ornl dynamic wireless power demonstration with electrochemical · 2015-03-30 · •gem vehicle...

ORNL Dynamic Wireless Power Transfer System Demonstration with Electrochemical Energy Buffers

Omer C. Onar, S. Campbell, C. P. White, C. Coomer, L. Seiber, M. Chinthavali, P. T. Jones, and J. M. Miller Power Electronics and Electric Machinery Group Oak Ridge National Laboratory

February 09, 2015, Panel Session #5

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

Outline

• Introduction and hardware system description

• Elements of wireless power transfer (WPT) system control

• Case study of ORNL’s in-motion WPT • Vehicle and grid side power

smoothing with electrochemical energy buffers

• Experimental test results


Introduction and System Description • Overall system functional block diagram • 5 cascaded power conversion stages, ensuring safety and

control flexibility

WPT coil set (Coupler)


Elements of WPT System Control • Inverter duty cycle, d, pulse width modulation,

• Voltage control, Udc, with active front-end rectifier with power factor correction,

• Frequency control for reactive power minimization due to load (battery SOC), gap (z), and misalignment changes.

𝑈𝑑𝑜 =𝜋

2√2|𝑈𝑠| + 𝑟𝑝 𝑖𝑝 + 𝑈𝑠𝑤

𝑃𝐹 = cos arg(𝑈𝑠) − arg(𝑖𝑝)

acU Front End Grid Interface

Converter

1T

2T 4T

+

-

doU1G

2G

3G

4G

sU

1C

1L 2L

M

2C oC

oU1I 2I +

-

bU bI3T

doI

2D

1D 3D

4D

HF InverterPrimary and

Secondary Coils

Bridge Rectifier & Filter

𝑈𝑠(𝑡) =4𝑈𝑑𝑜

𝜋 sin 𝑑𝜋2 cos(𝜔𝑡) (𝑉𝑟𝑚𝑠 )


Case Study of ORNL’s In-motion WPT

● Initial 2-coil track, upgraded to 6-coil track for internal funded in-motion wireless charging system

● System uses a Zylinx ZP24D-250RM 2.4GHz Radio Modem and optical sensors for communications and relative vehicle position determination.

2nd transmit

coil

1st transmit

coil

Receivecoil

acUActive Front End (AFE)

and PF Comp.

1T

2T 4T

+

-

doU1G

2G

3G

4G

sU

1TC1TL

RC

oC

oU

1I

RI

bU

bI

3T

HF Power Converter &Primary Pad

Secondary Coil, Rectifier, and

Filter to BatteryUb, Ib feedbacks,

BMS messages, fault, and status via DSRC

Ub, Ib feedbacks, BMS data commands to HF inverter,

other sensor inputs, and V2I communication with grid

Switching Frequency and Duty

Cycle Control

doI

2D

1D 3D

4D

G1 G2 G3 G4

Ub

Ib

Udo

Ido

2TC

+

-


Case Study of ORNL’s In-motion WPT • Definition of vehicle secondary coil relative to track coils



“up” field

“down” field



● Active power variation over the track when vehicle is moving.

● Reactive power variation over the track when vehicle is moving.

● DC-to-DC and coil-to-coil efficiency when vehicle is moving.

● Drastic reversals of power flows during vehicle pass-over.



● High reactive power content of inverter output.

● Waveforms for positions #1 (left) and #9 (right) – right before alignment and right after alignment (vehicle goes over duel coils)

2nd transmit

coil

1st transmit

coil

Receivecoil

Receivecoil

● Waveforms for positions #3 (left) and #7 (right) – Perfectly aligned with first and second coils.

Receivecoil

Receivecoil

● Higher coupling factor, less magnetizing current, more active power content of inverter output.



1 2 3 4 5 6 7 8 90

0.5

1

1.5

2

2.5

3

3.5

Driver side front tireFloor boardDriver seatHead rest

Position #

Elec

trom

agne

tic F

ield

(Hig

hest

Pea

k) [μ

T]

Driver Seat

Car floor board on the acceleration pedal

• Magnetic field measurements using NARDA EHP-50D E&H field analyzer near driver side front tire, floor board, driver seat, and head rest, all less than 6.25uT for all relative vehicle positions.


