A Mini Project Report

ON

“SUPERCAPACITORS AND BATTERY POWER MANAGEMENT FOR HYBRID

VEHICLE APPLICATIONS USING MULTI BOOST AND FULL BRIDGE

CONVERTERS”

Is submitted in the partial fulfillment for the award of the degree of

BACHELOR OF TECHNOLOGYIN

ELECTRICAL AND ELECTRONICS ENGINEERING

By

M.KRISHNAVENI 11B71A0206

A.PRADEEP 11B71A0244

E.SOUMYA 11B71A0249

P.SRINIVAS 11B71A0246

UNDER THE GUIDANCE OF

Mrs. M.PADMA

Asst. Professor

DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING

SINDHURA COLLEGE OF ENGINEERING & TECHNOLOGY

Approved by AICTE New Delhi, affiliated to JNTUH, Hyderabad.

Medipally, Godhavarikhani, Ramagundam (M), Karimnagar (D), T.S.

During the academic year 2011-2015.

SINDHURA COLLEGE OF ENGINEERING & TECHNOLOGY

(Approved by AICTE New Delhi, affiliated to JNTUH, Hyderabad)

DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING

CERTIFICATE

This is to certify that the mini project report entitled “Super Capacitor & Battery Power Management For Hybrid Vehicle Application Using Multi Boost & Full Bridge Converters” is submitted in the partial fulfillment for the award of the degree of BACHELOR OF TECHNOLOGY in ELECTRICAL AND ELECTRONICS ENGINEERING.

By

M.KRISHNAVENI 11B71A0206

A.PRADEEP 11B71A0244

E.SOUMYA 11B71A0249

P.SRINIVAS 11B71A0246

Bonafide students of SINDHURA COLLEGE OF ENGINEERING & TECHNOLOGY

During the academic year 2014-2015.

Mrs. M.PADMA Mr. J.MADHUKAR REDDY

INTERNAL GUIDE H.O.D, EEE Dept

Mr. R.NARAYAN DAS EXTERNAL EXAMINER

PRINCIPAL

DECLARATION

We the students of B.Tech in Electrical & Electronics Engineering, Sindhura

college of Engineering & Technology, Ramagundam, hereby declare that the Mini Project

entitled “SUPER CAPACITOR & BATTERY POWER MANAGEMENT FOR

HYBRID VEHICLE APPLICATION USING MULTI BOOST & FULL BRIDGE

CONVERTERS” is the original work carried out by us to the best of my knowledge and

belief. We hereby declare that this mini project bears no resemblance to any other project

submitted at Sindhura college of Engineering & Technology, Ramagundam or any other

colleges affiliated JNTUH for the award of the degree.

By

M.KRISHNAVENI 11B71A0206

A.PRADEEP 11B71A0244

E.SOUMYA 11B71A0249

P.SRINIVAS 11B71A0246

ACKNOWLEDGEMENT

The development of the project through an arduous task has been made easier with

the cooperation of many people. We are pleased to express thanks to the people whose

suggestions, comments and criticisms greatly encouraged in the betterment of the project.

We are very grateful to Mr. R.Narayan Das, Principal, Sindhura College of

Engineering & Technology for providing the required facilities in the college campus.

We express our sincere thanks to Mr. J.Madhukar Reddy, Associate Professor &

Head of the Department of Electrical and Electronics Engineering for the constant

cooperation and constructing, criticism, throughout the project.

We express our sincere thanks to our guide Mrs. M.Padma, Assistant Professor for

his valuable guidance, involvement and the interest shown by him on us has been the main

inspiration for the successful completion of the project.

We would also thank all the staff of Department of Electrical & Electronics Engineering and

Project Review Committee (PRC) members, who are helped us directly or indirectly for the successful

completion of the project.

We earnestly thank my Parents, Family and Friends for their constant encouragement and

moral support, which made the project work successful.

By

M.KRISHNAVENI 11B71A0206

A.PRADEEP 11B71A0244

E.SOUMYA 11B71A0249

P.SRINIVAS 11B71A0246

ABSTRACT

This project presents super capacitors and battery association methodology for ECCE

Hybrid vehicle. ECCE is an experimental Hybrid Vehicle developed at L2ESLaboratory in

collaboration with the Research Centre 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 super capacitor packs. Each super capacitors 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.

INDEX

S.NO TITLE PAGE NO

1. INTRODUCTION 12. SUPER CAPACITORS 2

2.1 Super Capacitor Construction 22.2 Equivalent Circuit 52.3 How to Measure the Capacitance 52.4 Capacitance 62.5 Life Expectancy 72.6 Applications for Super capacitors 72.7 Importance of Proper Design of SCES and Future Scope of Work 8

3. BOOST CONVERTER 93.1 Block Diagram 103.2 Operating Principle 103.3 Applications of Boost Converter 15

4. ELECTRIC VEHICLE 164.1 Vehicle Types 174.2 Advantages of Electric Vehicles 19

5. FULL BRIDGE CONVERTER 215.1 Half-Wave Rectifier 215.2 Full-Wave Rectifier 225.3 Peak Loss 245.4 Rectifier Output Smoothing 245.5 Voltage Doubling Rectifier 255.6 Basic Operation 265.7 Output Smoothing 27

6. POWER MANAGEMENT 306.1 Power Management System Helps To 31

7. DC/DC CONVERTER TOPOLOGIES & MODELING 337.1 Multi Boost & Multi Full Bridge Converters Modelling 337.2 Full Bridge Converter Simulation Results For Np=2 35

8. SIMULINK DIAGRAM 379. DESIGN AND EXPERIMENTAL RESULTS 39

9.1 Experimental Setup at Reduced Scale 409.2 Boost Converter Simulation & Experimental Results 41CONCLUSION 43REFERENCES 44

