Hybrid Drive Systems for Vehicles - IEA ht19/Lectures/EHS_L5_2019_hybrid.pdf · resistance, charger...

Hybrid Drive Systems for Vehicles

• L5

– Alternative drive train Components

Drawback with conventional drivetrains

• Limited ability to optimize

operating point

• No ability to regenerate braking

power

Solutions

• Smaller Engine

+ Reach higher operating points

- Still cannot regenerate

• Store energy in the vehicle mass

- Speed variations

- Still cannot regenerate

• Secondary energy storage

+ Selectable operating point (Pstorage

= Pice – Proad)

+ Can regererate

- Expensive

Smaller Engine – cylinder deactivation

IC E EM

PEBatt

GEARClutch

D

DIFFIC E Clutch

0 200 400 6000

50

100

150

0 200 400 6000

50

100

150

0 200 400 6000

50

100

150

Combustion On Demand

• Cylinder deactivation via free

valve control

• 4-stroke, 6-stroke, 8-stroke ...

Optimized efficiency

0

200

400

600

0

20

40

60

80

0

0.05

0.1

0.15

0.2

0.25

0.3

Speed [rad/s]Torque [Nm] 0

200

400

600

0

20

40

60

80

0

0.05

0.1

0.15

0.2

0.25

0.3

Speed [rad/s]Torque [Nm] 0

200

400

600

0

20

40

60

80

0

0.5

1

1.5

2

Speed [rad/s]

Number of Cylinders in use

Torque [Nm]

Max efficiency

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

x 104

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

ICE Power [W]

Optim

al E

ffic

iency

Blue=2-cylinder std, Red=2-cylinder COD

Secondary Energy Storage selection

• Why electric?

– Efficient secondary energy

converters (Electrical machines)

– Safe, quiet, flexible installation

– Increasing need for Auxilliary electric

power

– High torque density of Electrical

Mchines• Up to 30 Nm/kg

• ICE: <2 Nm/kg

Secondary energy storage – Hybridisation

Energy Storage Systems

How does a battery look?

Design criteria

Cost

OperationPerformance

Vehicle

Performance

Pb-Acid

NiMH

Li-ionP

ow

er

Den

sit

y

Energy Density

S.C

Effpower

What is a battery cell?

Different cell formats

Prismatic Cylindrical Pouch

Same principle inside

PouchCheaper than prismatic to manufacture

Need mechanical stability when packing

PrismaticSimplier building block for module

More mechanically stable than pouch

(still needs mechanical support in the module)

CylindricalEasy and cheap to manufacture

More difficult to pack

More difficult to get good contact when cooling

Short introduction to Battery Characteristics

Closed

no material transfer

Controlled

no spontaneous reaction

different energy levels

Reversible

rechargeable

high efficiency

The Battery Cell – a Chemical ReactorElectric

EnergyThermal Energy:

heating/cooling

SOC – state-of-chargeo Charge level related to reference

capacity1

o 0-1 or 0-100%

OCV – open circuit voltageo Battery voltage at rest°o Measured after 15-60min rest

period2

o Affected by temperature, age & hysteresis2

Nominal Voltageo Electrochemical voltage average OCV


1. Often 1C-rate discharge at +23°C

2. Applicable for NiMH & LFP. See separate slide.

100% SOC 0% SOC50% SOC

0204060801001

1.5

2

2.5

3

3.5

4

4.5

SOC [%]

Open C

ircuit V

oltage [V

]

LCO//Graphite

NMC//Graphite

LMO//Graphite

NCA//Graphite

LFP//Graphite

LMO//LTO

PbA

NiMH

Physical Background & Model Design

LiFePO4: SEM 60k

LiC6: SEM 60k

Highly porous structure to

maximise active area

+

-

Current

collectorSeparator

Anode Cathode

+

-

Thick

layers

Large

particles

Power- vs. Energy- optimised

Battery Cell Properties

• All parameters are non-linear

• Strong dependence on SOC,

temperature, current rate & direction, and

history.

