Using Ultracapacitors as Energy-storing Devices on a Mobile Robot

Platform Power System for Ultra-fast Charging

Carlos Arantes

, João Sepúlveda

, João Sena Esteves

, Hugo Costa

and Filomena Soares

Department of Industrial Electronics, University of Minho, Campus of Azurém, 4800-058 Guimarães, Portugal

Centre Algoritmi, Department of Industrial Electronics, University of Minho, Campus of Azurém, 4800-058 Guimarães,

Portugal

Keywords: Ultracapacitors, Batteries, Fast Electric Charger, Mobile Robot.

Abstract: The large charging times required by conventional batteries constitute an important limitation in many

applications. The use of ultracapacitors as energy storage elements allows substantially faster charging. This

paper presents a power supply system developed in order to validate the possibility of providing a mobile

robot platform with an electrical energy storage system based on ultracapacitors and batteries, ensuring both

the autonomy and the charging time required by this vehicle. Both simulations results and experimental

results – also presented in this paper – validate this possibility. Using exclusively one ultracapacitors

module as energy-storing device of the new power supply system, the mobile platform achieved an

autonomy of 22 minutes after a charging time of 1 minute and 57 seconds. The charging time is less than

10% of the autonomy time. The system also proved its ability to properly charge lead-acid batteries or

nickel–metal hydride batteries, which may be used as energy-storing devices, allowing the mobile platform

to achieve greater autonomy than the one obtained with ultracapacitors (at the cost of larger charging times).

1 INTRODUCTION

Conventional batteries usually require charging

times of, at least, some tens of minutes due to the

allowable values of their charging currents. These

charging times are an important limitation in many

applications, such as electric vehicles. Although

many authors proposed battery fast charging

techniques for different battery types (Petchjatuporn,

2005; Li, 2009; Hua, 2010), charging times cannot

be reduced much further, because the temperature

rises too much, deteriorating the batteries.

The charging currents of ultracapacitors may be

substantially higher than those allowed by common

batteries. So, ultracapacitors charging periods may

be much smaller than those required by batteries.

This paper addresses the possibility of using

ultracapacitors as energy-storing devices when very

reduced charging times are required.

Since batteries have much higher energy

densities than ultracapacitors, they are more suitable

to store large amounts of energy in order to provide

a large autonomy to onboard powered devices.

Regarding this aspect, the difference between

batteries and ultracapacitors may be substantially

reduced in a near future due to the introduction of

new materials (Bernholc, 2010).

The discharging currents of ultracapacitors may

also be substantially higher than those allowed by

common batteries. Due to this fact, ultracapacitors

are able to provide power peaks of significant value.

Several applications integrating batteries and

ultracapacitors on the same system are currently

available (Schneuwly, 2000; Wenzhong, 2005;

Miller, 2007; Awerbuch, 2008; Xiaofei, 2009;

Awerbuch, 2010; Dai, 2010; Haihua, 2010; Lei,

2010; Niemoeller, 2010; JennHwa, 2011; Monteiro,

2011; Musat, 2012). This integration results from the

need of having a single system capable of,

simultaneously:

1. Storing large amounts of energy in the batteries

for the sake of autonomy;

2. Providing power peaks of short duration but

significant value using the ultracapacitors,

extending the battery lifetime (Musat, 2012)

and/or ensuring the proper functioning of the

system (Schneuwly, 2000; Monteiro, 2011).

This paper also addresses the possibility of

integrating batteries and ultracapacitors in the same

device. However, the main reason for doing so is

different from the previously described. Having

Arantes C., Sepúlveda J., Sena Esteves J., Costa H. and Soares F..

Using Ultracapacitors as Energy-storing Devices on a Mobile Robot Platform Power System for Ultra-fast Charging.

