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Inductive Power Transfer

Presenter： Dr Siu-Chung Wong

Department of Electronics and Information EngineeringThe Hong Kong Polytechnic University

Innovative Technology SeriesWorkshop 6

1

4. Transformer

5. Control6. Design Example

1. Introduction

2. Basic Analysis

3. CompensationNetwork

Part 1：Introduction

2

Electric Power Transfer

Potentially not safe！

Conventional method：

• Metal Conductor Soldering

• Electrical Plug and Socket

• Brush Metal Contact

Introduction

3

Conventional Wireless

Introduction

4

5

Roadmap of WPT

t(year)1891

Tesla Coil

2007

MIT, lighten a 60 W lamp 2 m away

1831

Faraday，

Law of induction1894

First

patent

2008

WPC established

A4WP & PMA merge

WPC wireless charging standard Qi

2010

2010 commercialized

2015

2013SAE “J2954” for EV/PHEV

IEC61580Communication standard for EV

20141964，1968

Micro wave WPT

1978

H. J. G. Bolger, F. A. Kirsten and L.S. Ng, “Inductive power coupling for an electric highway system,” Vehicular Technology Conference, Vol.28, pp.137-144, March 1978

1980s

1987—SHARP microwave airplane1989-1996USA PATH

1987—implant

1980—Brush replacement

1990s

1996-EV1，SAE J1773HF IPT charging of EV

WPT classification

Long or very long distance

Can penetrate metal, very short distance, high frequency and lower power

CapacitiveInductive-

inductive and resonant

Inductive—Lower frequency，wider power

Resonant—Higher frequency, longer distance

Long Range —Laser/Microwave

6

Capacitive coupling

Input voltage: 340V

Output voltage: 196V

Output current: 5.21A

Frequency: 540KHz

Efficiency: 83%

Air gap: 100um

Wireless Electric Vehicle Charging via Capacitive Power Transfer Through a Conformal BumperJiejian Dai , Daniel C. Ludois , APEC 2015

7

8

—— Occupy a lot of space

—— higher loss

WPT – Long Range

—— Safety issue

9

WPT Inductive Power Transfer

IPT

2010……2000 2007 2008 2009 Now

Germany Wampflertrack IPT

Splashpower

WiPower

Seiko 0.5WIPT charger

Mojo Mobilitycoils

Seiko

2.5 WIPT

Japan

Airplane

IPT

Fulton InnovationIPT

东光 IPT

PowermatJapan HanedaAirport BusIPT

10

Less sensitive to transformer misalignment

High frequency operation

MIT Intel

Japan WPT

USA

SonyWPT

海尔“ 无尾” 电视

20102007 2008 2009 Now

Magnetic ResonantWPT

WPT Inductive Power Transfer

Safety Issue

Cardiac Pacemaker

Artificial HeartHomeMedical EV charger

WPT application

Industry

11

Transmit

Reflect

Underground pipe dection

3M—under ground positioning 0.6m-2m

HV

IoT power

Nina M. Roscoe and Martin D. Judd. Harvesting Energy from Magnetic Fields to Power Condition Monitoring Sensors[J]. Sensors Journal, IEEE ,2013:3

WPT application

12

First international IPT standard；

Established from City University Hong Kong

then the WPC （wireless power consortium)。

on Sept. 2015，WPC has 217 member。

Qi

Google“Nexus”and Nokia“Lumia”support this standard。

WPT standards

13

Initialized by Duracell Powermat；

on Sept. 2015, A4WP has 150 members including Qualcomm，Samsung，Broadcom and Intel.

