Power demand management in inductive power transfer systems

• US 9,077,194 B2
• Filed: 09/09/2010
• Issued: 07/07/2015
• Est. Priority Date: 09/09/2009
• Status: Active Grant

• Current Assignee: Auckland UniServices Limited (Auckland University)
• Original Assignee: Auckland UniServices Limited (Auckland University)
• Inventors: Covic, Grant Anthony, Boys, John Talbot
• Primary Examiner(s): DEBERADINIS, ROBERT L
• Application Number:
  US13/395,173
• Publication Number:
  US 20120319479A1
• Time in Patent Office: 1,762 Days
• Field of Search: 307/104
• US Class Current: 1/1
• CPC Class Codes: H02J 3/241 The oscillation concerning frequency
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence
• CPC Class Codes: H02J 7/00712 the cycle being controlled or terminated in response to electric parameters

Abstract

A method of controlling power delivered to one or more loads in an inductive power transfer (IPT) system includes varying a frequency of a current in a primary conductive path (109), detecting the frequency in a pick-up inductively coupled with the primary conductive path (109), and controlling the power supplied to a load (207) associated with the pickup dependent on the detected frequency of the current in the primary conductive path (109). The frequency of the current is determined by is determined by either or both the load on a power supply (104) of the IPT system or the load on an electricity supply network supplying the power supply (104).

Claims

1. A method of controlling power delivered to one or more loads in an inductive power transfer (IPT) system having a primary conductive path and one or more pick-up devices adapted to receive power inductively from the primary conductive path, the method comprising:

varying a frequency of a current in the primary conductive path;

detecting a frequency or an indication of the frequency in a pick-up inductively coupled with the primary conductive path; and

controlling power supplied to a load associated with said pickup dependent on the detected frequency or the indication of the frequency of the current in the primary conductive path.

2. A method as claimed in claim 1 wherein the frequency of the current is determined by power available to the system.

3. A method as claimed in claim 2 wherein the power available to the system is determined by either or both a load on a power supply of the IPT system or a load on an electricity supply network supplying the power supply.

4. A method as claimed in claim 3 wherein the load on the electricity supply network is determined by monitoring variations in a utility supply frequency of the electricity supply network.

5. A method as claimed in claim 4 wherein varying a frequency of the current in the primary conductive path comprises amplitude modulating an IPT-frequency alternating current by the utility supply frequency, the IPT-frequency being higher than the utility supply frequency, thereby varying a frequency of an envelope of a amplitude modulated current in the primary conductive path.

6. A method as claimed in claim 5 wherein detecting the frequency of the current in the primary conductive path comprises detecting the frequency of the envelope.

7. A method as claimed in claim 1 wherein varying the frequency of the current comprises varying a fundamental frequency of the current.

8. A method as claimed in claim 7 wherein detecting the frequency of the current in the primary conductive path comprises detecting the fundamental frequency of the current in the primary conductive path.

9. A method as claimed in claim 1 wherein the power supplied to the load is controlled dependent on a relationship between the detected frequency or the indication of the frequency and one or more predefined reference frequencies.

10. A method as claimed in claim 1 wherein the power supplied to the load is controlled between a maximum power level and a minimum power level in response to variations of the detected frequency between an upper threshold frequency and a lower threshold frequency.

11. A method as claimed in claim 1 wherein the Step of detecting the frequency or an indication of the frequency includes detecting an increased or reduced frequency which is indicative of a frequency of a current in the primary conductive path.

12. An inductive power transfer (IPT) system having a primary conductive path and one or more pick-up devices adapted to receive power inductively from the primary conductive path, the system comprising:

frequency varying means to vary a frequency of a current in the primary conductive path;

detection means to detect the frequency or an indication of the frequency in a pick-up inductively coupled with the primary conductive path; and

control means to control power supplied to a load associated with said pickup dependent on the detected frequency or the indication of the frequency of the current in the primary conductive path.

13. An IPT system as claimed in claim 12 wherein the frequency of the current is determined by power available to the system.

14. An IPT system as claimed in claim 13 wherein the power available to the system is determined by either or both a load on a power supply of the IPT system or a load on an electricity supply network supplying the power supply.

