hybrid drive systems for vehicles ion - lth ht16/lectures/ehs_l8_2016_safety.pdf · hybrid drive...

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© Mats Alaküla EHS

Hybrid Drive Systems for Vehicles

• More on Auxilliary Systems and EMC

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High voltage?

• > 1.5 V

• > 15 V

• > 50 V

• > 150 V

• > 300 V

• > 3 kV

• > 50 V is regarded

as high

• 48 V common

• 36/42 V …

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What is a dangerous equipment?

• 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

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Hybrid vehicle system

• Grounding

– 14 V negative earth in chassis

– 48 V negative earth in chassis?

– 400 V floating

chassie

12 V 42 V 300 V

Gen FAS RDU

48 V 400 V

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Toyota Prius safety system

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Basic dangers

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

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Current through body

• 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

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Approximate values for body

sensitivity to current

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Body Resistance

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!

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

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Thus:

• Have the greatest respect for the traction

battery!

– It is dangerous!

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Short circuit current

• 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

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Inductance

• Stored energy in the magnetic field.

• Unit is Henry

• Single conductor, 1 mikroHenry/m

• Equation u=L*di/dt

• What does that mean?

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To breake an inductive current

• The inductance

sets up a voltage to

keep the current

going.

• Arcs

• Used in ignition

coils and in light

tube igniters

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Light tube

u

-

nät

Lys

rör

Bimetallkontakt

Glimlampa

Glim

tändar

e

Induktor

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Electric strength of air

• 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

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Conclusions on braking an

inductive current:

• Very large voltages are created that may

start sparcs.

• Use fuses, protective clothing, fire

extinguisher

• Don’t let it happen!

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Power Electronics

• To convert electric energy

• Range: 0 – 1000 MW

• Switching amplifiers

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Why Switch?

• Traditional converters have low efficiency,

e.g. 25-60 %.

• Switching converters >95 %.

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Classes

A B och AB

20 – 25% 60 %

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Class D Audio Amplifiers

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Modulation

PWM

Spänning

Bärvåg

Tid

Önskad

spänning

till last

Tid

Pulsad utspänning

Verklig

spänning

till last

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PWM

A variable voltage is created with a pulse

width / pulse period.

Pulsad utspänning

Bärvåg

Tid

Önskad

spänning

till last

Verklig

till last

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PWM in Car

Long cables

Square voltages contain wide spectrum

Noise generated

Can be heard in the radio ...

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PWM

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

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4-Quadrant DC converter

• All combinations of u and I

i L, R + e -

id

sa

+ u -

sb 0 va vb

+Ud/2

-Ud/2

-

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4Q PWM : II

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

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3-phase

id

sa 0 va

+Ud/2

-Ud/2

sb vb sc vc

+ uab - + ubc -

- uca +

+

ua

-

+

ub

-

+

uc

- vo

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Control of 3 phase converters.

• Symmetric

references 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

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Ex: – UPS (Uninterruptable Power

Supply)

Likspännings-omvandling 2

Likspännings-omvandling 1

LikriktningVäxelriktning

+u

-nät

+ u -last

Batteri

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Conclusions on PWM

• Even if the average value of the voltage is

low, the instantaneous value can be high!

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EMC : I

• 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

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Parasitic currents

• Common mode – phenomenon

• Galvanic isolation

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This is what you think it looks like…

Induktor

Resistor

Batteri

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… and with some experience

maybe like this…

Parasitic components in conductors and circuit board

Induktor

Resistor

Batteri

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… but in reality like this!

Induktor

Resistor

Batteri

Internal non ideal compoents added

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EMC problems with PWM

BatteriKraftelektronisk

omvandlareLast

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Ex: Battery and Motor Capacitance

to Chassie

chassie

12 V 42 V300 V

Gen FAS

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Ex: Battery and Motor capacitance

to chassie ... " 0 V"

" -300 V" " 0V"

" 0V" " 0V"

chassie

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

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Communication in this environment

chassie

12 V42 V 300 V

Gen FAS

RDU controlcomputer

Vehicle controlcomputer

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Line Charging systems

• 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

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Example of a line charger

Optional transformer

a

b

c

Phase

Inductances

Phase

voltages

Traction

Battery

Motor Converter,

reconnected for

battery charging

Positive battery

potential

Negative batterypotential

0

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Auxiliary Power Unit (APU) : 1

• 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.

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APU : II

• 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.

hybrid drive systems for vehicles ion - lth ht16/lectures/ehs_l8_2016_safety.pdf · hybrid drive...

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