Case Study of ORNL’s In-motion WPT • Aluminum shielding reduces the Electromagnetic Field to safer levels

on the passenger side front tire. • Effective when grid side units have to be away from the primary pad;

reduces emissions from high frequency wires from inverter to the primary coil.

Position #

Elec

trom

agne

tic F

ield

at t

he P

asse

nger

Sid

e Fr

ont T

ire

(Hig

hest

Pea

k) [μ

T]

1 2 3 4 5 6 7 8 90

2

4

6

8

10

12

14

16

18

20

15.516 μT field reduction due to

aluminum shielding on the floor

Aluminum Shield


In-motion Wireless Charging Demonstration • World’s very first in-motion wireless charging system using coils (not

using rails or long wire loops as in previous technologies) with power smoothing.

• Dynamic Wireless Power Transfer (WPT) – ORNL demonstration: GEM EV and 6-coil track – Also addressed motion dependent power pulsations

• Achieved 3 industry firsts: 1) in-vehicle charge power smoothing using carbon ultracapacitors, 2) grid side power smoothing using lithium-capacitors (LiC), 3) both in combination


ORNL Dynamic WPT Demonstrator • Dynamic Wireless Power Transfer (WPT) Experimental Results

– Illustration of system hardware – Power flow as function of vehicle position

– Future directions in dynamic WPT o Infrastructure issues (roadway integrity) o Communications requirements (latency) o Grid power distribution (intermittency) o Coil sequencing and power modulation & alignment o Local energy storage (smoothening)

‒ Promote dc distribution along highway ‒ Highly distributed vs. centralized HF stage

HF inverter system with HF transformer and self contained thermal management system


ORNL Dynamic WPT Demonstrator • DWPT Experimental Results • GEM vehicle driving across roadway coils

Illustration of roadway coil current quenching (0.2ms) and inverter turn-ON coil current ring-up (1.4ms)

2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5130

135

140

145

150

155

160

165

170

Time [s]

Li-I

on C

apac

itor V

olta

ge [V

]

Powering first coil pair

Powering second coil pair

Powering third coil pair

Inverter OFF time

Inverter OFF time

Vehicle stays on top of the last coil

Inverter OFF time

2 3 4 5 6 7 8-10

0

10

20

30

40

50

Time [s]

Li-io

n C

apac

itor C

urre

nt [A

]

Inverter OFF time




Inverter OFF time Inverter OFF

time


Inverter turn-OFF transition and coil current fall

3.967 3.9675 3.968 3.9685 3.969 3.9695 3.97-250

-200

-150

-100

-50

0

50

100

150

200

250

Time [s]

Prim

ary

Coi

l Cur

rent

Rou

ted

by C

onta

ctor

s [A

]

Inverter turn-ON transition and coil current rise

3.993 3.9932 3.9934 3.9936 3.9938 3.994 3.9942 3.9944 3.9946 3.9948 3.995-250

-200

-150

-100

-50

0

50

100

150

200

250

Time [s]

Prim

ary

Coi

l Cur

rent

Rou

ted

by C

onta

ctor

s [A

]


ORNL Dynamic WPT Demonstrator • Feedback from electrified roadway

optical sensors are utilized to turn the inverter ON and OFF depending on the vehicle tire positions.

• Contactors are also controlled to direct the power from the inverter to the particular set of coils.

