hybrid drive systems for vehicles - iea.lth.se ht18/lectures/ehs_l9b_2018_safety.pdf ·...

More on Auxilliary Systems

and EMC

Hybrid Drive Systems for Vehicles

EHS

Auxiliary system – energy consumption

EHS

Subsystem energy usage, 4 kW

Water pump

5%

Compressor

21%

Servo pump

14%

24V DC/DC

29%Cooling Fans

31%

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%

Brakes

Suspension

Door opening

Air pressure driven loads

EHS

1

1

1

2

5

23

4

3

1 Brakes

2 Electronic control system

3 Valves

4 Air dryer

5 Compressor.

New technology selection

EHS

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

Control

EHS

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

AC-system on/off condition

duty cycle generator

EHS

-150

-100

-50

0

50

100

150

Pow

er [k

W]

Propulsion power Power limits

time

off

-

on

Reference Actual

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

power limit normal operation off-

controller

Potential improvements

of the auxiliary system

EHS

0

20

40

60

80

100 Potential improvements

Hybrid bus Conventional bus

Fu

el a

lloca

tio

n [%

] Auxiliary system

Propulsion system

Conventional electric loads

EHS

Electric generator load

in average 600 W

Assume efficiency 50 %

Mechanical Generator

load 1200 W

Drag powers ...

EHS

Remember generator load 1.2

kW !

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

Additional loads ...

EHS

48 V this time

EHS

CO2 and Load Migration

EHS

Different Voltages

EHS

EHS

> 1.5 V

> 15 V

> 50 V

> 150 V

> 300 V

> 3 kV

High voltage?

EHS

• > 50 V is regarded as high

• 48 V common

• 36/42 V …

Equipment where a fault can cause harm to a person or property.

12 V system can also be dangerous

– Can cause fire

– Hydrogen explosion possible

Even if the voltage is low, the short circuit current is high and thus also the possible heat dissipation

What is a dangerous equipment?

EHS

Toyota Prius safety system

EHS

1. Direct current through body

2. Short circuit current that cannot be interrupted

3. High output voltage from switching converters

– Also EMC

4. Parasitic currents from switching converters

5. Fire or explosion

Basic dangers

EHS

Current depends on

– Voltage

AC, especially 50 Hz, is worst

But, DC is also dangerous

– Resistance

Skin + body fluid. Skin most important

Moisturous skin worst. ”Murare” ...

> 80 mA in more than 0.2 seconds can lead to cardiac arrest

Current through body

EHS

Approximate values for body sensitivity to

current

EHS

Dry Skin, Hand-to-Hand resistance=100 kOhm

Wet or broken skin, Hand-to-Hand resistance < 1000 Ohms.

Conclusion on contact:

Already at 125 V is life threatening !

400 V is VERY DANGEROUS!

Body Resistance

EHS

0 50 100 150 200 250 300 350 400 450 500500

1000

1500

2000

2500

3000Kroppens inre resistans i Ohm

0 50 100 150 200 250 300 350 400 450 5000

0.2

0.4

0.6

0.8Ström genom kroppen i Ampere

Spänning i Volt

1000 V

220V

Have the greatest respect for the traction battery!

– It is dangerous!

Thus:

EHS

Very large short circuit currents

– Low inner resistance

– Several 1000 Ampére short circuit current

– Difficult to interrupt due to the inductance of the cables and the lack of zero crossings

Short circuit current

EHS

Stored energy in the magnetic field.

Unit is Henry

Single conductor, 1 mikroHenry/m

Equation u=L*di/dt

What does that mean?

Inductance

EHS

The inductance sets up a voltage to keep the current going.

Arcs

Used in ignition coils and in light tube igniters

To breake an inductive current

EHS

Light tube

EHS

u

-

nät

Lysr

ör

Bimetallkontakt

Glimlampa

Glim

tänd

are

Induktor

3 MV/m

Whe the air is ionized the temperature reaches several 1000 C in a plasma with strong light

Burns

Eyes damaged

Used in welding

Electric strength of air

EHS

Very large voltages are created that may start sparcs.

Use fuses, protective clothing, fire extinguisher

Don’t let it happen!

Conclusions on braking an inductive current:

EHS

To convert electric energy

Range: 0 – 1000 MW

Switching amplifiers

Power Electronics

EHS

Traditional converters have low efficiency, e.g. 25-60 %.

Switching converters >95 %.

Why Switch?

