Download - Electric Vehicles and Power Electronics.pdf
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Electric Vehicles and Power Electronics
Jih-Sheng (Jason) LaiVirginia Polytechnic Institute and State University
Center for Power Electronics Systems668 Whittemore Hall
Blacksburg, VA 24060TEL: 540-231-4741FAX: 540-231-6390
EMAIL: [email protected]
August 16, 2001
Presentation atUniversidad Technica Federico Santa Maria
Valparaiso, Chili
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Outline of Presentation Part A: Background and Introduction
What are Electric Vehicles? Why Electric Vehicles? Partnership for Next Generation Vehicles
Part B: Overview of EV/HEVs on the Market GM EV1 Ford Ranger Honda EVPlus, Insight Toyota Prius Ford P2000
Part C: Power Electronic Technologies in EV/HEV Energy Sources Traction Motors/Inverters Auxiliary Motors/Inverters Bi-directional Chargers Basic Structure of a Fuel Cell Vehicle
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Part A: Background and Introduction
What are Electric Vehicles? Why Electric Vehicles? Partnership for a New Generation of Vehicles Specification of Supercar EV/HEV Configurations
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EV/HEV Definitions
An Electric Vehicle is A vehicle fueled with mains electricity. An EV usually requires a battery pack as energy storage.
A Hybrid Vehicle isA chemically fueled vehicle equipped with at least one bi-directional energy reservoir. The fueled hybrid power unit (HPU) is usually a heat engine, but may be a fuel cell. Energy storage and delivery is usually electric.
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Driving Forces for EV/HEV
!!!! Simplicity (1910)!!!! Energy Security (1970)!!!! Environmental Concerns (1990)!!!! Customer Expectations (2000)
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US Customer Expectations for EV/HEVs
!!!! Range: Minimum 160 km/charge!!!! Safety: Same as ICE Vehicles!!!! Performance: Same as ICE Vehicles!!!! Cost: No more than ICE vehicles!!!! Features: No less than ICE vehicles
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Partnership for a New Generation of Vehicles
LONG-TERM GOAL Development of a SupercarGas mileage: 3X average of Concorde/Taurus/Lumina, or 80 mpg Load: Six passengers + 200 pounds of luggageRange: Similar to todays models At least 80 percent recyclable
Technology Areas Hybrid/electric vehicle drive trainsDirect-injection engines Fuel cells Lightweight materials
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Specifications of Baseline Vehicle and Supercar
Baseline Supercar
Curb Weight 3200 lbs 40% lessDrag coeff. 0.32 0.20Friction: 0.005 0.008 Engine: Internal Combustion flywheel, battery, ultracapacitorFuel Efficiency: 26.6 mpg 80 mpg (3X)Recycleability: 75% 80%Range (HWY): 380 miles same or betterAccel (0-62 mi): 12 seconds same or betterLuggage: 168 ft3 same or betterLoad: 6 passengers + 200 lb same or betterLife: 100,000 miles same or better
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PNGV Time Table
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Where are the Energy Goes in a Conventional Car?For Metro-Highway Driving Cycle
DrivelineEngine
100%
Aerodynamics6%
Accessories2%
Engine77% Driveline
6%
Rolling5%
Braking4%
Fuel
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Electric/Hybrid Electric Vehicle Configurations
Fueltank
Xmission
ICE
Diff.Wheels
Pure ICE Drive
ICE: Internal Combustion EngineXmission: TransmissionDiff.: Differential gear
ElectricMotor
Battery
Diff.Wheels
Pure Electric Drive
Parallel Hybrid Series Hybrid
Hybrid Drives
Fueltank
Xmission
ICE
Diff.Wheels
ElectricMotorBattery
FueltankICE
Diff.Wheels
ElectricMotor
Battery
Generator
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How Does a Hybrid Electric Vehicle Work?
