ABOVE RESONANCE FREQUENCY OPERATION FOR WIRELESS POWER TRANSFER

• US 20130270919A1
• Filed: 04/16/2012
• Published: 10/17/2013
• Est. Priority Date: 04/16/2012
• Status: Abandoned Application

• Current Assignee: UT-Battelle LLC
• Original Assignee: UT-Battelle LLC
• Inventors: Miller, John M.
• Application Number:
  US13/447,447
• Publication Number:
  US 20130270919A1
• Time in Patent Office: Days
• US Class Current: 307/104
• 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 50/10 using inductive coupling
• 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

Abstract

A wireless power transmission system includes a primary circuit and a secondary circuit, which are coupled through coupling coils. The primary circuit includes an alternating current (AC) power supply source that provides an alternating current signal through a series connection of a primary capacitor and a primary coil. The secondary circuit includes a parallel connection of a secondary coil, a secondary capacitor, and a load. The resonance frequency f₀ of the wireless power transmission system is a frequency at which the power transfer efficiency of the wireless transmission system achieves a maximum for an infinitesimally small resistive load. The operational frequency of the AC power supply source is selected to be above the resonance frequency f₀ so as to provide greater efficiency and/or greater power transfer rate in the presence of a finite impedance load.

Claims

1. An apparatus for wireless power transmission, said apparatus comprising:

an inductive coupling structure comprising a primary coil and a secondary coil, wherein at least one of said primary coil and said secondary coil is movable, said primary coil being a component of a primary circuit comprising a primary capacitor in a connection with said primary coil, and said secondary coil being a component of a secondary circuit comprising a secondary capacitor in connection with said secondary coil;

an alternating current (AC) power supply source present within said primary circuit; and

a finite impedance load present within said secondary circuit and connected to said secondary coil and said secondary capacitor, wherein said AC power supply source is configured to provide an input power to said primary coil and said primary capacitor at an operational frequency f that is greater than a resonance frequency f₀ at which said coupling coils provide a maximum power transfer efficiency between said primary circuit and said secondary circuit for a hypothetical circuit in which said finite impedance load is substituted with an infinitesimally small resistive load.

2. The apparatus of claim 1, wherein said primary coil and said primary capacitor are in a series connection.

3. The apparatus of claim 2, wherein said secondary coil and said secondary capacitor are in a parallel connection.

4. The apparatus of claim 3, wherein an output node of said AC power supply source is connected directly to an end of said series connection and another output node of said AC power supply source is connected directly to another end of said series connection.

5. The apparatus of claim 4, wherein one end of said finite impedance load is connected directly to an end of said parallel connection, and another end of said finite impedance load is connected directly to another end of said parallel connection.

6. The apparatus of claim 3, wherein said primary coil has a first self-inductance L₁ and said primary capacitor has a first capacitance C₁, wherein values for said first self-inductance L₁ and said first capacitance C₁ satisfy a relationship given by

7. The apparatus of claim 6, wherein said secondary coil has a second self-inductance L₂ and said secondary capacitor has a second capacitance C₂, wherein values for said second self-inductance L₂ and said second capacitance C₂ satisfy a relationship given by

8. The apparatus of claim 1, wherein at least one of said primary coil and said secondary coil is configured to be movable without limitation on a maximum separation distance between said primary coil and said secondary coil.

9. The apparatus of claim 1, wherein an entirety of a space between said primary coil and said secondary coil is an air gap.

10. The apparatus of claim 1, wherein a ratio of said operational frequency f to said resonance frequency f₀ is in a range from 1.0001 to 2.0000.

11. The apparatus of claim 1, wherein said secondary circuit further comprises a rectifier, wherein said secondary coil and said secondary capacitor are connected to input nodes of said rectifier, and a resistive load is connected to output nodes of said rectifier.

12. The apparatus of claim 1, wherein said AC voltage supply source comprises an H-bridge circuit including four insulated gate bipolar transistors.

13. The apparatus of claim 1, wherein said resonance frequency f₀ is from 1 kHz to 1 MHz.

14. The apparatus of claim 1, wherein said finite impedance load has a magnitude that provides two local peaks in a magnitude of current in said primary circuit as a function of frequency within a frequency range between 0 Hz and twice said resonance frequency f₀.

15. The apparatus of claim 1, wherein said primary circuit and said secondary circuit are located in two separate structures, of which at least one is movable.

16. The apparatus of claim 15, wherein a first structure including said primary circuit is stationary, and a second structure including said secondary circuit is movable.

17. The apparatus of claim 15, wherein a first structure including said primary circuit is movable, and a second structure including said secondary circuit is movable.

18. The apparatus of claim 15, wherein said second structure is a vehicle configured to move on a road, in off-road terrain on land, on water, in water, or in air.

