regenerative braking performance analysis on gang car electric

7/17/2019 Regenerative Braking Performance Analysis on GANG CAR Electric

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Regenerative Braking Performance Analysison GANG CAR Electric

Wahyu Parbowo, Agus Puradi

Electrical Power Engineering - School of Electrical Engineering and IormaticsBandung Institute of Technolo

J Ganeca 10, Bandung 40132, Indonesia@

@

Abstract- Increasing the driving range of an electric vehicle can

be achieved by applying regenerative braking. In this paper,how much regenerative braking affects the vehicle will bediscussed. The vehicle prototype on this study is Gang Car

Electric, a conversion from internal combustion engine cartype. The regenerative braking conguration enables thefeedback energy active as soon as the throttle pedal being

released and emulate engine retarding function of conventional

car. With that goal, we still want the vehicle to be able to cruisein a constant speed on the cruise mode. The proposedconguration is included in this paper.

Keywords -Regenerative, braking, electric car conversion,

Brushless DC motor

. NTRODUCTION

Electric car is a clean tecnology that has zero emission.Along with the development of power plant tecnology,electric car will have a cleaner energy source. The constraintof an electric car is the limited driving range because of thediculty to save electric energy.

Braking is one of the most important features on avehicle . The conventional braking diss ipates kinetic energythat was propelling the car forward as heat and becomeuseless. That wasted energy could have been used to dowork.Electric car, which has electric motor for propulsion,enable to convert the kinetic energy om braking to be

electric energy for battery charging. This tecnology iscalled regenerative braking and can extend the driving rangeof an electric vehicle .

Urban driving cycle has equent start and stop due to thecrowded streets. This will allow a lot of braking and a lot ofenergy recovery that can be used to charge the battery.

In this study, the urban electric car prototpe is made of aninteal combustion engine called Gang Car. Gang Car has alight weight platform characteristic, so it is suitable to beconverted into an electric car. The car is expected to be ableto stop in shor distances and in accordance with the driver'sfeel. To achieve this, the regenerative braking needs to becombined with mechanical braking om the car.

. RUSHLESS 4 QUADANT PEATION

Brushless dc motor is a syncronous motor withpermanent magnet with a trapezoidal-shaped back-emBrushless dc is widely used due to the absence of brush,making easier maintenance, and a great power in a smallsze.

Because of the permanent magnet, brushless dc motorcapable to operates as generator without excitation. It needsthe controller to be able to fetch the feedback current, thesame controller needed to drive the motor.

· r

Io

I

Fig . 1 . Four Quadrant Motor Operation

To get the forward braking operation (Quadrant IV), weneed thetorque to be negative in positive speed. This willhappen when the controller fetches the current from therotating Brushless DC due to the kinetic or potential energy.Thus, the brshless dc operates as a generator. [ 1 -5 ]

. EGENETIVE RKIG ON LECTC AR

Regenerative braking is a method that converts the energyduring braking into an electrical energy and fed it back intothe battery. The controller must have a bidirectionalconverter to be able to let the current ow both ways .

In Fig. 2 and Fig. 3 we can see a basic per-phase operationof a bidirectional inverter. On the normal mode switches S 1and S4 are on simultaneously. The inductor current i wouldbe increased due to the crent i. is the back-emf ommotor. When the switch S 1 off and S4 still on, the inductorcuent will ow into the eewheeling diode D2 and switchS4, which makes a d ischarging current path i.

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To increase the safety factor of the car, combination ofelectrical and mechanical brake needed. The braking forcedistribution on the ont and rear axle of the car need tofollow I curve on Fig. 5 below.

tt C

Fig . 2 .Converter (per phase) in normal mode [6]

In the regenerative mode, controller will utilize the backemfe as a voltage source. When S2 and S3 are on, thewinding will be energized. The inductor voltage will beequal to V + e and the current i is equal to i or i.During the turn off period of S2 and S3, the cuent i willow trough the eewheeling diode 1 and 4 and used to

charge the battery. [6 -8 ]

b

'-

�V

�

Fig. 3 .Converter (per-phase)[6]

To be able to utilize the back-emf to charge the highvoltage battery, dc-dc converter is needed.