(a) Shaft driven by both ICE and electric motor
(b) Shaft driven by electric motor and battery is charged
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Part B: Overview of EVs on the Market
GM EV1
Ford Ecostar, Ranger
Honda EVPlus, Insight
Toyata Prius
Ford P2000
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General Motor EV1
Power: 137 hpTop speed: 80 miles per hourDrag coeff.: 0.19Acceleration: 0 to 60 miles, less than 9 secondsRange: 55 to 95 miles with 26 lead-acid battery pack
75 to 130 miles with Nickel-Metal Hydride (NiMH) battery pack Charging: 220 V, 6.6 kW non-contact inductive charging, 6 hours Braking: front disk, rear drum, and regenerative
Price: $33,995 MSRPLease: $424 - $574 / mo
36-month lease $0.20/mile over 30,000 miles
http://www.gmev.com/index.htm
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GM Inductive Charge Coupler
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Ford Ranger and US Post Office Electric Vehicles
Battery:Fourth generation sealed lead acid 39x8 volt modules; 312 volt systemCapacity rating @ FUDS: 23 kWh (18 kWh at 80% discharge)On-board Charger: On-board, 240 V/30 A
Performance:0-50 mph acceleration: 13 secondsRated top speed (governed) : 75 mphCustomer range @ 72F: 50 milesRange - FUDS cycle @ 72F: 58 miles without A/C or heater operation
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Ford Ranger Schematic
90 hp, 3-phase AC induction
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Honda EVPlus
New Technology Features
Nickel-metal hydride batteries Permanent-magnet motor Single-speed, direct-drive transmission Regenerative braking On-board charger 110- or 220-volt Heating and air conditioning High-intensity headlightsStandard Features
EPA City: 100 miles; Highway: 84 miles (Use 80% battery capacity) Meets all federal motor vehicle safety standards Dual airbags and 3-point seat belts Anti-lock braking system (ABS) Power windows, door locks and mirrors AM/FM/CD audio system Remote keyless entry and security system Cargo area with "fold-flat" rear seats Walk-in feature for rear seat access
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Honda Insight Hybrid Electric Vehicle
Integrated Motor Assist: 1.0-liter, 3-cylinder gasoline engine + electric motorEPA mileage ratings: 61 mpg city/70 mpg highwayDriving range: 600 - 700 miles Drag coefficient: 0.25Electric motor: 36 ft-lb, 10-kW DC-brushless motor, 2.3 wide,
sits between the engine and transmission, mounted directly to the engine's crankshaft
Battery: A 144-volt nickel metal-hydride battery packInverter: An advanced electronic Power Control Unit (PCU),
adopted from Honda EV PLUS
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Drivetrain of Honda Insight
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Toyota Prius - A Hybrid Vehicle
Engine: 1.5-liter, DOHC, 16-valve, EFI 4-cylinder with Variable Valve Timing with intelligence (VVT-i)
Maximum Engine Output: 58 hp at 4,000 rpmMaximum Speed: 100 mph (engine and motor combined)Motor Type: permanent magnet, 30 kW/40 hp at 9402,000 rpmBattery Type: sealed nickel-metal hydride with 40 modulesCombined Horsepower: 58 hp engine + 40 hp motor + 3 hp batteries = 101 hpFuel Efficiency: 66 mpg (Japanese 1015 city drive mode)Maximum Range: 850 miles (combined city/highway)Regeneration Braking: Front disc/rear drum brakes with ABS
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Prius Hybrid Drivetrain
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Power Flow in Prius
BatteriesInverterGenerator
Motor
Engine
Electrical power path
Motive power path
Engine FlowStarting from rest/low speedsFull-throttle accelerationNormal drivingDeceleration/braking
Reduction Gear
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Emission Comparison of Prius and Corolla
10.314.72171570.2050.1240.8640.8080.0680.0251143Corolla
12.720.81551120.0630.0010.0620.0250.0330.0021237Prius
Sec.Km/LTECarTECarTECarTECar(kg)Vehicle
AccelFrom0-60 mi/h
FuelEco-nomy
Curb Weight
NonmethaneOrganic gases(NMOG), g/km
CarbonMononxide
g/km
Nitrogen oxideg/km
Carbon dioxide
g/km
Note: Car values are vehicle exhaust (tailpipe) emissions TE values are total emissions-Car plus upstream, including fuel
cycle emission Source: IEEE Spectrum, March 2001, Pages 47 50.
