multi boost output current (IL ) 50
(b) Battery current experimental result 50
19. Simulation circuit for full bridge converter 52
20. (a). Super capacitors module voltage and current 53
(b) DC-link and active load experimental currents 53
21. High frequency planar transformer voltages and currents 54
(a) Transformer input and output voltages 54
(b) Transformer input and output currents 54
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ABSTRACT
This paper presents supercapacitors and battery association methodology for
ECCE Hybrid vehicle. ECCE is an experimental Hybrid Vehicle developed at L2ES
Laboratory in collaboration with the Research Center in Electrical Engineering and
Electronics in Belfort (CREEBEL) and other French partners. This test bench has
currently lead-acid batteries with a rated voltage of 540 V, two motors each one coupled
with one alternator. The alternators are feeding a DC-bus by rectifiers.
The main objective of this paper is to study the management of the energy
provides by two supercapacitor packs. Each supercapacitors module is made of 108 cells
with a maximum voltage of 270V. This experimental test bench is carried out for studies
and innovating tests for the Hybrid Vehicle applications.
The multi boost and multi full bridge converter topologies are studied to define
the best topology for the embarked power management. The authors propose a good
power management strategy by using the multi boost and the multi full bridge converter
topologies. The simulation results of the two converter topologies are presented.
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CHAPTER-1
INTRODUCTION
11
1.INTRODUCTION
In the last few years the pollution problems and the increase of the cost of fossil
energy (oil, gas) have become planetary problems. The car manufacturers started to react
to the urban pollution problems in nineties by commercializing the electric vehicle. But
the battery weight and cost problems were not solved. The batteries must provide energy
and peaks power during the transient states. These conditions are severe for the batteries.
To decrease these severe conditions, the super capacitors and batteries associate with a
good power management present a promising solution. Environmental issues create a
demand for more energy efficient vehicles.
A conventional vehicle with an internal combustion engine (ICE), converts
chemically stored energy (gasoline, ethanol, diesel etc.) into kinetic energy in a process
afflicted with significant power losses. Combining the ICE with an electric energy storage
and drive system can improve the fuel efficiency through several means. The electrical
propulsion system allows the combustion engine to operate closer to its optimal operating
point through supplying the wheels with extra power when needed and absorb power
when the ICE produces excess power. Another benefit with hybrid electric vehicles (HEV)
is that when braking, the energy can be absorbed by the electrical system, instead of
converting all kinetic energy into heat via friction brakes. The electrical energy storage
typically consists of a battery with more or less complex support-electronics for charge
control and error prevention.
The storage unit has to store relatively large amounts of energy and handle high
power. With current battery technology, the energy storage capacity comes at a cost of
decreased power capability and the lifetime of the modern batteries is dependent of the
charge cycles. By introducing a supercapacitor as aid, the battery could be spared from the
power peaks and thus allow the battery to be optimized for energy storage or extend the
lifetime o f a given battery, which in turn could lower the cost of the entire unit. To fully
utilize the supercapacitor, a voltage converter is needed, which naturally should be as
efficient and simple as possible. With the converter it is also possible to have sophisticated
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control of the power flows, which can improve the system if proper strategies are used.
Interesting previous works made before this report include, “Comparing DC-DC
Converters for Power Management in Hybrid Electric Vehicles” (Shupbach & Balda
2003), which is a study of different topologies for supercapacitor handling. An in-depth
report on control strategies and optimizations are Andersson and Groot (2003) M.Sc thesis
report “Alternative Energy Storage System for Hybrid Electric Vehicles”. The work
“Comparison of Simulation Programs for Supercapacitor Modeling” by Andersson and
Johansson (2008) has also been a useful resource for modeling of the supercapacitor.
Doerffel (2007) have studied the ageing and deteriation processes of lithium-ion batteries,
and how to measure the state of health.
To ensure a good power management in hybrid vehicle, the multi boost and multi
full bridge converters topologies and their control are developed. Two topologies
proposed for the power management in ECCE Hybrid Vehicle are presented in Fig.1.
Figure 1 . Converter topologies for ECCE Hybrid Vehicle
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1.1 Energy storage unit:
The energy storage unit (ESU) in a car handles the storage of the electrical energy
and functions as a buffer for the electrical machine (and the generator in the series hybrid
configuration). The ESU has the possibility to either receive or deliver power from or to
the electrical machine (via a DC/AC inverter). Depending on application and
dimensioning parameters, such as hybridization level and size of the vehicle, is it possible
to configure the ESU in different combinations.
It is necessary to have a storage utility, which could be a battery or a
supercapacitor or a combination of the both, to work as the source of energy and power in
this thesis work, a combination consisting of a supercapacitor in parallel with a battery
will be studied. If there is a need to control the power flow or if there is a need to have
different voltage levels (i.e. the voltage over the capacitor is dimensioned to be lower than
the voltage over the battery or vice versa) it can be possible or necessary to install a
converter in series with the battery or the supercapacitor or both. If the converter is
installed in series with the battery it is possible, with the ability of power control, to get a
direct control over the power to the battery.
Another possible combination is to install two converters, one in series with the
supercapacitor and one in series with the battery, but this would lead to an unnecessary
complexity of the system. Therefore, in this paper, a converter has been installed in series
with the supercapacitor. The configuration is presented in Figure-2.
Figure 2. Overview of energy storage unit Battery
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The battery is suitable to provide the energy buffer to the HEV due to that battery
has the ability to store relatively high levels of electrical energy. In the market of today
there exist several model and sizes. The problems with batteries are mainly the cost,
lifetime and size. Supercapacitors also called ultracapacitors and electric double layer
capacitors (EDLC) are capacitors with capacitance values greater than any other capacitor
type available today.
Capacitance values reaching up to 400 Farads in a single standard case size are
available. Supercapacitors have the highest capacitive density available today with
densities so high that these capacitors can be used to applications normally reserved for
batteries. Supercapacitors are not as volumetrically efficient and are more expensive than
batteries but they do have other advantages over batteries making the preferred choice in
applications requiring a large amount of energy storage to be stored and delivered in bursts
repeatedly.
