Resonator Balancing in Wireless Power Transfer Systems

• US 20160012967A1
• Filed: 07/08/2015
• Published: 01/14/2016
• Est. Priority Date: 07/08/2014
• Status: Active Grant

• Current Assignee: WiTricity Corporation
• Original Assignee: WiTricity Corporation
• Inventors: Kurs, Andre B., Lestoquoy, Guillaume, Kesler, Morris P.
• Granted Patent: US 9,842,688 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B60L 2210/10 DC to DC converters
• CPC Class Codes: B60L 2210/30 AC to DC converters
• CPC Class Codes: B60L 2210/40 DC to AC converters
• CPC Class Codes: B60L 2270/147 electro magnetic [EMI]
• CPC Class Codes: B60L 53/122 Circuits or methods for driving the primary coil, e.g. supplying electric power to the coil
• CPC Class Codes: B60L 53/126 Methods for pairing a vehicle and a charging station, e.g. establishing a one-to-one relation between a wireless power transmitter and a wireless power receiver
• CPC Class Codes: H01F 27/2871 Pancake coils
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H02J 50/005 Mechanical details of housing or structure aiming to accommodate the power transfer means, e.g. mechanical integration of coils, antennas or transducers into emitting or receiving devices
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 7/00309 Overheat or overtemperature protection
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y02T 90/12 Electric charging stations
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles

Abstract

The disclosure features systems for wireless power transfer that include a resonator featuring a coil with at least two windings and at least one inductor having an inductance value, where the at least one inductor is connected in series to at least one of the windings, and where the inductance value is selected so that when the coil carries a current during operation of the system, the at least one inductor maintains a distribution of current flows among the at least two windings such that for each of the at least two windings, an actual current flow in the winding differs from a target current flow for the winding by 10% or less.

Claims

1. A system for wireless power transfer, comprising:

a resonator comprising a coil with at least two windings, each of the at least two windings comprising a plurality of loops formed by a conductive material and extending in a plane, wherein corresponding portions of each of the at least two windings are oriented in parallel, wherein at least one of the windings has a length that differs from a length of another one of the windings, and wherein the at least two windings are electrically connected in parallel; and

at least one inductor having an inductance value, wherein the at least one inductor is connected in series to at least one of the windings,

wherein the inductance value is selected so that when the coil carries a current during operation of the system, the at least one inductor maintains a distribution of current flows among the at least two windings such that for each of the at least two windings, an actual current flow in the winding differs from a target current flow for the winding by 10% or less.

2. The system of claim 1, wherein the at least one inductor comprises an adjustable inductance value.

3. The system of claim 1, wherein corresponding portions of each of the at least two windings are oriented in parallel along at least 80% of a length of at least one of the windings.

4. The system of claim 1, wherein the loops of each winding are interleaved.

5. The system of claim 1, wherein the loops of each winding are concentric and form a spiral.

6. The system of claim 1, further comprising an electronic processor coupled to the at least two windings and configured to control electrical currents in each of the windings based on the target current flows for the at least two windings.

7. The system of claim 6, wherein the electronic processor is configured to control electrical currents in each of the windings by:

determining a target inductance value for the at least one inductor based on a figure of merit related to the target current flows; and

adjusting the inductance value of the at least one inductor to match the target inductance value.

8. The system of claim 7, wherein the electronic processor is configured to determine the target inductance value by:

(i) for each one of the windings;

determining a self-inductance value of the one winding based on a measurement of inductance of the one winding when it is electrically disconnected from all other windings; and

determining a plurality of cross-inductance values of the one winding, wherein each cross-inductance value is based on a measurement of inductance of the one winding when it is electrically disconnected from another one of the windings;

(ii) determining the target current flows for each of the windings based on the self-inductance values and the cross-inductance values; and

(iii) determining the target inductance value based on the target current flows for each of the windings.

9. The system of claim 8, wherein the electronic processor is configured to determine the target current flows by:

constructing an inductance matrix based on the self-inductance values and the cross-inductance values of each of the windings;

calculating an adjusted inductance matrix by adding to the inductance matrix an inductance modification matrix comprising elements that correspond to changes in inductance of each of the windings due to the at least one inductor;

calculating an inverse matrix of the adjusted inductance matrix; and

determining the target current flows based on the inverse matrix.

10. The system of claim 9, wherein the inductance modification matrix is a diagonal matrix, and wherein diagonal elements of the inductance modification matrix are inductance values of respective members of the at least one inductor connected to the windings.

11. A method, comprising:

controlling electrical currents in each of at least two windings of a resonator coil for wireless power transfer, wherein each of the at least two windings comprises a plurality of loops formed by a conductive material and extending in a plane, wherein corresponding portions of each of the at least two windings are oriented in parallel, wherein at least one of the windings has a length that differs from a length of another one of the windings, wherein the at least two windings are electrically connected in parallel, and wherein at least one inductor having an inductance value is connected in series to at least one of the windings; and

maintaining a distribution of current flows among the at least two windings when the coil carries a current such that for each of the at least two windings, an actual current flow in the winding differs from a target current flow for the winding by 10% or less.

12. The method of claim 11, wherein corresponding portions of each of the at least two windings are oriented in parallel along at least 80% of a length of at least one of the windings.

13. The method of claim 11, wherein the loops of each winding are interleaved.

14. The method of claim 11, wherein the loops of each winding are concentric and form a spiral.

15. The method of claim 11, further comprising controlling electrical currents in each of the windings to maintain the distribution of current flows by:

determining a target inductance value for the at least one inductor based on a figure of merit related to the target current flows; and

adjusting the inductance value of the at least one inductor to match the target inductance value.

16. The method of claim 15, further comprising determining the target inductance value by:

(i) for each one of the windings;

determining a self-inductance value of the one winding based on a measurement of inductance of the one winding when it is electrically disconnected from all other windings; and

determining a plurality of cross-inductance values of the one winding, wherein each cross-inductance value is based on a measurement of inductance of the one winding when it is electrically disconnected from another one of the windings;

(ii) determining the target current flows for each of the windings based on the self-inductance values and the cross-inductance values; and

(iii) determining the target inductance value based on the target current flows for each of the windings.

17. The method of claim 16, further comprising determining the target current flows by:

constructing an inductance matrix based on the self-inductance values and the cross-inductance values of each of the windings;

calculating an adjusted inductance matrix by adding to the inductance matrix an inductance modification matrix comprising elements that correspond to changes in inductance of each of the windings due to the at least one inductor;

calculating an inverse matrix of the adjusted inductance matrix; and

determining the target current flows based on the inverse matrix.

18. The method of claim 17, wherein the inductance modification matrix is a diagonal matrix, and wherein diagonal elements of the inductance modification matrix are inductance values of respective members of the at least one inductor connected to the windings.

19. A resonator coil for wireless power transfer, the coil comprising:

a member formed of magnetic material; and

at least two windings electrically connected in parallel, each of the at least two windings comprising a plurality of loops formed by a conductive material,

wherein the loops of each of the at least two windings are interleaved so that corresponding portions of each of the at least two windings are oriented in parallel along at least 80% of a length of at least one of the windings; and

wherein each one winding of the at least two windings spatially overlaps at least one other winding at one or more points along a length of the one winding.

20. The coil of claim 19, further comprising at least one inductor having an adjustable inductance connected in series to at least one of the windings.