DOI: 10.5220/0005061801560164

In Proceedings of the 11th International Conference on Informatics in Control, Automation and Robotics (ICINCO-2014), pages 156-164

ISBN: 978-989-758-040-6

 2014 SCITEPRESS (Science and Technology Publications, Lda.)

batteries released from the requirement of providing

high power peaks remains an important property of a

power supply system. But the main goal of the

integration suggested in this paper is enabling a

vehicle to achieve a reasonable autonomy after a

very reduced charging time, when its energy-storing

devices (batteries and ultracapacitors) become

discharged and there is not enough time to properly

charge the batteries.

The main objective of the power supply system

presented in this paper is to validate the possibility

of providing a mobile robot platform with an

electrical energy storage system based on

ultracapacitors and batteries, ensuring both the

autonomy and the charging speed required by this

vehicle. Starting with fully discharged energy-

storing devices, the mobile platform must achieve, at

least

1. 15 minutes of autonomy after a charging

period not exceeding 2 minutes, when there

is not more time available for charging;

2. Some hours of autonomy, when there are

no charging time restrictions.

Conventional batteries easily accomplish the

second task. For example, the expected autonomy of

the mobile platform powered by a fully charged

12V, 12Ah, 144Wh lead-acid battery ranges from 7

to 9 hours.

So, the main effort was put on studying the

possibility of accomplishing the first task using only

ultracapacitors. That is the reason why the majority

of the results presented in this paper are related to

the use of one 16V, 116F, 4.12Wh ultracapacitors

module. Since batteries are not used in the first task,

this paper may be put in the context of

“environmental-friendly” approaches.

Conventional batteries are, still, much less

expensive than ultracapacitors. However,

ultracapacitors cost has been significantly

decreasing. For example, the cost of the

ultracapacitors module used in this work decreased

34% in a period of about one year. By now, it costs

4.3 times more than the 12V, 12Ah, 144Wh lead-

acid battery also used in this work.

On the other hand, ultracapacitors allow about

1000 times more charging/discharging cycles than

batteries. The rated number of cycles between rated

voltage and half rated voltage (under constant

current at 25ºC) allowed by the previously

mentioned ultracapacitors module is 500000.

The energy-storing device of the new power

supply system, described in Section 2, may be an

ultracapacitors module or a battery. Future versions

of the system will integrate energy-storing devices

of both kinds.

Section 3 presents simulation results performed

before implementing the physical system described

in Section 4. Some experimental results obtained

with the real system are presented in Section 5. The

general conclusions and some considerations

regarding future developments are provided in

Sections 6.

2 SYSTEM ARCHITECTURE

OVERVIEW

The developed power supply system has three

components:

 An energy-storing device, which may be an

ultracapacitors module, a lead-acid battery or a

nickel–metal hydride battery;

 A charger, intended to transfer energy from the

mains to the energy-storing device;

 A voltage regulator, intended to supply a

regulated voltage to the mobile robot platform,

regardless of the voltage of the energy-storing

device.

2.1 The Charger

Figure 1 shows the block diagram of the subsystem

that uses the charger. The energy-storing device may

be an ultracapacitor (or an ultracapacitors module,

like the 16V, 116F, 4.12Wh module used in this

work). The charger is also appropriate for lead-acid

batteries or nickel-metal hydride batteries.

Figure 1: Block diagram of the subsystem that uses the

charger.

In the majority of European countries, the

characteristics of single-phase standard electric

plugs are 230V AC, 50Hz and 16A (3.45kVA). The

charger circuit is fed by a 1.5kVA, 50Hz, 230V to

18V single phase transformer, followed by a 25A

rectifier bridge and a 25mF capacitive filter. A 5W,

10 resistor is connected in series with the filtering

capacitors, to avoid a large start up surge in the

electric current. Two seconds later, the resistor is

bypassed by a timer relay. This results in an

unregulated 24V DC power supply, which feeds a

power electronics converter, with a permitted ripple

of 5V and a rated power of 300W.

The power electronics converter of the charger is

a step-down DC-DC converter working with pulse

width modulation current-controlled voltage source,

at a switching frequency of 9.7kHz. The input is a

non-regulated 24V DC voltage and the output is a

regulated adjustable DC current. The control system

is a PI (proportional + integral) controller with a

sampling frequency of 1kHz, with a proportional

gain (Kp) of 8.2 and an integral gain (Ki) of 10.