The modern supercapacitor is not a battery per se but crosses the boundary into
battery technology by using special electrodes and electrolyte. Several types of electrodes
have been tried and we focuse on the double-layer capacitor (DLC) concept. It is carbon-
based, has an organic electrolyte that is easy to manufacture and is the most common
system in use today.
A supercapacitor is a component which has relatively high specific power ability
in Comparison to batteries much like a capacitor, while it has much higher specific energy
than a conventional capacitor, more like a battery. In order to have high capacitance, the
isolator is very thin, usually in order of tenths of nm (Lai et al. 1992). The maximum
voltage difference between the electrodes is related to the dielectric breakdown of the
isolator, which in turn is related to its thickness and material.
Due to the thin isolator in supercapacitor, the maximum voltage per cell becomes
relatively low, in order of 2-4V to avoid dielectric breakdown. The supercapacitor can not
only be charged and discharged more than one million times but also be stored with ten
15
times more energy than conventional electrolytic capacitors. In contrast, the
supercapacitor has the merits of a rapid charge and discharge of energy and a longer life
cycle, because of electrostatic nature of capacitor rather than chemical reaction.
1.2 Comparison of supercapacitor with lithium-ion (general capacitor):
Function Supercapacitor Lithium-ion (general)
Charge time
Cycle life
Cell voltage
Specific energy (Wh/kg)
Specific power (W/kg)
Cost per Wh
Service life (in vehicle)
Charge temperature
Discharge temperature
1–10 seconds
1 million or 30,000h
2.3 to 2.75V
5 (typical)
Up to 10,000
$20(typical)
10 to 15 years
–40 to 65°C (–40 to 149°F)
–40 to 65°C (–40 to 149°F)
10–60 minutes
500 and higher
3.6 to 3.7V
100–200
1,000 to 3,000
$2 (typical)
5 to 10 years
0 to 45°C (32°to 113°F)
–20 to 60°C (–4 to 140°F)
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1.3 Advantages and limitations of supercapacitors:
Advantages
Virtually unlimited cycle life; can be cycled millions of time
High specific power; low resistance enables high load currents
Charges in seconds; no end-of-charge termination required
Simple charging; draws only what it needs; not subject to
overcharge
Safe; forgiving if abused
Excellent low-temperature charge and discharge performance
Limitations
Low specific energy; holds a fraction of a regular battery
Linear discharge voltage prevents using the full energy
spectrum
High self-discharge; higher than most batteries
Low cell voltage; requires serial connections with voltage
balancing
High cost per watt
Equivalent circuit of supercapacitor
Figure 3. Supercapacitor equivalent circuit
This equivalent circuit is only a simplified or first order model of a super capacitor.
This causes super capacitors to exhibit behavior more closely to transmission lines than
capacitors. Below is a more accurate illustration of the equivalent circuit for
supercapacitor.
1.4 Proposed block diagram:
Figure 4. Electric vehicle/hybrid electric vehicle system using supercapacitors.
A hybrid vehicle is a vehicle which can run the mechanism by using multiple
sources such as diesel, petrol, gas, elect
components and so that it will provide flexibility, reliability, safe and secured target.
Figure4 shows the operation of hybrid vehicle in two modes. One is motoring
mode and the other is regenerative b
of current in the motoring mode and the red mark indicates the flow of current in the
regenerative braking mode. During the motoring mode the hybrid vehicle takes electric
This equivalent circuit is only a simplified or first order model of a super capacitor.
This causes super capacitors to exhibit behavior more closely to transmission lines than
capacitors. Below is a more accurate illustration of the equivalent circuit for
1.4 Proposed block diagram:
Electric vehicle/hybrid electric vehicle system using supercapacitors.
A hybrid vehicle is a vehicle which can run the mechanism by using multiple
sources such as diesel, petrol, gas, electricity. A hybrid vehicle is combination of different
components and so that it will provide flexibility, reliability, safe and secured target.
shows the operation of hybrid vehicle in two modes. One is motoring
mode and the other is regenerative braking mode. The blue arrow marks indicates the flow
of current in the motoring mode and the red mark indicates the flow of current in the
regenerative braking mode. During the motoring mode the hybrid vehicle takes electric
17
This equivalent circuit is only a simplified or first order model of a super capacitor.
This causes super capacitors to exhibit behavior more closely to transmission lines than
capacitors. Below is a more accurate illustration of the equivalent circuit for a
Electric vehicle/hybrid electric vehicle system using supercapacitors.
A hybrid vehicle is a vehicle which can run the mechanism by using multiple
ricity. A hybrid vehicle is combination of different
components and so that it will provide flexibility, reliability, safe and secured target.
shows the operation of hybrid vehicle in two modes. One is motoring
raking mode. The blue arrow marks indicates the flow
of current in the motoring mode and the red mark indicates the flow of current in the
regenerative braking mode. During the motoring mode the hybrid vehicle takes electric
18
energy from both battery and supercapacitor i.e., the steady state energy is supplied by
battery and energy at peak state (during switching, transient periods) is supplied by both
supercapacitor and battery. During the regenerative mode hybrid vehicle supplies the
electrical energy to both supercapacitor and battery. Since this process is recycled
electrical energy is utilized efficiently. Therefore the weight of the battery decreases and
life gets increased.
1.5 Power Flow:
The load power, coming from the outer parts of the HEV, can be both positive and
negative. A positive load power is in this work defined as that there is a surplus of power
in the outer system and the power is therefore flowing into the ESU (generator reference).
If the load power is negative there is a demand for power in the external system and power
is flowing out from the ESU. Inside the ESU the load power is divided between the power
to the battery and power to the supercapacitor, which is demonstrated in Figure 5.