LIST OF FIGURES

FIG.NO FIGURE NAME PAGE NO

1 Converter Topologies for ECCE Hybrid Vehicle 1

2.1(a) Activated carbon electrodes 3

2.1(b) Series RC Circuit with Parallel Resistance 3

2.2(a) Supercapacitor Equivalent Circuit 5

2.2(b) Equivalent circuit 5

2.3 Charge and Discharge Method 6

3 Circuit Diagram of Boost Converter 9

3.1 Block diagram of Boost Converter 10

3.2(a) Boost converter schematic 10

3.2(b) Two Configurations of a Boost Converter,

Depending on the State of the Switch S 11

3.2(c) Waveforms of Current and Voltage in a

Boost Converter Operating In Continuous Mode 12

3.2(d) Waveforms of Current and Voltage in a Boost Converter

Operating In Discontinuous Mode 14

4 Electric vehicle/hybrid electric system using super capacitors 17

5.1 Half Wave Rectifier Circuit, I/P & O/P Wave Forms 21

5.2(a) Full Wave Rectifier with Non-center Tapped Transformer 22

5.2(b) Full Wave Rectifier with Centre Tapped Transformer 22

5.2(c) A Three-phase Bridge Rectifier 23

5.2(d) 3-phase AC input, Half & Full Wave Rectified

DC Output Waveforms 23

5.4 RC-Filter Rectifier 24

5.5 Cockcroft Walton Voltage Multiplier 26

5.6 AC, Half-wave and Full Wave Rectified Signals 27

5.7(a) Three Phase Bridge Rectifier 29

5.7(b) 3-Phase AC input Waveform, Half-wave Rectified Waveform

& Full-wave Rectified Waveform 29

7.1(a) (a) Multi boost Converter Topology &

(b) Multi Full Bridge Converter Topology 33

7.1(b) (a) Multi Boost Control Strategy &

(b) Multi Full Bridge Control Strategy 34

7.2(a) (a) Super Capacitor Modules Voltages,

(b) Super Capacitor Modules Currents 35

7.2(b) (a) Battery current control result

(b) DC-link and active load currents 36

8 (a) Boost converter circuit 37

8 (b) Full bridge converter circuit 38

9 Full Bridge Converter with Chopping Devices 39

9.1 Boost and Full Bridge Converters Experimental Setup 41

9.2(a) Super Capacitor Modules Experimental and

Simulation Voltage Results 41

9.2(b) Super Capacitor Modules Experimental and

Simulation Current Results 42

9.2(c) DC-link voltage and current experimental validation 42

LIST OF TABLES

TABLE.NO TABLE NAME PAGE NO

Table 1 Full bridge Topology Simulations Parameters 36

Table 2 Full bridge Experimental parameters 39

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.

Super capacitors are storage devices which enable to supply the peaks of power to

hybrid vehicle during the transient states. During the steady states, batteries will provide

the energy requested. This methodology enables to decrease the weight and increases the

lifespan of the batteries. Hybridization using batteries and super capacitors for transport

applications is needed when energy and power management are requested during the

transient sates and steady states. The multi boost and multi full bridge converters will be

investigated because of the high power. For range problems, traction batteries used until

now cannot satisfy the energy needed for future vehicles. 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 Figure.

Fig 1: Converter Topologies for ECCE Hybrid Vehicle

2. SUPER CAPACITORS

Capacitors store electric charge. Because the charge is stored physically, with no

chemical or phase changes taking place, the process is highly reversible and the discharge-

charge cycle can be repeated over and over again, virtually without limit. Electrochemical

capacitors (ECs), variously referred to by manufacturers in promotional literature as Super

capacitors also called ultra capacitors 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 most significant advantage supercapacitors have over batteries is their ability to

be charged and discharged continuously without degrading like batteries do. This is why

batteries and super capacitors are used in conjunction with each other. The supercapacitors

will supply power to the system when there are surges or energy bursts since

supercapacitors can be charged and discharged quickly while the batteries can supply the

bulk energy since they can store and deliver larger amount energy over a longer slower

period of time.

2.1 Super Capacitor Construction:

What makes super capacitors different from other capacitors types are the

electrodes used in these capacitors. Supercapacitors are based on a carbon (nano tube)

technology. The carbon technology used in these capacitors creates a very large surface

area with an extremely small separation distance. Capacitors consist of 2 metal electrodes

separated by a dielectric material. The dielectric not only separates the electrodes but also

has electrical properties that affect the performance of a capacitor. Supercapacitors do not

have a traditional dielectric material like ceramic, polymer films or aluminum oxide to

separate the electrodes but instead have a physical barrier made from activated carbon that

when an electrical charge is applied to the material a double electric field is generated

which acts like a dielectric. The thickness of the electric double layer is as thin as a

molecule. The surface area of the activated carbon layer is extremely large yielding several

thousands of square meters per gram. This large surface area allows for the absorption of a

large amount of ions.

The charging/discharging occurs in an ion absorption layer formed on the electrodes

of activated carbon.

The activated carbon fiber electrodes are impregnated with an electrolyte where

positive and negative charges are formed between the electrodes and the impregnant. The

electric double layer formed becomes an insulator until a large enough voltage is applied

and current begins to flow. The magnitude of voltage where charges begin to flow is

where the electrolyte begins to break down. This is called the decomposition voltage

Fig 2.1(a): Activated carbon electrodes

The double layers formed on the activated carbon surfaces can be illustrated as a

series of parallel RC circuits.

As shown below the capacitor is made up of a series of RC circuits where R1, R2

…Rn are the internal resistances and C1, C2..., Cn are the electrostatic capacitances of the

activated carbons.

Fig 2.1(b): Series RC Circuit with Parallel Resistance

When voltage is applied current flows through each of the RC circuits. The amount of

time required to charge the capacitor is dependent on the CxR values of each RC circuit.