Figure 2 shows the step-down model developed with

PSIM simulation software.

In the converter shown in Figure 2, diode D5

ensures that the energy always flows one way,

towards the battery or the ultracapacitors module.

Diode D6, resistor R17 and capacitor C10 form a

RCD snubber whose goal is to mitigate the

overvoltages that occur when the MOSFET is turned

off. Regarding snubber parameters calculation, a

maximum current of 20A and a parasitic system

inductance of 100H were considered. In this

situation, capacitor C10 (150F, 100V) must be

capable of absorbing the energy stored in the

parasite coil through D6 and discharged through

resistor R17 (1Ω, 5W). Capacitor C4 (10F, 100V)

is a polypropylene capacitor that also contributes to

the mitigation of overvoltages.

Figure 2: PSIM model of the step-down converter of the

charger.

L1 is the output filter coil (14.6mH, 170mΩ at 1

kHz) that allows smoothing the current around an

average adjustable value. D7 is a diode that ensures

the path to the current when the MOSFET is turned

off. The diodes used are the schottky MBR1660 and

the MOSFET used is the P80PF55.

2.2 The Voltage Regulator

Figure 3 shows the block diagram of the subsystem

that uses the voltage regulator. The objective of this

component is to supply energy to the mobile robot

platform from the energy previously stored in the

battery or in the ultracapacitors module.

The main characteristics of the load (mobile

robot platform) are a nominal voltage of 12V and a

maximum power of 30W. Since the power supplied

to the mobile platform is mainly used to drive DC

motors, the voltage ripple is not a very relevant

issue.

Unlike a battery voltage, which is reasonably

constant during discharging process, a capacitor

voltage is directly proportional to its charge, causing

a large variation on its voltage when it supplies a

load. So, when the ultracapacitors module is used as

energy-storing device, a voltage regulator is required

in order to keep the load voltage set to the intended

value of 12V independently of the ultracapacitors

module voltage.

The voltage regulator also allows using different

types of batteries, with different rated voltages.

The voltage regulator consists of two DC-DC

converters: a step-up followed by a step-down. This

topology was preferred over the step-up/down

topology because, in that case, the output voltage

would have reversed polarity in relation to the input

voltage, and this would require the use of isolated

voltage sensors for measuring. With the

implemented topology, the measurement is carried

out using a simple resistive voltage divider.

The step-down sub-circuit maintains the output

voltage set on the intended value as long as the input

voltage remains above that value. When the input

voltage becomes lower than the output intended

value, the step-up sub-circuit elevates it to the output

intended value. There are still situations when none

of the sub-circuits operate as DC-DC converters, as

is the case in which the input voltage is between

13V and 12.5V. In this case, the step-up MOSFET

stays off while the step-down MOSFET stays on.

This results in a varying output voltage but, in

practice, the effect is negligible.

The two converters never switch simultaneously,

as this would entail unnecessary additional power

losses. Figure 4 shows the voltage regulator model

developed with PSIM simulation software.

In Figure 4, diode D1 ensures that the energy

only flows from the input to the output. Diode D2

provides a path for the current when the MOSFET

belonging to the step-up sub-circuit is open. L1 is a

coil belonging to the step-up sub-circuit, with an

inductance of 168.7H and a resistance of 170mΩ at

1kHz. L2 is a coil belonging to step-down

sub-circuit and has an inductance of 132.4H and a

resistance of 148mΩ at 1kHz. Capacitors C1 and C2,

both of 1mF, form capacitive filters that are intended

to minimize the ripple caused by high switching

frequencies of both MOSFETs.

The control algorithm consists of a PI controller

with proportional gain of 1 and integral gain of 10

runs the control algorithms of both sub-circuits. The

input voltage, read through one of the channels of

the microcontroller ADC, allows the selection of the

sub-circuit to be switched at any moment. The main

control cycle runs at a frequency of 1kHz, while

semiconductors (MOSFETs) switch at a frequency

of 7.8kHz.

