1
Lihua Chen
V. Anand Sankaran
Vehicle Electrification and Vehicle Electrification and Vehicle Electrification and Vehicle Electrification and
Traction Inverter DesignTraction Inverter DesignTraction Inverter DesignTraction Inverter Design
Ford Motor Company Dearborn, Michigan USA 48124
IEEE VPPC 2012 Special Presentation
2
Presentation Outline
� Vehicle Electrification and Ford Strategy
� Ford sustainability strategies
� Ford FHEV, PHEV, and BEV
� Design approaches and optimization
� Practical design aspects of traction inverter
� Specification and benchmarking
� Key component design
� Practical design aspects and challenges
3
4
5
6
7
Sustainability and Electrification Plan
MID TERM
AUTO STOP-START
SUBSTANTIAL WEIGHT
REDUCTION
WORLD CLASS BEVs
WORLD CLASS PHEVs
TECHNOLOGY MIGRATION
LONG TERM
CONTINUE LEVERAGE
OF ELECTRIFIED
VEHICLES AND
DEPLOYMENT OF
ALTERNATIVE
ENERGY SOURCES
2007 2012 2020 2030NEAR TERM
BEGIN MIGRATION TO ADVANCED TECHNOLOGY
EPAS
6-SPEED TRANSMISSIONS
ECOBOOST
WORLD-CLASS HYBRIDS
BEGIN BEV INTRODUCTION
FULL
IMPLEMENTATION
OF KNOWN
TECHNOLOGY
Ford’s sustainability strategy, founded on affordability for millions of customers, remains in place as we move to the mid-term.
8
Ford Electrification Projects
9
PHEV
BEV
HEV
Ford Global Electrification Product Projection
• Portfolio Approach = HEV/PHEV/BEV (customer-driven)
• Global Flexibility = Electrify Highest Volume Platforms
• Best Value = HEVs Remain Highest Volume
• Affordability Remains Key = Sharing Common Components
Ford’s electrified platform strategy provides global flexibility
2015 CY2010 CY 2020
FordGlobal Volume
HEV
PHEV
BEV
HEV
% of total Ford
volume 1% 2-5% 10-25%
10
41 36
CITY MPG
HIGHWAY MPG
Ford Full Hybrid Electric Vehicle
Fuel Economy is the #1 Purchase reason for hybrid customers in the U.S.
CITY MPG
HIGHWAY MPG
34 31
CITY MPG
HIGHWAY MPG
4747
Generation I Generation II Generation III
11
Ford Plug-in Hybrid Electric Vehicle
� Available this Fall, C-max Energi is Ford’s first Plug-in HEV and deliver 550 miles of total range including morn than 20 miles in EV mode
� C-max Energi is capable of recharge in 2.5 hours using 240V charge station
� Arrive this Fall, Fusion Energi is anticipated to deliver more than 100MPGe make it the most fuel efficient midsize car in America
Why Plug-in HEVReal-world city driving for optimal fuel economy and more ideal for longer commutes than an all-electric vehicle
12
Plug-in HEV Drive Mode and Energy Flow
13
Blended PHEV Hardware Commonality with HEV
Significant Re-
use of HEV
hardware to
leverage scale
Component HEV PHEV
High Voltage Battery Power vs. Energy
Traction Motor Same
Generator Same
Inverter(s) Same
Electric AC Same
DC/DC Converter Same
Regen Brakes Hardware Same
Transmission Same
Engine Same
Charger & Wiring New
Electric Pumps/Cooling CircuitsModified transaxle oil
lubrication/cooling circuit
14
What Makes a Battery Electric Vehicle?