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Ford P2000 Low Storage Requirement (LSR) Car
Features:
Low Storage Requirement (LSR) Direct Injection Aluminum Through-bolt Assembly (DIATA) engine Integrated Starter/Alternator Engine shut-down during braking and at rest Very fast engine restart Improve engine dynamics and shift fell Modified shift strategy for reduced emissions Weight and cost penalties low relative to full hybrid enables limited re-generative braking
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Comparison of P2000 LSR and Hybrid Vehicles
Series Parallel P2000
Platform 5 + passenger, Al-Intensive, Sedan5 passenger, Light-weight prototype
5 passenger, Light-weight prototype
HPU 55 kW, Turbo-Alternator 55 kW, 1.2 L, CIDI 55 kW, 1.2L, CIDI
Transmission none Auto 5-speed Auto 5-speed
Traction Motor 75 kW, EV transaxle 18/30 kW motor on 4x4 transfer case8 kW starter/alternator
Battery 180 kW x 6 kWh 48 kW x 2 kWh 15 kW x 0.4 kWhWeight 1401 kg 1258 kg 1000 kgFuel Economy (v. Taurus) City:
Metal Ceramic 1.8x 2.4x 2.9x 2.5x
Highway 1.4x 1.9x 2.2x 1.9x
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Ford P2000Hydrogen Fuel Cell Car
Chemical Energy Electrical Energy Mechanical Energy
HydrogenTank
FuelCell
TractionInverterMotor
TurboCompressor
Transxle
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Daimler-Chrysler NECAR IVA Fuel Cell Electric Vehicle with Built-in Reformer
Fuel: MethanolEmission: zeroTop Speed: 90 mphRange: 280 miles
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Part C: Power Electronic Technologies in EV/HEV
Energy Sources and Storages! Batteries! Fuel Cells
Traction Motors Soft-Switching Inverters Bi-Directional Chargers
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Energy Sources and Storages
Lead Acid Batteries Nickel Metal-Hydride (NiMH) Batteries Lithium Batteries Fuel Cells
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Lead Acid Batteries
Flood type: First design in 1880s With flat pasted plate immersed in a dilute sulfuric acid
electrolyte
Valve Regulated Lead Acid (VRLA) type: Original development in 1960s with sealed lead acid
batteries The gases produced during operation are recombined
to minimize water losses Typical gas recombination efficiency is 95% Gas recombination cell can be made with Absorptive
Glass Mat separator or Gel Electrolyte
Source: www.hawker.invensys.com
Electric Vehicles use deep charge/discharge type VRLA batteries
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VRLA Battery Charging Voltage and Currentfor a Typical Tubular Gel Product
Typical State of Charge Voltage 100% 2.13 V70% 2.09 V50% 2.06 V20% 2.02 V* Measuring open ckt voltage after
battery rested >24 hr.
Charging Voltage at diff temp.0C 2.35 V10C 2.28 V20C 2.23 V30C 2.20 V35 C 21.7 V
Charging Current Typically 10% of the 10-hour capacity, C10 In general, not exceed 30% of C10 For fast charge, keep 2.35 V per cell with 10% of C10 as the current
limit
Source: www.hawker.invensys.com
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Nickel Metal-Hydride (NiMH) Batteries
Negative Electrode: rare earth/nickel alloys LaNi5 (AB5 alloys) titanium and zirconium (AB2 alloys)
Positive Electrode: Sintered-type positive electrodes are economical and rugged while exhibiting excellent high-rate performance, long cycle life, and good capacity
Electrolyte: Alkaline, a dilute solution of potassium hydroxide
Energy Density: Improved energy density (up to 40 percent greater than Nickel Cadmium cells)
GM EV1 Test Range: 55 to 95 miles with 26 lead-acid battery pack 75 to 130 miles with Nickel-Metal Hydride (NiMH) battery pack
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Comparison of Nickel-Metal Hydride to Nickel Cadmium Batteries
Nominal Voltage Same (1.25V) Discharge Capacity NiMH up to 40% greater than NiCd Discharge Profile Equivalent Discharge Cutoff Voltages Equivalent High Rate Discharge Capability Effectively the same rates High Temp (>35oC) Discharge Capability NiMH slightly better than NiCd cells Operating Temperature Limits Similar, NiMH slightly better at cold temp Self-Discharge Rate Similar to NiCd Cycle Life Similar to NiCd Mechanical Fit Equivalent Selection of Sizes/Shapes/Capacities Equivalent Environmental Issues Reduced with NiMH because of elimination
of cadmium toxicity concerns. Collection of spent NiMH batteries is not mandated
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Lithium/Thionyl Chloride Batteries
Negative Electrode: mixture of carbon, Teflon, fiberglass, alcohol, and water
Positive Electrode: Lithium
Electrolyte: Thionyl Chloride
Lithium batteries have been widely used in computers and communications and will be competing with NiMH batteries for EV applications
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Fuel Cell Vehicle - Future Trend
Fuel Cell Electric Vehicles (FCEVs) are similar to a battery-powered EV except that fuel cells replace batteries. As with batteries, fuel cell emit no carbon dioxide, although carbon dioxide and other emissions may be created in vehicle manufacturing and fuel production.