Figure 3: Block diagram of the subsystem that uses the

voltage regulator.

Figure 4: PSIM model of the DC-DC converters of the

voltage regulator.

3 SIMULATION RESULTS

The PSIM simulation software was used to validate

all the developed blocks of the entire system, before

any circuit implementation and execution of any

experimental tests.

The simulations results also made possible

making minor adjustments to the controller gains,

allowing a better performance.

The most important simulations results are

presented in this section.

3.1 The Charger

The charger was simulated when feeding an 116F

ultracapacitor. A reference current of 20A and a

final voltage of 15V were considered. Figure 5

shows that the ultracapacitor charging is performed

successfully.

3.2 The Voltage Regulator

The voltage regulator was simulated considering an

116F ultracapacitor charged up to 15V, supplying a

12V, 2A load. In Figure 6, it is visible that the

circuit draws more current from the ultracapacitor as

its voltage drops, in order to maintain constant the

output power.

In Figure 7, the load current and voltage are

shown, when the voltage regulator is fed by a 116F

ultracapacitor previously charged up to 15V. Load

voltage and current values remain approximately

constant, except on a very short time period around

the 190th second, when slight drops in both voltage

and current are observed. This is due to an input

voltage interval where none of the DC-DC

converters – step-up or step-down – is switching, in

order to improve energy efficiency. However, these

small drops do not disturb the proper functioning of

the mobile platform.

Figure 5: PSIM simulation results of the charger when

charging an 116F ultracapacitor up to 15V.

Figure 6: PSIM simulation results of an 116F

ultracapacitor voltage and current, when the regulator

feeds a 12V, 2A load.

Figure 7: PSIM simulation results of load voltage and

current when an 116F ultracapacitor feeds the voltage

regulator.

4 SYSTEM IMPLEMENTATION

In this section, a detailed description of the real

system implementation is made. The implementation

was performed after simulating all the system

components in PSIM, and consistently obtaining the

desired results.

4.1 Hardware

The charger module is capable of charging 12V

lead-acid batteries, 9.6V nickel-metal hydride

batteries and 16V ultracapacitors. It is quite heavy

and bulky, because a 1.5kVA, 50Hz transformer was

used. So, it was decided that the charger would stay

out of the mobile platform, working as a charging

station. This strategy is valid, because the mobile

platform is able to move itself to the charging station

when recharging is needed.

The final version of the charger module was

implemented on a printed circuit board (PCB).

Figure 8 shows the charging of a 16V, 116F

ultracapacitors module, at a reference current of

20A.

The voltage regulator module is capable of

supplying a regulated 12V voltage to the mobile

platform using batteries or ultracapacitors as energy

sources. Its input voltage may be between 16V and,

approximately, 1.5V (this lower limit is mainly used

by ultracapacitors).

Figure 9 presents the voltage regulator module

implemented on a PCB. The DC-DC converters

diodes, MOSFETs and coils are clearly visible; the

AVR ATmega 328P microcontroller from Atmel

Corporation and the dedicated crystal are also

noticeable. Some LEDs provide visible signals.

The voltage regulator module and its power

source (batteries or ultracapacitors) are supposed to

be installed on board the mobile platform, which has

been done. Figure 10 shows a previously charged

16V, 116F ultracapacitors module serving as the

energy source of a four-wheeled mobile platform.

Figure 8: Charger module charging a 16V, 116F

ultracapacitors module at a reference current of 20A.

Figure 9: Voltage regulator module.

Figure 10: Voltage regulator module and a 16V, 116F

ultracapacitors module installed on board a four-wheeled

mobile platform. The picture was taken with a long

exposure and it is noticeable that the wheels are turning.