Figure 5. Power flow to the ESU
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The converter is able to divert power to or from the supercapacitor, depending on
outer Circumstances such as power control strategies. These control strategies are
optimized to give a better system performance and mitigating the battery stresses. In the
last few years th e pollution problems an d the increase of the cost of fossil energy (oil,
gas) have become planetary problems. The car manufacturers started to react to the urban
pollution problems in nineties by commercializing the electric vehicle. But the battery
weight and cost problems were not solved.
The batteries must provide energy and peaks power during the transient states.
These conditions are severe for the batteries. To decrease these severe conditions, the
super capacitors and batteries associate with a good power management present a
promising solution.
A Power management is nothing but efficiently directing power to different
components of a system. Power management is especially important for portable devices
that rely on battery power. By reducing power to components that aren't being used, a
good power management system can double or triple the lifetime of a battery.
20
CHAPTER-2
EFFECTIVENESS OF
BATTERY-
SUPERCAPACITOR
COMBINATION IN HYBRID
VEHICLES
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2.EFFECTIVENESS OF BATTERY-SUPERCAPACITOR
COMBINATION IN HYBRID VEHICLES
A significant portion of energy is dissipated in the brakes when driving
conventional gasoline-powered vehicles in urban areas, where periodic acceleration-
deceleration cycles are required. Therefore, recovering this energy through regenerative
breaking is an effective approach for improving vehicle driving range and this can only
be accomplished by electric vehicles (EV) or hybrid-electric vehicles (HEV).
Regenerative breaking in these vehicles captures some of the kinetic energy stored in the
vehicle’s moving mass by operating the vehicle’s traction motor as a generator that
provides braking torque to the wheels and recharges the batteries .
The battery bank of an EV is sized for peak power demand, and this often
compromises the desired weight and space specifications. On the other hand, The
auxiliary power unit (APU) of an HEV is designed to provide the normal average power
required by the vehicle, while the battery is sized to provide power surges needed during
acceleration and hill climbing and to accept momentary powers during breaking. While
EVs and HEVs are more efficient than conventional vehicles in urban areas, the electric
load profile consists ofhigh peaks and steep valleys due to repetitive acceleration and
deceleration.
The resulting current surges in and out of the battery tend to generate extensive
heat inside the battery, which leads to increased battery internal resistance – thus lower
efficiency and ultimately premature failure . The problem of battery overheating and loss
of capacity is more acute when batteries are near full state-of-charge (SOC) since they
cannot accept large busts of current from regenerative breaking without degradation at
this stage.
Supercapacitors (also referred to as ultracapacitors or electrochemical capacitors)
have much greater advantage over batteries when capturing and supplying short bursts of
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power due to their higher power density limits, and ability to charge and discharge very
quickly. Hence adding a supercapacitor bank will assist the battery during vehicle
acceleration and hill climbing, and with its quick recharge capability, it will assist the
battery in capturing the regenerative braking energy. This significant advantage a battery-
supercapacitor energy storage/supply system gained attention in recent years in
transportation systems as well as other applications . Applying supercapacitors also
allows for a smaller battery size, and there is almost no limit to number of their charge-
discharge cycles (since there are no chemical reactions involved in their energy storage
mechanism). Furthermore these devices require no maintenance and do not use toxic
materials.
Special considerations must be taken into account when integrating such a hybrid
energy storage system to achieve optimal performance. While direct connection of the
supercapacitor across the battery terminals does reduce transient currents in an out of the
battery, the best way to utilize the supercapacitor bank is to be able control its energy
content through a power converter. The paper reviews the direct supercapacitor-battery
shunt connection, after a short section addressing component modeling issues. The
desired connection is then addressed by using a DC/DC converter in the boost mode
when discharging, and in the buck mode when charging the supercapacitor bank.
2.1. Energy management:
The expanding functions of the vehicle electric/electronic system call for
significant improvements of the power supply system. A couple of years ago, broad
introduction of a higher system voltage level, 42V, initially in a dual-voltage 14/42V
system, was considered as a viable solution. However, the cost/benefit ratio associated
with this type of configuration in systems operating at 42V or less turned out to be too
low for widespread implementation. Furthermore, the electric propulsion that can be
generated at this voltage level is generally considered too low to make mild-hybrid
electric vehicles attractive.
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At the same time, several hardware components for the conventional 14Vsystem
experienced significant technological progress. For example, enhanced 14V clawpole
(Lundell) alternators were developed that can continuously generate an electric power
output of 3 kW or more. AGM batteries demonstrated at least three-fold longer shallow-
cycle life, compared to conventional SLI batteries. Finally, the introduction of high-level
energy management control strategies can ensure system robustness and optimal energy
efficiency and thus help stretch the boundaries of the 14V system.
2.1.1 Energy management functions can be separated into two groups:
Power Supply Management (PSM): Control of the on-board electric generation, i.e.
control of the alternator set point in conventional electrical systems, aiming at optimizing
all of the following: electrical function availability, battery life, vehicle performance (e.g.
reduced alternator load when maximum acceleration is demanded), or fuel consumption
(e.g. reduce alternator output at idle to allow for lower idle speed). Whereas many of
these functions can be considered state of the art in modern voltage regulation,
particularly the latter has garnered growing attention recently. Electric generation
contributes significantly to fuel consumption, at least in real-world conditions. An
average alternator output of 1 kW involves as much as 1–1.4 l gasoline fuel consumption
per 0 km, depending on vehicle parameters and driving conditions. Decoupling the
electric generation from the loads’ demands can significantly reduce this specific fuel
consumption contribution by optimizing the system efficiency of engine and alternator at
any point in time. This will introduce supply voltage fluctuations into the electrical
system and systematically exploit the battery as a short-term energy buffer. Significantly
more advanced strategies of PSM are of course needed for HEVs, where electric
generation plays a more vital role.
Power Distribution Management (PDM) is used to schedule the allocation of available
power and energy to electric loads on a subsystem or component level. Effectively, it
must ensure the controlled function delivery of individual electric features by
prioritization. Whenever a power deficiency occurs, the PDM algorithm aims at ensuring
rail voltage stability, charge balance and robustness, as well as minimizing battery charge
24
throughput in the case of peak loads. Depending on the definition of electric feature
priorities, a PDM strategy can dictate a temporary functional degradation under
appropriate conditions. Here, a careful balancing of priorities is required, especially for
functions that are directly perceivable by the customer. Advanced PDM algorithms will
schedule electric feature functionalities dynamically rather than statically.
