electric drives challenges and solutions for the future
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Electric DrivesChallenges and solutions for the future
Robert Eriksson
Nikitas Sidiropoulos
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Swedish Hybrid Center WS – Challenges with electric drives for vehicles Lund 2014-04-04
Robert Eriksson, Nikitas Sidiropoulos – Volvo Car Group 2014-04-04
VCC Electrification plan/ World leading PHEV
VCC’s history and Future regarding Electrification
• Efficiency in focus for 40 years
• Hybrid and Plug-In Hybrid vehicles studied and implemented
• World first Diesel PHEV
• BEV ”Test Fleet” cars, C30 Electric
• We plan for massive renewal of our product program with
Electrification as a key ingredients
2Robert Eriksson, Nikitas Sidiropoulos – Volvo Car Group 2014-04-04
Strategies for VCC 2015
3
Green Connected
Safe
Robert Eriksson, Nikitas Sidiropoulos – Volvo Car Group 2014-04-04
CO2 fleet average - 95 g by 2020Finding optimum customer
benefit at lowest possible
added cost
New attributes added
ZEV mandate
Local/regional requirements
Increased electrical power
higher efficiency.
Efficiency & Electrification
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CO2 reduction
Plug-In Technology
Kinetic Energy Recovery
Implications from Feature growth
Robustness to dynamic load
Robert Eriksson, Nikitas Sidiropoulos – Volvo Car Group 2014-04-04
Electric DrivesChallenges and solutions for the future
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Nikitas Sidiropoulos M.Sc.Electric Drives System LeaderVolvo Car GroupApril 4th, 2014
Robert Eriksson, Nikitas Sidiropoulos – Volvo Car Group 2014-04-04
Electric Drives – Present solutions
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IEM eRAD EMCIDD ISG
Generator power / 270-420 V Front Electric Drive SystemInverter: IGBT power modules (bondless) gen IElectric Machine: PMSM
Traction power / 270-420 V Rear Electric Drive SystemInverter: IGBT power modules (bonded) gen IElectric Machine: PMSM
V60 PHEV
Future eAWD PHEV
Robert Eriksson, Nikitas Sidiropoulos – Volvo Car Group 2014-04-04
Electric Drives – Challenges of the future
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Advantages
- Proven technology
- High performance and driveability
- Electric efficiency and range….
Technical and commercial challenges
- Double Inverter and Electric machine systems → high system cost
- Expensive HV components such as HVAC cables and connectors
- EMC / EMF
- Thermal performance and lifetime of IGBT modules
- Scaleability
- Battery energy still expensive → further efficiency improvements needed
- Switching noise
- PMSM rare earth element cost fluctuation
- Compactness…
Robert Eriksson, Nikitas Sidiropoulos – Volvo Car Group 2014-04-04
Electric Drives – Future solutions
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How do we face the technical and commercial challenges ?