1
2
3 4 5 6
7
89
10
11
11
1213
1
2
3
4
5
6
7
Motor Controller and Inverter
High Voltage Electric HVAC Compressor
Electric Water Pump
Traction Motor
Electric Power Steering
Gearbox
Modular Powertrain Cradle
9
10
High Voltage PTC Electric Coolant Heater and Controller
Vehicle Control UnitNo ICE, all BEV
8 Electric Vacuum Pump
11
12
13
Battery Pack and Battery Cells
AC Charger
DC-DC Converter
14 Plug in AC
14
• Powered by an electric
motor and high-voltage
lithium-ion battery cells
• Targeted range of 100
miles
• Other vehicle systems
(e.g., HVAC) also require
electric solutions
• 14 new components
• Have to rethink every
system
BEV Shares Common Technologies with HEV and PHEV
15
16
Ford Battery Electric Vehicle
17
Ford Hybrid System and Design Approaches
� Ford Powersplit hybrid system
� Design approach and optimization
18
Hybrid Electric Vehicle Types
Motor
ICE
� Parallel Hybrid:• Engine power = mechanical path• Motor provides assistance
� Series Hybrid:• EV Operation / Engine Stop-Start• High efficiency Regen Braking• Engine downsizing• Full-size drive needed
� PowerSplit Hybrid:• w/ benefits of both• Simple transmission
ICE
Motor
19
Battery
Inverters
Electric
Transaxle
I4 Gasoline Engine
w/ Atkinson Cycle
Super Ultra Low
Emissions (AT-PZEV)
Series Regenerative
Braking
Motors
Ford’s “PowerSplit” Hybrid System
20
Ford HEV Power Split Hybrid Powertrain
HV Battery
MotorGenerator
TractionInverter
Engine
engineenginebrake
o.w.c
brake
o.w.c
sun
ring
planetary
ring
sun
ring
planetary
ring
N3
N2e
N3
N2e
gen
erat
or
gen
erat
or
gen
erat
or
batteryN1
N5
N4
Electrical Connection
N2m
motor
Inter. shaft
batteryN1
N5
N4
Electrical Connection
N2m
motorbatteryN1
N5
N4
Electrical Connection
N2m
batteryN1
N5
N4
Electrical Connection
N2m
motor
Inter. shaft
21
Powersplit Operating Mode and Energy Flow
22
Ford Hybrid System Design Approach
23
E-Drive System Level Optimization
Traction
Generator
MotorInverter
GeneratorInverter
VariableVoltage
ConverterTractionHV
Battery
TractionMotor
VBAT
VINV
MotorInverter
GeneratorInverter
VariableVoltage
ConverterTractionHV
Battery
TractionMotor
VBATVBAT
VINVVINV
Optimum Boost for
Best Fuel Economy
Optimum Boost for
Best Fuel Economy
Torque
Speed
Lower Inverter & Motor Losses
from Higher
Inverter Voltage & Minimum-Loss Control
Lower Inverter & Motor Losses
from Lower
Battery Voltage
Up to 20% loss reduction
Up to 20% loss reduction
Torque
Speed
Lower Inverter & Motor Losses
from Higher
Inverter Voltage & Minimum-Loss Control
Lower Inverter & Motor Losses
from Lower
Battery Voltage
Up to 20% loss reduction
Up to 20% loss reduction
Optimum Battery
Voltage for Best
Fuel Economy
Optimum Battery
Voltage for Best
Fuel Economy
24
Drive Cycle Based Design Optimization
A driving cycle is a series of data points representing the speed of a vehicle versus time
Note: data for reference only
Motor Current Profile
0
50
100
150
200
250
300
390 490 590 690 790 890 990 1090 1190
Drive Time (s)M
otr
o R
MS
cu
rre
nt
(A)
Motor total power loss at
each operating point
Drive cycle profile of motor current
Speed [RPM]
Torq
ue
[NM
]
25
Customer Drive Patterns
� Low speed, stop and go city driving
� High speed highway driving
� Hilly terrain driving
� Driving with towing
� Off road driving
� Very high speed driving
Fuel economy & effectiveness of vehicle hybridization will vary significantly based on driving conditions.
In order to determine the right hybrid architecture, important to understand the customer usage/segment.