HIOLARY

-O

I Y <

" \

Fig. 4.Regenerative braking scheme

)

. 9> .

.7 _ . . L 0.5

g :;

3X

a

f l

5 7 9 x rtio ,

Fig. 5. Braking force distribution curve[2]

Series brake means the use of regenerative braking andmechanical braking is not simultaneously. When the brakingcommand om the driver (with brake pedal) can be met byregenerative braking force, the mechanical brake will notactive. This regenerative brake applied on the driven axlewill emulates the engine retarding nction in conventionalvehicles. When the commanded deceleration is greater thanthe available regenerative braking force, the electric motorwill operate to produce its maximum braking torque and theremaining braking force is met by the mechanical brakesystem. The braking force distribution is illustrated in Fig. 6.[2]

2

4 1

FI

_

B k

i

n

g

fo

c

on

b. max w h

I

FI-m

Fig. 6. Series braking force distribution [2]

The counterpart of series brake is parallel brake. It usesthe mechanical and electrical brake simultaneously so theneed of complex control for the mechanical brake willdisappear. Regenerative braking used when the commanded



deceleration is low, if it's high then the mechanical brakewill be used simultaneously with the electric regenerativebrake. With the simpler control, parallel brake has lessrecover energy om braking because the mechanical brakestill diss ipates the kinetic or potential energy of the car. [2]

The braking force distribution is illustrated in Fig. 7.

4B f

Fig. 7. Parallel braking force distribution [2]

ANG AR ONVERSION

Gang Car Electric, the prototpe used in this study, is aconversion om an internal combustion engine car. GangCar originally produced by PT. Dirgantara Indonesia in2003 a small and lightweight car for four passengers. Thelightweight characteristic made this car suitable forconversion into an electric car. Motor, controller, and batterare Golden Motor product that already bought before for

laborator experiment.

The motor used for the car is a 1 0 kW Brushless DC, 72Volt, 3000-6000 PM, 4 poles. The controller isHPC500H72500 , 72 Volt, 35 0 Ampere. And the battery packis LiFeP, 72 Volt, 100 Ah.

-I B.te

-

Fig. 8.G ang Car El ectr ic Configuration

. ONTROLLER AND RKING CHEME

The controller scheme for Gang Car Electric is illustratedin Fig. 9 below.

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G + 1AL L_-_

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----.

FWDJREV i;

is S

Fig. 9 . Control l er scheme for Gang Car Electr ic

The braking proposed for this study is parallel braking

because of its simplicity and low cost. To maximize theenergy recovery om the regenerative braking, theregenerative mode is activated as soon as the driver releasesthe trottle pedal. The current feedback to the battery is set tothe point where this brake emulates the engine retardfunction in conventional vehicle.

Noally closed switch for braking is used in the trottlepedal, so when the trottle is pressed, the switch will beopened and it deactivates the regenerative brake mode.Because the trottle won't be activated if the brake-switchstill close, it is important to ensure that the brake switch isopen when the trottle switch began to be closed.

To be able to use the cruise feature on the controller, thescheme as Fig. is proposed. The driver can choose to usethe regenerative mode or cruise mode while driving.

1 1

0

Bra k vth M C

N D 8

Fig. 10. Bring Scheme

.ESTING ETHOD

To veri the regenerative braking performance, Gang CarElectric will be tested on a track with NEDC (New EuropeanDriving Cycle). NEDC is used to simulate the driving cycle



in a city. The NEC driving cycle is illustrated in Fig . 1 1below. This test is conducted on a track as in Fig. 12 insteadof on a dynometer.

140

20

0E 8�' 600�

0

Time [sconds)Fig. 11. New Eu ropean Dr iving Cycle

Fig. 12.The track for dr iv ing cycle examinati on

Tests were also performed on a steep road to see howmuch energy recovery can be obtained. These tests wereperformed on Sabuga downhill. The Google earth's imagingis shown in Fig. 1 3 .