Duracell Powermat WiCC card

PMA(Power Matters Alliance)

Rezence (A4WP)merged

Corporations

14

EV charging technology

KIST, KoreaWasedaUniversity Japan

ZTE, China

Gap：26cm

Power：5*20kW

Efficiency：80%~85%

Announced：2013

Gap：10cm

Power：30kW

Efficiency：92%

Announced：2011

Gap：20cm

Power：30kW

Efficiency：92%

Announced：2014

15

QualcommIdaho National Laboratory, USA

Witricity

Gap：

Power：7.2kW

Charging Time：1hour

Announced：2015

Gap：11cm

Power：3.3kW

Efficiency：89.2%

Announced：2013

Operating frequency：85kHz

Power：2kW

Charging Time：1.5 hours

Announced：2014

EV charging technology

16

Installation

ABB（Geneve Airport and Palexpo convention center），15second charging at 400 kW，from top of the bus.

17

Wireless Power Transfer System

18

Inverter Rectifier

VCObufferFilterF/Vconverter

Controller

Driver

Circuit

VO

Gap

Primary Secondary...

Battery

pack

PFCCircuitSingle or

Three phase

~

Secondary

Feedback circuit VTI

M

Critical Technology

WPTTechnology

A

F

B

C

G

Electromagnetic compatibility

Transformer Coupling

E DCircuit Theory and Power ElectronicsSafety

Material

Communication

Control

19

Inverter Rectifier

VCObufferFilterF/V

converter

Controller

DriverCircuit

VO

Gap

Primary Secondary...

Battery

pack

PFCCircuitSingle or

Three phase

~

Secondary

Feedback

circuit VTI

M

IPT systemPrimary

Secondary

Gap

Inductances compensation

Optimization of TransformerOptimization of Transformer

Tactic：

Small Coupling Coefficient

Large parameter variation

Effective control

20

Critical Technology

Part 2：Basic Analysis

21

4. Transformer

5. Control

6. Design Example1. Introduction

2. Basic Analysis


Inverter Rectifier

VCObufferFilterF/V

converter

Controller

DriverCircuit

VO

Gap

Primary Secondary

...

Battery

pack

PFCCircuitSingle or

Three phase

~

Secondary

Feedback

circuit VTI

M

Transformer Model

Transformer model

Coupling

22

Transformer Equivalent Model

Coupling Model Three parameter model

* *

'ML

'LL

'1: n''ML

''LL

''1: n

Leakage inductance model

'

2' 1 2

2'

S

L S M L P SL

S S

MS

Ln

ML L L L L L M

LL L

MLL

''

2''

''

P

L SP

M P

MnL

ML LL

L L

12

2

P L M

S L M

P S

L L LL L n L

kML L

n: Turns ratio

Equivalent n

23

Part 3：Compensation network

24

4. Transformer5. Control

6. Design Example

1. Introduction

2. Basic Analysis


Why compensation?

Primary Windings

Secondary Windings

Gap

Large leakage inductance and small mutual inductance

Improve input power factor Reduce device rating Improve power transfer Improve efficiency Reduce sensitivity to transformer parameter variation

25

Circuit

InverterCompensation Rectifier LoadPower source Filter

C Filter LC Filter

SecondaryPrimary

Voltage source input Current source input

26

Primary circuit

Voltage source input Current source input

vAB +Capacitor clamped

Capacitor clamped

27

RE

Secondary Circuit

Phase of ORv2iand are identical，like a resistor。

C filter，output voltage assumed constant

LC filter，output current assumed constant

o oOS o

E L2 22 2

4 4sin( ) 8 8sin( )

2

V t Vv VR R

i I t II

Equivalent load resistor：

28

RE

OUTPUT EQUIVALENT

RESISTANCE

C filter，output voltage assumed constant

LC filter，output current assumed constant

E L2

8R R

2

E L8R R

29

System Simplification

Squarevoltage

Squarecurrent

30

Resonant Compensation

Series resonant

Parallelresonant

Voltage across L C compensated to zero。When high Q，voltages across L and C can be higher than the input。

1L LQR R C

Current flow through L and C cancelled out。

31

Secondary Capacitor Compensation

Parallel Series

Reflected Zr：2 2

rS

MZZ

Power transfer capability： 2 ReP rP I Z

Compensation Re(Zr) Im(Zr) Comment

Series 0 Im(Zr)=0

Parallel Capacitive load independent Im(Zr)

2 2

E

MR

2

2E

S

M RL

2

S

ML

1

S SL C

Primary current： A BP

P r

VIj L Z

32

Parallel

If Ip constant

Series

Output current is load independent

LS

jωMIP

iS

+

−

C

RE

vOS

i2

Output voltage is load independent

Can have load independent output.