Obviously the larger the CxR the longer it will take to charge the capacitor. The

amount of current needed to charge the capacitor is determined by the following equation:

In= (V/Rn) exp (-t/ (Cn*Rn))

Super capacitor is a double layer capacitor; the energy is stored by charge transfer

at the boundary between electrode and electrolyte. The amount of stored energy is

function of the available electrode and electrolyte surface, the size of the ions, and the

level of the electrolyte decomposition voltage. Supercapacitors are constituted of two

electrodes, a separator and an electrolyte. The two electrodes, made of activated carbon

provide a high surface area part, defining so energy density of the component. On the

electrodes, current collectors with a high conducting part assure the interface between the

electrodes and the connections of the super capacitor. The two electrodes are separated by

a membrane, which allows the mobility of charged ions and forbids no electronic contact.

The electrolyte supplies and conducts the ions from one electrode to the other.

Usually super capacitors are divided into two types: double-layer capacitors and

electrochemical capacitors. The former depends on the mechanism of double layers, which

is result of the separation of charges at interface between the electrode surface of active

carbon or carbon fiber and electrolytic solution. Its capacitance is proportional to the

specific surface areas of electrode material. The latter depends on fast faraday redox

reaction. The electrochemical capacitors include metal oxide supercapacitors and

conductive polymer supercapacitors. They all make use of the high reversible redox

reaction occurring on electrodes surface or inside them to produce the capacitance

concerning with electrode potential. Capacitance of them depends mainly on the

utilization of active material of electrode. The working voltage of electrochemical

capacitor is usually lower than 3 V. Based on high working voltage of electrolytic

capacitor, the hybrid super-capacitor combines the anode of electrolytic capacitor with the

cathode of electrochemical capacitor, so it has the best features with the high specific

capacitance and high energy density of electrochemical capacitor. The capacitors can work

at high voltage without connecting many cells in series. The most important parameters of

a super capacitor include the capacitance(C), ESR and EPR (which is also called leakage

resistance).

2.2 Equivalent Circuit:

Super capacitors can be illustrated similarly to conventional film, ceramic or

aluminum electrolytic capacitors

Fig 2.2 (a):Supercapacitor Equivalent Circuit

This equivalent circuit is only a simplified or first order model of a super capacitor.

In actuality supercapacitors exhibit a non ideal behavior due to the porous materials used

to make the electrodes. This causes supercapacitors to exhibit behavior more closely to

transmission lines than capacitors. Below is a more accurate illustration of the equivalent

circuit for a super capacitor.

Fig 2.2(b): Equivalent circuit

2.3 How To Measure The Capacitance:

There are a couple of ways used to measure the capacitance of supercapacitors.

1. Charge method

2. Charging and discharging method.

Charge Method:

Measurement is performed using a charge method using the following formula.

C=t/R

t= .632Vo where Vo is the applied voltage.

Fig 2.3: Charge and Discharge Method

This method is similar to the charging method except the capacitance is calculated during

the discharge cycle instead of the charging cycle.

Discharge time for constant current discharge

t= Cx (V0-V1)/I

Discharge time for constant resistance discharge

t= CRln (V1/V0)

Where t= discharge time, V0= initial voltage, V1= ending voltage, I= current.

2.4 Capacitance

Super capacitors have such large capacitance values that standard measuring

equipment cannot be used to measure the capacity of these capacitors.

Capacitance is measured per the following method:

1. Charge capacitor for 30 minutes at rated voltage.

2. Discharge capacitor through a constant current load.

3. Discharge rate to be 1mA/F.

4. Measure voltage drop between V1 to V2.

5. Measure time for capacitor to discharge from V1 to V2.

6. Calculate the capacitance using the following equation:

C= I*(T2-T1)

V1-V2

Where V1=0.7Vr, V2=0.3Vr (Vr= rated voltage of capacitor)

ESR

AC ESR - Measure using a 4 probe impedance analyzer at 1 kHz.

DC ESR - measured using the following procedure

1. Charge capacitor using a constant current.

2. After reaching rated voltage hold voltage for at least 1 minute.

3. Discharge capacitor at a rate of 1mA/F.

4. Measure the time it takes to have the voltage drop from V1 to V2.

5. Calculate ESR using the following formula:

ESR (DC) = VI

2.5 Life Expectancy

The life expectancy of supercapacitors is identical to aluminum electrolytic

capacitors. The life of supercapacitors will double for every 10°C decrease in the ambient

temperature the capacitors are operated in. Supercapacitors operated at room temperature

can have life expectancies of several years compared to operating the capacitors at their

maximum rated temperature.

L2=L1*2X X=Tm-Ta/2

L1= Load life rating of the super capacitor.

L2= expected life at operating condition.

Tm= Maximum temperature rating of the supercapacitor.

Ta= Ambient temperature the supercapacitor is going to be exposed to in the application.

2.6 Applications for Supercapacitors

Supercapacitors have found uses include:

• Computer systems

• UPS systems

• Power conditioners

• Welders

• Inverters

• Automobile regenerative braking systems

• Power supplies

• Cameras

• Power generators

2.7 Importance of Proper Design of SCES and Future Scope of Work

The utmost requirement of proper design and implementation of SCES is

maintaining the reliability of the power distribution system in the grid connected mode,

the switching transient mode, the island mode. This is also important in various analyses

such as sustained interruptions, voltage flicker, voltage sags, harmonics, voltage

regulation, voltage stability. There are other different aspects related to power distribution

system where the storage study is essential, some are listed as follows.

1. Calculation of load schedule,

2. Optimal use of non-conventional energy sources,

3. Dispatch ability of Power,

4. Ride trough capability of Supply

5. Reduced insulation,

6. Transformer connections and ground faults,

7. Design of system elements: transformer, feeders.

3. BOOST CONVERTER

A boost converter (step-up converter) is a power converter with an output DC

voltage greater than its input DC voltage. It is a class of switching-mode power supply

(SMPS) containing at least two semiconductor switches (a diode and a transistor) and at

least one energy storage element. Filters made of capacitors (sometimes in combination

with inductors) are normally added to the output of the converter to reduce output voltage

ripple.

Fig 3:Circuit Diagram of Boost Converter

Power can also come from DC sources such as batteries, solar panels, rectifiers and

DC generators. A process that changes one DC voltage to a different DC voltage is called

DC to DC conversion. A boost converter is a DC to DC converter with an output voltage

greater than the source voltage. A boost converter is sometimes called a step-up converter

since it “steps up” the source voltage. Since power (P = VI or P = UI in Europe) must be

conserved, the output current is lower than the source current.