Fig. 1 3 .Sabuga down track

The data logger built in the controller was used to obtainthe rotational speed of the rotor, voltage, and current of thebatter. The data logger was calibrated rst in the laboratorwith existing measuring instruments .

.ATA ANNTEPETATION

A. Driving Cycle Test

The driving cycle test with NEC can be used todetermine the fuel economy of Gang Car Electric. The speedprole om the test is shown in Fig. 14 .

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n

,

_

2

QQ

4 6

Time (second)

Fig. 14 . Speed prole test result

TLE I

EST SULT UMMY y (GM +7)

l vr rl Average

rrr rpAverage

p l r l ry upFbak ttg:

VCu

l ry rvry

wh r W

VlAmpere

7,98

W

8

NEDC test usually performed on a dynometer, accordingto reference [10] though it has represent a city iving cycle,energy consumption could be greater in reality.

This test was performed on a real road track, so the speedprole in Fig. 14 will sufce. Power om the battery duringthe test can be seen in Fig. 1 5 below.



�-Q 3o

-5

Time (second)

Fig . 1 5 . Power from battery without regenerative

Amount of energy required to complete the driving cycleis 278,298 Who Thus, the energy eciency of the car is asfollows:

Energy ConsumptionEnergy Effic iency = Total dis tance covereed

272,2 98 Wh

= 2,973 km = 91, 564 WhjkmThe feedback energy obtained om the test can be seen in

Fig. 1 6 . Keep in mind, this driving cycle testing did notperformed on a at trajector. The height prole of the trackis illustrated on Fig. 17 .

Despite the uphill road, the motor still able to produceenergy feedback when the driver releases the trottle pedal todecelerate.

:

! Q w

�u "Q Q

� �

u O

Time (second)

Fig. 16. Regenerative braking energy recovery. , � " .

' ,

Total energy obtained om regenerative braking is7,98Wh or 3% of its total energy consumption. With the 72V1 00Ah battery, Gang Car Electric will have the iving rangeas in Table 2 below:

TBLE 2DRIVING RNGE OF GANG C ELECTRIC

Without RegenerativeBraking

With Regenerative Braking

78,6 3 km

81 ,01 km

The regenerative braking driving range is not thatsignicant with just 3 % addition. This is likely occurring due

to the feedback setting on the controller. The setting used inthis test is for optimal driver feel to emulate the engineretarding nction of a conventional vehicle.

The amount of kinetic energy that can be converted toelectricity to charge the battery is calculated as below

P M 28743,3 5 Watt . s

. = � m v = 169126 ,6joulex 100% = 16, 99%

Where:

: Regenerative eciencym : Car mass(kg)

v : Car speed (m/s)P : feedback power (watt)M : braking time (s)

1 6,99% energy which usually wasted on conventional carcan be converted to electrical energy to charge the battery bythis braking conguration.

B. Downhill Test

This test obtained the energy feedback data when the cardrove on a downhill. Moreover, we used a much highersetting for feedback current to the battery on controller

setting as in Fig. 18.The track has an average slope of -9 ,5% and -1 7,6 %

maximum steepness. The total length of the track is 3 1 1meters. The current feedback reference in controller is set to20 Ampere (optimal iver feel) and 50 Ampere (optimalrecover energy - 0, 5C of the batter).

Crnt f fd hek) I 20 c £U b l ( ��

Fig. 18. Controller feedback current setting

Table 3 show the summary of the test and Fig. 19 show thespeed prole.

TBLE3DOWNHILL TEST RESULT SUMMY

Parameter 20 Ampere 50 Ampere

Total timeTrack lengthHeightTotal mass

Setting Setting

75 seconds 1 1 5, 99 seconds3 1 1 meters 3 1 1 meters24 meters 24 meters

790 kg 790 kg



(4 passenger) (4 passenger)Average rotor 123 6 rpm 71 2 mrotationTotal feedback 9,47 W 17 ,30 Wenergy

2 :

QQ

n-

Time (second)

Fig. 19 . peed prole of downhill test

The red line is for 50 A setting and the blue one is for 20A setting. The results show that with the larger cuent

feedback setting, the larger feedback energy obtained.Because the load aw a larger current, the negative torqueneeded is larger, thus the braking force is larger that makethe speed for the test lower.