A fuel cell produces electricity by combining hydrogen and oxygen in an electrochemical reaction. Fuel cells require no combustion, unlike a conventional gasoline- or diesel-powered engine. The only emission from hydrogen fuel cells is water vapor.
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Fuel Cell Vehicle Configurations with Different Sources
Hydrogen storage
Fuel Cell Stack
Inverter
Bi-directionaldc-dc
converter
Gear
Battery
Methanol storage
Fuel cell stack
Inverter
Bi-directionaldc-dc
converter
Gear
Battery
Fuel cell stack
Inverter
Bi-directionaldc-dc
converter
Gear
Battery
Methanol reformer
Gasoline storage
Partial oxidation
ref.
Motor
/Gen
Motor
/Gen
Motor
/Gen
(a) With hydrogen (b) With Methanol (c) With Gasoline
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Basic Hydrogen-Oxygen Fuel Cell
Fuel (H2)
Oxidant
(Air O2)
Water
(H2O)
Electrical loads+-2e- 2e-
1/2 O2
H2 2H+ 2H+
Ion Exchange Membrane(IEM)
Electrode (-) Electrode (+)
H2OElectrolyte
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Proton Exchange Membrane (PEM) Fuel Cell
CO2
Methanol Fuel
CH3CHOxidant
(Air O2)
Water
(H2O, N2, O2)
Electrical loads+-6e- 6e-
CO2+
6H+3H2O
6H++
3/2 O2
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
Proton Exchange Membrane(PEM)
Electrode (-) Electrode (+)
Water
H2O
Vaporizer
MethanolReformer
CO2Oxidization
Catalyst
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Fuel Cell Output Voltage and Current Characteristic
0
50
100
150
200
250
300
350
400
0 100 200 300
Stack Current(A)
Stac
k Vo
ltage
(V)
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Fuel Cell Output Power and Current Characteristic
0102030405060708090
0 100 200 300
Stack Current (A)
Net
Pow
er (k
W)
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20 kW Future Car Stack
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Traction Motors/Inverters
Motor Design Consideration1. Using Federal Urban Driving Schedule to Find Most
Critical Speed and Torque Region2. Optimize Motor Design in Proper Torque-Speed
Regions Motor Types Inverter Partitioning for Integrated Inverter-Motor Soft-Switching Inverter Considerations Bi-directional Chargers for Fuel Cell Vehicles
1. A 20-kW Non-isolated Bi-directional Converter2. A 5-kW Isolated Bi-directional Converter
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Motor Design Consideration 1 Using Federal Urban Driving Schedule to Find Most Critical
Speed and Torque Regions
FUDS CYCLE
0
20
40
60
0 500 1000 1500
Time (sec)
Spee
d (m
ph)
Battery Current (Pos=Discharge)
-100-50
050
100150
0 500 1000 1500
Time (seconds)
Cur
rent
(am
p)
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Torque-Speed Envelope
0
20
40
60
80
100
120
0 5 10 15 20 25Speed (x1000 rpm )
Torq
ue (l
bft,h
p) TorquePowerEfficiency
Motor Design Consideration 2 Optimize Motor Design in Proper Torque-Speed Regions Resulting High-Speed (20,000 rpm) Design that Cuts Size and Weight by 30%
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Motor Types
Induction Motor Permanent Magnet Motor Switched Reluctance Motor Other Combinations
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Inverter Partitioning for Integrated Inverter-Motor
INVERTERPOWER MODULE
COLD PLATE
INSULATOR
TRACTIONPOWER INPUT
COOLANT/LUBRICANT
INTPUT
GEAR LUBRICANT
GEAR ASSEMBLY
CONTROLLERMOUNTING BLOCK
MOTOR LINE COOLANT
OPTICALDRIVE SIGNAL
OPTICAL STATUS SIGNAL
ADVANCED AC MOTOR AND CASING
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Inverter Design and Partioning
InductionMotor
SensorConditioning
ia ib va vb