A boost converter may also be referred to as a 'Joule thief'. This term is usually used

only with very low power battery applications, and is aimed at the ability of a boost

converter to 'steal' the remaining energy in a battery. This energy would otherwise be

wasted since a normal load wouldn't be able to handle the battery's low voltage.

This energy would otherwise remain untapped because in most low-frequency

applications, currents will not flow through a load without a significant difference of

potential between the two poles of the source (voltage.)

3.1 Block Diagram

The basic building blocks of a boost converter circuit are shown in Fig.

Fig 3.1: Block diagram of Boost Converter

The voltage source provides the input DC voltage to the switch

control, and to the magnetic field storage element. The switch control directs the

action of the switching element, while the output rectifier and filter deliver an

acceptable DC voltage to the output.

3.2 Operating Principle

The key principle that drives the boost converter is the tendency of an inductor to

resist changes in current. When being charged it acts as a load and absorbs energy

(somewhat like a resistor), when being discharged, it acts as an energy source (somewhat

like a battery). The voltage it produces during the discharge phase is related to the rate of

change of current, and not to the original charging voltage, thus allowing different input

and output voltages.

Fig 3.2(a): Boost converter schematic

Voltage

Source

Magnetic

Field Storage

Switch Control

SwitchingElement

Output

Rectifier

Fig 3.2(b): The Two Configurations of A Boost Converter, Depending on The State of

The Switch S

The basic principle of a Boost converter consists of 2 distinct states (see figure):

in the On-state, the switch S (see figure) is closed, resulting in an increase in the inductor

current;

In the Off-state, the switch is open and the only path offered to inductor current is through

the fly back D, the capacitor C and the load R. This result in transferring the energy

accumulated during the On-state into the capacitor.

The input current is the same as the inductor current as can be seen in figure. So it

is not discontinuous as in the buck converter and the requirements on the input filter are

relaxed compared to a buck converter.

Continuous mode:

When a boost converter operates in continuous mode, the current through the

inductor (IL) never falls to zero. Figure shows the typical waveforms of currents and

voltages in a converter operating in this mode. The output voltage can be calculated as

follows, in the case of an ideal converter (i.e. using components with an ideal behavior)

operating in steady conditions:

Fig 3.2(c): Waveforms of Current and Voltage In A Boost Converter Operating In

Continuous Mode

During the On-state, the switch S is closed, which makes the input voltage ( Vi)

appear across the inductor, which causes a change in current (IL) flowing through the

inductor during a time period (t) by the formula:

At the end of the On-state, the increase of IL is therefore:

D is the duty cycle. It represents the fraction of the commutation period T during which

the switch is on. Therefore D ranges between 0 (S is never on) and 1 (S is always on).

During the Off-state, the switch S is open, so the inductor current flows through the

load. If we consider zero voltage drop in the diode, and a capacitor large enough for its

voltage to remain constant, the evolution of IL is:

Therefore, the variation of IL during the Off-period is:

As we consider that the converter operates in steady-state conditions, the amount of

energy stored in each of its components has to be the same at the beginning and at the end

of a commutation cycle. In particular, the energy stored in the inductor is given by:

So, the inductor current has to be the same at the start and end of the commutation

cycle. This means the overall change in the current (the sum of the changes) is zero:

Substituting   and   by their expressions yields:

This can be written as:

Which in turns reveals the duty cycle to be?

From the above expression it can be seen that the output voltage is always higher

than the input voltage (as the duty cycle goes from 0 to 1), and that it increases with D,

theoretically to infinity as D approaches 1. This is why this converter is sometimes

referred to as a step-up converter.

Discontinuous mode:

In some cases, the amount of energy required by the load is small enough to be

transferred in a time smaller than the whole commutation period. In this case, the current

through the inductor falls to zero during part of the period. The only difference in the

principle described above is that the inductor is completely discharged at the end of the

commutation cycle (see waveforms in figure ). Although slight, the difference has a strong

effect on the output voltage equation. It can be calculated as follows:

Fig 3.2(d): Waveforms of Current and Voltage In A Boost Converter Operating In

Discontinuous Mode

As the inductor current at the beginning of the cycle is zero, its maximum

value   (at t = DT) is

During the off-period, IL falls to zero after δT:

Using the two previous equations, δ is:

The load current Io is equal to the average diode current (ID). As can be seen on

figure 4, the diode current is equal to the inductor current during the off-state. Therefore

the output current can be written as:

Replacing ILmax and δ by their respective expressions yields:

Therefore, the output voltage gain can be written as flow:

Compared to the expression of the output voltage for the continuous mode, this expression

is much more complicated. Furthermore, in discontinuous operation, the output voltage

gain not only depends on the duty cycle, but also on the inductor value, the input voltage,

the switching frequency, and the output current.

3.3 Applications of Boost Converter

Battery powered systems often stack cells in series to achieve higher voltage.

However, sufficient stacking of cells is not possible in many high voltage applications due

to lack of space. Boost converters can increase the voltage and reduce the number of cells.

Two battery-powered applications that use boost converters are hybrid electric

vehicles (HEV) and lighting systems.

The NHW20 model Toyota Prius HEV uses a 500 V motor. Without a boost

converter, the Prius would need nearly 417 cells to power the motor. However, a Prius

actually uses only 168 cells and boosts the battery voltage from 202 V to 500 V. Boost

converters also power devices at smaller scale applications, such as portable lighting

systems. A white LED typically requires 3.3 V to emit light, and a boost converter can

step up the voltage from a single 1.5 V alkaline cell to power the lamp. Boost converters

can also produce higher voltages to operate cold cathode fluorescent tubes (CCFL) in

devices such as LCD backlights and some flashlights.

