Hybrid Drive Systems for Vehicles ion

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© Mats Alaküla EHS

Hybrid Drive Systems for Vehicles

• Auxilliary systems

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Auxilliary systems ?

• Fundamental support functions – Power Steering

– Power Brakes

– Air pressure (heavy vehicles)

– Lighting

– Ventilation

– Suspension

– 12/24 V system

• Comfort function – Air Conditioning

– Power windows, seats, ...

– Entertainment systems

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Auxilliary systems cannot be

disregarded

• Energy consumption and peak power

significant

– Sometimes in parity with the tractive energy

• Two distinct goals:

1. Minimize energy consumption

2. Limit peak power

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Means ..

• Technology selection – Mechanical to electric

– Pneumatic to electric

– Hydraulic open loop to closed loop

– Hydraulic to electric

– ... to increase efficiency

• Control and scheduling – Load ”shaving”, e.g.:

• reduce compressor speed at high load, or

– Intelligent use of braking energy, e.g.

• regenerate energy to aux systems like compressor when the bus is braking.

Industrial Electrical Engineering and Automation

Lund University, Sweden

Test vehicle:

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Drive train

Auxiliary system

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Energy balance in the bus

(in average powers)

Hydrogen

Power

58 kW

Fuel Cell System HV Dist.

System &

Battery

FC Losses

32 kW

55 % Bus Auxilaries

4.0 kW

7.0 %

Energy recovery

11 kW

FC Auxiliaries

2.5 kW

Propulsion

DC/AC

&

Motor

Electrical power

24 kW

41 %

29 kW

50 %

Battery

losses

1.6 kW

Losses

4.3 kW

Traction

Power

24 kW

Road

Regeneration loss

1.9 kW

Friction

12 kW

Braunschweig

Driving cycle

100 % system

No AC!

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Subsystem energy usage, 4 kW

Water pump

5%

Compressor

21%

Servo pump

14%

24V DC/DC

29%Cooling Fans

31%

Auxiliary system – energy

consumption

24 V System, 1170 W

Lights

25%

Losses in

battery

24%

Control

system

51%

Air (compressor) system, 830 W

Door

Opening

35%

Hand Brake

18%

Brake

15%

Suspension

System

32%

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Air pressure driven loads

• Brakes

• Suspension

• Door opening

1

1

1

2

5

23

4

3

1 Brakes

2 Electronic control

system

3 Valves

4 Air dryer

5 Compressor.

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Brake system

• Pneumatic (heavy vehicle) – Slow response time

– Easy connection of e.g. Trailer

• Retarder – Exhaust brake, or

– Hydraulic

• Hydraulic (light vehicle)

• Development towards electric – Better control

• In heavy vehicles

• in hybrid vehicles with regenerative braking and ”friction brake fill in”.

– Cheaper?

– Energy supply difficult. Local el energy generation?

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Steering

• Rack and pinion manual (traditional)

• Hydraulic assist (modern)

– Need hydraulic pump

– Losses

• Electric assist

– 80 % less losses than hydraulic

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AC system

• Large windows -> increased cooling demand

• Private car (< 4 kW)

• Bus (< 30 kW)

• Compressor inefficient

Condenser

Evaporator

Compressor

Refrigerant Circuit

Expansion Valve

Heat

Heat

Passenger compartmentt

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New technology selection

Pneumatic (air) system, 830 W

Door Opening

35%

Brake

15%

Suspension

32%

Parking Brake

18%

Pneumatic (air) system, 830 W

Door Opening

35%

Brake

15%

Suspension

32%

Parking Brake

18%

System

Pneum

[W]

El

[W]

Doors

230

20

Suspension

260

25

Parkering

Brake

150

10

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Peak shaving

600 800 1000 1200 1400 1600 1800 2000 2200 0

200

400

600

800

1000

1200

Speed [rpm]

To

rqu

e [N

m]

Max engine

torque

Aux. off limit

Aux. on limit

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Control

200 220 240 260 280 300 320 340 360 380 400 0

20

40

60

Sp

ee

d [

km

/h]

seconds

200 220 240 260 280 300 320 340 360 380 400

-50

0

50

100

Pro

pu

lsio

n [kW

]

seconds

200 220 240 260 280 300 320 340 360 380 400

0

5

10

15

20

seconds

Au

xili

ary

[kW

] AC

DC/DC

200 220 240 260 280 300 320 340 360 380 400

-80

-60

-40

-20

0

20

40

60

80

100

120

Po

we

r [k

W]

seconds

Propulsion AC+DC/DC+Propulsion

Peak Shaving

Run at full power

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AC-system on/off condition

duty cycle generator

-150

-100

-50

0

50

100

150 P

ow

er

[kW

]

Propulsion power Power limits

time

off

-

o

n

Reference Actual

off-peak power limit on-controller on-regen.

power limit normal operation off-

controller

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Potential improvements

of the auxiliary system

0

20

40

60

80

100 Potential improvements

Hybrid bus Conventional bus

Fu

el a

lloca

tio

n [%

] Auxiliary system Propulsion system

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Startor

CollectorRotor rings

Electrical Systems

• 12 V (light vehicles)

– 50 Ah <-> 600 Wh

• 24 V (heavy vehicles)

– 200 Ah <-> 4800 Wh

• Alternators (Efficiency 50 %)

– 80 A <-> 1.1 kW (light vehicles) INCREASING!

