Wireless Charging of EVs Prof. Dr. Pavol Bauer, Delft University of - - PowerPoint PPT Presentation

Wireless Charging of EVs

• Prof. Dr. Pavol Bauer, Delft University of Technology

Learning objectives

• 1. What are the advantages and disadvantages of wireless

charging?

• 2. What are the parts of an inductive wireless charging system?
• 3. How does an inductive power transfer system work?

Wireless Power Transfer Modes

• Transfer of energy without wired interconnects.
• Different types of wireless power transfer techniques based
• n energy carrier medium:

§ Inductive (Inductive power transfer or IPT) § Capacitive § Microwave § Laser § Acoustic

Today: Static Inductive Charging

Advantages Disadvantages Aesthetically favorable, no vandalism 5-10% higher losses Safety Higher costs compared to AC, DC charging Comfort Extra converters compared to AC charging

Image source: Plugless power

Inductive Power Transfer - Components

M DC DC DC AC DC /Rectified DC Input Inverter Primary Compensation Secondary Compensation Rectifier Regulator Traction motor Battery Electric Vehicle DC AC

Materials in Charge-pads

• 1. Current conducting materials
• 2. Magnetic flux channelling materials
• 3. Magnetic flux shielding

materials

Copper conductor Al shield Ferrite bars

Charge-pads in Practice

Wireless charging while driving

EV power pick-up charge pad Charging pad in the road generating a magnetic field

On-road charging of EVs

EV power pick-up charge pad Charging pad in the road generating a magnetic field

• Convenience
• Smaller batteries on EVs
• High cost of multiple charge pads

and power electronic converters

• Misalignment between coils
• Standardisation amongst EVs

Wireless Charging of EVs

• Prof. Dr. Pavol Bauer, Delft University of Technology

Coefficient of Coupling and Mutual Inductance

• L1, L2 are the inductances of the primary, secondary coils
• |k| = 0.01–0.5 (loosely coupled), |k| = 0.9-1 (tightly coupled)

V1 RL i1 i2 e1 e2 k L1 L2 !"# = !" − & !'# = !' − & & = ( !"!'

Coefficient of Coupling and Mutual Inductance

V1 RL i1 i2 e1 e2 k L1 L2

!"# = !" − & !'# = !' − &

C1 C2 I2 L1-M L2-M M I’1 E2 +

• Im

RL,eq

Equivalent load circuit model

V1

& = ( !"!'

Equivalent Circuit of IPT System

M DC DC DC AC DC /Rectified DC i/p VLF-LF Inverter Primary Compensation Secondary Compensation Rectifier Regulator Traction motor Battery Electric Vehicle

C1 C2 I2 L1-M L2-M M I’1 E2 +

• Im

RL,eq

Equivalent load circuit model

V1

Need for Compensation

!

"

P = !

"#" cos θ

θ

#′" Θ = 0* #" !

"

P = !

"#′"

C1 C2 I2 L1-M L2-M M I’1 E2 +

• Im

RL,eq V1 I2 L1-M L2-M M I1 E2 +

• Im

RL,eq V1

• Due to large leakage inductances – Poor efficiency (loss α #,).
• Compensate leakage inductance with capacitances

#′" < #" #" cos θ

Reactive Power Exchange in Inductors