4. ELECTRIC VEHICLE

An electric vehicle (EV), also referred to as an electric drive vehicle, uses one or

more electric motors for propulsion. Electric vehicles include electric cars, electric trains,

electric lorries, electric aero-planes, electric boats, electric motorcycles and

scooters and electric spacecraft.

Electric vehicles first came into existence in the mid-19th century, when electricity

was among the preferred methods for motor vehicle propulsion, providing a level of

comfort and ease of operation that could not be achieved by the gasoline cars of the time.

The internal combustion engine (ICE) is the dominant propulsion method for motor

vehicles but electric power has remained commonplace in other vehicle types, such as

trains and smaller vehicles of all types.

During the last few decades, increased concern over the environmental impact of

the petroleum-based transportation infrastructure, along with the spectre of peak oil, has

led to renewed interest in an electric transportation infrastructure. Electric vehicles differ

from fossil fuel-powered vehicles in that the electricity they consume can be generated

from a wide range of sources, including fossil fuels, nuclear power, and renewable sources

such as tidal power, solar power, and wind power or any combination of those. However it

is generated, this energy is then transmitted to the vehicle through use of overhead

lines, wireless energy transfer such as inductive charging, or a direct connection through

an electrical cable. The electricity may then be stored onboard the vehicle using

a battery, flywheel, or super capacitors. Vehicles making use of engines working on the

principle of combustion can usually only derive their energy from a single or a few

sources, usually non-renewable fossil fuels. A key advantage of electric or hybrid electric

vehicles is regenerative braking and suspension; their ability to recover energy normally

lost during braking as electricity to be restored to the on-board battery.

In 2003, the first mass-produced hybrid gasoline-electric car, the Toyota Prius, was

introduced worldwide, and the first battery electric car produced by a major auto company,

the Nissan Leaf will debut in December 2010. Other major auto companies have electric

cars in development, and the USA and other nations are building pilot networks of

charging stations to recharge them.

Fig 4: electric vehicle/hybrid electric system using super capacitors

4.1 Vehicle Types:

Hybrid electric vehicle

A hybrid electric vehicle combines a conventional (usually fossil fuel-powered) power

train with some form of electric propulsion. Common examples include hybrid electric

cars such as the Toyota Prius.

On- and off-road electric vehicles

Electric vehicles are on the road in many functions, including electric cars, electric

trolleybuses, electric bicycles, electric motorcycles and scooters, neighborhood electric

vehicles, golf carts, milk floats, and forklifts. Off-road vehicles include electrified all-

terrain vehicles and tractors.

Rail borne electric vehicles

A street car (or Tram) drawing current from a single overhead wire through

a pantograph. The fixed nature of a rail line makes it relatively easy to power electric

vehicles through permanent overhead lines or electrified third rails, eliminating the need

for heavy onboard batteries. Electric locomotives, electric trams/streetcars/trolleys,

electric light rail systems, and electric rapid transit are all in common use today, especially

in Europe and Asia.

Since electric trains do not need to carry a heavy internal combustion engine or large

batteries, they can have very good power-to-weight ratios. This allows high speed

trains such as France's double-deck TGVs to operate at speeds of 320 km/h (200 mph) or

higher, and electric locomotives to have a much higher power output than diesel

locomotives. In addition they have higher short-term surge power for fast acceleration, and

using regenerative braking can put braking power back into the electrical grid rather than

wasting it.

Maglev trains are also nearly always electric vehicles.

Airborne electric vehicles

Since the beginning of the era of aviation, electric power for aircraft has received a great

deal of experimentation. Currently flying electric aircraft include manned and unmanned

aerial vehicles.

Seaborne electric vehicles

Electric boats were popular around the turn of the 20th century. Interest in quiet and

potentially renewable marine transportation has steadily increased since the late 20th

century, as solar cells have given motorboats the infinite range

of sailboats. Submarines use batteries (charged by diesel or gasoline engines at the

surface), nuclear power, or fuel cells run electric motor driven propellers.

Space borne electric vehicles

Electric power has a long history of use in spacecraft. The power sources used for

spacecraft are batteries, solar panels and nuclear power. Current methods of propelling a

spacecraft with electricity include the arc jet rocket, the electrostatic, the Hall Effect

thruster, and Field Emission Electric Propulsion. A number of other methods have been

proposed, with varying levels of feasibility.

4.2 Advantages of Electric Vehicles:

Environmental

Due to efficiency of electric engines as compared to combustion engines, even when

the electricity used to charge electric vehicles comes a CO2 emitting source, such as a coal

or gas fired powered plant, the net CO2 production from an electric car is typically one

half to one third of that from a comparable combustion vehicle.

Electric vehicles release almost no air pollutants at the place where they are

operated. In addition, it is generally easier to build pollution control systems into

centralized power stations than retrofit enormous numbers of cars.

Mechanical

Electric motors are mechanically very simple. Electric motors often achieve

90% energy conversion efficiency over the full range of speeds and power output and can

be precisely controlled. They can also be combined with regenerative braking systems that

have the ability to convert movement energy back into stored electricity. This can be used

to reduce the wear on brake systems (and consequent brake pad dust) and reduce the total

energy requirement of a trip. Regenerative braking is especially effective for start-and-stop

city use.

Electric vehicles provide quiet and smooth operation and consequently have less

noise and vibration than internal combustion engines. While this is a desirable attribute, it

has also evoked concern that the absence of the usual sounds of an approaching vehicle

poses a danger to blind, elderly and very young pedestrians. To mitigate this situation,

automakers and individual companies are developing systems that produce warning

sounds when electric vehicles are moving slowly, up to a speed when normal motion and

rotation (road, suspension, electric motor, etc.) noises become audible.

Energy resilience

Electricity is a form of energy that remains within the country or region where it was

produced and can be multi-sourced. As a result it gives the greatest degree of energy

resilience.

Energy efficiency

Electric vehicle 'tank-to-wheels' efficiency is about a factor of 3 higher than internal

combustion engine vehicles. It does not consume energy when it is not moving, unlike

internal combustion engines where they continue running even during idling. However,

looking at the well-to-wheel efficiency of electric vehicles, their emissions are comparable

to an efficient gasoline or diesel in most countries because electricity generation relies on

fossil fuels.