33

Secondary Capacitor Compensation

Series Parallel

Suitable for driving large value LPto minimize input driving voltage.

Suitable for driving high winding current to minimize input current.

We need primary and secondary compensations

34

Primary Capacitor Compensation

Primary and Secondary Compensations

35

36


S/P voltage gain

P/P current gain P/S current gain

Resonant at 40 kHzS/S voltage gain

37


S/S Compensation

Resonant

Input inductive，current circulating loss Load independent output voltage

Low input resistance，small reactance

Resonant

Load independent current output Need open circuit protection

AB Ejv RM

2 2

E

MR

S

H

Even worse at light load

38

S/S compensation

Huh, J.; Lee, S.W.; Lee, W.Y.; Cho, G.H.; Rim, C.T., "Narrow-Width Inductive Power Transfer System for Online Electrical Vehicles," in Power Electronics, IEEE Transactions on , vol.26, no.12, pp.3666-3679, Dec. 2011

Output voltage 408V，output current 66.2A

39

S/S Compensation Example

Sallan, J.; Villa, J.L.; Llombart, A.; Sanz, J.F., "Optimal Design of ICPT Systems Applied to Electric Vehicle Battery Charge," in Industrial Electronics, IEEE Transactions on , vol.56, no.6, pp.2140-2149, June 2009

S/S uses less copper

40

Output voltage 408V，output current 66.2A

S/P Compensation

vAB

C1 LL’

vOSLM’ C3

1:n+

−

+

−

RE

' SLnM

L model output needs short circuit protection Input zero phase angle

Output load independent

vAB vOS

1:n+

−

+

−

RES

PLL control may fail due to high Q at light load

00.40.81.21.6

22.42.83.23.6

4

20kHz 30kHz 40kHz 50kHz 60kHz

RE=50

RE=200

RE=400

Vol

tage

gain

Inpu

t pha

se a

ngle

C1 design for voltage gain，C3design for phase angle

41

S/P Compensation Example

Kobayashi, K.; Yoshida, N.; Kamiya, Y.; Daisho, Y.; Takahashi, S., "Development of a non-contact rapid charging inductive power supply system for electric-driven vehicles," in Vehicle Power and Propulsion Conference (VPPC), 2010 IEEE , vol., no., pp.1-6, 1-3 Sept. 2010

Frequency 22 kHz

42

P/P Compensation

Input must be a current

LS REC2P

S

MIL

1

1

Ij C

2SM L

2

2E

S

M RL

1

1

Ij C

2

2E

S

M RL

RE1

1

S

E

L Ij MC R

Load independent output voltage

Input capacitive

S

43

P/P Compensation Example

Chwei-Sen Wang; Stielau, O.H.; Covic, G.A., "Design considerations for a contactless electric vehicle battery charger," in Industrial Electronics, IEEE Transactions on, vol.52, no.5, pp.1308-1314, Oct. 2005

Power：300W，primary current 15A，20kHz，load 6Ω，k=0.45，QS=1.77

44

P/S Compensation

Input must be a current sourceLP

jωMIP

M

vAB

+

–

–jωMIS+

−

+

−

C1

LS

RE

C2i1

1

1

Ij C

Load independent current output

Input capacitive

1

1

Ij C

2 2

E

MR

12

1

ER IMC

S

45

1

1

Ij C

1

1

Ij C

2 2

E

MR

12

1

ER IMC

Current input Input capacitive

S

* *

Load independent current output

'