EHS

Classes

EHS

A B och AB

20 – 25% 60 %

Class D Audio Amplifiers

EHS

PWM

Modulation

EHS

Spänning

Bärvåg

Tid

Önskad

spänning

till last

Tid

Pulsad utspänning

Verklig

spänning

till last

A variable voltage is created with a pulse width / pulse period.

PWM

EHS

Pulsad utspänning

Bärvåg

Tid

Önskad

spänning

till last

Verklig

till last

Long cables

Square voltages contain wide spectrum

Noise generated

Can be heard in the radio ...

PWM in Car

EHS

PWM

EHS

sa 0 va

+50

- 50

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04-200

-100

0

100

200va*, vb* & um

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04-200

-100

0

100

200va

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04-200

-100

0

100

200va*, vb* & um

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04-200

-100

0

100

200va

All combinations of u and I

4-Quadrant DC converter

EHS

i L, R + e -

id

sa

+ u -

sb 0 va vb

+Ud/2

-Ud/2

-

4Q PWM : II

EHS

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 -200

0

200 va*, vb* & um

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 -200

0

200 va

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 -200

0

200 vb

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 -500

0

500 u

3-phase

EHS

id

sa 0 va

+Ud/2

-Ud/2

sb vb sc vc

+ uab - + ubc -

- uca +

+

ua

-

+

ub

-

+

uc

- vo

Symmetric references

Control of 3 phase converters.

EHS

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

2

minmax

**

**

**

z

zcc

zbb

zaa

u

uuv

uuv

uuv

Ex: – UPS (Uninterruptable Power Supply)

EHS

Likspännings-omvandling 2

Likspännings-omvandling 1

LikriktningVäxelriktning

+u

-nät

+ u -last

Batteri

Even if the average value of the voltage is low, the instantaneous value can be high!

Conclusions on PWM

EHS

Electro Magnetic Compatibility

– Coexistence of electric and electronic systems

– Coexistence of the vehicle and sourrounding world

Connecting media:

– Conductive. E.g. Rectification noise from the generator

– Inductive and Capacitive. E.g. Between cables in the same bundle

EMC : I

EHS

Common mode – phenomenon

Galvanic isolation

Parasitic currents

EHS

This is what you think it looks like…

EHS

Induktor

Resistor

Batteri

… and with some experience maybe like this…

EHS

Parasitic components in conductors and circuit board

Induktor

Resistor

Batteri

… but in reality like this!

EHS

Induktor

Resistor

Batteri

Internal non ideal compoents added

EMC problems with PWM

EHS

BatteriKraftelektronisk

omvandlareLast

Ex: Battery and Motor Capacitance to Chassie

EHS

chassie

12 V 42 V300 V

Gen FAS

Obs AC voltage across the parasitic capacitances, with 300 V amplitude and switching frequency !!!!

Ex: Battery and Motor capacitance to chassie ...

EHS

" 0 V"

" -300 V" " 0V"

" 0V" " 0V"

chassie

Communication in this environment

EHS

chassie

12 V42 V 300 V

Gen FAS

RDU controlcomputer

Vehicle controlcomputer

1-phase, 10 A = 2.3 kW = 20 km driving distance charged per hour (=speed!)

3-phase, 16 A = 11 kW = 70-100 km driving distance charge per hour

Line Charging systems

EHS

Example of a line charger

EHS

Optional transformer

a

b

c

Phase

Inductances

Phase

voltages

Traction

Battery

Motor Converter,

reconnected for

battery charging

Positive battery

potential

Negative batterypotential

0

Heavy vehicles at rest. Driver living in the vehicle. Consuming low amounts of electric energy.

Energy provided via Diesel Engine at very low power. E.g. A 300 kW diesel providing 3 kW of electric

power.

Too low efficiency.

Auxiliary Power Unit (APU) : 1

EHS

Separate system:

– Fuel Cell based

– Hybrid drive system battery

Example:

– 400 kW Diesel, max efficiency 44 %

– Can run @ 20 kW with 40 % efficiency

– 5 kWh NiMH battery (50 kg)

– SOC variation allowed to be 40 %

– 2 kW load:

1 hour pure battery operation

5...10 minutes recharging from diesel @ 20 kW / 40 % eff.

Assume 85 % charge efficiency -> 40*0.85 = 34 %

– Probably 10 % less than Fuel Cell, but Hybrid drive benefits and single fuel.

APU : II

EHS