– 300 A <-> 8.4 kW in larger buses

• DC/DC converter in hybrids (Efficiency 90 %)

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Conventional electric loads

• Electric generator load in average 600 W

• Assume efficiency 50 %

• Mechanical Generator load 1200 W

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Drag powers ...

• Remember

generator load

1.2 kW !

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Additional loads ...

• Weight, volume and efficiency benefits in electrical drive of traditionally mechanically driven loads.

• Many more could be added: Electric compartment heating, GPS Navigation Systems, DVD based Passenger Entertainment Systems, BlueTooth connection for giving brought on Mobile Phones Hands free via the Sound Systems, Detachable Cooling Boxes, Electrically Operated Foldable Cabriolet Roof, Electrically Controlled Suspension and Levelling System, Reversing Distance Sensing System, 230 V/50 Hz outlet for electric power to e.g. electric hand tools or electric grills for tail gate parties

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To much ...?

• The conventional generator is not able to provide

enough power to supply all loads ...

• Higher power is needed!

• Can we continue with 12 Volt?

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Ernie I

- Hi mate, my battery is dead ...

- Do you have any jumper cables?

Damn!

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Ernie II

- Damn kind of you to help me out ! - That is of course a VERY OLD

yankee ..

- Are you sure that it can make

my Yamagucci spin?

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Ernie III

- OK, lets go !

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Ernie IV

- It was like connecting Tjernobyl

to the Duracell Rabitt

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The 12 V story

• 6 V to begin with

• 6 V electric generator and starter 1912

• 6 V not enough – higher load and compression

• 12 V introduced 1955

• Still used, up to 1 kW – No electric hazard

– Modest isolation requirements

– Easy fusing

• Maximum power ?

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Problems with increased load @

12 V

• Cable area becomes large

– 1 kW needs 8 mm diameter cable

– 4 kW need 16 mm diameter cable

– 10’s of kW needs ...

• Connectors becomes expensive

– Voltage drops must be kept very low

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So, how much more do we need?

• 1992 MIT and Mercedes Benz took the initiative to a 42 V system voltage

• 42 ?, = 3*14 = charging voltage of a 36 V battery.

• Problems with 42 V: – Still not enough, in particular for hybrid power levels

– Windings in machines bigger

– Fusing more expensive

– Filament lamps last shorter

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42 may not be the answer

• Lost its momentum early

• A higher voltage needed for power,

several 100 Volts

• Already a fact today in hybrid vehicles

• A new standard must be expected

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Multi voltage systems

• 12 Volt will be needed as service battery

• N*100 V will be used as traction battery

• 5 V will be used in control systems

• 36/42 will be used ... ?

• Difficulties: – ”Power bridges” are needed

– Foolproof, e.g. when jumpstarting

– Safety in accident

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Hybrid Market developments


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48 V this time


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CO2 and Load Migration

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Different Voltages

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Check with Simulink ...

• Parallell Hybrid Car

• NEDC

• Most benefits won at

10...15 % Hybridisation


40

60

80

100

010

2030

4050

75

80

85

90

EM/Total ratio [%]

Fuel Consumption [l/10km]

Total traction Power [kW]

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Late voices


http://www.greencarcongress.com/48v/

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Power bridges

• Necessary to transfer energy between the

12 V and the traction battery

• The 12 V has negative earth in the chassis

• The traction battery can have either

– Negative earth in chassis

– Floating relative to chassis

• Safety and EMC when line charging

+12-

TractionBattery

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A 4 quadrant power bridge

• Can transfer energy in both directions

• Provides galvanic isolation

• No redundancy for the 12 V system

• Controlled with Puls Width Modulation (PWM) – EMC must be considered

Traction Battery

+ 12 -

Transformer

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Example

© Mats Alaküla EHS http://www.continental-corporation.com/www/linkableblob/presseportal_com_de/8801716/data/img_2013_09_10_iaa_48v_eco1_uv-data.jpg

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Battery blocks individuals

• A traction battery is a chain of blocks, being

chains of cells.

• Each block is an individual

– Age, thermal history

• When charging

– Weakest block full first. What to do?

• When discharging

– Weakest block empty first. What to do?

• Intelligent system needed to take care of all

blocks to maximize charge/discharge.

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Charge Distribution System 1

• Simple bypass to

dump load

• Does not solve

the discharge

limitation ... S O Clim ite r

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Charge Distr. System 2

• Bidirectional power flow

between traction battery

block and 12 V service

battery

• Allows ”Robin Hood”

handling of blocks in

the traction battery.

• DC/DC converter

obsolete

• Increased lifetime of the

batteries

TractionBattery

+12-

Transformer

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Another way to charge distribution ...

CU

42 V

Service Battery

N*100 V

Traction Battery

LAN

Uni-directional,

Galvanically isolated

Power bridge

100 W max

Uni-directional,

Galvanically isolated

Power bridge

1000 W max

Documents

Hybrid Drive Systems for Vehicles ion