• OSV = Open Circuit Voltage

• R0, R1, C1 describe the battery

resistance, charger transfer and “double

layer effect”1

• R2, C2 describe the diffusion2 effect

1) The first layer, the surface charge (either positive or

negative), consists of ions adsorbed onto the object due to

chemical interactions. The second layer is composed of ions

attracted to the surface charge via the Coulomb force,

electrically screening the first layer.

https://en.wikipedia.org/wiki/Double_layer_(surface_science)

2) Movement of Lithium ions

https://www.sciencedirect.com/science/article/pii/S0360544217317127#fig1

http://www.mdpi.com/1996-1073/9/6/444

https://en.wikipedia.org/wiki/Double_layer_(surface_science)

0204060801001

1.5

2

2.5

3

3.5

4

4.5

SOC [%]

Open C

ircuit V

oltage [V

]

LCO//Graphite

NMC//Graphite

LMO//Graphite

NCA//Graphite

LFP//Graphite

LMO//LTO

PbA

NiMH


• Cell capacity [Ah]– Defined by cell design & choice of active material

Typical range: 5-100Ah

• Cell voltage [V]– Defined by choice of active material

Typical range 1-4.5V

• Cell energy [Wh]– Energy = Capacity • Voltage

Typical range: 5-400Wh

• Cell power [W]– Power = Voltage • Current

Limited by cell design & choice of active material

Typical range: 5-5000W


SOH – state-of-health

o Actual capacity related to reference

capacity

o 0-1 or 0-100%, sometimes 80-100%

o No standard definition

BOL – beginning of life

o Fresh / unused battery

EOL – end of life

o Aged battery with insufficient performance

o Can be defined by capacity, energy,

power etc.

No standard definition

0 50 100 150 200 250 3000

10

20

30

40

50

60

70

80

90

100

Cycles x 1k

Cap

acit

y [

%]

?


Cell Voltage = f(...)

o Material Selection

o State of Charge (SOC)

o Current / power

o Temperature

o Age

→No equilibrium / steady-state

0 10 20 30 40 50 60 70 80 90 1001.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4

3.6

3.8

SOC [%]

Cell

Voltage [

V]

Low current

Medium current

Open circuit voltage

Discharge

Charge





o Current / power

o Temperature

o Age


43 44 45 46 47 48 49 50 51 52 53

3.1

3.15

3.2

3.25

3.3

3.35

3.4

3.45

3.5

SOC [%]

Cell

Voltage [

V]

Low current

Medium current


Discharge

Charge





o Current / power

o Temperature

o Age


0 10 20 30 40 50 60 70 80 90 1001.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4

3.6

3.8

SOC [%]

Cell

Voltage [

V]

Low current

Medium current


Aged cell / high current

Discharge

Charge

State of Charge

• C-rate = P[kW] / W[kWh]

– C=1: 1 h full charge

– C=2: 30 min full charge

Vo

ltag

e

100% State of Charge 0%

Li-ion

NiMHS.C.

https://www.researchgate.net/figure/Discharge-curves-for-different-technologies-

and-different-batteries_fig1_224395476

Applied Modelling: Performance & Accuracy

IROCVU

I

→

Simple Battery model

• Constant parameters

• Very fast, suitable for

optimisation

• Very limited accuracy

+

-

OCV = constant

R = constant

+

-

Terminal

Voltage

OCVU-U R

1=

R

OCV-UU=IU=P 2


I

→

Simple Battery model with

SOC

• Simple look-up tables

• Still fast, suitable for

optimisation

• Still limited accuracy

+

-

OCV = f(SOC)

R = f(SOC)

+

-

Terminal

Voltage

ISOCRSOCOCVU


Enhanced battery model with SOC

& t


• Two internal states – not suitable

for optimisation+

-

OCV = f(SOC…)

R’ = f(SOC…)

C = f(SOC…)

+

-

Terminal

Voltage

R = constant


Advanced battery model with

SOC, T & t


• Three internal states – not

suitable for optimisation

+

-

OCV = f(SOC, T,I…)

R = f(SOC, T,I…)

C = f(SOC, T,I…)

Iout

+

-

Terminal

Voltage

R = f(SOC, T)

R = f(SOC, T)

Voltage Drop, Udrop (t)

-+


Separate high-frequency models

are needed for specific casesbatteries act as inductors at high frequency and as

capacitors at low

RCT

L*

α3

W

α2Rohm

CDL

α1

Ohm

jC

jCR

RLjZ

a

dla

W

ct

Ohm

1

2

3

1

1

1

1*

Models available form

Volvo GTT-ATR for

specific cells upon

request

Battery simulation model : I

b a t t i

b a t t e

b a t t R

e c h P a r g t e r m P

l o s s P

term

ech

batt

losstermech

battbattloss

batt

term

batt

batt

batt

battbatt

battbattbattbattbattbattbattbattterm

P

P

PPP

iRP

R

P

R

e

R

ei

iRieiiReP

arg

arg

2

2

2

22

)(

Battery Simulation model : II

-1 -0.5 0 0.5 1

x 105

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2Battery charge efficiency

Battery power [W]

Effi

cien

cy

SAFT data

© Mats Alaküla

SAFT Lithium teknologi

Tesla Model S&X, Milage vs remaining battery capacity

• Based on the

18650 cell.