Calculation of the amount of potential energy converted toelectricity is as follows:

• For 20 Ampere SettingP M 0 Watt. s

J = h = 1859 22 Joulex 00 = 18, 33

• For 50 Ampere SettingP M 62776,6 Watt . s

J = h

=1859 22 Joule

x 00 = 33, 5 0

With the same trajector, a higher feedback current settingcan convert more potential energy to charge the batter.According to reference [6] regenerative braking can utilize 8 -25 % of wasted energy. The regenerative efciency is in therange with the optimal driver feel 20 Ampere setting. Theinsignicant adding to the driving range could be due to thelosses om the battery and the mechanical losses om thecar.

Batter of the Gang Car Electric has 100 Ah capacities, soit is actually e to be charged with 50 Ampere current(0,5C). But, the braking force produced om the setting is

too large and just concentrated in rear axle. The distributionof this braking force could be dangerous for the car and thepassenger in it.

With the 20 Ampere setting in this study, Gang CarElectric can emulate the retarding engine of intealcombustion engine car. This regenerative braking force isapplied to rear axle and enough to decelerate the car withoutmaking a huge different om conventional car.

VIII. ONCLUSION

The conversion of Gang Car into an urban electric carprototpe is successfully done. The Gang Car Electric with10kW Brushless DC motor has 91,56h/km energyconsumption.

Parallel regenerative braking system applied to Gang CarElectric can nction properly as designed. As soon as thedriver releases the trottle pedal, regenerative braking modeis activated. The crise mode can still be used up to thedriver.

The regenerative braking scheme can increase the ivingrange of Gang Car Electric. It's 78,6 km withoutregenerative braking and 8 1 ,0 1 km with regenerativebraking. Regenerative braking eciency for 20 Amperesetting is 18,33% and 33,50% for 50 Ampere setting. So, toincrease the recovery energy the feedback current setting canbe set higher, but it will make a badbraking forcedistribution.

EFEENCES

[ ] D. Torres, P. Heath, "Regenerative Braking of BLDCMotors [online document], Microchip Tecnologync. , 04 April 20 1 3 , Available:http://ww .microchip. com/downloads/en/DeviceDoc/Regenerative%20 Braking%2020B LDC%20Motors.pdf

[2] Ehsani. Merdad et a, Modern Electric HybridElectric and Fuel Cell Vehicle: FundamentalsTheory and Des ign USA: CRC Press LLC, 2005.

[3 ] S. Leitman, B. Brant, Build Your Own Electric

Vehicle Ed. 3, Singapore: McGraw Hill Education,2 0 3 .

[4] A. E. Fitzgerald, C. Kingsley Jr., S.D . Umans,Electric Machine, Ed. 6, Singapore: McGraw Hill,2003.

[5] Steve, J . Chapman, Electric Machine Fundamental,Ed. 2, Singapore: McGraw-Hil, 1 99 1 .

[6] M.K. Yoong, et.al. , Studieso

RegenereativeBraking in Electric Vehicle IEEE, 201 .

[7] Ned Mohan, Power Electronics Jon Wiley & SonsInc., Singapore, 2003 .

[8] R. Krisnan, Electric Motor Drives, Prentice HallInteational Inc., London, UK, 2001.

[9] Dozeno. Jimmy, UiKinerja Motor Listrik DCkW danSistemKendalinyapadaPrototipe MobilListrik ITB- TugasAkhir, TeknikTenagaListrik TB,2012 .

[ 1 0] M. Peter, G. Jon, B. Anup, dan R. ddo,Discrepancies Between Type-approval and realworld Fuel-consumption and C02 Values, ICCT,no. 2012-02, 2012 .

regenerative braking performance analysis on gang car electric

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