Electric energy management actively uses the energy storage system (battery,
supercapacitor, etc.) and hence relies on precise status information about this device. A
battery monitoring system (BMS) has to deliver these essential inputs to the energy
management control system.
2.2 Component Modeling:
This section reviews the modeling of the main power system components in an
electric vehicle; namely, the battery bank, the supercapacitor bank, and the electrical
load. More details on electrical component modeling can be found in power electronics
textbooks.
2.2.1 Battery Bank:
Batteries are quite difficult to model as they undergo thermally-dependent
electrochemical processes while delivering and accepting energy. Thus the electrical
behavior of a battery is a nonlinear function of a number of constantly changing
parameters, such as internal temperature, state-of charge, rate of charge/discharge, etc. …
The capacity of a battery depends on the discharge rate as wells as temperature. This
relationship is described by Peuket’s equation relating the discharge current I (A) to the
time t (hr) it takes it to discharge, I. Given the battery capacity CTo at temperature To, the
capacity at some other temperature is computed by CT = CTo1 + (T-To) where is
a constant.
25
An approximate model that is often used for batteries is a Thevenins equivalent
circuit that consists of the open circuit voltage in series with an effective internal
resistance. Both voltage and resistance values are functions of the battery SOC, and these
relations are generally supplied the manufacturer. SOC is defined the percentage of
energy left in a battery (after supplying a certain amount of amp-hours) relative to its full
capacity.
The open-circuit voltage is often approximated by a linear function of the
SOC: Voc = a1+ a2 SOC, at some specific temperature (e.g., 80o F). The battery internal
resistance has static and dynamic values that depend of battery SOC, whether the battery
is being charged or discharged and rate of charge/discharge. In short duration studies,
however, the amount of amp-hours in and out of the battery is a small fraction of the
battery capacity. Hence it is fair to assume that battery internal voltage is constant during
such periods, and a quasi-steady state model with fixed open-circuit voltage and internal
resistance constitutes an acceptable battery model . Note that two resistance values are
used in this case, one during charging and another during discharging.
2.2.2 Supercapacitor Bank:
As in conventional capacitors, the resistance and inductance of the terminal wires
and electrodes of supercapacitors are represented by a series R-L circuit. Further, non-
perfect insulation between the device electrodes results in leakage current that is
represented by a large shunt resistance. The difference between conventional and
supercapacitors is that the latter are much more efficient, i.e., the series resistance is a lot
lower and the shunt resistance is much higher in value. The self-discharge time constant
of supercapacitors several orders of magnitude larger than that of conventional
capacitors. More sophisticated models suitable for dynamic studies are found. The study
under investigation is a short-duration analysis of the power (or current) distribution
between the battery bank and supercapacitor bank during acceleration and deceleration.
Hence, the leakage resistance can be ignored without much error, and the supercapacitor
bank can simply be represented by a series R-C circuit.
26
2.2.3 Electrical Load:
The electrical load in electric vehicles consists mainly of an inverter-fed induction
motor for motive power. During regenerative breaking, the motor is turned into a
generator by reducing the frequency of its terminal voltage, thus reversing power flow
and producing braking torque. Detailed modeling of inverter-fed motor drives is found in
standard power electronics and drives textbooks. As far as the power source in
concerned, power demand is sufficient for analysis. Since the DC bus voltage is not
allowed to vary significantly from its nominal value, current demand gives a good
approximation of power demand. Thus the load can be modeled simply by a time-varying
current source that reverses direction as the vehicle switches from coasting or
acceleration to regenerative braking.
2.3 Vehicle energy storage system using supercapacitors:
2.3.1 System specifications:
To control the energy stored in supercapacitor bank, it is need that the voltage of
the supercapacitor bank should be controlled. If not, the supercapacitor voltage depends
on the battery voltage, so that there is no possibility to control the energy stored in
supercapacitor bank. Thus, DC/DC converter is indispensable to regulate the bank
voltage level. Moreover, because the current can flow to supercapacitor when the
supercapacitor is charged and the current can flow from supercapacitor when the
supercapacitor is discharged, the DC/DC converter has to have a bi-directional nature.
Figure 6. shows the system configuration with battery pack and supercapacitor bank as an
energy storage. The DC/DC converter is on boost-mode operation as the inverter supplies
traction power to the motor. On the other hands, the DC/DC converter is on buck-mode
operation as the regenerative energy come to supercapacitor bank.
27
Figure 6. System configuration of the supercapacitor implemented.
Table 1. Specification of system.
From the required specification of Table 1, the number of supercapacitor cell is
designed to be 30, on the basis that the maximum voltage of each supercapacitor cell is
2.3V (92% of continuous voltage rating), and the minimum voltage of each
supercapacitor cell is 1.25V (50% of continuous voltage rating). As a consequence, the
capacitance of the supercapacitor bank used in this study becomes 2700/30=90F and
28
equivalent series resistance (ESR) 1mΩ×30=30mΩ, to make the maximum stored energy
become 210kJ. The the total volume and weight of the supercapacitor bank is 18l and
22kg, respectively.
2.3.2. The topology of bi-directional DC/DC converter:
There can be lots of converter topology for realizing a bi-directional DC/DC
converter; single-stage buck/boost type and full-bridge type as a typical one. Full-bridge
type topology has merits compared to single-stage buck/boost type topology. 1) Electrical
isolation between input and output is guaranteed. 2) Higher boost ratio can be
implemented. 3) System protection is possible when output stage short take place. From
these facts, full-bridge type topology is employed in this study, in spite that the full-
bridge type topology is somewhat bulky, requires more components rather than single
stage buck/boost type.
Figure 7. The bi-directional DC/DC converter(full-bridge type topology).