r
Hall Sensors
OpticalEncoder
IGBT Modules
Interface Circuit
DSP Circuit
Battery
Fuel CellUnit
Pow
er F
low
Con
trol
Gate Driver withProtection
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Using Optical Fiber to Link Integrated Power Stage and Control Interface
SensingBoard
DSPInterfaceBoard
GateDriver
GateDriver
GateDriver
IGBT Based Inverter Power Stage
Optical fiber link
Motor
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Compact Gate Driver with Optical Fiber Link
PWM
Fault
Optical Fiber
IGBT Module
MC
3315
3 +15V
-5V
54
78
23
Ron
Roff
+15V
6 1
-5V
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Soft-Switching Inverter Considerations
Zero-Voltage-Transition Auxiliary Resonant Commutated Pole (ARCP) Inverter for AC Motor Drives
Zero-Current Transition (ZCT) Inverter Advantages:
Allow high switching frequencies Low switching losses Low EMI
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Turn-on Loss Reduction with Soft-Switching
Vce(100v/div)
Is(10A/div)
Vce(100v/div)
Is(10A/div)
Hard-switching Soft-switching
Voltage, Vswitch
Power, Pswitch
Current, Iswitch
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Turn-off Loss Reduction with Soft-Switching
Vce(100v/div)
Is(10A/div) Is(10A/div)
Vce(100v/div)
Hard-switching Soft-switching
Current, Iswitch
Voltage, Vswitch
Power, Pswitch
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A Zero-Voltage-Transition Inverter for AC MotorsAuxiliary Resonant Commutated Pole (ARCP)
Lra
Vs
C1 C3
C4 C6
C5
C2
S1 S3 S5
S4 S6 S2
Csp
Csn
acmotor
Lrb
Sb
Sa
Lrc
Scauxiliary circuits
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Basic Operating Principle of ZVT Soft-Switching
t1 t2 t3 t4
ILr
IS1
IS2IC2
IC1Sr
Ix ILoad
0
0
0
0
C1
C2
ILoad
S2
S1
LrILr
C1
C2
ILoad
S2
S1
LrILr
From t1 to t2 From t2 to t2
t2 t3
C1
C2
ILoad
S2
S1
LrILr
C1
C2
ILoad
S2
S1
LrILr
From t2 to t3 From t3 to t4
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ARCP ZVT Inverter Test Results
ia
SX1 SX2
LX1
CX1
CX2ia
S1
S2
CS
CS
Vdc
Auxiliary Circuit
D1
D2
DS1
DS2
M1
A : vg(S2) (20 V/div)B : ia (200 A/div)C : iax (200 A/div)D : vS2 (200 V/div)
A
BC
D
2 s/div
SX1 SX2
LX1
CX1
CX2
S1
S2
CS
CS
Vdc
Auxiliary Circuit
D1
D2
M1ia
91
92
93
94
95
96
97
50.2 80.9 5.0 20.7 50.5 101.4 5.9 12.2 41.6 10.1 14.8 31.9 13.3 20.4
1920 3770 5635 7560 9460
Torque [N-m]
Speed [rpm]
Inve
rter
effi
cien
cy [%
]
with diodeswithout diodes
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Zero Current Transition Inverter
ACMotor
CsVs
Sr4 Sr6 Sr2
Sr3 Sr5Sr1 S1 S3 S5
S4 S2S6
Lr Cr
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Basic Operation of ZCT Soft Turn-on
ILr
IS1
VCr
S1
ILoad
0
ILoad
S2
S1
LrILr ILoad
S2
S1
LrILr
From t0 to t1 From t1 to t2
Cr
ILoad
S2
S1
LrILr ILoad
S2
S1
LrILr
From t2 to t3 From t3 to t4
+ VCr
Cr
0
t1 t2 t3 t4
0
0
VCE1
Sr0
t0
0
currentdirectionin thisperiod
currentdirectionin thisperiod
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Test Results of 30-kW Soft-Switching Inverters
5 /d i
Ix (200 A/div)
Iload (200A/div)
5ms/div
ARCP ZVT
ZCT Vce (250 V/div)
ILoad (200A/div)
5ms/div
Ix (200 A/div)
Vce (200 V/div)
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Basic Operation of ZCT Soft Turn-off
ILr
IS1
VCr
S1
ILoad
0
ILoad
S2
S1
LrILr ILoad
S2
S1
LrILr
From t5 to t6 From t6 to t7
Cr
ILoad
S2
S1
LrILr ILoad
S2
S1
LrILr
From t7 to t8 From t8 to t10
+ VCr
Cr
0
t8 t9t6 t10
0
0
VCE1
Sr0
t5
0
Initial VCr is negative
Vdc
t7
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Soft-Switching Inverter Assembled in EV1 Chassis
Development...