Cost of recharge

The GM Volt will cost "less than purchasing a cup of your favorite coffee" to

recharge. The Volt should cost less than 2 cents per mile to drive on electricity, compared

with 12 cents a mile on gasoline at a price of $3.60 a gallon. This means a trip from Los

Angeles to New York would cost $56 on electricity, and $336 with gasoline. This would

be the equivalent to paying 60 cents a gallon of gas.

Stabilization of the grid

Since electric vehicles can be plugged into the electric grid when not in use, there is

a potential for battery powered vehicles to even out the demand for electricity by feeding

electricity into the grid from their batteries during peak use periods (such as mid afternoon

air conditioning use) while doing most of their charging at night, when there is unused

generating capacity. This Vehicle to Grid (V2G) connection has the potential to reduce the

need for new power plants.

5. FULL BRIDGE CONVERTER

A bridge is an arrangement of four (or more) diodes in a bridge configuration that

provides the same polarity of output for either polarity of input. When used in its most

common application, for conversion of an alternating current (AC) input into direct

current a (DC) output, it is known as a bridge rectifier. A bridge rectifier provides full-

wave rectification from a two-wire AC input, resulting in lower cost and weight as

compared to a rectifier with a 3-wire input from a transformer with a center-

tapped secondary winding.

A rectifier is an electrical device that converts alternating current (AC), which

periodically reverses direction, to direct current (DC), current that flows in only one

direction, a process known as rectification. Rectifiers have many uses including as

components of power supplies and as detectors of radio signals. Rectifiers may be made

of solid state diodes, vacuum tube diodes, mercury arc valves, and other components.

A device which performs the opposite function (converting DC to AC) is known as

an inverter.

5.1 Half-Wave Rectifier:

In half wave rectification, either the positive or negative half of the AC wave is

passed, while the other half is blocked. Because only one half of the input waveform

reaches the output, it is very inefficient if used for power transfer. Half-wave rectification

can be achieved with a single diode in a one-phase supply, or with three diodes in a three-

phase supply.

Fig 5.1: Half Wave Rectifier Circuit, I/P & O/P Wave Forms

The output DC voltage of a half wave rectifier can be calculated with the following two

ideal equations:

5.2 Full-Wave Rectifier:

A full-wave rectifier converts the whole of the input waveform to one of constant

polarity (positive or negative) at its output. Full-wave rectification converts both polarities

of the input waveform to DC (direct current), and is more efficient.

However, in a circuit with a non-center tapped transformer, four diodes are required

instead of the one needed for half-wave rectification. Four diodes arranged this way are

called a diode bridge or bridge rectifier:

Fig 5.2(a): Full Wave Rectifier With Non-center Tapped Transformer

For single-phase AC, if the transformer is center-tapped, then two diodes back-to-

back (i.e. anodes-to-anode or cathode-to-cathode) can form a full-wave rectifier. Twice as

many windings are required on the transformer secondary to obtain the same output

voltage compared to the bridge rectifier above.

Fig 5.2(b): Full Wave Rectifier with Center Tapped Transformer

A very common vacuum tube rectifier configuration contained one cathode and

twin anodes inside a single envelope; in this way, the two diodes required only one

vacuum tube. The 5U4 and 5Y3 were popular examples of this configuration.

Fig5.2(c): A Three-phase Bridge Rectifier

Fig 5.2(d): 3-phase AC input, Half & Full Wave Rectified DC Output

Waveforms

For three-phase AC, six diodes are used. Typically there are three pairs of diodes,

each pair, though, is not the same kind of double diode that would be used for a full wave

single-phase rectifier. Instead the pairs are in series (anode to cathode). Typically,

commercially available double diodes have four terminals so the user can configure them

as single-phase split supply use, for half a bridge, or for three-phase.

Most devices that generate alternating current (such devices are called alternators)

generate three-phase AC. For example, an automobile alternator has six diodes inside it to

function as a full-wave rectifier for battery charging applications.

The average and root-mean-square output voltages of an ideal single phase full

wave rectifier can be calculated as:

Where:

Vdc,Vav - the average or DC output voltage,

Vp - the peak value of half wave,

Vrms - the root-mean-square value of output voltage.

π = ~ 3.14159

5.3 Peak Loss:

An aspect of most rectification is a loss from the peak input voltage to the peak

output voltage, caused by the built-in voltage drop across the diodes (around 0.7 V for

ordinary silicon p-n-junction diodes and 0.3 V for Schottky diodes). Half-wave

rectification and full-wave rectification using two separate secondaries will have a peak

voltage loss of one diode drop. Bridge rectification will have a loss of two diode drops.

This may represent significant power loss in very low voltage supplies. In addition, the

diodes will not conduct below this voltage, so the circuit is only passing current through

for a portion of each half-cycle, causing short segments of zero voltage to appear between

each "hump".

5.4 Rectifier Output Smoothing:

While half-wave and full-wave rectification suffice to deliver a form of DC output,

neither produces constant-voltage DC. In order to produce steady DC from a rectified AC

supply, a smoothing circuit or filter is required.[1] In its simplest form this can be just

a reservoir capacitor or smoothing capacitor, placed at the DC output of the rectifier.

There will still remain an amount of AC ripple voltage where the voltage is not completely

smoothed.

Fig 5.4: RC-Filter Rectifier

This circuit was designed and simulated using Multi sim 8 software.

Sizing of the capacitor represents a tradeoff. For a given load, a larger capacitor

will reduce ripple but will cost more and will create higher peak currents in the

transformer secondary and in the supply feeding it. In extreme cases where many rectifiers

are loaded onto a power distribution circuit, it may prove difficult for the power

distribution authority to maintain a correctly shaped sinusoidal voltage curve.