29
As shown in Fig. 7, the bi-directional full-bridge topology DC/DC converter is
operated on boost mode at the time electric power is supplied from supercapacitor stage
(low voltage stage) to battery stage (high voltage stage), and on buck mode at the time
electric power is absorbed from battery stage to supercapacitor stage. Because the
supercapacitor stage of the DC/DC converter has low voltage level, a current control is
necessary in the cause of reducing current’s burden on semiconductors.
At the battery stage of the DC/DC converter, voltage control is necessary to match
to DC bus voltage of the inverter. Also, soft switching technique of zero voltage-zero
current switching is applied to this system for improving the DC/DC converter efficiency.
2.4 Vehicle application requirements:
The energy storage requirements vary a great deal depending on the type and size
of the vehicle being designed and the characteristics of the electric powertrain to be used.
Energy storage requirements for various vehicle designs and operating strategies are
shown in Table 2 for a mid-size passenger car. Requirements are given for electric
vehicles and both charge sustaining and plug-in hybrids.
These requirements can be utilized to size the energy storage unit in the vehicles
when the characteristics of the energy storage cells are known. In some of the vehicle
designs considered in Table, ultracapacitors are used to provide the peak power rather
than batteries.
For ultracapacitors, the key issue is the minimum energy (Wh) required to
operate the vehicle in real world driving because the energy density characteristics of
ultracapacitors are such that the power and cycle life requirements will be met in most
cases if the unit is large enough to met the energy storage requirement.
30
Table 2. Energy storage unit requirements for various types of electric passenger cars
Type of
electric
driveline
System
Voltage V
Useable
energy
storage
Maximum
pulse power at
90-95%
efficiency kW
Cycle life
(number of
cycles)
Useable
depth of-
discharge
Electric
300-400 15-30 kWh 70-150 2000-3000
deep
70-80%
Plug-in
hybrid
300-400
6-12 kWh
battery 100-
150 Wh
ultracapacitors
50-70 2500-3500
deep
60-80%
Charge
sustaining
hybrid
150-200
100-150 Wh
ultracapacitors
25-35 300K-500K
Shallow
5-10%
Micro-
hybrid
45
30-50 Wh
ultracapacitors
5-10 300K-500K
Shallow
5-10%
31
CHAPTER-3
ULTRACAPACITOR-
BATTERY INTERFACE FOR
POWER ELECTRONIC
APPLICATIONS
32
3.ULTRACAPACITOR-BATTERY INTERFACE FOR
POWER ELECTRONIC APPLICATIONS
The electrical load in electric vehicles consists mainly of an inverter-fed induction
motor for motive power. During regenerative breaking, the motor is turned into a
generator by reducing the frequency of its terminal voltage, thus reversing power flow
and producing braking torque. As far as the power source in concerned, power demand is
sufficient for analysis. Since the DC bus voltage is not allowed to vary significantly from
its nominal value, current demand gives a good approximation of power demand. Thus
the load can be modeled simply by a time-varying current source that reverses direction
as the vehicle switches from coasting or acceleration to regenerative braking.
1. The role of the ultracapacitor is to maintain the battery current as constant as
possible with slow transition from low to high current during transients to limit battery
stress. On the other hand, the ultracapacitor ought to charge as fast as possible without
exceeding maximum current from regenerative breaking, and to discharge most of its
stored energy during acceleration. Energy flow in and out of the ultracapacitor can be
controlled with pulse-with-modulated (PWM) DC/DC converter. Adding a
ultracapacitor bank to a battery- or fuel cell driven vehicle makes sense and advantages
by far outweigh the disadvantages. A direct parallel connection will reduce battery stress
by assisting with transient currents during acceleration and deceleration. The parallel
combination of the battery system and UC bank also exhibits good performance for the
stand-alone residential applications during the steady-state, load-switching, and peak
power demand. Without the UC bank, the battery/fuel cell system must supply this extra
power, thereby increasing the size and cost of the attery/fuel cell system .
2. The ultracapacitor addition removes 20% of the mass of the battery pack of the
electric vehicle. Another method for reducing the size of the capacitor bank would use
some battery power during each shot. If the application were to permit this, the
ultracapacitor stack would still supply most of the power while the load was at its peak,
but the battery would supply a lower, consistent level over the full ten-second duration.
Such a hybrid approach can significantly reduce the size of the ultracapacitor stack.
33
3. Time domain and frequency domain measurements both confirmed that
ultracapacitors are very efficient for low frequency use. Both also show that the
capacitance drops (with corresponding decrease in efficiency) for frequencies greater
than 0.1 Hz is measured by various frequency response of ultracapacitors. The time
domain measurements show that capacitor loss becomes very significant (70% for some
tests) for fast discharge times . As Ultra-capacitors are always used for energy storage or
energy buffer applications, their poor high frequency response makes them completely
unsuitable for high frequency applications and are therefore more suitable for dc
circuits. Thus the Ultracapacitors should be connected to any high frequency charging
converter with a small inductance of about 20µH in series to the converter.
4. The main problem with the application of ultracapacitors is that maximum
voltage of each cell in the stack (2 ,5 V) should not be exceeded. It is probably
reasonable to limit the number of cells in series in batteries, and to match voltages of
interconnected DC links using a converter containing an AC medium frequency link
with transformer.
5. Ultra-capacitors are used as an energy storage buffer by simultaneously charging
and discharging them by paralleling them to an energy source like a battery, fuel cell,
DC-DC converter , etc. and a load. The voltage and current ripple caused by the
charging converter can often cause over charging or temperature rise of the capacitor.
The increasing filter inductance or increasing the switching frequency of the buck
derived DC-DC converter that is usually used for charging will be one solution, they
will significantly either increase both size and cost or increase losses in the converter.
Moreover, increasing inductance requires higher turns and this increases both the
radiated fields from the inductor and the inter-winding capacitance of the inductor.