26
Customer Usage Profiles
� Based on Public Road Vehicle Database (PRVD)
� Cross-section of driving patterns selected, speed and grade vs. time information used
� Multiple Cycles Selected
� Used to specify targets for VDS and SDS requirements, for example component torque/power and thermal limit requirements
� Used with HEV system simulation to determine driving styles and road conditions that stress the HEV system and each HEV subsystem for Life Test and Key Life Test Development
City Cycle1 Highway Drive Cycle1
City Cycle2 Highway Drive Cycle2
Rural Drive Cycle Mountain Drive Cycle
High Speed Drive Cycle
Mild
Moderate
Aggressive
27
Traction Inverter Challenge & Opportunity
� Application/Usage (Drive Cycles)
� Peak to Average Power Ratio
� Thermal Cycling
� Power Cycling
� Technology
� Silicon Technology – Industry Standards vs. Custom
� Power Module Packaging and Cooling Technology
� Capacitor Technology
� Inductor Technology
� Commonality and Reuse
� Power Density – Package Size
� Fixed vs. Tunable
� Connection Systems
� Supplier Partnerships
28
Practical Design Aspects of Traction Inverter
� Specification and Benchmarking
� Key Component Design
� Power Module
� Capacitor
� Power Inductor
� Design Aspects and Challenges
29
E-Drive System Power Stage
30
Boundary Diagram of Traction Inverter
31
Main Circuit of Traction Inverter
P
N
Co
Ci
L
U V W
U V W
Iout
Motor INV
Generator INV
VVCM
G
HV
Battery
32
Traction Inverter Power Rating
Output power [kW]
System voltage [V]
200 400 600 800
100
50
0
25
75
Mild/Medium HEV
Full HEV
PHEV/BEV
Note: data for reference only
33
Inverter Specification Development
The traction inverter design specifications are directly developed
from vehicle drive cycles and driver demands
Note: generic vehicle simulation models are available
34
Traction Inverter Technical Specifications
� Motor / Generator Inverter Functional Requirements
� Variable Voltage Converter Functional Requirements
� High Voltage Interface Requirements
� Low Voltage Interface Requirements
� Mechanical/ Packaging Requirements
� Vibration Requirements
� Safety Requirements
� EMI/EMC Requirements
� Cooling and Environmental Requirements
� Reliability and FMEM Requirements
35
BOM of Traction Inverter
Power Modules
Motor inverter PM
Generator inverter PM
VVC power module
Capacitors Input Capacitor
DC-link Capacitor
Power Inductor
ConnectorsLow Voltage Connector
High Voltage Connector
Circuit Boards
Controller board
Gate drive board
GD Power supply board
Current sensors DC current sensor
AC current sensor
Internal busbar and harness
Cold plate, bracket, and housing
36
2010MY Ford Fusion HEV
Engine Transaxle Engine Transaxle
Photo taken at NAIAS 2010
2010 Motor Trend Car of the Year: Ford Fusion
37
Ford Traction Inverter Migration
Gen I Traction INV Gen II Traction INV Gen III Traction INV
Transaxle-top mounted Transaxle-top mounted plus Variable Voltage Converter
Remote-mounted and fully integrated design
38
Ford Fusion HEV Gen II Transaxle
Controller Board
Generator
Motor
Photo taken at NAIAS 2010
Traction Inverter
39
Gen II Traction Inverter Internal Layout
VVC and G INV Power module
Motor INVPower module
VVC PowerInductor
AC current sensors
Coolantports
40
Input Capacitor
Power Supply Bd.
Bus Bars (2)
Support Brkt.
Power Module (3)
AC Current Sens.
HV Header Asy (2)
Power Supply Bd.Main Capacitor
Interlock AsyBus Bars (4 total)
VVC Inductor
Gate Drive Bd (3)
Resistor
DC Current Sen.