For a given tolerable ripple the required capacitor size is proportional to the load

current and inversely proportional to the supply frequency and the number of output peaks

of the rectifier per input cycle. The load current and the supply frequency are generally

outside the control of the designer of the rectifier system but the number of peaks per input

cycle can be affected by the choice of rectifier design.

A half-wave rectifier will only give one peak per cycle and for this and other

reasons is only used in very small power supplies. A full wave rectifier achieves two peaks

per cycle and this is the best that can be done with single-phase input. For three-phase

inputs a three-phase bridge will give six peaks per cycle and even higher numbers of peaks

can be achieved by using transformer networks placed before the rectifier to convert to a

higher phase order.

To further reduce this ripple, a capacitor-input filter can be used. This

complements the reservoir capacitor with a choke (inductor) and a second filter capacitor,

so that a steadier DC output can be obtained across the terminals of the filter capacitor.

The choke presents a high impedance to the ripple current.

5.5 Voltage Doubling Rectifier:

The simple half wave rectifier can be built in two versions with the diode pointing

in opposite directions, one version connects the negative terminal of the output direct to

the AC supply and the other connects the positive terminal of the output direct to the AC

supply. By combining both of these with separate output smoothing it is possible to get an

output voltage of nearly double the peak AC input voltage. This also provides a tap in the

middle, which allows use of such a circuit as a split rail supply.

A variant of this is to use two capacitors in series for the output smoothing on a

bridge rectifier then place a switch between the midpoint of those capacitors and one of

the AC input terminals. With the switch open this circuit will act like a normal bridge

rectifier with it closed it will act like a voltage doubling rectifier. In other words this

makes it easy to derive a voltage of roughly 320V (+/- around 15%) DC from any mains

supply in the world, this can then be fed into a relatively simple switched mode power

supply.

Fig 5.5: Cockcroft Walton Voltage Multiplier

Cascaded stages of diodes and capacitors can be added to make a voltage

multiplier (Cockroft-Walton circuit). These circuits can provide a potential several times

that of the peak value of the input AC, although limited in current output and regulation.

Voltage multipliers are used to provide the high voltage for a CRT in a television receiver,

or for powering high-voltage tubes such as image intensifiers or photo multipliers.

The essential feature of a diode bridge is that the polarity of the output is the same

regardless of the polarity at the input. The diode bridge circuit is also known as the Graetz

circuit after its inventor, physicist Leo Graetz.

5.6 Basic Operation:

According to the conventional model of current flow originally established

by Benjamin Franklin and still followed by most engineers today, current is assumed to

flow through electrical conductors from the positive to the negative pole. In actuality, free

electrons in a conductor nearly always flow from the negative to the positive pole. In the

vast majority of applications, however, the actual direction of current flow is irrelevant.

Therefore, in the discussion below the conventional model is retained.

Fig 5.6(a): AC, Half-wave and Full Wave Rectified Signals

In each case, the upper right output remains positive and lower right output

negative. Since this is true whether the input is AC or DC, this circuit not only produces a

DC output from an AC input, it can also provide what is sometimes called "reverse

polarity protection". That is, it permits normal functioning of DC-powered equipment

when batteries have been installed backwards, or when the leads (wires) from a DC power

source have been reversed, and protects the equipment from potential damage caused by

reverse polarity.

5.7 Output Smoothing:

For many applications, especially with single phase AC where the full-wave

bridge serves to convert an AC input into a DC output, the addition of a capacitor may be

desired because the bridge alone supplies an output of fixed polarity but continuously

varying or "pulsating" magnitude, an attribute commonly referred to as "ripple" (see

diagram to right).

The function of this capacitor, known as a reservoir capacitor (or smoothing

capacitor) is to lessen the variation in (or 'smooth') the rectified AC output voltage

waveform from the bridge. One explanation of 'smoothing' is that the capacitor provides a

low impedance path to the AC component of the output, reducing the AC voltage across,

and AC current through, the resistive load. In less technical terms, any drop in the output

voltage and current of the bridge tends to be canceled by loss of charge in the capacitor.

This charge flows out as additional current through the load. Thus the change of load

current and voltage is reduced relative to what would occur without the capacitor.

Increases of voltage correspondingly store excess charge in the capacitor, thus moderating

the change in output voltage / current.

The capacitor and the load resistance have a typical time constant τ =

RC where C and R are the capacitance and load resistance respectively. As long as the load

resistor is large enough so that this time constant is much longer than the time of one

ripple cycle, the above configuration will produce a smoothed DC voltage across the load.

In some designs, a series resistor at the load side of the capacitor is added. The

smoothing can then be improved by adding additional stages of capacitor–resistor pairs,

often done only for sub-supplies to critical high-gain circuits that tend to be sensitive to

supply voltage noise.

In a practical circuit, when a capacitor is directly connected to the output of a

bridge, the bridge diodes must be sized to withstand the current surge that occurs when the

power is turned on at the peak of the AC voltage and the capacitor is fully discharged.

Sometimes a small series resistor is included before the capacitor to limit this current,

though in most applications the power supply transformer's resistance is already sufficient.

Output can also be smoothed using a choke and second capacitor. The choke tends

to keep the current (rather than the voltage) more constant. This design is not generally

used in modern equipment due to the high cost of an effective choke compared to a

resistor and capacitor.

Some early console radios created the speaker's constant field with the current

from the high voltage ("B +") power supply, which was then routed to the consuming

circuits, (permanent magnets were then too weak for good performance) to create the

speaker's constant magnetic field. The speaker field coil thus performed 2 jobs in one: it

acted as a choke, filtering the power supply, and it produced the magnetic field to operate

the speaker.

Poly-phase Bridge:

The diode bridge can be generalized to rectify poly-phase AC inputs. For example, for

a three-phase AC input, a half-wave rectifier consists of three diodes, but a full-

wave bridge rectifier consists of six diodes.

Fig 5.7(a): Three Phase Bridge Rectifier

Fig 5.7(b): 3-phase AC Input Waveform, Half-wave Rectified Waveform, and Full-

wave Rectified Waveform

6. POWER MANAGEMENT

Power management is a feature of some electrical appliances,

especially copiers, computers and computer peripherals such as monitors and printers, that

turns off the power or switches the system to a low-power state when inactive. In

computing this is known as PC power management and is built around a standard

called ACPI. This supersedes APM. All recent (consumer) computers have ACPI support.