• Model 3 use

the 2170 cell

https://www.teslarati.com/tesla-battery-life-80-percent-capacity-840km-1-million-km/

+3

3 %

vo

lum

e

+3

3 %

en

erg

y

-25 %

co

st/

en

erg

y

Battery Lifetime : II

• Calculate the total converted

energy as:

Wconv=Wbatt*DoD/100*NoC

• And the battery cost per kWh

converted energy as:

SEKperkWh = CostPerkWh*Wbatt /

Wconv

CostPerkWh = 3000 [SEK]

Battery Lifetime : III

• Note! – The total

converted energy falls fast

with increased DoD !!!

• The cost per converted

kWh increases rapidly

with increased DoD

0 20 40 60 80 10010

3

104

105

106

NoC

Depth Of Discharge [%]

0 20 40 60 80 10010

0

101

102

103


Con

verte

d E

nerg

y [M

Wh]

0 20 40 60 80 1000

0.5

1

1.5

2


Cos

t[SE

K/k

Wh]

Battery Lifetime : IV

1002,

Dbatt

avech

W

tP

DoD

• Assume that DoD is driven by

a constant charge Power

• then… :

DDoD

SOC

PchargePch,ave

0 t

0

5

10

15

200

20 4060

80100

0

2

4

6

8

10

12

DoD [%]

Battery Lifetime in Years, used 8h/day, 300 days/year

Pch,ave/Wbatt [1/h]

[yea

rs]

Battery Lifetime : V

NoC

W

P

DoD

NoCP

WDoDLifetime

W

tP

DoD

batt

avech

avech

batt

batt

avech

D

100

2

100

2

1002

,

,

,

• The battery lifetime can be calculated as:

• Now, plot the battery lifetime as a function of DoD and (Pch,ave/Wbatt)– Assume 8h/day, 300 days/year

Battery Lifetime: Conclusions

• Deep discharge of a

battery costs lifetime

– Best with less than 10 % DoD

• The battery may have a

high power density BUT

using it is expensive, i.e. a

high power/energy ratio

costs lifetime

– Best with an average battery

power in the range 3…4 x the

battery energy capacity.

Electric Motor Drive

Systems

What is an Electrical Machine?

• ”A device that convertes between

Electric and Mechanic energy,

both ways”

• Physical principles?

› Some kind of field ...

» Acoustic field

» Piezoelectric deformation

» Electrostatic field

» Magnetic field

http://www.shinsei-motor.com/English/techno/index.html

Energy density, Magnetic vs Electric

0

2

2

B

2

2

0

E

Magnetic Energy Density

Electric Energy Density

12

0 1085.8

7

0 104

3/ mWs5104

3/ mWs1104

Tesla1

MV/m3

47

Linear Motion

• In many applications the “most wanted”

• Often translated from a rotation

Generic Force

Force = Flux density * Current * length (twice)

Power = Force * Speed = Voltage * current

Voltage = Force *speed / current

= Flux density * length * speed

Current

ForceFlux density

Lorentz force

= current in magnetic field

Multi Phase, otherwise it stops

End windings don’t contribute to torque,

but takes a lot of space …

Linear movement from generic force

Rotating movement from generic force

Conclusions on force and movement

• The same generic circuit accomplish both linear and rotating

movement.

• One phase is not enough for continuous force.

• Qualitative:

Voltage ~ Speed

Current ~ Force

Add the Reluctance torque ...

External Magnetic Field

Electrically or

permanently

magnetized =

Lorenz

forces

Only

Reluctance

force

Lorentz

AND

Reluctance forces

No Torque

Different mechanical arrangements

• Windings in the rotor

• Windings in the stator

• Windings in both sides

Magnetic circuits

• The magnetic core provides mechanic support and construction

• Soft and hard magnetic materials

– Solid, laminated or powder cores – high μ & Bsat vs Ploss

– Discrete, multipole magnets – high BrHc vs cost & integration

• Establish magnetic coupling – linkage vs leakage

Electric circuits

• Initially referred as 3φ symmetric and sinusoidal

• Insulated electric conductor (Wire) wound as coils or formed as waves

• Distributed or concentrated windings

– Arrangement measured by winding factor - ratio of actual MMF to full-pitched winding MMF

• Manufacturability and assembling

Stator, Rotor and Airgap

• The stator is static (not

moving)