4.2 Software

As mentioned before, the charger module must be

capable of charging ultracapacitors and different

kinds of batteries. And the voltage regulator module

must provide a regulated 12V voltage to the mobile

platform. The PI control algorithms of both modules

were implemented on AVR ATmega 328P

microcontrollers.

The operation mode of the charger module depends

on the type of energy-storing device to be charged.

The following algorithms have been chosen for

implementation because they are the most used for

each type of energy-storing device:

 The NDV (Negative Delta Voltage) for

nickel-metal hydride batteries;

 Constant current followed by constant

voltage for lead-acid batteries;

 Constant current until voltage reaches a

predetermined value for ultracapacitors.

Regardless of the type of energy-storing device,

charging time is not controllable because it depends

on the characteristics of the energy-storing device

and its initial state of charge.

A user-friendly interface with a LCD (Liquid

Crystal Display) and some push buttons was also

developed, allowing the user to select the type of

energy-storing device to be charged and define

charging parameters. Charging options include: type

of battery; battery voltage; battery charging current;

battery capacity; ultracapacitor maximum voltage

and ultracapacitor charging current.

The control algorithm flowchart of the voltage

regulator module is shown in Figure 11. This

module is also able to detect load overcurrents and,

if necessary, automatically shuts down to prevent

damages to the system components.

5 EXPERIMENTAL RESULTS

A few experimental tests were made to the system in

order to ensure the correct functioning of each

module and, also, to further validate the proposed

concept.

5.1 The Charger

The charger module was tested with three energy-

storing devices:

 One 16V, 116F, 4.12Wh ultracapacitors module;

 One 12V, 12Ah, 144Wh lead-acid battery;

 One 9.6V, 800mAh, 7.68Wh nickel-metal

hydride battery.

The expected autonomy of the mobile platform

after a full charge is rather low. It ranges,

approximately, from 30 to 35 minutes. The purpose

of using this battery is just to verify the ability of the

charger to work properly with nickel-metal hydride

batteries.

The results show that the maximum error

resulting from the difference between the desired

value and the actual value of a battery charging

current never exceeded 4%. The end-of-charge

algorithm worked as expected for both types of

batteries. The charging times are, approximately, 8

hours for the lead-acid battery and 4 hours for the

nickel-metal hydride battery.

In ultracapacitors charging mode, the charger

module imposed a current around 20A, charging the

116F ultracapacitors module up to 15V in 1 minute

and 57 seconds. Since the difference between the

reference current and output current never exceeded

700mA, the resulting maximum error is 3.5%.

5.2 The Voltage Regulator

The voltage regulator module, powered by the 116F

ultracapacitors module previously charged up to

15V, was tested on the mobile platform. The tests

were performed on a flat and levelled ground. Under

these operating conditions, the platform absorbed,

approximately, 0.8A while keeping a constant speed

of 62.8cm/s. The system worked at full performance

for 22 minutes. It was also found that, under the

conditions described above, the voltage regulator

succeeded in imposing the required output voltage of

12V until its input voltage, provided by the

ultracapacitors module, dropped to about 1.5V.

Some tests with excessive overcurrents at the

load were also conducted. In all tested situations, the

system was able to detect the overcurrent and did

shut down before the occurrence of any damage.

6 CONCLUSIONS AND FUTURE

DEVELOPMENTS

A power supply system for a mobile robot platform

has been developed. The system may use

ultracapacitors, lead-acid batteries or nickel-metal

hydride batteries as energy-storing devices.

It proved its ability to charge one 116F, 4.12Wh

ultracapacitors module up to 15V in 1 minute and 57

seconds. The system also proved its ability to

properly charge different types of batteries,

following the reference current with an error less

than 4%, and effectively detecting the full charge

state. The algorithms used in this project for battery

charging, sought to diminish charging times, but

without causing significant battery deterioration.