Testing...
On the Road...
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Bi-directional Charger for Fuel Cell Powered Electric Vehicles
Inverter
Vol
tage
Cla
mp
CompressorMotor
Expanding Unit
CM
EUC
ontr
olle
r
OtherLoads
Bi-d
irec
tiona
l Po
wer
Flo
w
dc-d
c C
onve
rter
High Voltage Bus (>300V)+
Motor
Energy Storage Cap.
Fuel
Cel
l
Batteryfor Startup
+
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Why Bi-directional DC-DC Converter is Needed?
1. Need to have high voltage to start up the CMEU controller.2. Need to stabilize the bus voltage during transient
conditions. 3. Need battery to charge the dc bus bus for the initial startup
power (Boost operation)3. Need to keep battery charged (Buck operation)
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Circuit Topology Considerations for the Bi-directional DC-DC Converter
1. Single-directional vs. bi-directional2. Isolated vs. non-isolated3. Multiple-leg Interleaved vs. single-leg 4. Voltage source vs. current source for either primary or
secondary side5. Low side battery with 12 V, 42 V, or 180 V vs. high side
fuel cell at about 300 V
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Non-Isolated Buck Converter L
R+
Vg
C
+
v
vgs
Q1
D1g
sd
vgs
iL
v
Gate on Gate off
DTs DTs
Inductor charged
Inductor discharged
Capacitor charged
Capacitor discharged
gDVV =
Average output voltage:
where D is the duty ratio. Because D < 1, V is always less than Vg " buck converting
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Non-Isolated Boost Converter
+
CQ1
D1L
RVg
v
+
iL iD
iQ iCvL+
vgs
vgs
iL
v
Gate on Gate off
DTs DTs
Inductor charged
Inductor discharged
Capacitor discharged
Capacitor charged
gg VDV
DV
'1
11
=
=
Average output voltage:
where D is the duty ratio, and D = 1 D. Because D < 1, Vis always greater than Vg "boost converting
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Non-Isolated Single-Directional Boost ConverterNon-Interleaved vs. Interleaved
Load
L1
L2
S1u S2u
S1d S2d
+
Vbatt
i1
i2 VFC
Load
L
Su
Sd
+
Vbatt
iVFC
(b) Interleaved(a) Non-Interleaved
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A Non-Isolated Bi-Directional DC-DC Converter with Interleaved Control
Ld2
Ld3
S2u S3u
S2d S3d
VFC
Power module
Vbatt
Load
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Ripple Current Cancellation Effect in a 20 kW Interleaved Boost Converter
33 A/div50 s/div
IL1 IL2
IL1 + IL2
33 A/div
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Efficiency Test Results of a 20 kW Interleaved Boost Converter
86889092949698
0 5000 10000 15000 20000 25000
Predicted
experimental
Output Power (W)
Effic
ienc
y (%
)
DCM operated converter has parasitic ringing losses at the light load condition, and the efficiency is suffered.