These radiated fields and the feed through noise through the inter-winding capacitance
from the inductor mainly couple to surrounding circuits and increase EMI. Thus a better
solution would be to use additional filter circuits that attenuate both voltage ripple and
ripple current during charging.
34
CHAPTER-4
DC/DC CONVERTERS
TOPOLOGIES AND
MODELING
35
4. DC/DC CONVERTERS TOPOLOGIES AND MODELING
4.1. Multi boost and Multi full bridge converters modeling
Figure 8(a) shows the multi boost converter topology. The general model for this
topology is given by equation (1); where (α1) and (n) define respectively the duty cycle
and parallel input converter number.
The voltage drops in the Ln and λ inductances are given by equation (2).
Figure 8 (a). Multi boost Converter topology
(1)
(2)
36
Figure 8(b). Multi full bridge converter topology
The converter average model has a nonlinear behavior because of crosses between
α1 control variable and Vbus1 parameter. The Vbus1, Vsc1, Vsc2, Vscn , Ich and Vbat
variables can to disturb the control, they must be measured and used in the estimate of the
control law to ensure a dynamics of control . The multi boost converter topology control
law which results from the boost converter modeling is presented by α1 duty cycle (3);
where Np = max(n) is the maximum number of parallel converters.
The multi boost converter control strategy is presented in Fig.9 (a). It ensures the
super capacitor modules discharge with variable current. The super capacitors reference
current (Iscref) is obtained starting from the power management between batteries and
hybrid vehicle DC-link. This control strategy includes the super capacitors and batteries
current control loops. PWM1 signal ensures the multi boost converters control during
(3)
37
super capacitor modules discharge. These modules being identical, the energy
management between the modules and the hybrid vehicle DC-link enables to write the
super capacitors current references (4).
To simplify the super capacitors current references estimation, the multi boost
converter efficiency (η) was fixed at 85%.
The multi full bridge converter control strategy proposed in this paper consists to
establish the full bridge converters standardized voltage . The control law which result
from the multi full bridge converter modeling is presented by equation(5), where (m)
defines the transformer turns ratio.
This standardized voltage is compared with two triangular carrier waves of
amplitude Vmax = 1V with a switching frequency of 20 kHz. The inverter control
strategy is presented in Fig. 9(b); where Q1, Q2, Q3 and Q4 are the control signals
applied to K1, K2, K3 and K4 switches.
(4)
(5)
38
Figure 9(a) Multi boost control strategy
Figure 9(b) Multi full bridge control strategy
Figure 9. Multi boost and Multi full bridge converters control strategy
39
CHAPTER-5
DESIGN FOR
EXPERIMENTAL RESULTS
40
5. DESIGN FOR EXPERIMENTAL RESULTS
Wiring in power electronic design is a general problem for electrical energy
system and the voltage inverters do not escape to this problem. The switch action of
semiconductors causes instantaneous fluctuations of the current and any stray inductance
in the commutation cell will produce high voltage variations. Semiconductors, when
switching off, leads to high voltage transitions which is necessary to control within
tolerable limits. The energy stored in parasitic inductances, during switching on, is
generally dissipated by this semiconductor.
In the case of the single-phase inverter, each cell includes two switches and a
decoupling capacitor placed at the cell boundaries, which presents a double role. It
enables to create an instantaneous voltage source very close to the inverter. The (C)
capacitor associated to an inductor enables to filter the harmonic components of the
currents which are generated by the inverter. Parasitic inductances staying in the mesh
include the capacitor inductance, the internal inductance of semiconductors and the
electric connection inductances. A good choice of the components with an optimal wiring
enables to minimize parasitic inductances.
Using the semiconductors modules solves the connection problems between
components. All these efforts can become insufficient, if residual inductances remain too
high or if the inverter type is the low voltages and strong currents for which the voltage
variations are much important. In both cases, the use of the chopping devices is
necessary. These devices must be placed very close to the component to avoid any
previous problem.
The parameters used for experimental tests are presented in table 3. and the
principle of such circuits is given in Fig. 10.
41
Table 3: Full bridge experimental parameters
Symbol Value Name
R1= R2=R3 = R4 10Ω Chopping circuits
resistances
C1=C2=C3=C4 220µF Chopping circuits capacitors
λ 25µH Battery current smoothing
inductance
m 3 Planar transformer turns
ratio
Vbus1 60V-43V DC-link voltage
C 6800 µF Super capacitors voltage
smoothing capacitor
L1 50µH Super capacitors currents
smoothing inductance
Figure 10. Full bridge converter with chopping devices
During switching off of the semiconductors, the corresponding current stored in
wiring inductances circulates in the following meshes C1, D1 ; C2 , D2; C3, D3 and C4 , D4
which limits the voltages applied to the switches. When electrical energy is fully
transferred in C1, C2, C3 and C4 capacitors, the current becomes null and the meshes
become closed. The C1, C2, C3 and C4 capacitors are used only for transient energy tank
42
and it is necessary to recycle this switching energy while controlling the voltage at the
semiconductors boundary. This function is ensured by R1, R2, R3 and R4 resistances. R1,
R2, R3 and R4 resistances are identical and C1, C2, C3 and C4 capacitors are also identical.
5.1 Experimental setup at reduced scale:
11(a) Boost converters setup for Np = 2
For reasons of cost components and safety, the experimental test benches were carried
out at a reduced scale .
• The boost converter test bench Fig.11 (a) is made of: a battery module of 4 cells in
series, two super capacitors modules of 10 cells (Maxwell BOOSTCAP2600) in series for
each one, an active load which is used to define power request, two boost converters in
parallel which ensure power management in hybrid vehicle.
43
11(b) Full bridge converter setup for Np = 1
Figure 11. Boost and full bridge converters experimental setup
• For the full bridge converter test bench Fig.11 (b), a batteries module, a super capacitors
module, two high frequency planar transformer, the DC/AC and AC/DC converters have
been designed. The super capacitors modules voltages must be between 27 V and 13.5 V.
