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More on Auxilliary Systems
and EMC
Hybrid Drive Systems for Vehicles
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Auxiliary system – energy consumption
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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
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1
1
1
2
5
23
4
3
1 Brakes
2 Electronic control system
3 Valves
4 Air dryer
5 Compressor.
New technology selection
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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
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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
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-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
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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
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Electric generator load
in average 600 W
Assume efficiency 50 %
Mechanical Generator
load 1200 W
Drag powers ...
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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 ...
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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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> 1.5 V
> 15 V
> 50 V
> 150 V
> 300 V
> 3 kV
High voltage?
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• > 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?
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Toyota Prius safety system
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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
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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
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Approximate values for body sensitivity to
current
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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
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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:
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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
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Stored energy in the magnetic field.
Unit is Henry
Single conductor, 1 mikroHenry/m
Equation u=L*di/dt
What does that mean?
Inductance
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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
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Light tube
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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
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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:
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To convert electric energy
Range: 0 – 1000 MW
Switching amplifiers
Power Electronics
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Traditional converters have low efficiency, e.g. 25-60 %.
Switching converters >95 %.
Why Switch?
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Classes
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A B och AB
20 – 25% 60 %
Class D Audio Amplifiers
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PWM
Modulation
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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
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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
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PWM
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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
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i L, R + e -
id
sa
+ u -
sb 0 va vb
+Ud/2
-Ud/2
-
4Q PWM : II
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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
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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.
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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)
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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
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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
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Common mode – phenomenon
Galvanic isolation
Parasitic currents
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This is what you think it looks like…
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Induktor
Resistor
Batteri
… and with some experience maybe like this…
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Parasitic components in conductors and circuit board
Induktor
Resistor
Batteri
… but in reality like this!
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Induktor
Resistor
Batteri
Internal non ideal compoents added
EMC problems with PWM
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BatteriKraftelektronisk
omvandlareLast
Ex: Battery and Motor Capacitance to Chassie
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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 ...
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" 0 V"
" -300 V" " 0V"
" 0V" " 0V"
chassie
Communication in this environment
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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
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Example of a line charger
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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
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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
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