15. An IPT system as claimed in claim 14 wherein the load on the electricity supply network is determined by monitoring variations in a utility supply frequency of the electricity supply network.

16. An IPT system as claimed in claim 14 wherein the frequency varying means vary a frequency of the current in the primary conductive path by amplitude modulating an IPT-frequency alternating current by the utility supply frequency, the IPT-frequency being higher than the utility supply frequency, thereby varying a frequency of an envelope of an amplitude modulated current in the primary conductive path.

17. An IPT system as claimed in claim 16 wherein the frequency detection means detect the frequency of the envelope.

18. An IPT system as claimed in claim 12 wherein the frequency varying means vary the frequency of the current by varying a fundamental frequency of the current.

19. An IPT system as claimed in claim 18 wherein the frequency detection means detect the fundamental frequency of the current in the primary conductive path.

20. An IPT system as claimed in claim 12 wherein the control means control the power supplied to the load dependent on a relationship between the detected frequency or the indication of the frequency and one or more predefined reference frequencies.

21. An IPT system as claimed in claim 12 wherein the control means control the power supplied to the load between a maximum power level and a minimum power level in response to variations of the detected frequency between an upper threshold frequency and a lower threshold frequency.

22. An IPT system as claimed in claim 12 wherein the detection means detect an increased or reduced frequency which is indicative of a frequency of a current in the primary conductive path.

23. An IPT pick-up circuit, comprising:

detection means to detect a frequency of a current in a primary conductive path with which a pick-up may, in use, be inductively coupled; and

control means to control output power of the pick-up dependent on the detected frequency.

24. An IPT pick-up circuit as claimed in claim 23 wherein the detection means detect an envelope frequency of the current.

25. An IPT pick-up circuit as claimed in claim 23 wherein the detection means detect a fundamental frequency of the current.

26. An IPT pick-up circuit as claimed in claim 23 wherein the control means control the output power dependent on a relationship between the detected frequency and one or more predefined reference frequencies.

27. An IPT pick-up circuit as claimed in claim 23 wherein the control means control the output power between a maximum power level and a minimum power level in response to variations of the detected frequency between an upper threshold frequency and a lower threshold frequency.

28. An IPT pick-up circuit, comprising:

a pick-up coil for inductive coupling with a primary conductive path of an IPT system;

a frequency detector adapted to indirectly measure a frequency of an alternating current in the primary conductive path; and

a power controller coupled with the pick-up coil and the frequency detector, wherein the power controller is adapted to vary a power output of the pick-up circuit in response to variations in the frequency measured by the frequency detector.

29. An IPT system power supply for supplying current to a primary conductive path of an IPT system, the power supply comprising frequency varying means to vary a frequency of a current in the primary conductive path whereby the frequency of the current is determined by the power available.

30. An IPT system power supply as claimed in claim 29 wherein the power available is determined by either or both a load on the power supply or a load on an electricity supply network supplying the power supply.

31. An IPT system power supply comprising:

a three-phase input for receiving power from an utility supply network at a utility supply frequency;

a frequency detector for measuring the utility supply frequency; and

an inverter to provide an alternating current to a primary conductive path of the IPT system at an operating frequency greater than the utility supply frequency, the inverter being further adapted to adjust the operating frequency in response to variations in the utility supply network.

32. An IPT system power supply as claimed in claim 31 wherein the power supply is adapted to measure the utility supply frequency by measuring a frequency of the three-phase input and averaging over the three phases.

33. An IPT system power supply as claimed in claim 31 wherein an operating frequency of the supply is adjusted between a minimum and a maximum frequency centred on an IPT frequency to which one or more pick-ups of the IPT system are tuned, the operating frequency being selected dependent on the utility supply frequency.

34. A method of controlling power delivered to one or more loads in an inductive power transfer (IPT) system comprising:

providing an indication of a utility supply frequency or power supply frequency to a pick-up circuit; and

using the indication to control power output of the pick-up circuit.

35. A method as claimed in claim 34 wherein the indication is provided via inductive coupling between a power supply of the IPT system or by a communications channel.