Alireza Dayerizadeh Principle Investigator: Dr. Srdjan Luki 1 - - PowerPoint PPT Presentation

Dynamic Wireless Charging for Electric Vehicles: Approaches for Reflexive Field Containment Using Reactive Components

NCSU Invention Disclosure: 18-084

Alireza Dayerizadeh Principle Investigator: Dr. Srdjan Lukić

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Dynamic Wireless Power Transfer

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Why Dynamic Wireless Power Transfer?

• Increased range and reduced charging times.
• Reduced vehicle energy storage requirements

Wireless Power Transfer: An Alternative to Conductive Charging.

• Source to load efficiencies of over 90% are possible at coupling coefficients of 0.2.

Electric-vehiclenews.com. (2018). UK To Test Dynamic Wireless Charging For Electric Cars. [online] Available at: http://www.electric-vehiclenews.com/2015/08/uk-to-test-dynamic-wireless-charging.html

Dynamic Wireless Power Transfer

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Dynamic WPT may be accomplished through an array of segmented transmitting coils that sequentially couple to a passing receiving coil, thus isolating the field emissions to the coupled coil. Challenges include:

• Precise Receiver Position Feedback is required.
• Efficient and fast methodology to selectively energize coupled coil.

Dynamic Approach One

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Position sensor and relays for power flow control to coupled coils.

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Dynamic Approach Two Power each coil with a dedicated inverter (cost prohibitive in large applications).

Dynamic Approach Two

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Exploit reflected impedance of receiving coil to control emitted field reflexively

Reflexive Field Containment Approach

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• Large uncompensated

reactance ln uncoupled TX coils Ls Req C2 C1 Cp Lp M

Series-Parallel-LCC

Cp1 Lp1 Lp2 Lpn Cp2 Cpn Ccomp CF LF Inverter

Allows for Segmented TX Coils

2 2 2 2 2 2

( ) ( )

eq reflected Total s s s s

M R M M M Z n n j Q n j Z L L L w w w = = ×

• ×

=

• ×
• Reflected reactance brings

TX coil into resonance

• Current flow is boosted

When Coupled… When Uncoupled…

Transmitter Design

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Ccomp CF LF Vs ΔX Rr

Uncoupled Coupled

It,coupled It,uncoupled ICcomp IS

, s t coupled r

V I R =

, s t uncoupled

V I j X = D

Improving Field Containment

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Saturable Inductor increases reactance in TX coil.

The Saturable inductor:

• Maximizes the difference between

coupled and uncoupled currents in the TX coil.

• Saturates as the system becomes

coupled.

• Improves system current gain (and

field attenuation performance).

LMax

Lmax Cp Lp C2 C1 Ls Req M Transmitter Receiver Vin

Saturable Inductor Characteristics

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• AC current means that inductor is not

continuously saturated.

• Inductance must be modelled to account for

AC saturation behavior.

1 2

2 1 ( )

[ ( ) ]

max sat sat sat eff peak peak peak

L I I I L sin I I I p

• =

+

• 1

4

[ ( )]

max sat eff peak

L I L sin I p

• =

Simulation – Comparison to Reference System

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Current gain 11 Current gain 3 System With Saturable Inductor Reference System

Hardware Validation

12 Input Voltage

171.1 V

Input Current

8.65 A

Input Power

1480 W

Output Power

1208.4 W (95.2^2/7.5)

Efficiency

81.6%

Current Gain

11.1

Transmitter (TX)* Lp 190uH Cp 22.65nF Lmax 180uH Leff 23uH Csat 143nF Receiver System Ls 237uH C1 16.56nF C2 82.81nF n 6 RLoad 7.5

Inverter Output Voltage and Current - Coupled Inverter Output Voltage and Current - Uncoupled

Impacts

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• Aid in the proliferation of electric vehicles.
• Aids in the meeting of field emissions standards.
• Technology may be used in: autonomous vehicles and

consumer electronics.

Conclusion

• Entirely passive field containment approach for the

dynamic charging of electric vehicles.

• Builds upon previously published work.