© 2011 ANSYS, Inc. April 27, 20151

Wireless Power Transfer System Design

Julius Saitz

ANSYS

© 2011 ANSYS, Inc. April 27, 20152

WPT System

© 2011 ANSYS, Inc. April 27, 20153

Near-Field (Inductive coupling, resonant)

• Do not rely on propagating EM waves

• Operate at distances less than a wavelength of transmission signal

• Resonance obtained by use of external circuit capacitor

• Electric and magnetic fields can be solved separately

Far-Field (resonant)

• Operating range to ~10 meters

• Self capacitance of coil turns are of importance

• Requires full wave solver with coupled electric and magnetic fields

Wireless Power Transfer (WPT)

Focus of this presentation

© 2011 ANSYS, Inc. April 27, 20154

Magnetic Analysis

Inductance/Resistance calculations versus frequency

Ensure linear mode operation

Relative Position sensitivity study

Loss evaluation

Effect of temperature on magnetic performance

Circuit Analysis

Operate in resonant mode, considering magnetic results

Compute efficiency considering relative position

Transient simulation considering frequency dependent effects

Thermal Management

Consider local losses distribution in thermal evaluation

Consider changing of electrical properties with temperature

Design Challenges

Wireless Power Transfer

© 2011 ANSYS, Inc. April 27, 20155

Outline

Large Gap Transformer Design Using Computational Electromagnetics

Combination of Circuit and Magnetic Analysis for Resonance

Thermal Management

© 2011 ANSYS, Inc. April 27, 20156

Large Gap Transformer Design Using Computational Electromagnetics

© 2011 ANSYS, Inc. April 27, 20157

• Low reluctance flux path is available

• Mutual Coupling between the coils can be easily determined using Magnetic Circuit approach

• Leakage flux can be considered to be negligible

• Mutual inductance can be derived using flux balance

• Analytical solution possible within permissible level of accuracy

Regular Transformer

© 2011 ANSYS, Inc. April 27, 20158

• No Specific path for the magnetic flux

• Leakage flux is significant enough and can not be neglected

• Analytical methods are proposed for calculation of Mutual inductance using Maxwell’s formula for two coaxial circular coils

Large Gap Transformer

𝑴 =𝟐𝝁𝟎 𝑹𝒑𝑹𝒔

𝒌𝟏 −

𝒌𝟐

𝟐𝑲 𝒌 − 𝑬 𝒌

Application of these formulas to real life cases is almost impossible

Computation Electromagnetics can help to reduce problem complexity significantly

© 2011 ANSYS, Inc. April 27, 20159

Maxwell

© 2011 ANSYS, Inc. April 27, 201510

Transformers

Insulation – Dielectric Withstand, Maximum E-field

Load Analysis Foil Losses

Lorentz Force

Tank Wall Losses Bus Bars

Inductance

Losses and Temperature in Ferrite Core

Converters

Creep Stress

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40Distance (m)

-1E+006

0E+000

1E+006

2E+006

3E+006

4E+006

V/m

xformer4Creep Stress Curves (V/m) ANSOFT

Curve Info

Allowable Withstand C...

Sorted_E_Tangent$PermOil='2.2'

E_Tangent$PermOil='2.2'

Cumulative_Stress$PermOil='1'

Cumulative_Stress$PermOil='2.2'

Cumulative_Stress$PermOil='6'

© 2011 ANSYS, Inc. April 27, 201511

GapSliding

WPT Magnetic simulation Flow ChartMagnetic Field Solver

+ Circuit / System Simulator

Magnetostatic

Eddy Current

(time harmonic) Circuit / System

Simulator

(AC / TR)Impedance Model

Circuit / Drive / Controller designWaveform, Efficiency, Power factor, Response

Eddy Current

Fields, Losses

Core, Winding

© 2012 ANSYS, Inc. April 27, 201512

Magnetostatic Analysis– Saturation

– Magnetic shielding

– Self and Mutual Inductance

– Coupling Coefficient

M

L1

L2

© 2011 ANSYS, Inc. April 27, 201513

Parametric Analysis using Maxwell

© 2011 ANSYS, Inc. April 27, 201514

Eddy Current (Frequency domain)

• Impedance vs frequency

• State Space Model for Circuit Analysis

• Losses

• Eddy current shielding

Shield Plate (Aluminum)

Core(Power Ferrite)

© 2011 ANSYS, Inc. April 27, 201515

Combination of Circuit and Magnetic Analysis for Resonance

© 2012 ANSYS, Inc. April 27, 201516

Inductive Type Coupling – Near Field

1) Electromagnetic analysis to determine R, L, M

Magnetic → R, L, MR

C C

R

LLM

2) Resonant circuit realized by a lumped capacitance parameter in the circuit simulator

© 2011 ANSYS, Inc. April 27, 201517

System Approach with Simplorer

Secondary Coil

Primary Coil

Reduced Order Model (ROM)

