Double-sided LCC compensation method for wireless power transfer

Patent metadata

Field	Value
Publication number	US-9789777-B2
Application number	US-201414328077-A
Country	US
Kind code	B2
Filing date	Jul 10, 2014
Priority date	Jul 11, 2013
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

A double-sided LCC compensation network and a tuning method are proposed for a wireless power transfer system. With the proposed topology, the resonant frequency is independent of coupling coefficient and load conditions. The parameter values are tuned to realize zero voltage switching (ZVS) for the sending side switches. A wireless charging system with up to 7.7 kW output power was designed and built using the proposed topology and achieved 96% efficiency from DC power source to battery load.

First claim

What is claimed is:

1. A wireless power transfer system, comprising:
a send unit configured to transfer power using inductive power transfer, wherein the send unit includes:
an inverter configured to receive a DC input signal and convert the DC input signal to an AC output signal at a desired resonant frequency, wherein the inverter is further defined as a full bridge converter circuit comprised of four switches;
a send coil configured to receive the AC output signal from the inverter and generate an alternating electromagnetic field; and
a send side compensation circuit interconnecting the inverter with the send coil, wherein the compensation circuit is comprised of a send side inductor and a send side series capacitor serially coupled together at a node and to a positive terminal of the send coil, and a send side parallel capacitor coupled at the node and in parallel with the send coil;
a receive unit configured to receive power via inductive power transfer from the send coil of the send unit, wherein the receive unit includes

a receive coil configured to receive the alternating electromagnetic field from the send coil of the send unit and output an AC charging signal;
a receive side converter configured to receive the AC charging signal from the receive coil and convert the AC charging signal to a DC charging signal; and
a receive side compensation circuit interconnecting the receive coil with the receive side converter, wherein the receive side compensation circuit is comprised of a receive side inductor and a receive side series capacitor serially coupled together at a node and to a positive terminal of the receive coil, and a receive side parallel capacitor coupled at the node and in parallel with the receive coil; and
a controller electrically coupled to the four switches of the inverter and operates to turn all of the four switches on and off at a zero voltage switching condition, wherein the turn off current delivered by the controller is computed in accordance with

I
OFF

=

2

⁢

(

U
ab
2

U
AB

⁢

(

Δ
⁢

⁢

L

e
⁢

⁢
2

L

f
⁢

⁢
2

-

1
4

)

ω
0

⁢

L

f
⁢

⁢
2

+

U
AB

4
⁢

ω
0

⁢

L

f
⁢

⁢
1

)

where U AB is first order root mean square value of input voltage to the inverter, U ab is first order root mean square value of output voltage of receive side converter, L f1 , is inductance of send side inductor, L f2 is inductance of receive side inductor,ω 0 is resonant frequency and Δ e2 is an increase in value of L f2 to ensure the turn off current is positive.

2. The wireless power transfer system of claim 1 wherein the switches are further defined as power metal-oxide-semiconductor field effect transistors (MOSFETs).

3. The wireless power transfer system of claim 1 wherein an equivalent receive side inductance for the received side series capacitor and the receive side inductor has a value larger than equivalent send side inductance for the send side series capacitor and the send side inductor.

4. The wireless power transfer system of claim 1 wherein ΔL 2 is computed in accordance with

Δ
⁢

⁢

L

e
⁢

⁢
2

=

1
4

⁢

L

f
⁢

⁢
2

+

I

OFF
⁢

⁢

Assignees

• Univ Michigan Regents

Inventors

• Mi Chris
• Deng Junjun
• Nguyen Trong-Duy
• Li Weihan
• Li Siqi

Classifications

• B60L53/122

  Circuits or methods for driving the primary coil, e.g. supplying electric power to the coil · CPC title

• H02J2105/37

  exchanging power with electric vehicles [EV] or with hybrid electric vehicles [HEV] · CPC title

• H02J7/92 Primary

  with prioritisation of loads or sources · CPC title

• Y02T90/14

  Plug-in electric vehicles · CPC title

• H02J50/10

  using inductive coupling · CPC title