t2 f wireless power transfer

8/12/2019 T2 F Wireless Power Transfer

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Wireless PowerTransfer

John M. Miller

Matthew B. Scudiere

John W. McKeeverCliff White

for:

Oak Ridge National Laboratory's Power Electronics SymposiumFriday, July 22, 7:30 AM3:30 PM (EDT)Oak Ridge National Laboratory (ORNL) Conference Center,Oak Ridge, Tennessee

Patents Pending


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2 Managed by UT-Battellefor the U.S. Department of Energy

Introduction What is the Need?

There is need for an efficient method for transferringlarge power levels over moderate distances to hybridelectric vehicles (HEVs) in the near future:

First to parked vehicles,

Then expand to opportunity charging, and

Eventually to highway charging while driving.

Loosely coupled resonant mode transformers have the

potential to accomplish this. Magnetic resonance coupling for wireless power

transfer is termed WPT.


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Introduction Near Term Vision for WPT Electric vehicle charging must be:

Safe, compact and efficient in order to be convenient for customers Power levels commensurate with application:

3 kW to 7 kW residential and garage; 60 kW to >100 kW on-road dynamic

WPT alignment tolerance should be under closed loop DSRC control between

the transmit coil and vehicle mounted capture coil.

Graphics Left: J.M. Miller, Wireless Power Transfer for Electric Vehicles, PREA meeting, Utah State Univ, Energy Dynamics

Laboratory, Ogden, UT, 7 Feb. 2011

Right: J.M.Miller, ORNL internal presentation.


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Background: Barriers to Success

Efficiency

across cascade of components >90%

coil-to-coil ~98%

Meet international field emission standards (ICNIRP and

ARPANSA)* Efficient high frequency power inverter (20140 kHz)

Implement vehicle to infrastructure (V2I)communications compliant with DOT recommendationsfor DSRC

* International Commission on Non-Ionizing Radiation Protection N RP, Secretariat, c/o Gunde Ziegelberger, c/oBundesamt fur Strahlenschutz, Ingolstaedter Landstrasse 1, 85764 Oberschleissheim, Germany.

* The Radiation rotection Series is published by the Australian Radiation Protection and Nuclear Safety Agency(ARPANSA)


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Background: Measures of Success

Interoperability Any OEM vehicle with any WPT charger

Means coil size fixed, operating frequency fixed, alignmenttolerance & emissions fixed and communications fixed.

Safety and emissions

Transparent to vehicle occupants

Communications

DSRC following U.S. DOT recommendations for V2I

Private and secure


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Objective: PEV Stationary WPT Charging

Solution demands a system design that focuses on utility tovehicle battery terminal overall efficiency

SAE J2954 targets plug-battery efficiency >90%

Zone 1: Active field, ~1m2,


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Objective: Integrating WPT into a PEV

Solution: Design and develop coupling coil system suitablefor vehicle integration for stationary and on-road stationary at

high power levels (SAE Level 2: 3 kW to 7 kW) & high eff.Technically: a non-radiating, near field reactive zone power transfer method

Practically: a convenient, safe and flexible means to charge electric vehicles.

Vehicle to WPT communications

RFID localizer for positioning

Use existing on-board charger,

or dedicated fast-charge and

energy management strategy

Active zone field meetsinternational standards (ICNIRP)

Smart grid compliant utility feed

and modern power electronics

Graphic: Lindsey Marlar ORNL graphics services


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Approach: ORNL WPT System

Synthesize the driving point high power waveform, magnetically couple, rectify

and deliver charging power to the vehicle on-board energy storage system.

Isupply

Vdc_linkItransmitter

Vcapacitor

Vload

Iload

HALF-BRIDGE INVERTER

Vtransmitter_in

CONSTANT

VOLTAGE

LOAD

RECEIVERTRANSMITTER

Ireceiver_

loop

Rectifier

Series-parallel L-C magnetic resonant coupling


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Approach: Analytical PerspectiveWireless power transfer to unloaded vs. loaded coupling

Maximum impedance

frequency unloaded:

fo1 = 24.8 kHz

fo2= 25.6 kHz

fzmx~ fo1


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Approach: Analytical Perspective

For S-P resonant coil system the operating frequencies shift due to:

Degree of receiver coil loading (charging power demanded)

Coefficient of coupling between coils (vehicle receiver coil to transmit pad gap)

Tuning of various receiver coils relative to transmit coil tuning.

Coupling mode theory facilitates

understanding the fundamentals of WPT

and what parameters are key to optimized

performance.

During vehicle ESS charging the presence

of a dc potential at the secondary forces the

current and voltage responses to be very

nonlinear: fzmxto fzmntransitions


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Approach: Analytical Perspective

Resonance shifting is not an issue for stationary wireless charging, but

For on-road dynamic charging is an issue

Will require dynamic load tracking and inverter control using DSRCIllustration of ideal cases: k= 0.3, 0.22, 0.15, 0.1 and RL=2.5

Then, k=0.22 and RL= 5, 2.5, 1.8, 0.8

For a given value of coupling coefficient, k, the maximum power transfer occurs

when the reflected load matches the surge impedance of the system.


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Timeline and Milestones

Duration

(mo)

Task Milestone

2 Resolve instrumentation issues on laboratory sensorsand monitoring equipment. Validate accuracy at

WPT operating frequency

Manufacturer contacted, sensor/equipment

calibration validated and documented.