Inverter OFF time

3.8 3.85 3.9 3.95 4 4.05 4.1 4.15 4.2-5

0

5

10

15

20

25

30

35

40

Time [s]

Li-io

n C

apac

itor C

urre

nt [A

]




3.965 3.97 3.975 3.98 3.985 3.99 3.995-5

0

5

10

15

20

25

30

35

40

Time [s]

Li-io

n C

apac

itor C

urre

nt [A

]


Inverter turn-OFF time


ORNL Dynamic WPT Demonstrator • Primary coil current due to inverter turn OFF and ON and coil sequencing


2 3 4 5 6 7 8-250

-200

-150

-100

-50

0

50

100

150

200

250

Time [s]

Prim

ary

Coi

l Cur

rent

Rou

ted

by C

onta

ctor

s [A

]





3.8 3.85 3.9 3.95 4 4.05 4.1 4.15 4.2-250

-200

-150

-100

-50

0

50

100

150

200

250

Time [s]

Prim

ary

Coi

l Cur

rent

Rou

ted

by C

onta

ctor

s [A

]




3.965 3.97 3.975 3.98 3.985 3.99 3.995-250

-200

-150

-100

-50

0

50

100

150

200

250

Time [s]

Prim

ary

Coi

l Cur

rent

Rou

ted

by C

onta

ctor

s [A

] Powering second coil pair



ORNL Developments in WPT Charging

Grid side LiC Vehicle side carbon UC

LiC

rack

fabr

icat

ed b

y El

ectro

Sta

ndar

ds

Labo

rato

ries,

Cra

nsto

n, R

I. D

r. R

ay S

epe

• The need for energy buffer: – We keep saying dynamic WPT can reduce the vehicle ESS. – However, high power is needed for effective energy transfer to the vehicle. – Energy storage capacity can be reduced, but power rating of the ESS should be increase. – How? – Decoupling power and energy components of the vehicle ESS – Also effectively reduces the vehicle battery and grid side power ripples.


Dual ESS Hybridization for in-motion WPT • Employing fast response EC based energy storage buffers have not been applied for wireless

power transfer systems. • Particularly for in-motion wireless applications, using EC energy storage systems for the purpose

of grid support or vehicle battery current ripple reduction makes use of a high power capable buffer available for both transmit and receive sides of the system.

• Both transmit side and the receive side have component that are relatively sensitive to the fast transients or high ripples.

acU Active Front End (AFE)

and PF Comp.

1T

2T 4T

+

-

doU1G

2G

3G

4G

sU

1C

1L 2L

M

2C oC

oU1I 2I +

-

bU bI3T

HF Power Converter

Bridge rectifier

doI

2D

1D 3D

4DPrimary Pad Secondary Pad

Vehicle battery

Vehicle (motional) side circuitGrid side circuit


Grid-side energy buffering/peak current reduction • Architecture 1: EC energy storage system is connected to the AC grid through a bi-directional

rectifier/inverter: • In this scheme, EC bidirectional

converter is first controlled in rectifier mode to smoothly charge the EC in normal conditions.

• This rectifier operation is stopped when the EC voltage reaches to its maximum value.

• Then, as soon as a vehicle starts passing through the primary coil, EC converter is operated in inverter mode.

• In this mode, EC is discharged with a high pulse power so that the charging power required for the car is not supplied from the grid.

• Once the vehicle moves away from the primary pads, EC converter is again operated in rectifier mode to relatively more slowly recharge the EC.


and PF Comp.

1C

1L

1I

Primary Pad

HF Power Inverter

BidirectionalRectifier/Inverter

AC

Grid

Electrochemical Capacitor

ECU

+

-

+

-

acU

ECI1T

2T 4T

1G

2G

3G

4G

sU

3TCL

1D

2D

3D

4D

LI

dI

Controller with PWM

Regulation Strategy

1G

2GacU

dI

LI3G

4G


Grid-side energy buffering/peak current reduction • Architecture 2: EC energy storage system is connected to DC link through a DC/DC converter:

• In this configuration, instead of using a bi-directional rectifier/inverter, a bi-directional DC/DC converter is utilized by moving the EC to the DC side of the circuit.

• In this case, the EC is recharged from the DC link through a DC/DC converter under normal conditions. As soon as a vehicle starts passing through the primary pads, the EC is discharged to the DC link through the bi-directional DC/DC converter. After vehicle completes the WPT charging track, DC/DC converter is operated to relatively more slowly recharge the EC. In this configuration, the EC charging power is commanded by a controller with relatively slower dynamics.


and PF Comp.