The batteries module which imposes the DC-bus voltage presents a rated voltage
of 48 V and the DC link voltage level must be between 43 V and 60 V. The converters
are controlled by a PIC18F4431 microcontroller with 10 kHz control frequencies for
boost converters and 20 kHz for the full bridge converter.
44
CHAPTER-6
SIMULATION RESULTS
45
6.SIMULATION RESULTS
6.1 General:
Simulation has become a very powerful tool on the industry application as well as
in academics, nowadays. It is now essential for an electrical engineer to understand the
concept of simulation and learn its use in various applications. Simulation is one of the
best ways to study the system or circuit behavior without damaging it .The tools for doing
the simulation in various fields are available in the market for engineering professionals.
Many industries are spending a considerable amount of time and money in doing
simulation before manufacturing their product. In most of the research and development
(R&D) work, the simulation plays a very important role. Without simulation it is quiet
impossible to proceed further. It should be noted that in power electronics, computer
simulation and a proof of concept hardware prototype in the laboratory are
complimentary to each other. However computer simulation must not be considered as a
substitute for hardware prototype. The objective of this chapter is to describe simulation
of impedance source inverter with R, R-L and RLE loads using MATLAB tool.
6.2 Introduction to Matlab:
MATLAB is a high-performance language for technical computing. It integrates
computation, visualization, and programming in an easy-to-use environment where
problems and solutions are expressed in familiar mathematical notation. Typical uses
includes
1. Math and computation
2. Algorithm development
3. Data acquisition
4. Modeling, simulation, and prototyping
5. Data analysis, exploration, and visualization
6. Scientific and engineering graphics
7. Application development, including graphical user interface building
46
MATLAB is an interactive system whose basic data element is an array that does
not require dimensioning. This allows you to solve many technical computing problems,
especially those with matrix and vector formulations, in a fraction of the time it would
take to write a program in a scalar non-interactive language such as C or FORTRAN.
The name MATLAB stands for matrix laboratory. MATLAB was originally
written to provide easy access to matrix software developed by the LINPACK and
EISPACK projects. Today, MATLAB engines incorporate the LAPACK and BLAS
libraries, embedding the state of the art in software for matrix computation.
MATLAB has evolved over a period of years with input from many users. In
university environments, it is the standard instructional tool for introductory and
advanced courses in mathematics, engineering and science. In industry, MATLAB is the
tool of choice for high-productivity research, development and analysis.
MATLAB features a family of add-on application-specific solutions called
ToolBoxes. Very important to most users of MATLAB, toolboxes allow you to learn and
apply specialized technology. Toolboxes are comprehensive collections of MATLAB
functions (M-files) that extend the MATLAB environment to solve particular classes of
problems. Areas in which toolboxes are available include signal processing, control
systems, neural networks, fuzzy logic, wavelets, simulation and many others.
6.3 The Matlab System:
The MATLAB system consists of five main parts:
6.3.1 Desktop tools and development environment:
This is the set of tools and facilities that help you use MATLAB functions and
files. Many of these tools are graphical user interfaces. It includes the MATLAB desktop
and Command Window, a command history, an editor and debugger, a code analyzer and
other reports, and browsers for viewing help, the workspace, files, and the search path.
47
6.3.2 The Matlab mathematical function library:
This is a vast collection of computational algorithms ranging from elementary
functions, like sum, sine, cosine, and complex arithmetic, to more sophisticated functions
like matrix inverse, matrix eigen values, Bessel functions, and fast Fourier transforms.
6.3.3 The Matlab language:
This is a high-level matrix/array language with control flow statements, functions,
data structures, input/output, and object-oriented programming features. It allows both
"programming in the small" to rapidly create quick and dirty throw-away programs, and
"programming in the large" to create large and complex application programs.
6.3.4 Graphics:
MATLAB has extensive facilities for displaying vectors and matrices as graphs,
as well as annotating and printing these graphs. It includes high-level functions for two-
dimensional and three-dimensional data visualization, image processing, animation, and
presentation graphics. It also includes low-level functions that allow you to fully
customize the appearance of graphics as well as to build complete graphical user
interfaces on your MATLAB applications.
6.3.5 The Matlab external interfaces:
This is a library that allows you to write C and FORTRAN programs that interact
with MATLAB. It includes facilities for calling routines from MATLAB (dynamic
linking), calling MATLAB as a computational engine, and for reading and writing MAT-
files.
6.3.6 Matlab documentation:
MATLAB provides extensive documentation, in both printed and online format,
to help you learn about and use all of its features. If you are a new user, start with this
Getting Started book. It covers all the primary MATLAB features at a high level,
including many examples. The MATLAB online help provides task-oriented and
48
reference information about MATLAB features. MATLAB documentation is also
available in printed form and in PDF format.
6.3.7 Matlab online help:
To view the online documentation, select MATLAB Help from the Help menu in
MATLAB. The MATLAB documentation is organized into these main topics:
6.3.8 The role of simulation in design:
Electrical power systems are combinations of electrical circuits and electro-
mechanical devices like motors and generators. Engineers working in this discipline are
constantly improving the performance of the systems. Requirements for drastically
increased efficiency have forced power system designers to use power electronic devices
and sophisticated control system concepts that tax traditional analysis tools and
techniques. Further complicating the analyst's role is the fact that the system is often so
nonlinear that the only way to understand it is through simulation.
Land-based power generation from hydroelectric, steam, or other devices is not
the only use of power systems. A common attribute of these systems is their use of power
electronics and control systems to achieve their performance objectives.
Sim Power Systems is a modern design tool that allows scientists and engineers to
rapidly and easily build models that simulate power systems. Sim Power Systems uses
the Simulink environment, allowing you to build a model using simple click and drag
procedures. Not only can you draw the circuit topology rapidly, but your analysis of the
circuit can include its interactions with mechanical, thermal, control, and other
disciplines. This is possible because all the electrical parts of the simulation interact with
the extensive Simulink modeling library. Since Simulink uses MATLAB as its
computational engine, designers can also use MATLAB toolboxes and Simulink block
sets. Sim Power Systems and Sim Mechanics share a special Physical Modeling block
and connection line interface.