© 2011 ANSYS, Inc. April 27, 201518

Frequency Domain Analysis: System Level

© 2011 ANSYS, Inc. April 27, 201519

Parametric Analysis: Frequency Domain

Bode Plot: Load Voltage vs Gap

Bode Plot: Load Voltage vs Slide

GapSliding

Geometric parameters areAvailable in the circuit environment

© 2011 ANSYS, Inc. April 27, 201520

Transient Analysis

© 2011 ANSYS, Inc. April 27, 201521

Efficiency Map

Output/Input Power

Tuned capacitance for each conditions

90%

50%

20%

[%]100

cos

in

out

P

P

VIP

Effi

cien

cy[%

]

Sliding [mm]Gap [mm]

Max.96%

Gap

[m

m]

Sliding [mm]

Efficiency[%]

© 2011 ANSYS, Inc. April 27, 201522

Optimize the Design: Various Shape Types

Disk Coil type Solenoid Coil type

© 2011 ANSYS, Inc.23

Efficiency as a function of sliding direction and distance

• Gap between coils kept constant

© 2011 ANSYS, Inc.24

Efficiency as a function of gap between coils

• Zero sliding

Gap

© 2011 ANSYS, Inc. April 27, 201525

System Simulation – WPT

0

0

0

R1

(1/87-0.004) ohm

R2

(1/348-0.001) ohm

Cs

1.93uF

Cp

5.24uF

Rload

10ohm

W

+

WM1

W

+

WM2

D4

D3

D2

D1

IGBT4

IGBT3

IGBT2

IGBT1

C1

1000uF

TRANS4

DT4

TRANS3

SINE1.VAL > TRIANG1.VAL

TRANS2

DT1

TRANS1

SINE1.VAL < TRIANG1.VAL

STATE_11_4

SET: TSV4:=0SET: TSV3:=0SET: TSV2:=0

SET: TSV1:=0DEL: DT4##Dead_Time

STATE_11_3

SET: TSV4:=0SET: TSV3:=1SET: TSV2:=1

SET: TSV1:=0

STATE_11_2

SET: TSV4:=0

SET: TSV3:=0SET: TSV2:=0

SET: TSV1:=0DEL: DT1##Dead_Time

STATE_11_1

SET: TSV4:=1

SET: TSV3:=0SET: TSV2:=0

SET: TSV1:=1

TRIANG1

AMPL=1FREQ=Carrier_Freq

SINE1

AMPL=Modulation_IndexFREQ=Frequency

ICA:FML_INIT1

Modulation_Index:=0

Carrier_Freq:=10kFrequency:=10k

DC_Source:=200Dead_Time:=2u

~

3PHAS

~

~

A * sin (2 * pi * f * t + PHI + phi_u)

PHI = 0°

PHI = -120°

PHI = -240°

THREE_PHASE1

D5

D6

D7

D8

D9

D10 Battery

- +

LBATT_A1

D11

D12

D13

D14

C2

1e-006farad

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00Time [ms]

-40.00

-20.00

0.00

20.00

40.00

Y1 [A

]

Curve Info rms

WM1.ITR 9.4139

WM2.ITR 10.5939

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00Time [ms]

-300.00

-100.00

100.00

300.00

Y1 [V

]

Curve Info rms

WM1.VTR 154.9045

WM2.VTR 120.2425

1.90 1.92 1.94 1.96 1.98 2.00Time [ms]

-40.00

-20.00

0.00

20.00

40.00

Y1 [A

]

-200.00

-100.00

0.00

100.00

200.00

Y2 [V

]

MX1: 1.9753MX2: 1.9783

-6.0797

-1.2036-0.0090

131.1979

-0.51411.340627.9814

156.0455

0.0030

Curve Info Y Axis rms

WM1.ITR Y1 9.3501

WM2.ITR Y1 10.5176

WM1.VTR Y2 153.6594

WM2.VTR Y2 119.4615

Current_1st_1:src

Current_1st_2:src

Current_2nd_1:src

Current_2nd_2:src

Current_1st_1:snk

Current_1st_2:snk

Current_2nd_1:snk

Current_2nd_2:snk

0

0

0

R1

(1/87-0.004) ohm

R2

(1/348-0.001) ohm

Cs

1.93uF

Cp

5.24uF

Rload

10ohm

W

+

WM1

W

+

WM2

D4

D3

D2

D1

IGBT4

IGBT3

IGBT2

IGBT1

C1

1000uF

TRANS4

DT4

TRANS3

SINE1.VAL > TRIANG1.VAL

TRANS2

DT1

TRANS1

SINE1.VAL < TRIANG1.VAL

STATE_11_4

SET: TSV4:=0SET: TSV3:=0SET: TSV2:=0

SET: TSV1:=0DEL: DT4##Dead_Time

STATE_11_3

SET: TSV4:=0SET: TSV3:=1SET: TSV2:=1

SET: TSV1:=0

STATE_11_2

SET: TSV4:=0

SET: TSV3:=0SET: TSV2:=0

SET: TSV1:=0DEL: DT1##Dead_Time

STATE_11_1

SET: TSV4:=1

SET: TSV3:=0SET: TSV2:=0

SET: TSV1:=1

TRIANG1

AMPL=1FREQ=Carrier_Freq

SINE1

AMPL=Modulation_IndexFREQ=Frequency

ICA:FML_INIT1

Modulation_Index:=0

Carrier_Freq:=10kFrequency:=10k

DC_Source:=200Dead_Time:=2u

~

3PHAS

~

~

A * sin (2 * pi * f * t + PHI + phi_u)