P

MnL

* *

P

21 21 1P P SL C L M C

C1 design for transfer function，C2 design for input phase angle

Input zero phase angle

46

P/S Compensation

S/S Compensation optimizationLoad independent output and high efficiency

Primary Secondary

Efficiency

set Optimum frequency for maximal efficiency

Wei Zhang; Siu-Chung Wong; Tse, C.K.; Qianhong Chen, "Design for Efficiency Optimization and Voltage Controllability of Series–Series Compensated Inductive Power Transfer Systems," Power Electronics, IEEE Transactions on , vol.29, no.1, pp.191,200, Jan. 2014

47

Efficiency at ωM:

Efficiency maximized at QO1

Efficiency increase with decreasing QO


48


When λ<1/3 (k<0.577), near load QO1，ωM andωSare nearly identical

replaceωM withωS

ωS is load independent

Efficiency at ωS and ωM

When QP=QS

With a known load，design a transformer such that ωM ≈ ωS to have maximum efficiency


49


S/S compensation voltage gain：

Frequencies：


50


Load independent |Gv|

Maximum Eff.

Operating freq. ωH ωM ≈ ωS (λ<1/3)

ωH cannot be ωS

CS design for efficiency

CP design for efficiency，such that ωH close toωS


51


CP=1.1CPn CP=1.3CPn

100k 125k 150k 175k 200k0

0.2

0.4

0.6

0.8

1ηT

Frequency

0

0.4

0.8

1.2

1.6

2

|Gv|

100k 125k 150k 175k 200k0

0.2

0.4

0.6

0.8

1ηT

Frequency

0

0.4

0.8

1.2

1.6

2

|Gv|

Define ：

Design Cp makingωH closer toωS to have a higher efficiency

maximize efficiency of S/S compensated converter to have load

independent output


52


AB Ejv RM

2 2

E

MR

If a constant output current is needed，S/S compensation should operate at ωS. Proper output open circuit protection should be given.

53


Realization of Load Independent Output

LS

jωMIP

iS

+

−

C

RE

vOS

i2

Voltage source output Current source output

54

LP LS

-jωMIS jωMIP

ip isM

+

−

+

−vOS

+

-

C1LrAB

r

vj L

Realization of Input Current

Primary side LCL compensation

vAB

LP LS

-jωMIS jωMIP

ip isM

+

−

+

−vOS

+

-

Secondary

Compensation

C1

Lr

+

−

Norton E

q.

LP LS

-jωMIS jωMIP

ip isM

+

−

+

−vOS

+

-

AB

r

vj L

55

Primary and Secondary LCL Compensation

IT is load independent and so is IO

Suitable for multiple secondary windings application

LCL need external indicator as large as LM，lower system power density.

56

LCC COMPENSATION

Lf CP

LP’

-jωMIS

ip

ieq

Minimize ' 211P P SL L C

211

ABeqv

P S

VIj L C

Compared with LCL compensation，LCC compensation can have higher injected current.

Esteban, B.; Sid-Ahmed, M.; Kar, N.C., "A Comparative Study of Power Supply Architectures in Wireless EV Charging Systems," Power Electronics, IEEE Transactions on , vol.30, no.11, pp.6408,6422, Nov. 2015

57

1

1 1

1iS

CQC C

Current gain (normally less than 3 due to magnetics):

Siqi Li; Weihan Li; Junjun Deng; Nguyen, T.D.; Mi, C.C., "A Double-Sided LCC Compensation Network and Its Tuning Method for Wireless Power Transfer," Vehicular Technology, IEEE Transactions on , vol.64, no.6, pp.2261,2273, June 2015

Parallel capacitor Cf reduce inductance Lf； Load independent current output；

58

LCC COMPENSATION

LCC COMPENSATION-INTEGRATED

Weihan Li; Han Zhao; Siqi Li; Junjun Deng; Tianze Kan; Mi, C.C., "Integrated LCC Compensation Topology for Wireless Charger in Electric and Plug-in Electric Vehicles," Industrial Electronics, IEEE Transactions on , vol.62, no.7, pp.4215,4225, July 2015