1C

1L

1I

Primary Pad

HF Power Inverter

BidirectionalDC/DC

Converter

Electrochemical CapacitorECU

+

-

+

-

dcU

ECI

DC

Lin

k


Grid-side energy buffering/peak current reduction • Architecture 3: EC energy storage system is passive parallel (directly) connected to the DC link:

• In this case, EC supplies a large burst of power to the HF inverter as a vehicle passes through the primary pad. Although this configuration does not provide an active energy management on the EC, the AFE rectifier’s DC link voltage dynamics can be slowed down so the high charging power does not reflect back to the grid.


and PF Comp.

1C

1L

1I

Primary Pad

HF Power Inverter


+

-

ECdc UU

ECIDC

Lin

k


Grid-side energy buffering/peak current reduction • Architecture 4: EC energy storage system is connected to the DC link with a cascaded DC/DC

converter:

• In this case, the EC and its DC/DC converter are in a cascaded form with the AFE converter and the HP power inverter. In this scheme, the DC/DC converter does not have to be bidirectional as compared to the Architecture 2 shown earlier; therefore, cost and size savings are possible.


and PF Comp.

1C

1L

1I

Primary Pad

HF Power Inverter

BidirectionalDC/DC

Converter


ECU

+

-

+

-

dcU

ECI

DC

Lin

k


Vehicle-side energy buffering/peak current reduction • Architecture 1: EC energy storage system is connected to the battery terminals via a cascaded

DC/DC converter:

• In this case, the high power pulse received by the secondary coils is rectified and dumped onto the DC link.

• Due its relatively faster dynamics, EC receives this high charging pulse. • When the vehicle completes the WPT pad tracks, EC is controlled in a way that it relatively more

slowly recharges the battery over a period of time.

2L

2C oCbU

bI

Seco

ndar

y Pa

d

Vehicle Battery

Bridge Rectifier


+

-

dcUD

C L

ink

Bidirectional DC/DC Converter

+

-

+

-

ECU

ECI

1T

1G

CL

1D

2T2G

2DController with PWM

Regulation Strategy

1G

2G

ECUdcV

bI

ECI


Vehicle-side energy buffering/peak current reduction • Architecture 2: EC energy storage system is connected to the DC link through a cascaded DC/DC

converter and it is connected to the battery terminals via another cascaded DC/DC converter:

• This architecture provides a more flexible control of the EC power and in this case the EC voltage is decoupled from the EC link voltage.

2L

2C oCbU

bI

Seco

ndar

y Pa

d

Vehicle battery

Bridge Rectifier


ECU

DC Link

DC/DC Converter

+

-

dcU DC/DC Converter

+

-

+

-


Vehicle-side energy buffering/peak current reduction • Architecture 3: EC energy storage system is connected to the DC link through a parallel bi-

directional buck-boost DC/DC converter:

• EC is recharged with a high power pulse when the vehicle is moving on the WPT pads. • Once the charge is received and vehicle moves away, EC is controlled to slowly recharge the

vehicle battery over a period of time. • This configuration provides that the EC voltage is decoupled from that of the battery voltage and

DC link voltage and enables actively controlling the charge and discharge power of the EC.

2L

2C oCbU

bI

Seco

ndar

y Pa

d

Vehicle battery

Bridge Rectifier


+

-

dcU

DC

Lin

k

BidirectionalDC/DC

Converter

+

-

+

-

ECU

ECI


Vehicle-side energy buffering/peak current reduction • Architecture 4: Two parallel individual DC/DC converters are utilized for vehicle battery and the

EC:

• This configuration involves two separate bi-directional DC/DC converters; one for the vehicle battery and other one for the EC for maximized flexibility in controls and active energy management among the storage devices.

2L

2C oCbU

bI

Seco

ndar

y Pa

d

Vehicle battery

Bridge Rectifier


+

-

dcU

DC

Lin

k

BidirectionalDC/DC

Converter

+

-

+

-

ECU

ECI

BidirectionalDC/DC

Converter


Simulations for a 6-coil track – ideal case • The power delivered from the grid with and

without the EC assistance with respect to the positions as the vehicle is passing through the transmit pads.