PHI = 0°

PHI = -120°

PHI = -240°

THREE_PHASE1

D5

D6

D7

D8

D9

D10 Battery

- +

LBATT_A1

D11

D12

D13

D14

C2

1e-006farad

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00Time [ms]

-40.00

-20.00

0.00

20.00

40.00

Y1 [A

]

Curve Info rms

WM1.ITR 9.4139

WM2.ITR 10.5939

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00Time [ms]

-300.00

-100.00

100.00

300.00

Y1 [V

]

Curve Info rms

WM1.VTR 154.9045

WM2.VTR 120.2425

1.90 1.92 1.94 1.96 1.98 2.00Time [ms]

-40.00

-20.00

0.00

20.00

40.00

Y1 [A

]

-200.00

-100.00

0.00

100.00

200.00

Y2 [V

]

MX1: 1.9753MX2: 1.9783

-6.0797

-1.2036-0.0090

131.1979

-0.51411.340627.9814

156.0455

0.0030

Curve Info Y Axis rms

WM1.ITR Y1 9.3501

WM2.ITR Y1 10.5176

WM1.VTR Y2 153.6594

WM2.VTR Y2 119.4615

Current_1st_1:src

Current_1st_2:src

Current_2nd_1:src

Current_2nd_2:src

Current_1st_1:snk

Current_1st_2:snk

Current_2nd_1:snk

Current_2nd_2:snk

AC200V Rectify Inverter

Wireless Power Transformer Battery

Controller

© 2011 ANSYS, Inc. April 27, 201526

Thermal Management

© 2011 ANSYS, Inc. April 27, 201527

Temperature in ANSYS Mechanical or CFD

Core Loss

Ohmic Loss

Temperature

© 2012 ANSYS, Inc. April 27, 201528

Summary

ANSYS offers a comprehensive modeling solution for Wireless Power Transfer systems:

– Magnetostatic

– Frequency domain

– Circuit and system level

– Thermal

Wireless Power TransferElectromagnetics

System Level ModelingElectromagnetic-Circuit

0

0

0

R1

7.2mOhm

R2

3.6mOhm

Cs

1.72uF

Cp

4.96uF

Rload

13ohm

W

+

WM1

W

+

WM2

D4

D3

D2

D1

IGBT4

IGBT3

IGBT2

IGBT1

C1

1000uF

TRANS4

DT4

TRANS3

SINE1.VAL > TRIANG1.VAL

TRANS2

DT1

TRANS1

SINE1.VAL < TRIANG1.VAL

STATE_11_4

SET: TSV4:=0

SET: TSV3:=0SET: TSV2:=0

SET: TSV1:=0

DEL: DT4##Dead_Time

STATE_11_3

SET: TSV4:=0

SET: TSV3:=1SET: TSV2:=1

SET: TSV1:=0

STATE_11_2

SET: TSV4:=0

SET: TSV3:=0

SET: TSV2:=0SET: TSV1:=0

DEL: DT1##Dead_Time

STATE_11_1

SET: TSV4:=1

SET: TSV3:=0

SET: TSV2:=0SET: TSV1:=1

TRIANG1

AMPL=1FREQ=Carrier_Freq

SINE1

AMPL=Modulation_IndexFREQ=Frequency

ICA:FML_INIT1

Modulation_Index:=0

Carrier_Freq:=20k

Frequency:=20k

DC_Source:=400

Dead_Time:=2u

~

3PHAS

~

~

A * sin (2 * pi * f * t + PHI + phi_u)

PHI = 0°

PHI = -120°

PHI = -240°

THREE_PHASE1

D5

D6

D7

D8

D9

D10 Battery

- +

LBATT_A1

D11

D12

D13

D14

C2

1uF

2.00 2.20 2.40 2.60 2.80 3.00Time [ms]

-150.00

-100.00

-50.00

0.00

50.00

100.00

150.00

Y1 [

A]

Curve Info rms

WM1.ITR 41.6165

WM2.ITR 34.8648

2.00 2.20 2.40 2.60 2.80 3.00Time [ms]

-800.00

-300.00

200.00

700.00

Y1 [

V]

Curve Info rms

WM1.VTR 281.0066

WM2.VTR 321.9453

2.900 2.925 2.950 2.975 3.000Time [ms]

-250.00

-125.00

0.00

125.00

250.00

Y1 [

A]

-1000.00

-500.00

0.00

500.00

873.02

Y2 [

V]

MX1: 2.9200

MX2: 2.9811

-408.7847-315.0105-64.8250

-40.2840

-377.1247-319.5653 -53.6971

-0.0037

0.0610

Curve Info Y Axis rms

WM1.ITR Y1 38.9542

WM2.ITR Y1 34.1140

WM1.VTR Y2 276.0822

WM2.VTR Y2 316.6292

PWR

Probe

PWR_Probe1

Current_1:srcCurrent_2:src

Current_1:snkCurrent_2:snk

PWR

Probe

PWR_Probe2