Coupling Circuits

Magnetic coupling can improve power density。

59

Weihan Li; Han Zhao; Siqi Li; Junjun Deng; Tianze Kan; Mi, C.C., "Integrated LCC Compensation Topology for Wireless Charger in Electric and Plug-in Electric Vehicles," Industrial Electronics, IEEE Transactions on , vol.62, no.7, pp.4215,4225, July 2015

Coupling Equivalent

Matching：

60

LCC COMPENSATION-INTEGRATED

SP/S Compensation

Villa, J.L.; Sallan, J.; Sanz Osorio, J.F.; Llombart, A., "High-Misalignment Tolerant Compensation Topology For ICPT Systems," Industrial Electronics, IEEE Transactions on , vol.59, no.2, pp.945,951, Feb. 2012

Primary series compensation Primary parallel compensation

vAB

+

-

CP

LP LS

-jωMIS jωMIP

ip isM

+

−

+

−

2 21in P P

P S

MZ j L Rj C Z

2 2

11in

P

P PS

Zj C

Mj L RZ

Primary series compensation Primary parallel compensation

IP increases，can be over current. Ismay also increases. IP decreases，so as Is.

Misalignment, coupling reduced

combine

61


Load power

Input power

原边串联电容将虚部补偿掉。

62

SP/S Compensation


Input zero phase angle；

Insensitive to misalignment。

Input resistance change with output load。

63

SP/S Compensation

'

1

1lL

C

2 '

2

1Mn L

C

S/S AND S/P COMPENSATION

i1 i2

vAB

+

- RE

vOS

+

-

1:n

LM

* *

11

1lL

C

22

1lL

C

Input inductive

Voltage gain a function of n and k

S/S compensation

S/P compensation

'2

1S P

S

L LnnM k L n

（假设）

Input resistive

Voltage gain a function of n only

Hou Jia，Chen Qianhong，Wong Siu-Chung，Tse Chi. K.，Ruan Xinbo．Analysis and control of series/series-parallel compensated resonant converter for contactless power transfer[J]．IEEE Journal of Emerging and Selected Topics in Power Electronics，2015，3(1)：124－136．

64

Compensation：

Voltage gain a function of n only

Input resistive

vAB

vLMC1 C2LL1 LL2

vOSLM C3

1:n

Z1 Z2

+

−

+

−

RE

22

1 1 2 2 3

1 1 1

l l ML C L C n L C

Hou Jia，Chen Qianhong，Wong Siu-Chung，Tse Chi. K.，Ruan Xinbo．Analysis and control of series/series-parallel compensated resonant converter for contactless power transfer[J]．IEEE Journal of Emerging and Selected Topics in Power Electronics，2015，3(1)：124－136．

65

S/SP COMPENSATION

2

3 1 3 1 23

1 2

8v

M M

M M E

nGj C Z Z Z j L Z j L

j L j C C L R

Voltage gain

4 2 2 2= ( )+ ( ) 1p s M p s p p s sC C n L L L L C L C

=0，gain becomes load independent

Voltage gain at

2

3 1 3 1 2

8

1v i

i M

M

nGC Z Z Z j L Z

L

If 0，gain becomes LMindependent

L1 1 L2 2

1 1i L C L C

Finally： 28

v iG n

Input impedance2 2

in P1

S2 3

11 1 || E

MZ j Lj C j L R

j C j C

Input impedance at ： M E

in 2 2 2M 3 E M1i

j L RZn L C R j n L

If 0, then a pure

resistorE2

Rn

2M 3

1n L C

66

S/SP COMPENSATION

20 30 40 50 60fs(kHz)