HVAC Bar Module
VVC PM & GDB
DC Busbar
Terminal
Gen III Traction Inverter Internal Layout
Figure source: Ford Gen III traction inverter supplier
41
Practical Design Aspects of Traction Inverter
� Specification and Benchmarking
� Key Component Design
� Power Module
� Capacitor
� Power Inductor
� Design Aspects and Challenges
42
Traction Inverter Key Components
Input Capacitor DC link Capacitor
Power InductorIPU and Gate Drive
43
Power Module Design
Integrated Power Module
U V W
Gate Drive Circuit
GD Power Supply
P
N
Equivalent Circuit
An integrated power module provides the physical containment for power semiconductor devices and gate control circuit. This package provides an easy way to cool the devices and to connect them to the outer circuit
44
Insulated Gate Bipolar Transistor
The IGBT combines the characteristics of the MOSFETs with the bipolar transistors as a switch in a single device
(Figure source: E. Motto, Powerex)
Equivalent CircuitIGBT Structure
45
Typical Power Module Package
Thermal
Grease
Copper Leadframe
Solder
Copper
Copper
A lN DBC
Solder
SiliconFirst
Bond
Stich
Bond
Heatsink
Copper
Baseplate
Power Cycling
Issues
Thermal Cycling
Issues
Actual PM Package
PM Package Structure(Wirebound)
46
Power Module Current Rating
The actual PM current rating for traction inverters may be different from that of traditional PM datasheet
Operating duration
PM CurrentRating
Coolant temperature:T1<T2<T3
T1
T2
T3
Actual PM Usage
Actual PM DesignPulsed Current vs. Continuous Current
47
Usage based Power Module Optimization
Power ElectronicsSystem Specs
VehicleTargets
CustomerUsage
Power ModuleSilicon and Cooling
Technologies & Design
Silicon Area
Cost & Size
Junction Temp & ∆∆∆∆T
Operating duration
Power Demand
Power module optimization to properly meet both transient power and continuous power demands
Transient power vs. continuous power
48
IGBT E_off vs. V_ce(sat)
Eoff [mJ/pulse]
New
Gen
Vce(sat) [v]
Power Loss [W]/ E
off [mJ/pulse]
Power loss@fsw1
Power loss@fsw2
Eoff vs. Vce(sat)
Revolutionary solution Optimum solution
� New semiconductor technologies provide revolutionary solution
� Optimization based on actual HEV applications
49
Power Module Technology Evolution
1984 1989 1994 1999 2004 2012 2018
Year
IGBT
Silicon A
rea
Low Density (5um)Planar PT Technology
High Density (3um)
Planar PT Technology
High Density (1um)Trench PT Technology
High Density (1um)
Trench LPT Technology
Newer StructuresHigher Density
Ultra Thin Wafers
New Materials, New technology?
50
Reliability and Failure Modes
� Three major internal module connections are stressed in power cycling. What can be observed over time?
� Bond wire: cracks propagate within wire and end up with a bond lift-off.
� Solder joint chip to DCB: delamination of the joint appears and increases the thermal resistivity.
� System solder joint DCB to base plate: delamination of the joint due to the different coefficient of thermal expansion of DCB and base plate.
Si chip
DCB
base plate
Solder
Solder
Bond wire
Source: Infineon
51
From Drive Cycle to PM Lifetime
Source: Infineon
52
Capacitor Design Consideration
� DC bus ripple voltage
� Capacitor ripple current
� Capacitor thermal stress
� Capacitor reliability and durability
� System control bandwidth and stability
� Battery max allowable ripple current
� HV accessory loads over voltage limitation
� Capacitor over voltage stress (caused by malfunctions)
� Size and cost
53
Capacitor Production Categories
Source: Panasonic
54
Trend of Capacitor for HEVs
Source: Panasonic
55
Film Capacitor Structure
Source: Panasonic
Packaged film capacitor module
Film capacitor internal structure
56
Film Capacitor Technologies
Source: Panasonic
57
Capacitor Ripple Current Calculation
vvcGMcap iiii −−=
Instantaneous current based Instantaneous power based
Vc
ivvc
icap
iM
iG
Motor INV
Gen INV
VVC
vvcGMcap PPPP −−=
ccapcap VCti ∆×=∆×)(
2
1 2
2
2
1 VVCtP capcap −×=∆×
58