• Without the EC assistance on the primary side, the grid is more stressed and grid power has large dips and current ripples. However, under the EC assistance, only the average and much smoother power variations are reflected to the grid. All the grid power ripples and transients are eliminated since the EC is utilized as an energy buffer on the grid side

• Positive effect on the battery power variations.

• Similar to the grid power variations, ripples and dips in vehicle battery power can also be eliminated with the EC assistance.

• With the proper utilization of the EC, vehicle battery is only subject to the much smoother average power variations whereas EC energy storage system handles the ripples and high power variations.

0 5 10 15 20 25 300

500

1000

1500

2000

2500

3000

3500

Grid power without EC assistanceGrid power with EC assistance

Position #

Grid

Pow

er W

ith an

d W

ithou

t EC

Ass

istan

ce [W

]

0 5 10 15 20 25 300

500

1000

1500

2000

2500

3000

Vehicle battery power without EC assistanceVehicle battery power with EC assistance

Position #

Veh

icle

Bat

tery

Pow

er W

ith a

nd W

ithou

t EC

Ass

ista

nce

[W]


Example design case: Ultra-capacitor sizing

• Let’s take the case moving from one coil to the other.

• There are 2 peak power transfer points on the track.

• The integral of the power transfer curve indicates that the energy transferred between two peak power points is 1794.3 Watt-seconds.

• Therefore: • 2469.7-675.3738 = 1794.3 Watt-

seconds of energy should be captured by the ultra-capacitor so that the battery receives only the average of the overall energy transfer between these points.

0 0.5 1 1.5 2 2.5 3 3.5 40

500

1000

1500

2000

2500

Time [s]

Pow

er [W

]

Power transfer curve

Time [s]

Ener

gy [W

s]Energy transfer curve

0 0.5 1 1.5 2 2.5 3 3.5 40

500

1000

1500

2000

2500

3000

675.3738

2469.7


Example design case: Ultra-capacitor sizing • Maxwell K2 series ultra-capacitors have ideal maximum current rating. Particularly, maximum

current rating of BCAP0650 can carry 88 Arms maximum which is sufficient for our application. • GEM vehicle on-board battery pack is a lead-acid battery with 72V nominal voltage with 82V max

during charging. • Rated voltage of BCAP0650 is 2.70 V. In order to get a string of ultra-capacitors with ~82 V of

rated voltage, 30 ultra-capacitor cells are required in series:

• The rated capacitance of the string becomes 36.11 Farads:

• The voltage variation can be calculated by:

• Therefore:

• Hence, with 1.16 V of variation (discharge or discharge) in the ultra-capacitor string’s voltage, 1794.3 Watt-seconds of energy can be captured or delivered by the ultra-capacitor.

V8170.230

F67.2130650

22

21

initialfinal VVCE

VCEVV initialfinal 84.70

67.213.17942722 222


Experimental test results • Current ripple smoothing with Li-ion capacitors on the grid side unit and

carbon electrochemical ultra-capacitors on the vehicle side.


Summary • Current ripple smoothing with Li-ion capacitors on the grid side unit and

carbon electrochemical ultra-capacitors on the vehicle side.

Current ratio (Ipk/Iavg) Grid-side WPT base station

In-vehicle

III. No smoothing 53A 16A IV. Grid-side only with LiC 10A 16A VA.Vehicle side with UC 10A 2.6 VB.Vehicle side with LiC 10A 2.6

Pulse reduction 81% 84% for UC 84% for LiC


Questions & Discussions

• Contact Information

– Omer C. Onar, [email protected], 865-946-1351 – P.T. Jones, [email protected], 865-946-1472 – Madhu Chinthavali, [email protected], 865-946-1411

mailto:[email protected]



ornl dynamic wireless power demonstration with electrochemical · 2015-03-30 · •gem vehicle...

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