[IEEE 2012 IEEE Vehicle Power and Propulsion Conference (VPPC) - Seoul, Korea (South)...

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

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

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


N2m

motorbatteryN1

N5

N4


N2m

batteryN1

N5

N4


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


from Lower

Battery Voltage

Up to 20% loss reduction


Torque

Speed


from Higher

Inverter Voltage & Minimum-Loss Control


from Lower

Battery Voltage



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


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




� Power Module

� Capacitor

� Power Inductor


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


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




� Power Module

� Capacitor

� Power Inductor


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!

[IEEE 2012 IEEE Vehicle Power and Propulsion Conference (VPPC) - Seoul, Korea (South)...

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