• The rotor rotates

• The air gap seperates

them– Usually < 1 mm

Air gap

# of poles = p

N

S

N

S

N

S

e = d

dt

e = d

dt+

-

+

-

59

mechel

p

2

elmech Tp

T 2

elelelelmechmech TTp

pT

2

2PowerMechanical

Core back, teeth etc ... Tooth

Slot

Stator Core Back

Rotor Core Back

1 Pole =

2 x ½ pole

Torque and Power

• Torque = Force * radiuson the shaft

T = F * r

• Power = Torque*Speedon the shaft

P = T *

but, also …

• Power = Voltage * Currenton the electrical terminals

P = U * I

r

F

U,I

Tangential force

• Interaction of flux and current

• ”F= B i l ”

112

sgmeistangential KBlDF

r

Ftangential

Inner stator

diameter

Equivalent active

magnetic length

Air gap flux density Stator Angular

Current Density

mAtp

iD

NkK e

is

ss /

2cosˆ6

)( 1

s

Stator inner diameter

Stator current / meter air gap periphery

Angular current density

Number of winding turns

Winding factor Number of poles

Phase current amplitude

Shear Force & Torque

• Current and Flux interact for tangential

force

s = Force/Unit area is a key figure

• A good design accomplish about

s = 10 000 … 30 000 [N/m2]

• … in continuous operation and

2…4 times that in transient operation

r

s

21111

/2

2 mNKB

lD

KBlD

A

F sgm

eis

sgmeis

avg

s

11

2

4sgmeis KBlDT

Conclusion on torque

The torque is proportional to the:

– Magnetic flux density – Limited by material propertied to about 1.0 ... 1.5 Tesla

– Spatial current ”density” – Limited by cooling capability

– Axial length of the machine

– Diameter SQUARED !

11

2

4sgmeis KBlDT

= Rotor Volume

Hybrid Topologies

DEngine El

Mach

El. mach

El.

mach

Inner or Outer Rotor, Radial or Axial flux …

RotorRotor

Stator

Stator Stator

Stator

Ro

tor

Sta

tor

Sta

tor

Ro

tor

Inner rotor

Radial flux

Outer rotor

Radial flux

Axial flux

End winding

Distributed or Concentrated winding

Axially shorter end

winding

Cheaper assembly

Lower torque quality

Longer end winding

More expensive

assembly

Higher torque quality

Shear Force & Torque

Current and Flux interact for

tangential force

s = Force/Unit area is a key

figure

A good design accomplish

about s = 10000-30000

[N/m2] in continuous

operation and 2..4 times more

in transient operation

s

Form Factor

• For the same torque, a machine can

be either short and wide, or long and

slender …

• Assume 25000 [N/m2], and a desired

torque of 1000 Nm, AND that the

stator outer radius is 0.15 – 0.5 meter.

– How long will the machine be to fulfill

the torque requirement?

• The long and slender machine will

accelerate faster

– Torque ~ radius2*length

– Inertia ~ radius4*length

• Acceleration = Torque/Inertia ~ 1/radius2 High torque density but

low acceleration

Low torque

density but high

acceleration

0 0.1 0.2 0.3 0.4 0.5 0.6 0.70

0.1

0.2

0.3

0.4

0.5

0.6

Radius

Length

Eaton

• ”ISAM”

• ”Short and Wide”

• Concentrated

winding

• PM motor from

Hitachi

Voith• ”ExSAM”

• ”Long and slender”

• Induction motor from

??

– Probably very close

to standard

industrial … good

commonality

• 150 kW 520 nm @

motor or input shaft?Siemens 1FHX

Volvo/Renault/Mack/Nissan

• ”ISAM”

• ”Short and Wide”

Some Cars

”ISAM”

PM Motor

Concentrated

windings”

Complex

PM Machines

Distributed windings

97000 N/m2 !!!

Conclusions on force and movement• The same generic circuit accomplish both linear and rotating

movement.

• One phase is not enough for continuos force

• Qualitative:

– Voltage ~ Speed

– Current ~ Force

Field Weakening : I

• Remember:– Voltage ~ flux density * speed

– Torque ~ flux density * current

– Power ~ speed*torque = voltage*current

• The required voltage ”hits the roof” at some speed. What to do, to increase speed beyond?– Answer: Reduce flux density’

– Consequences:

• The voltage requirement is kept constant, as desired

• The torque capability drops as the flux density.

• The power is kept constant, since the speed increases in the same rate as the torque drops with increasing speed.

Field Weakening : II

0

50

100

150

200

250

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000 [rpm]

[Nm]

[kW, V]B

ase s

pee

d

Const

torqueConstant

power

Field weakening ratio 1:4

Ma

x s

pee

d

Max voltage and power

Example from Toshiba”Large Torque and High Efficiency Permanent Magnet Reluctance

Motor for A Hybrid Truck” - Masanori Arata et. Al, EVS-22

Permanent Magnet Synchronous Machines

• Same as the generic machine

• Voltage and frequency proportional to

speed

• Current proportional to torque

• High torque density

– 1...10 Nm/kg

– Compare to ICE 1...2 Nm/kg

• High efficiency

– Up to 97%

• Higher efficiency, higher torque density

and more expensive than other

machines

– Due to the permanent magnets.