19. The apparatus of claim 1, wherein said AC power supply source is configured to generate an alternating voltage at said operational frequency f from a direct current power source.

20. The apparatus of claim 1, wherein said AC power supply source is configured to generate an alternating voltage at said operational frequency f from an alternating current power supply that operates at a frequency from 50 Hz to 60 Hz and at a voltage from 110 V to 220V.

21. A method of operating an apparatus for wireless power transmission, said method comprising:

providing an apparatus for wireless power transmission, said apparatus comprising;

an inductive coupling structure comprising a primary coil and a secondary coil, wherein at least one of said primary coil and said secondary coil is movable, said primary coil being a component of a primary circuit comprising a primary capacitor in a connection with said primary coil, and said secondary coil being a component of a secondary circuit comprising a secondary capacitor in connection with said secondary coil; and

an alternating current (AC) power supply source present within said primary circuit;

connecting a finite impedance load to said secondary circuit, wherein said finite impedance load is connected to said secondary coil and said secondary capacitor; and

providing an input power to said primary coil and said primary capacitor, employing said AC power supply source, at an operational frequency f that is greater than a resonance frequency f₀ at which said coupling coils provide a maximum power transfer efficiency between said primary circuit and said secondary circuit for a hypothetical circuit in which said finite impedance load is substituted with an infinitesimally small resistive load.

22. The method of claim 21, wherein said primary coil and said primary capacitor are in a series connection in said apparatus.

23. The method of claim 22, wherein said secondary coil and said secondary capacitor are in a parallel connection in said apparatus.

24. The method of claim 23, wherein an output node of said AC power supply source is connected directly to an end of said series connection and another output node of said AC power supply source is connected directly to another end of said series connection in said apparatus.

25. The method of claim 24, wherein said connecting of said finite impedance load to said secondary circuit further comprises:

connecting one end of said finite impedance load directly to an end of said parallel connection; and

connecting another end of said finite impedance load directly to another end of said parallel connection in said apparatus.

26. The method of claim 23, wherein said apparatus is provided such that said primary coil has a first self-inductance L₁ and said primary capacitor has a first capacitance C₁, wherein values for said first self-inductance L₁ and said first capacitance C₁ satisfy a relationship given by

27. The method of claim 26, wherein said apparatus is provided such that said secondary coil has a second self-inductance L₂ and said secondary capacitor has a second capacitance C₂, wherein values for said second self-inductance L₂ and said second capacitance C₂ satisfy a relationship given by

28. The method of claim 21, further comprising moving at least one of said primary coil and said secondary coil prior to said providing of said input power to said primary coil and said primary capacitor.

29. The method of claim 21, further comprising positioning said primary coil and said secondary coil such that an entirety of a space between said primary coil and said secondary coil is an air gap prior to said providing of said input power to said primary coil and said primary capacitor.

30. The method of claim 21, wherein said providing of said input power further comprises selecting said operational frequency f such that a ratio of said operational frequency f to said resonance frequency f₀ is in a range from 1.0001 to 2.0000.

31. The method of claim 21, wherein said secondary circuit further comprises a rectifier, wherein said secondary coil and said secondary capacitor are connected to input nodes of said rectifier, and a resistive load is connected to output nodes of said rectifier.

32. The method of claim 21, wherein said AC voltage supply source comprises an H-bridge circuit including four insulated gate bipolar transistors in said apparatus.

33. The method of claim 21, wherein said resonance frequency f₀ is from 1 kHz to 1 MHz in said apparatus.

34. The method of claim 21, wherein said finite impedance load has a magnitude that provides two local peaks in a magnitude of current in said primary circuit as a function of frequency within a frequency range between 0 Hz and twice said resonance frequency f₀.

35. The method of claim 21, wherein said primary circuit and said secondary circuit are provided as two separate structures, of which at least one is movable, and said method further comprises moving said at least one of said primary circuit and said secondary circuit prior to said providing of said input power to said primary coil and said primary capacitor.

36. The method of claim 35, wherein a first structure including said primary circuit is stationary, and a second structure including said secondary circuit is movable, and said method further comprises moving said secondary circuit prior to said providing of said input power to said primary coil and said primary capacitor.

37. The method of claim 35, wherein a first structure including said primary circuit is movable, and a second structure including said secondary circuit is movable, and said method further comprises moving said primary circuit prior to said providing of said input power to said primary coil and said primary capacitor.

38. The method of claim 35, wherein said second structure is a vehicle configured to move on a road, in off-road terrain on land, on water, in water, or in air.

39. The method of claim 21, further comprising generating an alternating voltage at said operational frequency f from a direct current power source within said AC power supply source.

40. The method of claim 21, further comprising generating an alternating voltage at said operational frequency f from an alternating current power supply that operates at a frequency from 50 Hz to 60 Hz and at a voltage from 110 V to 220V within said AC power supply source.