Cancelation of Capacitor Ripple Current
Note: data for reference only
Source: Ohio State University
Current Ripple =ƒ (carrier phase shift, power factors, output frequencies)
Out frequency:
Motor INV: 160 Hz
Generator INV: 320 Hz
0
0.5
1 090
180 270360
80
85
90
95
100
105
110
115
Angle in Degrees
Current Ripple Plot as Function of Triangle Wave Angle and Power Factor
Power Factor
Curr
ent
Rip
ple
Am
plit
ude (
A)
59
Drive Cycle Based Ripple Current Profile
Motor Phase A RMS Ripple
0
50
100
150
200
250
300
350
400
0 100 200 300 400 500 600
Seconds
RM
S R
ipp
le (
A)
Motor Phase A RMS Ripple
Generator Phase A RMS Ripple
0
50
100
150
200
250
300
350
400
0 100 200 300 400 500 600
Seconds
RM
S C
urr
en
t (A
)
Generator Phase A RMS
RippleIcap RMS and RMS 30s-Averaged
0
50
100
150
200
250
300
350
400
0 100 200 300 400 500 600
Operating Time (s)
Cu
rren
t (A
)
Icap
Icap rms 35s average
DC Link Ripple Current Profile
Motor Current
Generator Current
-150
-100
-50
0
50
100
150
2000 2500 3000 3500 4000 4500 5000 5500 6000
VVC CurrentNote: data for reference only
60
Input Capacitor Design
Factors drive input capacitor design
� Battery impedance and max allowable ripple current
� Trade-off design with power inductor
� Capacitor over voltage stress (caused by malfunctions)
61
Power Inductor Design
Manufacture process of power Inductor
Source: B. You, Changsung
Note: at VPPC 2012,the Changsung Corporation will give a special presentation of power inductor design for EV/HEV applications, which provides good information for this topic
62
Practical Design Aspects of Traction Inverter
� Specification and Benchmarking
� Key Component Design
� Power Module
� Capacitor
� Power Inductor
� Design Aspects and Challenges
63
Challenges of Power Electronics
� High Quality Specifications
� Spent significant effort in developing high quality
specifications and KLT based on drive cycles
� Design Optimization
� Use of real world usage profiles
� Reliability Issues
� Thermal cycling
� Power cycling
� Vibration cycling – 1st powertrain mounted power
electronics in the Industry.
� EMC Issues
� Robustness and Part to Part Variability
� Worst case scenarios
� Six-sigma tools/methodology
64
Sudden Battery Contactor Open
Battery Contactor
� Unannounced power flow collapse
� Sudden control interruption and oscillation
� Key component transient overstress
� Fault protection and system recovery
65
Motor Rotor-Locked Operation
Output DC Current:
Ia = 2*Ib = 2*IcPower loss/ TJ
�Worst case scenarios drive power module sizing
� Innovative solutions demanded to reduce worst case stresses
Hotspot in PM
66
Why Need Smart Functions?
�Worst-case-driven design result in hardware oversize
� Some worst cases may never happen in most HEVs, but, all customers overpay
for them $$$
� Smart functions provide alternative/optimal solutions for hardware design
�Monitoring feedbacks provide opportunities for system level optimization
� Intelligent gate drive provide direct, fast, and effective solutions
67
Active Fault Protection
t
t
Voltage overshoot
Ic
Vce
t
Ic
t
Voltage overshoot
Vce
Nominal current
Over current
Fault current
Conv. Gate Drive Active Gate DriveDevicekiller
68
Advanced Power Electronics Control
� System modulator to control both the power electronic circuit’s steady-state and transient behaviors
� Dynamically optimize traction inverter performance based on actual HEV drive conditions
Conventional PWM control
Advanced PWM control
69
Ford EMI/EMC Regulations
� Ford EMI/EMC reference
� Component EMC Specifications EMC-CS-2009
(http://www.fordemc.com/docs/requirements.htm)
� EMI/EMC tests:_ a variety of aspects
� Emissions vs. immunity
� Conducted vs. radiated
� Transients vs. continuous emission or disturbance
70
Thank you very much for your attention!
Drive Drive Drive Drive One One One One and Go and Go and Go and Go Further!Further!Further!Further!
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