The Induction Machine : I

• Same stator as the PMSM

• The rotor is a short circuited ”cage”

• The rotor current must be induced magnetically– Losses related to magnetization

”competes” with losses due to torque generation.

• Robust construction

• Low cost

• Low/no maintenance

• Heavily standardized for industrial applications

• Voltage and frequency proportional to speed, like PMSM

Comparison – Electric Drives

1.0 2.0

AC (IM)

PM

2.0

4.0

6.0

8.0

Tmax [Nm/kg]

Pcontinuous [kW/kg]

Electrical machine losses

• Several types:

– Copper losses (Ri2)

– Iron losses (k1*f*B2 + k2*(f*B)2)

– Windage losses (surface speed)

– Other friction losses

• Approximately calculated by– [EtaEM,Tem,Wem] =

CreateEMmap(Pem_max,wem_max,Tem_max)

Hysteresis losses

Eddy current losses

0200

400600

800

0

50

100

150

200

0

0.5

1

Speed [rad/s]

Electrical machine efficiency

Torque [Nm]

The Traction motor efficiency

0200

400600

800

0

50

100

150

200

0

0.5

1

Speed [rad/s]

Electrical machine efficiency

Torque [Nm]

Torque limitPower limit

Speed limit

Power Electronics

• Needed to condition the battery voltage to the

different electrical drives

• Use switching technology for high efficiency

– Conventional converters (like loudspeaker amplifiers)

efficiency 25-60 % due to continuous control of the voltage.

– Switching means “on/off” control of voltage, leading to

efficiency above 95 %.

1 Phase Pulse Width Modulation (PWM)

Modulating wave Voltage reference

Output voltage0 0.005 0.01 0.015

0

20

40

60

80

100

0 0.005 0.01 0.0150

20406080

100

sa va

+100

- 0

Three-phase Converters

id

sa 0 va

+Ud/2

-Ud/2

sb vb sc vc

+ uab - + ubc -

- uca +

+

ua

-

+

ub

-

+

uc

- vo

Traction motor

Three-phase Pulse Width Modulation

• The voltages

contain high

harmonics that

cause:

– Audible noise

– Torque ripple

– EMC problems

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02-500

0

500

uaref & tri

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02-500

0

500va

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02-500

0

500vo

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02-500

0

500ua

varef

tri

va

v0

u=va-v0 grundton 50 Hz

Simple Converter Loss Model

Switching and Conduction losses

Reverse recovery Losses

3-phase converter losses

Loss estimation

Example : V_to = 0.95; % [V]

V_do = 1.65; % [V]

R_t_on = 0.5/300; % [Ohm]

R_d_on = 0; % [Ohm]

E_d_rr = 0.0485; % [J]

E_on = 26e-3; % [J]

E_off = 55.5e-3; % [J]

V_dc_n = 600; % [V]

I_n = 450; % [A]

Udc = 600; % [V]

P_max = 200000; % [W]

Converter Efficiency for different fsw &

cos(j)

0

100

200

300

400 0

200

4000

50

100

150

200

U ph-ph [V RMS]

P out [kW]

I phase [A RMS]

0

100

200

300

400 0

200

4000

2000

4000

6000

8000

U ph-ph [V RMS]

P loss [W]

I phase [A RMS]

0

100

200

300

400 0

200

40050

60

70

80

90

100

U ph-ph [V RMS]

Efficiency [%]

I phase [A RMS]

0

100

200

300

400 0

200

4000

50

100

150

200

U ph-ph [V RMS]

P out [kW]

I phase [A RMS]

0

100

200

300

400 0

200

4000

1000

2000

3000

U ph-ph [V RMS]

P loss [W]

I phase [A RMS]

0

100

200

300

400 0

200

40020

40

60

80

100

U ph-ph [V RMS]

Efficiency [%]

I phase [A RMS]

fsw=1000 3000 10 000 Hz, cosj)=1

fsw= 3000 Hz, cosj)=0 0.25 0.5 0.75 1

Power Electronic Efficiency

• Mostly depending on the ratio

• Almost constant over wide operating range

• Can be represented by a constant, e.g. 0.97

Output voltage

DC link voltage

Hybrid Drive Systems for Vehicles - IEA ht19/Lectures/EHS_L5_2019_hybrid.pdf · resistance, charger...

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