Both simulations results and experimental results

presented in this paper validate the possibility of

providing the mobile robot platform with an

electrical energy storage system integrating

Vi is the measured input voltage

Vo is the measured output regulated voltage

Kp and Ki are the gains of the PI controller

h is the sample period

Figure 11: Control algorithm flowchart of the voltage regulator module.

ultracapacitors and batteries. Such integration,

suggested as future work, would ensure both the

autonomy and the charging speed requirements of

the platform. In fact, using exclusively one 116F,

4.12Wh ultracapacitors module as energy-storing

device, the mobile platform achieved an autonomy

of 22 minutes after a charging time of 1 minute and

57 seconds, exceeding the autonomy required by the

platform when the charging time is limited to 2

minutes. It should be noted that the charging time is

less than 10% of the autonomy time. On the other

hand, the expected autonomy of the mobile platform

12Ah, 144Wh lead-acid battery, like the one used in

this work, ranges from 7 to 9 hours, fully satisfying

the autonomy required by the platform when there

are no charging time restrictions.

Integrating ultracapacitors and batteries in the

same power supply system also would release the

batteries from the requirement of providing high

power peaks, extending their lifetime.

Battery energy densities are much larger then the

ones offered by ultracapacitors but the introduction

of new materials may reduce the difference in a near

future.

An ultracapacitor is much more expensive than a

battery with the same energy storage capacity.

However, ultracapacitors cost has been significantly

decreasing. Furthermore, because ultracapacitors

allow much more charging/dicharging cycles than

batteries, the cost difference between the two

components is mitigated.

In addition to the suggested integration of

ultracapacitors and batteries in the same power

supply system, the following tasks are suggested as

future work: implementing control algorithms

capable of identifying the battery type to be charged

and its voltage; using a high-frequency transformer

instead of a 50Hz transformer, which would reduce

the cost, size and weight of the charger module,

allowing its installation onboard the mobile

platform; developing more compact PCBs using

surface-mount devices (SMD).

ACKNOWLEDGEMENTS

This work has been supported by FCT – Fundação

para a Ciência e Tecnologia within the Project

Scope: Pest-OE/EEI/UI0319/2014.

REFERENCES

Awerbuch, J. J.; Sullivan, C. R.; Control of Ultracapacitor-

Battery Hybrid Power Source for Vehicular

Applications; ENERGY 2008, Energy 2030

Conference, 2008, Page(s): 1 – 7. Digital Object

Identifier: 10.1109/ENERGY.2008.4781003.

Awerbuch, J. J.; Sullivan, C. R.; Filter-based Power

Splitting in Ultracapacitor-Battery Hybrids for

Vehicular Applications; COMPEL 2010, Control and

Modeling for Power Electronics, 2010, Pages(s): 1 –

8. Digital Object Identifier: 10.1109/

COMPEL.2010.5562429.

Bernholc, J.; Ranjan, V.; Zheng, X. H.; Jiang, J.; Lu, W.;

Abtew, T. A.; Boguslawski, P.; Nardelli, M.B.;

Meunier, V.; Properties of High-Performance

Capacitor Materials and Nanoscale Electronic

Devices, HPCMP-UGC 2010, High Performance

Computing Modernization Program Users Group

Conference, 2010, Page(s): 195 – 200. Digital Object

Identifier: 10.1109/HPCMP-UGC.2010.76.

Dai Haifeng; Chang Xueyu; A Study on Lead Acid

Battery and Ultra-capacitor Hybrid Energy Storage

System for Hybrid City Bus; ICOIP 2010,

International Conference on Optoelectronics and

Image Processing, 2010, Page(s): 154 – 159. Digital

Object Identifier: 10.1109/ICOIP.2010.321.

Haihua Zhou; Bhattacharya, T.; Duong Tran; Siew, T. S.

T.; Khambadkone, A. M.; Composite Energy Storage

System Involving Battery and Ultracapacitor With

Dynamic Energy Management in Microgrid

Applications; IEEE Transactions on Power

Electronics, 2010, Page(s): 923 – 930. Digital Object

Identifier: 10.1109/TPEL.2010.2095040.