49
6.3.9 Sim power systems libraries:
You can rapidly put Sim Power Systems to work. The libraries contain models of
typical power equipment such as transformers, lines, machines, and power electronics.
Mat lab Library
50
Mat lab Library
51
6.3.10 Matlab Library:
American utility located in Canada, and also on the experience of Ecole de
Technologies superiors and Universities Laval. The capabilities of Sim Power Systems
for modeling a typical electrical system are illustrated in demonstration files. And for
users who want to refresh their knowledge of power system theory, there are also self-
learning case studies.
The Sim Power Systems main library, powerlib, organizes its blocks into libraries
according to their behavior. The powerlib library window displays the block library icons
and names. Double-click a library icon to open the library and access the blocks. The
main Sim Power Systems powerlib library window also contains the powerguide block
that opens a graphical user interface for the steady-state analysis of electrical circuits.
6.4 Full bridge converter simulation circuit for Np = 2:
The simulation has been made for Np = 2 as shown in figure 12. The maximum
and minimum voltages of the super capacitor modules are respectively fixed at 270V and
135V. The hybrid vehicle requested current (Ich) is respectively fixed at 100A from 0 to
0.5s, 400A from 0.5s to 18s and 100A from 18s to 20s. Battery reference current (Ibatref)
is fixed at 100A independently of the hybrid vehicle power request. Super capacitor
modules voltages (Vsc1, Vsc2) presented in Fig.13 (a) are identical. The currents
amplitudes (Isc1, Isc2) presented in Fig.13 (b) are also identical.
Control enables to maintain the battery current (Ibat) at 100A; but around 0.5s and
18s the battery current control loop has not enough time to react Fig.14 (a). The
important power of the transient states is ensured by the super capacitors modules (IL)
Fig. 14(b). Simulation parameters are presented in table 4.
52
Figure 12. Full bridge converter simulation circuit for Np = 2
Table 4. Full bridge topologie simulations parameters
Symbol Value Name
λ 25µH Battery current smoothing inductance
m 3 Planar transformer turns ratio
Vbus1 604V-432V DC-link voltage
L1=L2 50µH Super capacitors currents smoothing inductances
53
Figure 13 (a). Super capacitor modules voltages
Figure 13(b). Super capacitor modules currents
54
Figure 14. (a): Battery current control result
Figure 14(b): DC-link and active load currents
55
6.5 Boost converters simulation results:
6.5.1 Simulation circuit for boost converter:
The boost converters experimental test is carried out in the following conditions:
During the super capacitors discharge, the batteries current reference (Ibatref) is fixed at
13A so that, the super capacitors modules provide hybrid vehicle power request during
the transient states. For these tests, the hybrid vehicle request (Ich) was fixed at 53A. The
experimental and simulations results of the modules voltage are compared in Fig.16 (a)
and Fig.16 (b). The (Isc1) and (Isc2) experimental currents are not identical Fig.17 (a),
Fig.17 (b) because the super capacitors dispersion and the power electronic circuits
(boost converters) inequality.
The first boost converter ensures 50% and the second ensures also 50% of the
DC-link current (IL). In other words the two super capacitors modules ensure a (IL)
current of 40A to hybrid vehicle as presented in Fig.18 (a), and 13A only is provided by
the batteries Fig.18 (b).
Figure 15. Simulation circuit for boost converter
56
16(a) First module voltage
16(b) Second module voltage
Figure 16. Super capacitor modules experimental and simulation voltage results
57
17(a) First module current
17(b) Second module current
Figure 17. Super capacitor modules experimental and simulation current results
58
18(a) Multi boost output current (IL )
18(b) Battery current experimental result
Figure 18. DC-link voltage and current experimental validation
59
6.6 full bridge converters simulation results:
The Q1, Q2, Q3 and Q4 control signals applied to K1, K2, K3 and K4
semiconductors. For electric constraints reasons of the available components,
(transformer, IGBT, active load), the full bridge experimental test conditions are different
to that of boost converters topology. The super capacitors module maximum voltage
(Vsc1) is fixed at 22V because of battery module voltage (48V), the transformer turns
ratio (m=3) and active load which is limited to 80V. The battery current reference
(Ibatref) and active load current request (Ich) are respectively fixed at 5A and 15A.
The super capacitors power is not constant (Vsc1, Isc1) because of the consumed current by
R1, R2, R3 and R4 resistances Fig.12 (a). The battery current experimental result is
presented in Fig.12 (b). The voltages and currents ripples which appear in Fig. 11 (b),
Fig.12 (a) and Fig. 12 (b) are caused by leakage inductances of the transformer and
wiring of the power electronics devices.
The voltages and currents of the high frequency planar transformer are
respectively presented in Fig. 13 (a) and Fig. 13 (b). The transformer secondary voltage
(Vs2) transient which corresponds to the change of sign of the current (Is2) is caused by
the transformer leakage inductance.
60
Figure 19.simulation circuit for full bridge converter
61
Figure 20 (a). Super capacitors module voltage and current
20(b): DC-link and active load experimental currents
62
Figure. 21(a) Transformer input and output voltages
Figure 21(b) Transformer input and output currents
Figure 21. High frequency planar transformer voltages and currents
63
CONCLUSION
In this paper, multi boost and multi full bridge converter topologies and their
control strategies for batteries and super capacitors coupling in the hybrid vehicle
applications were proposed. For reasons of simplicity and cost, the multi boost converter
is the most interesting topology regarding the multi full bridge converter topology. It
enables a good power management in hybrid vehicle.
Full bridge experimental tests conditions were different from that of boost
converter topology, so at this time it is not easy to make a good comparison between the
two topologies. However, multi full bridge converter topology is well suitable to adapt
the level of available voltage to the DC-link. For low voltage and high current
applications such as super capacitors, the full bridge converter seems to be less
interesting because of its higher cost (many silicon and passive components), and a lower
efficiency.
64
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