Motivation:

PC power management for computer systems is desired for many reasons, particularly:

Reduce overall energy consumption

Prolong battery life for portable and embedded systems

Reduce cooling requirements

Reduce noise

Reduce operating costs for energy and cooling.

Lower power consumption also means lower heat dissipation, which increases

system stability, and less energy use, which saves money and reduces the impact on the

environment.

Processor level techniques:

The power management for microprocessors can be done over the whole processor,

or in specific areas.

With dynamic voltage scaling and dynamic frequency scaling, the CPU core

voltage, clock rate, or both, can be altered to decrease power consumption at the price of

potentially lower performance. This is sometimes done in real time to optimize the power-

performance tradeoff.

Examples:

AMD Cool'n'Quiet

AMD PowerNow! [1]

IBM EnergyScale [2]

Additionally, processors can selectively power off internal circuitry (power gating). For

example:

Newer Intel Core processors support ultra-fine power control over the functional units

within the processors.

AMD Cool Core technology get more efficient performance by dynamically activating or

turning off parts of the processor.[3]

Intel VRT technology split the chip into a 3.3V I/O section and a 2.9V core section. The

lower core voltage reduces power consumption.

6.1 Power Management System Helps To:

Avoid Black-outs

In case of a lack of power, Load Shedding secures the electrical power to critical loads by

switching off non-critical loads according to dynamic priority tables.

Reduce Energy Costs / Peak Shaving

When all on-site power generation is maximized and the power demand still tends to

exceed the contracted maximum electricity import, the system will automatically shed

some of the low priority loads.

Enhanced Operator Support

At sites where electricity is produced by several generators, the demands with respect to

control activities by operators are much higher. Advanced functions such as intelligent

alarm filtering, consistency analysis, operator guidance, and a well organized single-

window interface support the operator and prevent incorrect interventions.

Achieve Stable Operation

The Power Control function shares the active and reactive power between the different

generators and tie-lines in such a way that the working points of the machines are as far as

possible away from the border of the individual PQ-capability diagrams so that the plant

can withstand bigger disturbances.

Optimize Network Design

Because the set points for the generators, turbines and transformers are calculated in such

a way that no component will be overloaded and the electrical network can be used up to

its limits, over-dimensioning of the network is no longer needed.

Minimize Cabling and Engineering

All the signals and information which are available in protection/control relays,

governor/excitation controllers and other microprocessor based equipment can be easily

transmitted to the Industrial PMS via serial communication links. This avoids marshalling

cubicles, interposing relays, cable ducts, spaghetti wiring, cabling engineering and

provides extra functionality such as parameter setting/reading, stored events, disturbance

data analysis and a single window to all electrical related data.

7. DC/DC CONVERTERS TOPOLOGIES AND

MODELING

7.1. Multi Boost and Multi Full Bridge Converters Modeling:

• Figure 7.1(a)(a,b) shows the multi boost converter topology.

Fig 7.1(a): (a) Multi boost Converter Topology & (b) Multi Full Bridge Converter

Topology

The general model for this topology is given by equation; 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.

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 [3]. The multi boost converter [4] topology

control law which results from the boost converter modeling is presented by α1 duty cycle;

where Np = max(n) is the maximum number of parallel converters.

The multi boost converter control strategy is presented in Fig 7.1(b) (a).

Fig 7.1(b): (a) Multi Boost Control Strategy & (b) Multi Full Bridge Control

Strategy

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 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.

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, 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.(b); where Q1, Q2, Q3 and Q4 are the control signals applied to K1,

K2, K3 and K4 switches. The simulations and experimental parameters are presented in

table 1 below.

7.2 Full Bridge Converter Simulation Results For Np = 2:

The simulation has been made for Np = 2. 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.

Fig 7.2(a): (a) Super Capacitor Modules Voltages, (b) Super Capacitor Modules

Currents

(a) (b)

Fig 7.2(b) (a): Battery current control result, (b): DC-link and active load currents

Super capacitor modules voltages (Vsc1, Vsc2) presented in Fig 7.2(a) (a) are

identical. The currents amplitudes (Isc1, Isc2) presented in Fig 7.2(a) (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 7.2 (b) (a). The important

power of the transient states is ensured by the super capacitors modules (IL) Fig 7.2(b) (b).

Simulation parameters are presented in TABLE 1.

TABLE 1: FULL BRIDGE TOPOLOGIE SIMULATIONS PARAMETER

8. SIMULINK DIAGRAM

8 (a): Boost converter circuit

8 (b): Full bridge converter circuit

9. DESIGN AND 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 2 and the principle of such circuits is given in Fig 9.

TABLE 2: FULL BRIDGE EXPERIMENTAL PARAMETERS

Fig 9: 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

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.

9.1 Experimental Setup at Reduced Scale

For reasons of cost components and safety, the experimental test benches were carried

out at a reduced scale (1/10).

• The boost converter test bench Fig (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.

• For the full bridge converter [9] test bench Fig (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.

Fig 9.1: Boost and Full Bridge Converters Experimental Setup

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.

9.2. Boost Converters Simulation and Experimental Results

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 (a) and

Fig (b). The (Isc1) and (Isc2) experimental currents are not identical

Fig 9.2(a): Super Capacitor Modules Experimental and Simulation Voltage Results

Fig (a), Fig (b) because the super capacitors dispersion and the power electronic circuits

(boost converters) inequality.

Fig 9.2(b): Super Capacitor Modules Experimental and Simulation Current Results

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 (a), and 13A only is provided by the batteries Fig (b).

Fig 9.2(c): DC-link voltage and current experimental validation

CONCLUSION

In this project, 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. The system control is ensured by PIC18F4431

microcontroller type which includes 9 analog inputs and 8 PWM outputs. 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.

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