Hua, A. C. -C.; Syue, B. Z. -W.; Charge and discharge

characteristics of lead-acid battery and LiFePO4

battery; IPEC 2010, International Power Electronics

Conference, 2010, Page(s): 1478 – 1483. Digital

Object Identifier: 10.1109/IPEC.2010.5544506.

JennHwa Wong; Idris, N. R. N.; Anwari, M.; Taufik, T.; A

Parallel Energy-Sharing Control for Fuel cell-Battery-

Ultracapacitor Hybrid Vehicle; ECCE 2011, Energy

Conversion Congress and Exposition, 2011, Page(s):

2923 – 2929. Digital Object Identifier: 10.1109/

ECCE.2011.6064162.

Lei Wang; Hui Li; Maximum Fuel Economy-oriented

Power Management Design for a Fuel Cell Vehicle

Using Battery and Ultracapacitor; IEEE Transactions

on Industry Applications, 2010, Page(s): 1011 – 1020.

Digital Object Identifier: 10.1109/TIA.2010.2045097.

Li Siguang; Zhang Chengning; Xie Shaobo; Research on

Fast Charge Method for Lead-Acid Electric Vehicle

Batteries; ISA 2009, International Workshop on

Intelligent Systems and Applications, 2009, Page(s): 1

– 5. Digital Object Identifier: 10.1109/

IWISA.2009.5073068.

Miller, J. M.; Energy Storage Technology Markets and

Application’s: Ultracapacitors in Combination with

Lithium-ion; ICPE 2007, International Conference on

Power Electronics, 2007, Page(s): 16 – 22. Digital

Object Identifier: 10.1109/ICPE.2007.4692343.

Monteiro, J.; Garrido, N.; Fonseca, R.; Efficient

Supercapacitor Energy Usage in Mobile Phones; ICCE

2011, 2011 International Conference on Consumer

Electronics – Berlin, 2011, Pages(s): 318 – 321.

Digital Object Identifier: 10.1109/ICCE-

Berlin.2011.6031796.

Musat, A. M.; Carp, M.; Borza, P.; Musat, R.; Sojref, D.;

Hybrid Storage Systems and Dynamic Adapting

Topologies for Vehiche Applications; OPTIM 2012,

2012 13th International Conference on Optimization

of Electrical and Electronic Equipment, 2012, Page(s):

1842 – 1566. Digital Object Identifier: 10.1109/

OPTIM.2012.6231910.

Niemoeller, B. A.; Krein, P. T.; Battery-Ultracapacitor

Active Parallel Interface with Indirect Control of

Battery Current; PECI 2010, Power and Energy

Conference at Illinois, 2010, Pages(s): 12 – 19. Digital

Object Identifier: 10.1109/PECI.2010.5437163.

Petchjatuporn, P.; Wicheanchote, P.; Khaehintung, N.;

Kiranon, W.; Sunat, K.; Chiewchanwattana, S.;

Intelligent ultra fast charger for Ni-Cd batteries;

ISCAS 2005, IEEE International Symposium on

Circuits and Systems, 2005, Page(s): 5162 - 5165 Vol.

5. Digital Object Identifier: 10.1109/

ISCAS.2005.1465797.

Schneuwly, A.; Gallay, R.; Properties and Applications of

Supercapacitors from the State-of-Art to Future

Trends; Proceeding PCIM 2000, 2000.

Wenzhong Gao; Performance Comparison of a Fuel Cell-

Battery Hybrid Powertrain and a Fuel Cell-

Ultracapacitor Hybrid Powertrain; IEEE Transactions

On Vehicular Technology, 2005, Page(s): 846 – 855.

Digital Object Identifier: 10.1109/TVT.2005.847229.

Xiaofei Liu; Qianfan Zhang; Chunbo Zhu; Design of

Battery and Ultracapacitor Multiple Energy Storage in

Hybrid Electric Vehicle; VPPC 2009, Vehicle Power

and Propulsion Conference, 2009, Page(s): 1395 –

1398. Digital Object Identifier: 10.1109/

VPPC.2009.5289462.