Modularized Battery Management Systems for Lithium-Ion Battery Packs in EVs

83 Pages·2016·4.33 MB·English

DEGREE PROJECT IN ELECTRICAL ENGINEERING,
SECOND CYCLE, 30 CREDITS
STOCKHOLM, SWEDEN 2016
Modularized Battery Management
Systems for Lithium-Ion Battery
Packs in EVs
YIZHOU ZHANG
KTH ROYAL INSTITUTE OF TECHNOLOGY
SCHOOL OF ELECTRICAL ENGINEERING
Modularized Battery Management Systems for Lithium-Ion
Battery Packs in EVs
YIZHOUZHANG
MasterofScienceThesisinElectricalMachinesandDrives
attheSchoolofElectricalEngineering
KTHRoyalInstituteofTechnology
Stockholm,Sweden,August2016.
Examiner:OskarWallmark
IndustrialSupervisor:ChristianFleischer
TRITA-EE2016:136
ModularizedBatteryManagementSystemsforLithium-IonBatteryPacksinEVs
YIZHOUZHANG
(cid:13)c YIZHOUZHANG,2016.
SchoolofElectricalEngineering
DepartmentofElectricalEnergyConversion
KungligaTekniskaho¨gskolan
SE–10044Stockholm
Sweden
Abstract
The(Batterymanagementsystem)BMShasthetaskofensuringthatfortheindividualbat-
terycellparameterssuchastheallowedoperatingvoltagewindowortheallowabletemperature
range are not violated. Since the battery itself is a highly distinct nonlinear electrochemical de-
viceitishardtodetectitsinternalcharacteristicsdirectly.Therequirementofpredictingbattery
packs’ present operating condition will become one of the most important task for the BMS.
Therefore,specialalgorithmsforbatterymonitoringarerequired.
Inthisthesis,amodelbasedbatterystateestimationtechniqueusinganadaptivefiltertech-
nologyisinvestigated.Differentbatterymodelsarestudiedintermsofcomplexityandaccuracy.
Followingupwiththeintroductionofdifferentadaptivefiltertechnology,theimplementationof
thesemethodsintobatterymanagementsystemisdecribed.Evaluationsondifferentestimation
methods are implemented from the point of view of the dynamic performance, the requirement
onthecomputingpowerandtheaccuracyoftheestimation.Realtestdrivedatawillbeusedas
a reference to compare the result with the estimation value. Characteristics of different moni-
toring methods and models are reported in this work. Finally, the trade-offs between different
monitor’sperformanceandtheircomputationalcomplexityareanalyzed.
Keywords: batterymanagementsystem,electricvehicle,KalmanFilter,Li-ionbatterycell
model,stateestimation.
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Sammanfattning
BMS (eng. battery management system) har till uppgift att se till att viktiga parametrar
sa˚som tillspa¨nnings- och temperaturintervall uppra¨ttha˚lls fo¨r varje individuell battericell. Da˚en
battericells beteende a¨r icke-linja¨rt a¨r det sva˚rt att besta¨mma cellens interna karakteristika di-
rekt.Attkunnafo¨rutsa¨gadessakarakteristikafo¨rettkomplettbatteripackkommerattenmycket
viktigfunktionhosframtidaBMS.
I detta examensarbete har en modellbaserad tillsta˚ndsestimeringsmetod med anva¨ndande
avadaptivfiltreringunderso¨kts.Olikabatterimodellerharstuderatsmedavseendepa˚komplexitet
ochnoggrannhet.Efterintroduktionenavolikametoderfo¨radaptivfiltreringhardessametoder
implementeratsienBMSmodell.Utva¨rderingavdeolikametodernafo¨ratta˚stadkommatillsta˚ndsestimering
harsedanutfo¨rtsmedavseendepa˚dynamiskprestanda,kravpa˚bera¨kningskraftochnoggrannhet
hos de resulterande estimaten. Data fra˚n uppma¨tta ko¨rdata fra˚n ett fordon har anva¨nts som ref-
erens fo¨r att ja¨mfo¨ra de olika estimaten. Slutligen presenteras en ja¨mfo¨relse mellan de olika
tillsta˚ndsestimeringsmetodernasprestandana¨rdeappliceraspa˚deolikabatterimodellerna.
Nyckelord:BMS,elbil,Kalmanfiltrering,litiumjonbatterimodell,tillsta˚ndsestimering.
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Acknowledgements
ThepresentthesiswascarriedoutatNationalElectricVehicleSweden.
First, I would like to thank my industrial supervisor Dr. Christian Fleischer for giving me
this opportunity by offering such an interesting and challenging topic. Second, I would like to
express my gratitude to my examiner Dr. Oskar Wallmark for giving me feedback from time to
timeandguidingmeintherightdirection.
IwouldalsoliketothankallmycolleguesinNEVSforsharingtheirknowledgeandgiving
feedbackonmythesiswork.Furthermore,Iwouldliketothanktoallmyfriendsforsupporting
meallthetimeandforthegoodtimewehadtogetherduringmymasterstudyperiod.
YizhouZhang
Trollha¨ttan,Sweden
August2016
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Contents
Abstract iii
Sammanfattning v
Acknowledgements vii
Contents ix
1 Introduction 1
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 PresentationofNEVS . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.3 BatteryManagementSystem . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 MotivationsandObjectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 ThesisOutline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Li-ionBatteryCellEquivalentElectricCircuitModel 5
2.1 lntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 TheRintModel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 TheRCModel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
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