At Vin = 200 V, Vo = 300 V
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Isolated Buck Converter
Q1 Q3
Q2 Q4
Vg
L
Cfa
b
+
C Rv+
1 : n
Suitable for high voltage input and low voltage output Zero-voltage switching can be achieved with phase-shift modulation
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Isolated Boost Converter
Suitable for low voltage input and high voltage output The main problem is high voltage stress on the switching devices
Q1 Q3
Q2 Q4
Vg
L
Cfa
b
+
C Rv+
1 : n
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Low-Voltage Side Half-Bridge Current-Fed Isolated Bi-directional Converter
L1 L2
Cc
S1 S2
S5
S6S7
S8
CoVb
1:nLlk
!!!! Low switch counts!!!! Simple transformer winding structure!!!! Low transformer current Start-up problem Low choke ripple frequency (fs) Duty cycle limitation#### Passive clamp is easy to implement but lossy
Rc
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Low-Voltage Side Full-Bridge Current-Fed Isolated Bi-directional Converter
!!!! Simple voltage clamp circuit implementation!!!! Simple transformer winding structure and lower turns ratio!!!! Low transformer current!!!! High choke ripple frequency (2fs) Start-up problem High switches count
L
S1
S2
S5
S7 S6
S8
CoVb
1:nLlk
S3Cc
S4
Sc
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Complete Bi-directional dc-dc Charger with Clamping and Start-up Circuits
Lk+
_
S1
S3 S2
S4S5
S7Cc
L
Sc
A
S6
S8
B D
C-Ip
Ic
Vpn
+
_
Tr
1:n
Vo
CoCinIs
Vb
+
_
1:n LkfDf
IL
Ifp
n
Start-up circuit
Active Clamp circuit
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Prototype of a Liquid Cooled Bi-directional DC-DC Converter to be Installed in a Fuel
Cell Vehicle
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Start-up Mode Operation
IL
Is
Vo
ILref
125 A/d
20 A/d
100 A/d
100 V/d
Start-upcommandinitiation
Transitionfrom start-upto regularboost
Average current loop regulated
Loadengaged atVo=255 V
Voregulated Vb = 12 V, IL = 161 A, Vo = 280 V,
Pd = 1.83 kW in steady state
Start Up Process:
t0-t1 Start up mode, open loop controlled
t1-t2 Boost mode, open loop controlled
t2-t3 Boost mode, inner current loop regulated
t3- Boost mode, outer voltage loop regulated
t0 t1 t2 t3
JSL
Switch Voltage and Current Waveforms in Boost (Discharging) Mode Operation
S3
Is
Vpn
10 A/d
10 V/d
Vb = 8 V, IL = 228 A, Vo = 288 V, Pd = 1.55 kW
-
40
JSL
Comparison of Measured Efficiency Profile forDischarging (Boost) Mode Operation
400 600 800 1,000 1,200 1,400 1,6000.82
0.84
0.86
0.88
0.9
0.92
0.94
Po
Efficie ncy
Full-Bridge
L-Type
10 V
8 V
10 V
8 V
Test conditions:
Start-up, battery discharging
Battery voltage: Vb = 8 and 10 VHigh side voltage: Vo = 288 VSwitching freq.: fs = 20 kHz
1. Higher battery voltage, higher overall efficiency.2. Full bridge is more efficient than the L-type half-bridge converter in overall
operating range.3. Efficiency at light-load exceeds 90% with full-bridge version.4. L-type converter is lossy due to passive clamp circuit.
JSL
Switch Voltage and Current Waveforms in Buck (Charging) Mode Operation
Vcd
Is
Vpn
250 V/d
20 A/d
50 V/d
Vb = 15 V, IL = 335 A, Vo = 425 V, Pcp = 5 kW
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41
JSL
Comparison of Measured Efficiency Profile forCharging (Buck) Mode Operation
1,000 2,000 3,000 4,000 5,0000.7
0.7250.75
0.7750.8
0.8250.85
0.8750.9
0.9250.95
Pch (W)
Efficie ncy
Full-Bridge
L-TypeTest conditions:
Regenerative Mode Battery voltage: Vb=15 V High voltage bus: Vo=425 V
1. L-type half-bridge efficiency reaches only 90% 2. Full bridge converter is more efficient with peak efficiency 95% because
more devices in parallel on low-voltage side active clamp circuit provides lossless snubbing soft-switching with zero-voltage zero-current operations
JSL
Summary and Discussions
Development of EV/HEV is very vital in recent years HEV has hit the market since 1999 Fuel cell is becoming the choice of energy source for future
EVs Power electronics is the main driver of EV/HEV Key power electronics technologies are traction motor/inverter
drives and bi-directional chargers Power electronics engineers are in great demand