Discussion Forum: Electric Vehicles vs Hybrid Vehicles, 20 June 2008
Hybrid Electrical Vehicles
Prof M J Kamper and Dr R Wang
Electrical Machines Laboratory
University of Stellenbosch
Stellenbosch, South Africa
Overview
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History
Vehicle Powertrains
HEV Configurations
Degree of Hybridization
Plug-in HEVs
Electrical Motor Drives
HEV Example at SU
Conclusions
Historic Review
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HEV
First EV (1881)
HEV won hill climbing race (1902)
First 4WD EV (1898)
First mass produced HEV (1997)
Vehicle Powertrains
Conventional Vehicle
Hybrid Electric Vehicle
Battery
Petrol
ICE
ICE
Battery
Petrol
Plug-In Hybrid Electric Vehicle
Battery Electric Vehicle
Electric EM
Motor
EM
ICE
EM
Battery
Petrol
4
HEV Configurations
Series Hybrid
5
ICE-assisted EV
Simple drivetrain (no clutches)
Flexible location of ICE
3 Propulsion devices
Heavy-duty electrical machine
Large battery pack
HEV Configurations
Parallel
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Parallel Hybrid
ICE or Motor or both in Parallel
Electrical-assisted ICE vehicle
2 Propulsion devices
Sizing of devices depends
Simple power converter
Generally two clutches
Small-medium battery pack
HEV Configurations
Series-Parallel Hybrid
More complex and costly
3 Propulsion devices
Three propulsion power
Two clutches
Smaller battery pack
NB: Power Flow Control
7
Degree of Hybridization
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“micro” HEVs: stop/start and variable charging capacity;
“mild” HEVs: regenerative braking, engine start/stop, electric
assisted driving;
“full” HEVs: full electric launch/drive capability, a higher
percentage of system power from the electric motor part of the
propulsion system;
“series” or “range extender” HEVs: a full-sized electric motor
drive in addition to including regenerative braking and significant
“All Electrical Range” (AER).
Degree of Hybridization
Full Hybrid
ADVANCED ENGINE
ELECTRIC ACCESSORIES
ENGINE DOWNSIZING
PETROLEUM ONLY
REGENERATIVE BRAKING
ENGINE IDLE-OFF
A Full Hybrid: 57 kW ICE, 50 kW electric motor, 1.5 kWh battery (2004)
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Plug-In HEV (PHEV)
Converted Prius
ADVANCED ENGINE
Fuel Flexibility
ENGINE DOWNSIZING
ELECTRIC ACCESSORIES
PETROLEUM
AND/OR
ELECTRICITY
ENGINE IDLE-OFF
REGENERATIVE BRAKING
BATTERY RECHARGE
57 kW gasoline engine, 50 kW electric motor, 9.0 kWh battery (48km)
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Plug-In HEV
Rational
25
Matching motorist’s
driving habit
Probability (%)
Reduction of petrol
usage and thus related
emission
0-10 miles
10-20 Miles
20-30 miles
30-40 miles
40-50 miles
50-60 miles
60-70 miles
70-80 miles
80-90 miles
90-100 miles
20
15
10
5
0
Daily Mileage
Fuel Consumption Comparison
35
30
25
CV
HEV
PHEV20
PHEV40
20
Km/L
15
10
5
0
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Vehicle Types
USA Figure (1995)
Challenge for PHEV
Cost vs fuel saving
100%
90%
Incremental Cost (%)
80%
70%
60%
50%
Prius (Corolla)
40%
HEVs
PHEVs?
Civic
Escape
30%
Highlander
20%
Accord
10%
Vue
0%
0%
10%
20%
30%
40%
50%
60%
Gasoline Savings (%)
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70%
80%
90%
100%
Electrical Motor Drives
Motor Design Requirements:
Light weight / High power density
High efficiency
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Integrated Design
Power Converter Design
Considerations:
Temperature sensitivity of bus
capacitors;
Environmental impact;
Drive efficiency;
EMC issues;
Last but not the least COST.
HEV Example at SU
Parallel HEV developed by EMLab (1998)
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Parallel HEV
HEV Example at SU
Configuration
Power Electronic Converter
and Batteries
60 kW Inverter with 22 x 12 V
batteries (280V DC voltage bus,
420 kg, 90 km range)
Parallel HEV Configuration
30 kW peak, Reluctance
Synchronous Machine and ICE
15
HEV Example at SU
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Performance
Conclusions
HEV is a near-term technology for improving fuel
economy and emission.
The mainstream powertrain topologies are power-split
and parallel.
There are different degrees of hybridization.
PHEV is potentially a better system than normal HEV,
but there are also challenges.
Fuel prices vs battery cost will determine HEV
configuration and user term.
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Thank You
Prof M J Kamper and Dr R Wang
Electrical Machines Laboratory
Department of Electrical and Electronic Engineering
University of Stellenbosch
Stellenbosch, South Africa
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