Technologies under investigation:
- Single Inverter and Electric Machine system → topology impact
- Maximisation of common parts of Inverter and Electric Machines in different platforms / topologies
- Integrated Inverter and Electric Machine
- Next generation power module (bondless, more efficient, scaleable)
- Increased switching frequency / reduced IGBT losses with new materials such as SiC / GaN
- Electric Machine with reduced REE content
Robert Eriksson, Nikitas Sidiropoulos – Volvo Car Group 2014-04-04
Electric Drives – Future solutions – eFAD/HyFAD
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Single Electric Drive system
Maximisation of common parts with eRAD topology
Advantages
- Single Electric Drive system → reduced system cost
- Inverter parts commonality with ISG/eRAD topology
- Strategic partnership with Electric Drive system supplier
Challenges
- Increased complexity (Electric Machine – transmission interface)
- Engine bay package
C30 EV
Future EV
Future FWD PHEV
Robert Eriksson, Nikitas Sidiropoulos – Volvo Car Group 2014-04-04
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Integrated Electric Drive
Advantages
- Elimination of HVAC cables, connectors, brackets ... → part numbers and cost reduced
- Significant weight reduction
- Free space can be used for spare wheel or increased luggage capacity
- Improved EMC
- Common parts with Front Electric Drive components
- C/o Electric Machine from present solution
- Could be used for both eRAD and eFAD topology
- Could be an enabler for high power charger
Challenges
- Vibration withstandability of power electronics
- Packageability in engine bay (HyFAD topology)
- Investment
- Scaleability
Inverter and Electric Machine as one unit
Integrated cooling and housing
Using next generation of power module
Package protected for all targeted platform variants
Close co-op with strategic partner
Decision for production pending
Electric Drives – Future solutions – IED
Robert Eriksson, Nikitas Sidiropoulos – Volvo Car Group 2014-04-04
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Next generation power module (~2017)
Advantages
- Improved thermal performance and life time (~8 x higher for VCC customer profile)
- Reduced inverter losses and improved vehicle duty cycle efficiency (range & CO2)
- Package protected
Challenges
- IGBTs in <200 V region (Mosfet can be more efficient but no commonality with 400 V)
- High temperature operation
From bonded wires → bondless technology
Sintered – no solder joints
Reduced conduction and switching losses by use of more efficient chip
Improved scaleability (phase current rating 400 – 700 A, voltage rate 650 V)
Power cycling and life time studied with in-house developed software tool
(rainflow analysis of IGBT and Diode delta Tj)
Increased in-house SW control
Electric Drives – Future solutionsNext Gen power modules
Robert Eriksson, Nikitas Sidiropoulos – Volvo Car Group 2014-04-04
12
SiC / GaN power module (~2020)
Advantages
- Smaller chip size
→ compactness
→ lower switching losses
→ enabler for higher switch frequencies (16-20 kHz) & reduced switching noise
& lower DC link capacitance
Trade off versus
- Reduced conductive losses and improved vehicle duty cycle efficiency
- Thermal capability
Challenges
- Cost (SiC module today ~ same cost as complete inverter)
- Chip size, current capability & manufacturing (material imperfections, difficult to process)
- Tier 1 ability / willingness to shift to new power module technology
Improved material enables smaller chip for same current rating compared to Si
SiC Mosfet 600-1200 V (switch transient in VCC applications <750 V)
GaN Fet 70-600 V
SiC thermal conductivity ~3 x better than Si
Mosfet Ron @ 1 kV
Si 10000 mΩ•mm2 (3600)
SiC 35 mΩ•mm2 (13)
GaN 2.8 mΩ•mm2 (1)
→ much smaller conductive losses for same chip size
OR
→ same conductive losses but for much smaller chip size
Electric Drives – Future solutions – SiC / GaN
Robert Eriksson, Nikitas Sidiropoulos – Volvo Car Group 2014-04-04
13
EM with reduced REE content
Advantages
- Less Nd, Dy and thus lower component cost and sensitivity to market price
- Close co-operation with supplier to ensure feasiblity
- C/o Inverter and stator solution with conv. PMSM (tbd)
- Could be used for both eFAD (larger space available) and eRAD applications
- Could be an enabler for sensorless drive (if Ld/Lq distinction kept at saturation)
Challenges
- Performance with same active dimensions as conv. PMSM design
- Harmonics
Idea: MBPM – Multi Barrier Permanent Magnet Machine
Similar to conv. PMSM but higher utilisation of reluctance
Volvo Cars in-house study of different rotor designs
Maxwell used as software tool
Target is to reduce magnet content with ~20% and keep acceptable performance density
Other machine concepts such as IM, SyRM, SRM and EMSM benchmarked and studied
→ conclusion is that torque and power density is too inferior to meet VCC installation requirements
Electric Drives – Future solutions – MBPM
Robert Eriksson, Nikitas Sidiropoulos – Volvo Car Group 2014-04-04
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