10 Design, develop and fabricate a SAE level 2 WPTcharger rated 7 kW at PF and frequency level

dictated by vehicle systems team.

Demonstration and validation against program

targets using laboratory WPT apparatus. Verify

that 20 kHz < f < 140 kHz is attainable.

6 Analysis, model and simulation of level 2 WPTcharging system

Validate simulation against laboratory apparatus to

extent possible.

4 Extend WPT design to next generation coil andevaluate performance against targets.

Next generation coil design meets specifications

8 Develop vehicle integrate coils and install on mulevehicle.

Demonstrate WPT to vehicle mounted receiver coil

and passive load. Validate targets met.

8 Procure DSRC and integrate into mule vehicle andinterface to vehicle CAN (w/ OEM help)

Demonstrate WPT to mule vehicle battery pack

with grid converter regulation via DSRC.

3 Validation of stationary charging at 37 kW usingDSRC for regulation and messaging.

Must demonstrate that power, plug to battery

efficiency, magnetic field emissions and packaging

constraints are met.


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Summary of Accomplishments

Prior LDRD developed Evanescent Power Transfer apparatus is used for testing

Alternative coupling coil designs directed research activities into ac resistiveeffects contributing to coil losses: skin and proximity effects

Analytical work continues on both parasitic effects and on application ofmagnetic vector potential to the coupling field itself.

Coil designs aimed at vehicle integration are not covered in this presentation.


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Validation of laboratory instrumentation accuracy

Current sensor calibration at high frequencyInstrumentation errors due to low power factor (Agilent LCR)

Error in losses due to current redistribution in conductors

Reconfigured the WPT apparatus for:Initial 120 Vdc lamp loads (series connected), to

240 Vdc (parallel connected), to

270 Vdc using new, higher power bulbs.

Refinement of DSP load voltage regulator.


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Developing deeper understanding of transmit and receiver coil

electromagnetic behavior Experimental finding that multiple ribbon coils operating in parallel

offer no benefit in terms of loss reduction.Two such coils in close proximity (~15mm) exhibit virtually unchanged Racand Ls

Top: End on view of flux lines for 3 turn ribbon coil antenna. Bottom: end on view of ribbon coil conductor current density plots

shown extensive skin effect and proximity effects in two outside bars.:

:

Source: Field flux plot simulation: Dr. Pan-Seok Shin


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Developing deeper understanding of transmit and receiver coil

electromagnetic behavior

Plot of coil field at 20kHz excitation in air

L and R of Ribbon Antennae

12

13

14

15

16

17

18

1 10 100

Frequency, kHz

Inductance

(L),

H

0

5

10

15

20

25

30

35

40

45

50

Resistance

(R),m

L_1_3-turn ribboncoil

L_3_3-turn ribboncoils

L_4_3-turn ribboncoils

L_4_3-turn Cu tubecoils

R_1_3-turn ribboncoil

R_3_3-turn ribboncoilscoils

R_4_3-turn ribboncoils

R_4_3-turn Cu tubecoils

untt:

u

u

r

.:

-

n/

u

/

-.

-

/

-.

-

/

-.

-

/

-.

-

Anamolous Racbehavior at 12 kHz has been

resolved and found to be due to LCR meter

Source: coil CAD drawings courtesy: Dr. Matthew Scudiere, Laboratory test data: Dr. John McKeever

Field flux plot simulation: Dr. Pan-Seok Shin


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Validated coefficient of coupling, coil spacing, and alignment sensitivity of WPT


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Future Work

Develop design for grid converter and communications (base side)


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Future Work: WPT Communications

Source: Walton Fehr, Mgr. Systems Engineering, U.S. Dept. Transportation, Layered

Communications Enabling V-I Applications: Connected Vehicle Core Systems, 12 June 2011


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Future Work: Design Considerations

Power inverter must match the WPT network

Analysis of efficiency considered inverter kVA/kW requirement

Off resonance kVA/kW rating can be excessive

Therefore, inverter must maintain close tracking of coupled power factor

Further study of secondary rectification and filtering stage mustbe performed.

ORNL internal power inverter development supports the WPTsystems project

Industrial partner would greatly accelerate progress in WPT forLevel 2 stationary charging case.

Transition from laboratory to in-vehicle


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Topics to be Addressed for WPTVehicle Integration

Interoperability with existing Electric Vehicle Supply Equipment

Recommend stationary charging demonstration as 1stin-vehicle appl.

Field shaping and shielding for vehicle mounted receiver

Minimize loading due to proximity with vehicle chassis, and

Insure WPT will not corrupt CAN network(s)

Comply with International Regulations (ICNIRP)

ORNL WPT has 15 from antenna at 4kW

ICNIRP requires


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Conclusions

Only need a simple design to efficiently transfer large power

levels over moderate distances.

Demonstrated >4 kW at 10 separation with 92% transferefficiency.

Can be constructed with commercial-off-the-shelf components(20 kHz IGBTs).

Challenges being addressed by the ORNL team:

Minimization of coupling coil ac resistance effects,

load tracking and compliance with interoperability, power inverter kVA/kW limits and

appropriate vehicle to grid side communications.

t2 f wireless power transfer

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