0

2

4

6

8

10

Gv

fH_kmax40k

fL_kmax23.7k

Resonant frequency fr = 40 kHz

Compensation capacitor C1 = 48.89nF, C2 = 44.2nF, C3 = 51.4nF

Transformer parameter

10 cm: kmax = 0.475, Ll1 = 324.967 , Ll2 = 362.56 , LM = 310.948 20 cm: kmin = 0.231, Ll1 = 435.275 , Ll2 = 462.95 , LM = 134.85

RL RLmin = 100 Ω, RLmid = 400 Ω, RLmax = 800 Ω

Constant freq.control

67

S/SP COMPENSATION

Fundamental approximation is not able to keep up with the accuracy. 。

Lot of higher harmonics

68

S/SP COMPENSATION

Higher Harmonic Equivalent Circuit

_4 in

AB mV

Vm

Input voltage:

2 _4 o

mI

Im

Output current:

69

m=3,5,7,9,…: _

_

LM m

AB m

Vk

Vm=1: _1 _1LM ABV V

Voltage across LM

sine square

_11 sinLM AB s ABv t k V t kv t

Secondary current

m=1: _1 _1 3_1

1S AB r

E

I nV j CZ

m=3,5,7,9,…: _ 0S mI

_1 1sinS S si t I t sine

70

Higher Harmonic Equivalent Circuit

_4 in

AB mV

Vm

Input voltage:

2 _4 o

mI

Im

Output current:

MLi

Waveforms of Resonant Circuit

_11 sinLM AB s ABv t k V t kv t

sine square

_1 1sinS S si t I t sine

71

Output Waveforms

Harmonic current and voltage

Output current harmonics

72

Experimental Comparisons

Po =1.5 kW

39.2kHz

Po =0.8 kW

Input current Voltage across parallel capacitor

73

Result from calculation with higher harmonics

Experimental result

Result from calculation with Fundamental approximation

0.74

0.76

0.78

0.8

0.82

300 500 700 900 1100 1300 1500Po(W)

Gv

200

74

S/SP COMPENSATION

Switching of Series or Parallel Compensation on the Secondary Side

Battery charging needs two stages：

Constant Current，until battery reach a voltage level，Constant voltage，until current diminishing to nearly none.

Constant voltage ， S1 and S2 open， S3 connects RL to L2，forming a S/Scompensation，Ls = L1 + L2（dotted blue）

Constant current ， S1 and S2 close， S3 connects RL in parallel with Cssp ，forming a S/P compensation， Ls = L1。（solid red）

Auvigne, C.; Germano, P.; Ladas, D.; Perriard, Y., "A dual-topology ICPT applied to an electric vehicle battery charger," Electrical Machines (ICEM), 2012 XXthInternational Conference on , vol., no., pp.2287,2292, 2-5 Sept. 2012

75

DYNAMIC TUNING

a Soft-Switched Variable Inductorinside the resonant circuit

Hu, A.P.; Hussmann, S., "Improved power flow control for contactless moving sensor applications," Power Electronics Letters, IEEE , vol.2, no.4, pp.135,138, Dec. 2004. doi: 10.1109/LPEL.2004.841311

When there are variation of parameters, such as load, coupling and driving frequency，system compensation may deviate from optimal point.

76

Z. Pantic and S. M. Lukic, “A new tri-state-boost-based pickup topology for inductive power transfer applications,” in Proc. IEEE Energy Convers. Congr. Expo., Phoenix, AZ, Sep. 2011, pp. 3495–3502.Pantic, Z.; Lukic, S.M., "Framework and Topology for Active Tuning of Parallel Compensated Receivers in Power Transfer Systems," Power Electronics, IEEE Transactions on, vol.27, no.11, pp.4503,4513, Nov. 2012

Use extra inductor or capacitor；Need bidirectional current switch；Discrete alteration of Capacitance or

inductance.

Three mode boost inductor secondary compensation

freewheeling period

77

DYNAMIC TUNING

Part 4：Transformer Optimization

78

5. Control6. Design Example

1. Introduction

2. Basic Analysis3. Compensation

Network

4. Transformer

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